WorldWideScience

Sample records for alloy a356 solidification

  1. Evaluation of microstructure of A356 aluminum alloy casting ...

    Indian Academy of Sciences (India)

    The objective of this investigation was to evaluate the effect of vibrations (during solidification) on the metallurgical properties of A356 aluminum casting. Mechanical vibrations were applied to A356 aluminum alloy through set up. A356 melt has been subjected to mechanical vibration with the frequency range from 0 to 400 ...

  2. Solidification behavior and rheo-diecasting microstructure of A356 aluminum alloy prepared by self-inoculation method

    Directory of Open Access Journals (Sweden)

    Ming Li

    2017-01-01

    Full Text Available Semisolid slurry of A356 aluminum alloy was prepared by self-inoculation method, and the microstructure and solidification behavior during rheo-diecasting process were investigated. The results indicate that the semisolid slurry of A356 aluminum alloy can be prepared by self-inoculation method at 600 °C. Primary α-Al particles with fine and spherical morphologies are uniformly distributed when the isothermal holding time of slurry is 3 min. Liquid phase segregation occurs during rheo-diecasting process of semisolid slurry and the primary particles (α1 show obvious plastic deformation in the area of high stress and low cooling rate. A small amount of dendrites resulting from the relatively low temperature of the shot chamber at the initial stage of secondary solidification are fragmented as they pass through the in-gate during the mould filling process. The amount of dendrite fragments decreases with the increase of filling distance. During the solidification process of the remaining liquid, the nucleation rate of secondary particles (α2 increases with the increase of cooling rate, and the content of Si in secondary particles (α2 are larger than primary particles (α1. With the increase of cooling rate, the content of Si in secondary particles (α2 gradually increases. The morphologies of eutectic Si in different parts of die casting are noticeably different. The low cooling rate in the first filling positions leads to coarse eutectic structures, while the high cooling rate in the post filling positions promotes small and compact eutectic structures.

  3. Impact of External Pressure on the Heat Transfer Coefficient during Solidification of Al-A356 Alloy

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Ilkhchy, A.Fardi; Moumani, E.

    In this paper the interfacial heat transfer coefficient (IHTC) is correlated to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of the casting under different pressures were obtained using the Inverse Heat Conduction...... Problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented...

  4. Precipitation hardening of cast Zr-containing A356 aluminium alloy

    International Nuclear Information System (INIS)

    Baradarani, B.; Raiszadeh, R.

    2011-01-01

    The effect of small additions of zirconium on the hardness, grain size, precipitate type and size of cast A356 aluminium alloy was investigated. The cast alloys were solution treated and then artificially aged for different periods of time. Hardness tests and scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) studies were carried out on the as-cast, as-solutionised and age-hardened specimens. Incoherent, coarse Al 3 Zr particles formed in the microstructure during the solidification of the alloy and caused grain refinement in the as-cast structure. These particles dissolved and reprecipitated as smaller-size particles during the solution treatment, causing the hardness of the alloy to remain constant at high temperatures for long periods of time due to the slow diffusion of Zr in the α-Al.

  5. Effects of Eutectic Si Particles on Mechanical Properties and Fracture Toughness of Cast A356 Aluminum Alloys

    International Nuclear Information System (INIS)

    Lee, Kyu Hong; Lee, Sung Hak; Kwon, Yong Nam

    2007-01-01

    The present study aims at investigating the effects of eutectic Si particles on mechanical properties and fracture toughness of three A356 aluminum alloys. These A356 alloys were fabricated by casting processes such as rheo-casting, squeeze-casting, and casting-forging, and their mechanical properties and fracture toughness were analyzed in relation with microfracture mechanism study. All the cast A356 alloys contained eutectic Si particles mainly segregated along solidification cells, and the distribution of Si particles was modified by squeeze-casting and casting-forging processes. Microfracture observation results showed that eutectic Si particles segregated along cells were cracked first, but that aluminum matrix played a role in blocking crack propagation. Tensile properties and fracture toughness of the squeeze cast and cast-forged alloys having homogeneous distribution of eutectic Si particles were superior to those of the rheo-cast alloy. In particular, the cast-forged alloy had excellent hardness, strength, ductility, and fracture toughness because of the matrix strengthening and homogeneous distribution of eutectic Si particles due to forging process

  6. Gating system optimization of low pressure casting A356 aluminum alloy intake manifold based on numerical simulation

    Directory of Open Access Journals (Sweden)

    Jiang Wenming

    2014-03-01

    Full Text Available To eliminate the shrinkage porosity in low pressure casting of an A356 aluminum alloy intake manifold casting, numerical simulation on filling and solidification processes of the casting was carried out using the ProCAST software. The gating system of the casting is optimized according to the simulation results. Results show that when the gating system consists of only one sprue, the filling of the molten metal is not stable; and the casting does not follow the sequence solidification, and many shrinkage porosities are observed through the casting. After the gating system is improved by adding one runner and two in-gates, the filling time is prolonged from 4.0 s to 4.5 s, the filling of molten metal becomes stable, but this casting does not follow the sequence solidification either. Some shrinkage porosity is also observed in the hot spots of the casting. When the gating system was further improved by adding risers and chill to the hot spots of the casting, the shrinkage porosity defects were eliminated completely. Finally, by using the optimized gating system the A356 aluminum alloy intake manifold casting with integrated shape and smooth surface as well as dense microstructure was successfully produced.

  7. Enthalpies of a binary alloy during solidification

    Science.gov (United States)

    Poirier, D. R.; Nandapurkar, P.

    1988-01-01

    The purpose of the paper is to present a method of calculating the enthalpy of a dendritic alloy during solidification. The enthalpies of the dendritic solid and interdendritic liquid of alloys of the Pb-Sn system are evaluated, but the method could be applied to other binaries, as well. The enthalpies are consistent with a recent evaluation of the thermodynamics of Pb-Sn alloys and with the redistribution of solute in the same during dendritic solidification. Because of the heat of mixing in Pb-Sn alloys, the interdendritic liquid of hypoeutectic alloys (Pb-rich) of less than 50 wt pct Sn has enthalpies that increase as temperature decreases during solidification.

  8. Thermal and microstructural analysis of an aluminium A356 alloy solidified by magnetic agitation

    International Nuclear Information System (INIS)

    Bustos, O; Ordonez, S; Jarami, Dario; Colas, R

    2008-01-01

    A magnetic agitation device was designed using a permanently rotating magnetic field, in order to study the effect of applying a variable magnetic field to agitate cast metals during the solidification process. The procedure used to verify the machine's functioning involved smelting and casting a predefined amount of A356 alloy in the device with and without the application of the magnetic field and then characterizing the material obtained with standard procedures of metallographic analysis. The results obtained show that the application of a permanently rotating magnetic field produces a destruction of the cast dendritic structure. This is explained by the fact that a magnetic field that varies over time induces a f.e.m. in a fluid conductor that becomes an increased convective transport through the Lorentz force. This work also studied the kinetics of solidification. The alloy was heated to 680 o C and was cast in molds preheated to 200 o C. Tests were carried out with and without the application of magnetic agitation. The cooling curves were recorded to evaluate the effect of the magnetic agitation on the alloy's form of solidification. The thermal analysis of the cooling curves shows a decrease in the temperatures under which the formation of dendrites from the primary phase as well as from the eutectic Al-Si phase begins when a magnetic field is imposed. A series of intermetallic AlFeSi type compounds appear in these alloys, which display noticeable refining and redistribution from the magnetic agitation (au)

  9. Solidification paths of multicomponent monotectic aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mirkovic, Djordje; Groebner, Joachim [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Street 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, Rainer [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Street 42, D-38678 Clausthal-Zellerfeld (Germany)], E-mail: schmid-fetzer@tu-clausthal.de

    2008-10-15

    Solidification paths of three ternary monotectic alloy systems, Al-Bi-Zn, Al-Sn-Cu and Al-Bi-Cu, are studied using thermodynamic calculations, both for the pertinent phase diagrams and also for specific details concerning the solidification of selected alloy compositions. The coupled composition variation in two different liquids is quantitatively given. Various ternary monotectic four-phase reactions are encountered during solidification, as opposed to the simple binary monotectic, L' {yields} L'' + solid. These intricacies are reflected in the solidification microstructures, as demonstrated for these three aluminum alloy systems, selected in view of their distinctive features. This examination of solidification paths and microstructure formation may be relevant for advanced solidification processing of multicomponent monotectic alloys.

  10. The solidification velocity of nickel and titanium alloys

    Science.gov (United States)

    Altgilbers, Alex Sho

    2002-09-01

    The solidification velocity of several Ni-Ti, Ni-Sn, Ni-Si, Ti-Al and Ti-Ni alloys were measured as a function of undercooling. From these results, a model for alloy solidification was developed that can be used to predict the solidification velocity as a function of undercooling more accurately. During this investigation a phenomenon was observed in the solidification velocity that is a direct result of the addition of the various alloying elements to nickel and titanium. The additions of the alloying elements resulted in an additional solidification velocity plateau at intermediate undercoolings. Past work has shown a solidification velocity plateau at high undercoolings can be attributed to residual oxygen. It is shown that a logistic growth model is a more accurate model for predicting the solidification of alloys. Additionally, a numerical model is developed from simple description of the effect of solute on the solidification velocity, which utilizes a Boltzmann logistic function to predict the plateaus that occur at intermediate undercoolings.

  11. Relationships Between Solidification Parameters in A319 Aluminum Alloy

    Science.gov (United States)

    Vandersluis, E.; Ravindran, C.

    2018-03-01

    The design of high-performance materials depends on a comprehensive understanding of the alloy-specific relationships between solidification and properties. However, the inconsistent use of a particular solidification parameter for presenting materials characterization in the literature impedes inter-study comparability and the interpretation of findings. Therefore, there is a need for accurate expressions relating the solidification parameters for each alloy. In this study, A319 aluminum alloy castings were produced in a permanent mold with various preheating temperatures in order to control metal cooling. Analysis of the cooling curve for each casting enabled the identification of its liquidus, Al-Si eutectic, and solidus temperatures and times. These values led to the calculation of the primary solidification rate, total solidification rate, primary solidification time, and local solidification time for each casting, which were related to each other as well as to the average casting SDAS and material hardness. Expressions for each of their correlations have been presented with high coefficients of determination, which will aid in microstructural prediction and casting design.

  12. General characteristics of eutectic alloy solidification mechanisms

    International Nuclear Information System (INIS)

    Lemaignan, Clement.

    1977-01-01

    The eutectic alloy sodification was studied in binary systems: solidification of non facetted - non facetted eutectic alloy (theoretical aspects, variation of the lamellar spacing, crystallographic relation between the various phases); solidification of facetted - non facetted eutectic alloy; coupled growth out of eutectic alloy; eutectic nucleation [fr

  13. Microstructure and mechanical properties of lost foam cast 356 alloys

    Directory of Open Access Journals (Sweden)

    Qi-gui Wang

    2015-05-01

    Full Text Available Microstructure and mechanical properties of lost foam cast aluminum alloys have been investigated in both primary A356 (0.13% Fe and secondary 356 (0.47%. As expected, secondary 356 shows much higher content of Fe-rich intermetallic phases, and in particular the porosity in comparison with primary A356. The average area percent and size (length of Fe-rich intermetallics change from about 0.5% and 6 祄 in A356 to 2% and 25 祄 in 356 alloy. The average area percent and maximum size of porosity also increase from about 0.4% and 420 祄 to 1.4% and 600 祄, respectively. As a result, tensile ductility decreases about 60% and ultimate tensile strength declines about 8%. Lower fatigue strength was also experienced in the secondary 356 alloy. Low cycle fatigue (LCF strength decreased from 187 MPa in A356 to 159 MPa in 356 and high cycle fatigue (HCF strength also declined slightly from 68 MPa to 64 MPa.

  14. Solidification microstructures of aluminium-uranium alloys

    International Nuclear Information System (INIS)

    Ambrozio Filho, F.; Vieira, R.R.

    1976-01-01

    The solidification of microstrutures of aluminium-uranium alloys in the range of 4 to 20% uranium is investigated. The solidification was obtained both in ingot molds and under controlled directional solidification. The conditions for the presence of primary crystals and eutectic are discussed and an analysis of the influence of variables (growth rate and thermal gradient in the liquid) on the alloy structure is made. The effect of cooling rate on the alloy structures has been determined. It is found that the resulting structure can be derived from the kinectics concept, as required by the coupled-zone theory. Suggestions on the qualitative intervals of composition and temperatures with eutectic growth are presented [pt

  15. Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy

    DEFF Research Database (Denmark)

    Fardi Ilkhchy, A.; Jabbari, Masoud; Davami, P.

    2012-01-01

    The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat...... conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula...... was presented for correlation between external pressure and heat transfer coefficient. Acceptable agreement with data in literature shows the accuracy of the proposed formula....

  16. Effect of Solidification Rate and Rare Earth Metal Addition on the Microstructural Characteristics and Porosity Formation in A356 Alloy

    Directory of Open Access Journals (Sweden)

    M. G. Mahmoud

    2017-01-01

    Full Text Available The present study was performed on A356 alloy with the main aim of investigating the effects of La and Ce additions to 356 alloys (with and without 100 ppm Sr on the microstructure and porosity formation in these alloys. Measured amounts of La, Ce, and Sr were added to the molten alloy. The results showed that, in the absence of Sr, addition of La and Ce leads to an increase in the nucleation temperature of the α-Al dendritic network with a decrease in the temperature of the eutectic Si precipitation, resulting in increasing the freezing range. Addition of 100 ppm Sr results in neutralizing these effects. The presence of La or Ce in the casting has a minor effect on eutectic Si modification, in spite of the observed depression in the eutectic temperature. It should be noted that Ce is more effective than La as an alternate modifying agent. According to the atomic radius ratio, rLa/rSi is 1.604 and rCe/rSi is 1.559, theoretically, which shows that Ce is relatively more effective than La. The present findings confirm that Sr is the most dominating modification agent. Interaction between rare earth (RE metals and Sr would reduce the effectiveness of Sr. Although modification with Sr causes the formation of shrinkage porosity, it also reacts with RE-rich intermetallics, resulting in their fragmentation.

  17. Effect of Dynamic Composite Refinement and Modification on Microstructure of A356 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    WANG Zheng-jun

    2017-01-01

    Full Text Available To make up for the inadequacy of Sr modification,Al-5Ti-1B-1RE master alloy refiner was prepared,then were used together with Al-10Sr master alloy for dynamic composite refinement and modification of A356 alloy.The A356 alloy microstructure of modification was studied and compared with the theoretical calculating results.The results show that the melt is fiercely stirred and vibrated by the JJ-1 laboratory electric stirrer;the refining effect of α-Al phase is excellent;the coarse and needle-like eutectic Si phase transforms into tiny,widely dispersed spherical particles and well-distributed at the grain boundaries.And mechanical property of the A356 alloy increases obviously.The grain size control study results are consistent with Johnson-Mehl equation theory.At the same time,the contents of gases of the A356 alloy are significantly reduced,which can not be achieved by Sr alone.Quantitative calculating results of degassing mechanism are consistent with the approximate calculating equations of thermodynamics and Stokes Law.

  18. Simulation and Experimental Study on the Steady Conduction Solution for Continuous Rheo-Casting for A356 Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Duc, Do Minh; Hai, Nguyen Hong; Quang, Pham [Hanoi University of Science and Technology (HUST), Hanoi (Viet Nam)

    2017-03-15

    Computational fluid dynamic modeling of a continuous rheo-casting technology was conducted, consistent with the manufacturing of 3 {sup mm-thin} plates made of aluminum alloy A356. The A numerical simulation on of the stabilizing time of the material crystallization was carried out using the ANSYS FLUENT code. Solidification and melting models were simulated with heat transfer and solid-liquid phase transformation involving the latent heat of crystallization were simulated. The calculated temperature distribution and the evolution of cooling rate through the material were examined and used to clarify their influence on microstructure, and further investigated with hardness testing. The thickness of the mushy zone was determined for the steady conduction solution of the continuous rheo-casting process.

  19. Microstructure and Corrosion Resistance Property of a Zn-AI-Mg Alloy with Different Solidification Processes

    Directory of Open Access Journals (Sweden)

    Jiang Guang-rui

    2017-01-01

    Full Text Available Zn-Al-Mg alloy coating attracted much attention due to its high corrosion resistance properties, especially high anti-corrosion performance at the cut edge. As the Zn-Al-Mg alloy coating was usually produced by hot-dip galvanizing method, solidification process was considered to influence its microstructure and corrosion properties. In this work, a Zn-Al-Mg cast alloy was melted and cooled to room temperature with different solidification processes, including water quench, air cooling and furnace cooling. Microstructure of the alloy with different solidification processes was characterized by scanning electron microscopy (SEM. Result shows that the microstructure of the Zn-Al-Mg alloy are strongly influenced by solidification process. With increasing solidification rate, more Al is remained in the primary crystal. Electrochemical analysis indicates that with lowering solidification rate, the corrosion current density of the Zn-Al-Mg alloy decreases, which means higher corrosion resistance.

  20. Influence of prior natural aging on the subsequent artificial aging response of aluminium alloy A356 with respective globular and dendritic microstructures

    CSIR Research Space (South Africa)

    Moller, H

    2011-01-01

    Full Text Available on the subsequent artificial aging response of SSM-HPDC A356 [9, 10]. An artificial aging treatment at 180◦C for 4 h can, however, negate the effects of any prior natural aging [10]. A recent review paper [15] on the heat treatment of Al- Si-Cu-Mg alloys (which..., 8]. The assumption is that these heat treatments are not necessarily the optimum treatments, as the difference in solidification history and microstructure of SSM processed components should be considered [7–11]. However, a recent paper...

  1. Simulation and Experimental Study on the Steady Conduction Solution for Continuous Rheo-Casting for A356 Alloy

    International Nuclear Information System (INIS)

    Duc, Do Minh; Hai, Nguyen Hong; Quang, Pham

    2017-01-01

    Computational fluid dynamic modeling of a continuous rheo-casting technology was conducted, consistent with the manufacturing of 3 "m"m"-"t"h"i"n plates made of aluminum alloy A356. The A numerical simulation on of the stabilizing time of the material crystallization was carried out using the ANSYS FLUENT code. Solidification and melting models were simulated with heat transfer and solid-liquid phase transformation involving the latent heat of crystallization were simulated. The calculated temperature distribution and the evolution of cooling rate through the material were examined and used to clarify their influence on microstructure, and further investigated with hardness testing. The thickness of the mushy zone was determined for the steady conduction solution of the continuous rheo-casting process.

  2. Containerless solidification of acoustically levitated Ni-Sn eutectic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Geng, D.L.; Xie, W.J.; Wei, B. [Northwestern Polytechnical University, Department of Applied Physics, Xi' an (China)

    2012-10-15

    Containerless solidification of Ni-18.7at%Sn eutectic alloy has been achieved with a single-axis acoustic levitator. The temperature, motion, and oscillation of the sample were monitored by a high speed camera. The temperature of the sample can be determined from its image brightness, although the sample moves vertically and horizontally during levitation. The experimentally observed frequency of vertical motion is in good agreement with theoretical prediction. The sample undergoes shape oscillation before solidification finishes. The solidification microstructure of this alloy consists of a mixture of anomalous eutectic plus regular lamellar eutectic. This indicates the achievement of rapid solidification under acoustic levitation condition. (orig.)

  3. Microstructure Development and Characteristics of Semisolid Aluminum Alloys; FINAL

    International Nuclear Information System (INIS)

    Merton Flemings; Srinath Viswanathan

    2001-01-01

    A drop forge viscometer was employed to investigate the flow behavior under very rapid compression rates of A357, A356 diluted with pure aluminum and Al-4.5%Cu alloys. The A357 alloys were of commercial origin (MHD and SIMA) and the rheocast, modified A356 and Al-4.5Cu alloys were produced by a process developed at the solidification laboratory of MIT

  4. Numerical simulation of freckle formation in directional solidification of binary alloys

    Science.gov (United States)

    Felicelli, Sergio D.; Heinrich, Juan C.; Poirier, David R.

    1992-01-01

    A mathematical model of solidification is presented which simulates the formation of segregation models known as 'freckles' during directional solidification of binary alloys. The growth of the two-phase or dendritic zone is calculated by solving the coupled equations of momentum, energy, and solute transport, as well as maintaining the thermodynamic constraints dictated by the phase diagram of the alloy. Calculations for lead-tin alloys show that the thermosolutal convection in the dendritic zone during solidification can produce heavily localized inhomogeneities in the composition of the final alloy.

  5. Rapid solidification growth mode transitions in Al-Si alloys by dynamic transmission electron microscopy

    International Nuclear Information System (INIS)

    Roehling, John D.; Coughlin, Daniel R.; Gibbs, John W.; Baldwin, J. Kevin; Mertens, James C.E.; Campbell, Geoffrey H.; Clarke, Amy J.; McKeown, Joseph T.

    2017-01-01

    In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate rapid solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent solidification. Solely α-Al solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower solidification velocities to planar eutectic growth at higher solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous solidification models, and implications regarding the models are discussed.

  6. Role of cerium, lanthanum, and strontium additions in an Al-Si-Mg (A356) alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nabawy, Ahmed M.; Samuel, Agnes M.; Samuel, Fawzy H. [Universite du Quebec, Chicoutimi (Canada). Dept. des Sciences Appliquees; Alkahtani, Saleh A.; Abuhasel, Khaled A. [Salman Bin Abdulaziz Univ., Riyadh (Saudi Arabia). Mechanical Engineering Dept.

    2016-05-15

    The effects of individual and combined additions of cerium (Ce), lanthanum (La), and strontium (Sr) on the eutectic modification and solidification characteristics of an Al-Si-Mg (A356) aluminum alloy were investigated using optical microscopy and thermal analysis techniques. Addition of Ce, La, and Sr resulted in different depression levels of the eutectic nucleation temperature and eutectic growth undercooling, generating modified eutectic structures exhibiting different levels of modification. Microstructural results showed that the best modification levels using individual additions were achieved by Sr which produced a fine fibrous eutectic structure, followed by La, which produced a refined lamellar structure, with Ce providing the lowest level of modification. On the other hand, a combined addition of Ce and Sr provided the highest modification level, with the production of a very fine fibrous eutectic silicon structure. In general, the addition of Sr helped to further increase the refinement obtained in the alloys containing La or Ce + La additions. In the latter alloy, the main intermetallic phases observed were La(Al,Si){sub 2} and Al{sub 20}(La,Ce)Ti{sub 2}Si. The improved modification levels were found to be proportional to the depression in the eutectic nucleation temperature and the eutectic growth undercooling. A high cooling rate also improved the modification level by at least one level.

  7. Solidification processing of monotectic alloy matrix composites

    Science.gov (United States)

    Frier, Nancy L.; Shiohara, Yuh; Russell, Kenneth C.

    1989-01-01

    Directionally solidified aluminum-indium alloys of the monotectic composition were found to form an in situ rod composite which obeys a lambda exp 2 R = constant relation. The experimental data shows good agreement with previously reported results. A theoretical boundary between cellular and dendritic growth conditions was derived and compared with experiments. The unique wetting characteristics of the monotectic alloys can be utilized to tailor the interface structure in metal matrix composites. Metal matrix composites with monotectic and hypermonotectic Al-In matrices were made by pressure infiltration, remelted and directionally solidified to observe the wetting characteristics of the alloys as well as the effect on structure of solidification in the constrained field of the fiber interstices. Models for monotectic growth are modified to take into account solidification in these constrained fields.

  8. Solidification Mapping of a Nickel Alloy 718 Laboratory VAR Ingot

    Science.gov (United States)

    Watt, Trevor J.; Taleff, Eric M.; Lopez, Felipe; Beaman, Joe; Williamson, Rodney

    The solidification microstructure of a laboratory-scale Nickel alloy 718 vacuum arc remelted (VAR) ingot was analyzed. The cylindrical, 210-mm-diameter ingot was sectioned along a plane bisecting it length-wise, and this mid-plane surface was ground and etched using Canada's reagent to reveal segregation contrast. Over 350 photographs were taken of the etched mid-plane surface and stitched together to form a single mosaic image. Image data in the resulting mosaic were processed using a variety of algorithms to extract quantities such as primary dendrite orientation, primary dendrite arm spacing (PDAS), and secondary dendrite arm spacing (SDAS) as a function of location. These quantities were used to calculate pool shape and solidification rate during solidification using existing empirical relationships for Nickel Alloy 718. The details and outcomes of this approach, along with the resulting comparison to experimental processing conditions and computational models, are presented.

  9. Continuous Solidification of Immiscible Alloys and Microstructure Control

    Science.gov (United States)

    Jiang, Hongxiang; Zhao, Jiuzhou

    2018-05-01

    Immiscible alloys have aroused considerable interest in last few decades due to their excellent physical and mechanical characteristics as well as potential industrial applications. Up to date, plenty of researches have been carried out to investigate the solidification of immiscible alloys on the ground or in space and great progress has been made. It is demonstrated that the continuous solidification technique have great future in the manufacturing of immiscible alloys, it also indicates that the addition of surface active micro-alloying or inoculants for the nucleation of the minority phase droplets and proper application of external fields, e.g., static magnetic field, electric current, microgravity field, etc. may promote the formation of immiscible alloys with an expected microstructure. The objective of this article is to review the research work in this field.

  10. Analysis of weld solidification cracking in cast nickel aluminide alloys

    International Nuclear Information System (INIS)

    Santella, M.L.; Feng, Z.

    1995-01-01

    A study of the response of several nickel aluminide alloys to SigmaJig testing was done to examine their weld solidification cracking behavior and the effect of Zr concentration. The alloys were based on the Ni-8Al-7.7Cr-1.5Mo-0.003B wt% composition and contained Zr concentrations of 3, 4.5, and 6 wt%. Vacuum induction melted ingots with a diameter of 2.7 in and weight about 18 lb were made of each alloy, and were used to make 2 x 2 x 0.030 in specimens for the Sigmajig test. The gas tungsten arc welds were made at travel speeds of 10, 20, and 30 ipm with heat inputs of 2--2.5 kJ/in. When an arc was established before traveling onto the test specimen centerline cracking was always observed. This problem was overcome by initiating the arc directly on the specimens. Using this approach, the 3 wt% Zr alloy withstood an applied stress of 24 ksi without cracking at a welding speed of 10 ipm. This alloy cracked at 4 ksi applied at 20 ipm, and with no applied load at 30 ipm. Only limited testing was done on the remaining alloys, but the results indicate that resistance to solidification cracking increases with Zr concentration. Zirconium has limited solid solubility and segregates strongly to interdendritic regions during solidification where it forms a Ni solid solution-Ni 5 Zr eutectic. The volume fraction of the eutectic increases with Zr concentration. The solidification cracking behavior of these alloys is consistent with phenomenological theory, and is discussed in this context. The results from SigmaJig testing are analyzed using finite element modeling of the development of mechanical strains during solidification of welds. Experimental data from the test substantially agree with recent analysis results

  11. Finite-element solidification modelling of metals and binary alloys

    International Nuclear Information System (INIS)

    Mathew, P.M.

    1986-12-01

    In the Canadian Nuclear Fuel Waste Management Program, cast metals and alloys are being evaluated for their ability to support a metallic fuel waste container shell under disposal vault conditions and to determine their performance as an additional barrier to radionuclide release. These materials would be cast to fill residual free space inside the container and allowed to solidify without major voids. To model their solidification characteristics following casting, a finite-element model, FAXMOD-3, was adopted. Input parameters were modified to account for the latent heat of fusion of the metals and alloys considered. This report describes the development of the solidification model and its theoretical verification. To model the solidification of pure metals and alloys that melt at a distinct temperature, the latent heat of fusion was incorporated as a double-ramp function in the specific heat-temperature relationship, within an interval of +- 1 K around the solidification temperature. Comparison of calculated results for lead, tin and lead-tin eutectic melts, unidirectionally cooled with and without superheat, showed good agreement with an alternative technique called the integral profile method. To model the solidification of alloys that melt over a temperature interval, the fraction of solid in the solid-liquid region, as calculated from the Scheil equation, was used to determine the fraction of latent heat to be liberated over a temperature interval within the solid-liquid zone. Comparison of calculated results for unidirectionally cooled aluminum-4 wt.% copper melt, with and without superheat, showed good agreement with alternative finite-difference techniques

  12. Solidification processing of intermetallic Nb-Al alloys

    Science.gov (United States)

    Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

    1992-01-01

    Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

  13. Phase-field simulation of peritectic solidification closely coupled with directional solidification experiments in an Al-36 wt% Ni alloy

    International Nuclear Information System (INIS)

    Siquieri, R; Emmerich, H; Doernberg, E; Schmid-Fetzer, R

    2009-01-01

    In this work we present experimental and theoretical investigations of the directional solidification of Al-36 wt% Ni alloy. A phase-field approach (Folch and Plapp 2005 Phys. Rev. E 72 011602) is coupled with the CALPHAD (calculation of phase diagrams) method to be able to simulate directional solidification of Al-Ni alloy including the peritectic phase Al 3 Ni. The model approach is calibrated by systematic comparison to microstructures grown under controlled conditions in directional solidification experiments. To illustrate the efficiency of the model it is employed to investigate the effect of temperature gradient on the microstructure evolution of Al-36 wt% Ni during solidification.

  14. Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, Shashi Prakash [Noida Institute of Engineering and Technology, Greater Noida (Korea, Republic of)

    2014-01-15

    In the present investigation, A356/C355 aluminium alloys are welded by friction stir welding by controlling various welding parameters. A356 and C355 aluminium alloys materials have a set of mechanical and physical properties that are ideally suited for application in aerospace and automobile industries and not widely used because of its poor weldebility. To overcome this barrier, weldebility analysis of A356 and C355 aluminium alloys with high speed steel (Wc-Co) tool has been investigated. An attempt has been made to investigate the influence of the rotational speed of the tools, the axial force and welding speed on tensile strength of A356/C355 aluminium alloys joint. The experiments were conducted on a milling machine. The main focus of investigation is to determine good tensile strength. Response surface methodology (box Behnken design) is chosen to design the optimum welding parameters leading to maximum tensile strength. The result shows that axial force increases, tensile strength decreases. Whereas tool rotational speed and welding speed increase, tensile strength increases. Optimum values of axial force (3 /KN), tool rotational speed (900 RPM) and welding speed (75 mm/min.) during welding of A356/C355 aluminium alloys joint to maximize the tensile strength (Predicted 223.2 MPa) have been find out.

  15. Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint

    International Nuclear Information System (INIS)

    Dwivedi, Shashi Prakash

    2014-01-01

    In the present investigation, A356/C355 aluminium alloys are welded by friction stir welding by controlling various welding parameters. A356 and C355 aluminium alloys materials have a set of mechanical and physical properties that are ideally suited for application in aerospace and automobile industries and not widely used because of its poor weldebility. To overcome this barrier, weldebility analysis of A356 and C355 aluminium alloys with high speed steel (Wc-Co) tool has been investigated. An attempt has been made to investigate the influence of the rotational speed of the tools, the axial force and welding speed on tensile strength of A356/C355 aluminium alloys joint. The experiments were conducted on a milling machine. The main focus of investigation is to determine good tensile strength. Response surface methodology (box Behnken design) is chosen to design the optimum welding parameters leading to maximum tensile strength. The result shows that axial force increases, tensile strength decreases. Whereas tool rotational speed and welding speed increase, tensile strength increases. Optimum values of axial force (3 /KN), tool rotational speed (900 RPM) and welding speed (75 mm/min.) during welding of A356/C355 aluminium alloys joint to maximize the tensile strength (Predicted 223.2 MPa) have been find out.

  16. Numerical model for dendritic solidification of binary alloys

    Science.gov (United States)

    Felicelli, S. D.; Heinrich, J. C.; Poirier, D. R.

    1993-01-01

    A finite element model capable of simulating solidification of binary alloys and the formation of freckles is presented. It uses a single system of equations to deal with the all-liquid region, the dendritic region, and the all-solid region. The dendritic region is treated as an anisotropic porous medium. The algorithm uses the bilinear isoparametric element, with a penalty function approximation and a Petrov-Galerkin formulation. Numerical simulations are shown in which an NH4Cl-H2O mixture and a Pb-Sn alloy melt are cooled. The solidification process is followed in time. Instabilities in the process can be clearly observed and the final compositions obtained.

  17. Centrifugal casting of ZA8 zinc alloy and composite A356/silicon carbide: Study and modeling of phases' and particles' segregation

    Science.gov (United States)

    Balout, Bahaa

    Centrifugation is a casting technology that allows the production of cylindrical and graduated parts with different mechanical properties through the section. The need for materials with good quality and specific mechanical properties has been driven this technology in order to produce different types of materials such as zinc alloys and graduated metal matrix composites reinforced by hard and wear resistant particles. The goal of this research project is to study and model the eutectic macrosegregation, the solidification speed, and the speeds of solidification fronts during centrifugal casting of ZA8 zinc-aluminum alloy in order to improve the part quality and increase its strength and field reliability. Moreover, the segregation of the particles during centrifugal casting of an aluminum matrix composite reinforced by silicon carbide particles (A356/SiC) is also studied to improve and control the graduation of the parts. The cooling rate, the speed, acceleration/deceleration, displacement, and segregation of the particles across the section will be modeled by discretization of Stokes' law in time in order to take into consideration the change in the centrifugal radius and melt viscosity during cooling process. This study will allow the control of the graduation degree of particles across the section in order to improve the properties and wear resistance of the composite. This composite can be used in systems where friction is critical and load is high (reinforcements of parts for the cylinders of pneumatic systems). The results show that the maximum macrosegregation zone of the eutectic across the casting section corresponds to the last point of solidification. The eutectic macrosegregation produced during centrifugal casting of thin walled part is a normal segregation which varies depending on the solidification speed and the ratio between the speeds of solidification fronts. On the other hand, it was found that the position and volume fraction of the particles

  18. Effect of Sc addition and T6 aging treatment on the microstructure modification and mechanical properties of A356 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Pramod, S.L. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Ravikirana [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Department of Physics and Nanotechnology, SRM University, Chennai 603203 (India); Rao, A.K. Prasada [College of Engineering and Design, Alliance University, Bengaluru 562106 (India); Murty, B.S., E-mail: murty@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Bakshi, Srinivasa R., E-mail: sbakshi@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2016-09-30

    Effect of Sc addition and T6 aging treatment on the secondary dendritic arm spacing (SDAS), modification of eutectic Si morphology, β-Al{sub 5}FeSiand π-Al{sub 8}Mg{sub 3}Si{sub 6}Fe{sub 1} phases and its effect on mechanical properties in A356 alloy has been investigated. Addition of 0.4 wt%Sc in A356 alloy resulted in a 50%reduction in the secondary dendritic arm spacing (SDAS). Sc addition changed the morphology of eutectic Si from plate like to fibrous and globular. The needle like morphology of β-Al{sub 5}FeSi phase in A356 alloy changed to Al{sub 5}Fe(Si,Sc) phase having smaller size and irregular morphology. Transmission electron microscopy (TEM) diffraction pattern and Energy dispersive spectroscopy (EDS) analysis revealed the presence of β-Al{sub 5}FeSiand π-Al{sub 8}Mg{sub 3}Si{sub 6}Fe{sub 1} phases in A356 alloy which changed to β-Al{sub 5}Fe(Si,Sc), π-Al{sub 8}Mg{sub 3}(Si,Sc){sub 6}Fe{sub 1} and additional V-AlSi{sub 2}Sc{sub 2}phase was observed in Sc containing alloys. Addition of 0.4 wt%Sc to A356 alloy improved its Vickers hardness, Ultimate tensile strength (UTS), Yield strength (YS) and ductility by 20%, 25%, 20% and 30% respectively. Artificial aging treatment resulted in significant improvement in the tensile properties for both A356 and Sc added A356 alloys.

  19. Influence of temper condition on microstructure and mechanical properties of semisolid metal processed Al–Si–Mg alloy A356

    CSIR Research Space (South Africa)

    Moller, H

    2009-01-01

    Full Text Available The microstructures and mechanical properties of strontium modified semisolid metal high pressure die cast A356 alloy are presented. The alloy A356-F (as cast) has a globular primary grain structure containing a fine eutectic. Solution treatment...

  20. Production of A356 aluminum alloy wheels by thixo-forging combined with a low superheat casting process

    Directory of Open Access Journals (Sweden)

    Wang Shuncheng

    2013-09-01

    Full Text Available The A356 aluminum alloy wheels were produced by thixo-forging combined with a low superheat casting process. The as-cast microstructure, microstructure evolution during reheating and the mechanical properties of thixo-forged wheels made from the A356 aluminum alloy were studied. The results show that the A356 aluminum alloy round billet with fine, uniform and non-dendritic grains can be obtained when the melt is cast at 635 篊. When the round billet is reheated at 600 篊 for 60 min, the non-dendritic grains are changed into spherical ones and the round billet can be easily thixo-forged into wheels. The tensile strength, yield strength and elongation of the thixo-forged wheels with T6 heat treatment are 327.6 MPa, 228.3 MPa and 7.8%, respectively, which are higher than those of a cast wheel. It is suggested that the thixo-forging combined with the low superheat casting process is an effective technique to produce aluminum alloy wheels with high mechanical properties.

  1. Comparative Evaluation of Cast Aluminum Alloys for Automotive Cylinder Heads: Part I—Microstructure Evolution

    Science.gov (United States)

    Roy, Shibayan; Allard, Lawrence F.; Rodriguez, Andres; Watkins, Thomas R.; Shyam, Amit

    2017-05-01

    The present study stages a comparative evaluation of microstructure and associated mechanical and thermal response for common cast aluminum alloys that are used for manufacturing automotive cylinder heads. The systems considered are Al-Cu (206-T6), Al-Si-Cu (319-T7), and Al-Si (356-T6, A356-T6, and A356 + 0.5Cu-T6). The focus of the present manuscript is on the evaluation of microstructure at various length scales after aging, while the second manuscript will deal with the mechanical and thermal response of these alloys due to short-term (aging) and long-term (pre-conditioning) heat treatments. At the grain-scale, the Al-Cu alloy possessed an equiaxed microstructure as opposed to the dendritic structure for the Al-Si-Cu or Al-Si alloys which is related to the individual solidification conditions for these alloy systems. The composition and morphology of intermetallic precipitates within the grain and at the grain/dendritic boundary are dictated by the alloy chemistry, solidification, and heat treatment conditions. At the nanoscale, these alloys contain various metastable strengthening precipitates (GPI and θ^'' in Al-Cu alloy, θ^' in Al-Si-Cu alloy, and β^' in Al-Si alloys) with varying size, morphology, coherency, and thermal stability.

  2. Sufficient condition for generation of multiple solidification front in one-dimensional solidification of binary alloys

    International Nuclear Information System (INIS)

    Bobula, E.; Kalicka, Z.

    1981-10-01

    In the paper we consider the one-dimensional solidification of binary alloys in the finite system. The authors present the sufficient condition for solidification in the liquid in front of the moving solid-liquid interface. The effect may produce a fluctuating concentration distributin in the solid. The convection in the liquid and supercooling required for homogeneous nucleation are omitted. A local-equilibrium approximation at the liquid-solid interface is supposed. (author)

  3. The role of ultrasonic cavitation in refining the microstructure of aluminum based nanocomposites during the solidification process.

    Science.gov (United States)

    Xuan, Yang; Nastac, Laurentiu

    2018-02-01

    Recent studies showed that the microstructure and mechanical properties of aluminum based nanocomposites can be significantly improved when ultrasonic cavitation and solidification processing is used. This is because ultrasonic cavitation processing plays an important role not only in degassing and dispersion of the nanoparticles, but also in breaking up the dendritic grains and refining the as-cast microstructure. In the present study, A356 alloy and Al 2 O 3 nanoparticles are used as the matrix alloy and the reinforcement, respectively. Nanoparticles were added into the molten A356 alloy and dispersed via ultrasonic cavitation processing. Ultrasonic cavitation was applied over various temperature ranges during molten alloy cooling and solidification to investigate the grain structure formation and the nanoparticle dispersion behavior. Optical Microscopy and Scanning Electron Microscopy were used to investigate in detail the differences in the microstructure characteristics and the nanoparticle distribution. Experimental results indicated that the ultrasonic cavitation processing and Al 2 O 3 nanoparticles play an important role for microstructure refinement. In addition, it was shown in this study that the Al 2 O 3 nanoparticles modified the eutectic phase. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Modelling of solidification processing and continuous strip casting for copper-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoudi, Jafar [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Processing

    2000-04-01

    An experimental and numerical study was carried out to investigate the solidification process in a copper continuous strip casting process. Heat flow and solidification process has been experimentally studied. Cooling curves during solidification were registered using a thermocouple of type K connected to a data acquisition system. Temperature measurements in the mould and cooling water were also performed. The numerical model considers a generalized set of mass, momentum and heat equations that is valid for the solid, liquid and solidification interval in the cast. A k-{epsilon} turbulence model, produced with the commercial program CFX, is used to analyse the solidification process of pure copper in the mould region of the caster. The fluid flow, temperature and heat flux distributions in the mould region of the caster were computed. The shape and location of the solidification front were also determined. The effects of the parameters such as heat transfer coefficient, casting speed, casting temperature, heat of fusion and specific heat on the shape and location of the solidification front and the heat transport at the mould-cast interface were investigated. The predicted temperature and heat flux distributions were compared with experimental measurements, and reasonable agreement was obtained. The solidification behaviour of pure copper and different copper base alloys has been studied. A series of solidification experiments using DTA furnace, mirror furnace and levitation technique were performed on different copper-base alloys. The undercooling, cooling rates of the liquid and the solid states, solidification times and temperatures were evaluated from the curves. The cooling curves for different samples were simulated using a FEM solidification program. It was found that the calculated values of the heat of fusion were much lower than the tabulated ones. The fraction of solid formed before quenching, in the DTA experiments, has been observed to be much higher

  5. Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

    Directory of Open Access Journals (Sweden)

    Szymanek M.

    2015-12-01

    Full Text Available The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS. The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr refines their structure.

  6. Comparative evaluation of cast aluminum alloys for automotive cylinder heads: Part I Microstructure evolution

    International Nuclear Information System (INIS)

    Roy, Shibayan; Allard, Lawrence Frederick Jr; Rodriguez, Andres; Watkins, Thomas R.; Shyam, Amit

    2017-01-01

    The present study stages a comparative evaluation of microstructure and associated mechanical and thermal response for common cast aluminum alloys that are used for manufacturing automotive cylinder heads. The systems considered are Al-Cu (206-T6), Al-Si-Cu (319-T7), and Al-Si (356-T6, A356-T6, and A356 + 0.5Cu-T6). The focus of the present manuscript is on the evaluation of microstructure at various length scales after aging, while the second manuscript will deal with the mechanical and thermal response of these alloys due to short-term (aging) and long-term (pre-conditioning) heat treatments. At the grain-scale, the Al-Cu alloy possessed an equiaxed microstructure as opposed to the dendritic structure for the Al-Si-Cu or Al-Si alloys which is related to the individual solidification conditions for these alloy systems. The composition and morphology of intermetallic precipitates within the grain and at the grain/dendritic boundary are dictated by the alloy chemistry, solidification, and heat treatment conditions. At the nanoscale, these alloys contain various metastable strengthening precipitates (GPI and θ''θ'' in Al-Cu alloy, θ'θ' in Al-Si-Cu alloy, and β'β' in Al-Si alloys) with varying size, morphology, coherency, and thermal stability.

  7. Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy

    Science.gov (United States)

    Wang, Changshuai; Su, Haijun; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

    2017-09-01

    Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy, considered as boiler and turbine materials in 700 °C advanced ultra-supercritical coal-fired power plants, have been investigated by differential thermal analysis and directional solidification quenching technique. Results reveal that P decreases the solidus temperature, but only has negligible influence on liquidus temperature. After P was added, the solidification sequence has no apparent change, but the width of the mushy zone increases and dendritic structures become coarser. Moreover, P increases the amount and changes the morphology of MC carbide. Energy-dispersive spectroscopy analysis reveals that P has obvious influence on the segregation behavior of the constitute elements with equilibrium partition coefficients (ki) far away from unity, whereas has negligible effect on the constituent elements with ki close to unity and has more influence on the final stage of solidification than at early stage. The distribution profiles reveal that P atoms pile up ahead of the solid/liquid (S/L) interface and strongly segregate to the interdendritic liquid region. The influence of P on solidification characteristics and segregation behavior of Ni-Fe-Cr-based alloy could be attributed to the accumulation of P ahead of the S/L interface during solidification.

  8. Effects of erbium modification on the microstructure and mechanical properties of A356 aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.M., E-mail: shizm@imut.edu.cn; Wang, Q.; Zhao, G.; Zhang, R.Y.

    2015-02-25

    The effects of erbium (Er) modification on the microstructure and mechanical properties of A356 aluminum alloys were investigated using optical microscope, X-ray diffraction, scanning electronic microscope and mechanical testing. Experimental results show that additions of Er refined the α-Al grains and eutectic Si phases in its as-cast state; the addition of 0.3 wt% of Er has the best effects on them. The Fe-containing Al{sub 3}Er phases were introduced by the modifications; by a T6 treatment, the eutectic Si phases were further sphereodized; the large Al{sub 3}Er and β-Al{sub 5}FeSi phases were changed into fine particles and short rods; which enhanced the hardness of the alloys. The highest strength and elongation were obtained for the 0.3 wt% of Er-modified and T6-treated A356 alloy.

  9. Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

    CSIR Research Space (South Africa)

    Moller, H

    2010-01-01

    Full Text Available p phase. This phase, which dissolves in alloy A356 during solution treatment, persists in F357 and decreases the amount of magnesium in solid solution. This is the likely origin of the decrease in the aging response of the F357 alloy. The tensile...

  10. Divorced Eutectic Solidification of Mg-Al Alloys

    Science.gov (United States)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  11. Comparison of modification with strontium and the refining with antimony in A 356 aluminium alloys

    International Nuclear Information System (INIS)

    Fuoco, Ricardo; Correa, Edison Roberto; Correa, Alzira V.O.; Bocalini Junior, Mario

    1992-01-01

    Strontium and Antimony treated A356 aluminium alloy samples were metallographically characterized in the as cast and solution and aged conditions. Antimony treated alloy has shown slower spheroidizing kinetics of the Silicon particles during solution treatment, lower porosity level and higher tensile strength and elongation than Strontium treated one. (author)

  12. Solidification of eutectic system alloys in space (M-19)

    Science.gov (United States)

    Ohno, Atsumi

    1993-01-01

    cast by the Ohno Continuous Casting Process and they show the unidirectionally solidified structure. Each flight and ground sample was made of these same rods. The dimensions of all samples are 4.5 mm in diameter and 23.5 mm in length. Each sample is put in a graphite capsule and then vacuum sealed in a double silica ampoule. Then the ampoule is put in the tantalum cartridge and sealed by electron beam welding. For onbard experiments, a Continuous Heating Furnance (CHF) will be used for melting and solidifying samples under microgravity conditions. Six flight samples will be used. Four samples are hypo-eutectic and two are hyper-eutectic alloys. The surface of the two hypo-eutectic alloy samples are covered with aluminum oxide film to prevent Marangoni convection expected under microgravity conditions. Each sample will be heated to 700 C and held at that temperature for 5 min. After that the samples will be allowed to cool to 500 C in the furnace and they will be taken out of the furnace for He gas cooling. The heating and cooling diagrams for the flight experiments are shown. After collecting the flight samples, the solidified structures of the samples will be examined and the mechanisms of eutectic solidification under microgravity conditions will be determined. It is likely that successful flight experiment results will lead to production of high quality eutectic alloys and eutectic composite materials in space.

  13. A comparison of acoustic levitation with microgravity processing for containerless solidification of ternary Al-Cu-Sn alloy

    Science.gov (United States)

    Yan, N.; Hong, Z. Y.; Geng, D. L.; Wei, B.

    2015-07-01

    The containerless rapid solidification of liquid ternary Al-5 %Cu-65 %Sn immiscible alloy was accomplished at both ultrasonic levitation and free fall conditions. A maximum undercooling of 185 K (0.22 T L) was obtained for the ultrasonically levitated alloy melt at a cooling rate of about 122 K s-1. Meanwhile, the cooling rate of alloy droplets in drop tube varied from 102 to 104 K s-1. The macrosegregation was effectively suppressed through the complex melt flow under ultrasonic levitation condition. In contrast, macrosegregation became conspicuous and core-shell structures with different layers were formed during free fall. The microstructure formation mechanisms during rapid solidification at containerless states were investigated in comparison with the conventional static solidification process. It was found that the liquid phase separation and structural growth kinetics may be modulated by controlling both alloy undercooling and cooling rate.

  14. The solidification behavior of dilute aluminium-scandium alloys

    International Nuclear Information System (INIS)

    Norman, A.F.; Prangnell, P.B.; McEwen, R.S.

    1998-01-01

    The solidification behavior of dilute Sc containing Al alloys has been investigated. In binary Al-Sc alloys, Sc additions greater than the eutectic composition (0.55 wt%) were found to produce a remarkable refinement in the grain size of aluminum castings, of two orders of magnitude, due to the formation of the primary Al 3 Sc intermetallic phase during solidification. The refinement in grain size only occurred in hypereutectic compositions and was shown to be far greater than can be achieved by conventional Al grain refiners. Grain refinement by the addition of Sc is accompanied by a change in growth morphology from dendritic, in the large unrefined grains, to fine spherical grains with a divorced eutectic appearing on the grain boundaries in the refined castings. Similar levels of refinement were observed in Al-Sc-Zr and Al-Cu-Sc alloys. In the latter, a change in the segregation behavior of Cu was observed, from a strongly interdendritic segregation pattern to a more homogeneous distribution. The supersaturated Al-Sc solid solution can decompose via a discontinuous precipitation reaction to form coherent rod-like precipitates of the L1 2 Al 3 Sc phase

  15. Effect of chemical composition and cooling conditions on solidification hot cracking of Ni-based alloys

    International Nuclear Information System (INIS)

    De Vito, Sophie

    2000-01-01

    Ni-based alloys 690 present solidification hot cracks during welding of vapour generators. Hot cracks are qualitatively known to be due to the formation of inter-dendritic liquid films and of secondary phases down to low temperatures. This study aims at establishing the link between thermodynamics, solidification and hot cracking. Experimental solidification paths of high purity alloys (with varying Nb and Si contents) are obtained from quenching during directional solidification and TIG-welding experiments. They are compared to Thermo-Calc computations, assuming no diffusion in the solid. From directional solidification samples, good agreement between computed and experimental solidification paths is shown in the quenched liquid. Secondary arms of dendrites are affected by solid state diffusion of Nb. Combined effect of diffusion and solute build-up in the liquid phase modifies micro-segregation in the solid region. Solidification paths from welding specimens are similar to those of the solid region of quenched samples. Nb solid state diffusion is negligible but undercooling compensates the effect of solid state diffusion in directional solidification. Evolution of liquid fraction at the end of the solidification is in accordance with the hot cracking classification of the alloys. Nb favours formation of inter-dendritic liquid films and eutectic-like phases down to low temperature. (author) [fr

  16. Investigation on the formation of the preferred orientations in a TbDyFe alloy with directional solidification

    International Nuclear Information System (INIS)

    Jiang Chengbao; Xu Huibin

    1999-01-01

    The formation of the preferred orientations in a TbDyFe alloy was studied by transmission electron microscopy (TEM). It was found that there were several different preferred orientations in the experimental TbDyFe alloy with directional solidification. left angle 110 right angle, left angle 112 right angle and left angle 113 right angle preferred orientations were observed in this alloy solidified by our self-made super high gradient temperature directional solidification device. The preferred orientations changed with the variation of the solidification conditions. Two {111} twinning systems resulted in the left angle 110 right angle preferred orientation and a single {111} twinning system resulted in the left angle 112 right angle preferred orientation. The twinning displacement was observed and this formatted the left angle 113 right angle preferred orientation. (orig.)

  17. Interdiffusion between U(Mo,Pt) or U(Mo,Zr) and Al or Al A356 alloy

    International Nuclear Information System (INIS)

    Komar Varela, C.; Mirandou, M.; Arico, S.; Balart, S.; Gribaudo, L.

    2009-01-01

    Solid state reactions in chemical diffusion couples U-7 wt.%Mo-0.9 wt.%Pt/Al at 580 deg. C and U-7 wt.%Mo-0.9 wt.%Pt/Al A356 alloy, U-7 wt.%Mo-1 wt.%Zr/Al and U-7 wt.%Mo-1 wt.%Zr/Al A356 alloy at 550 deg. C were characterized. Results were obtained from optical and scanning electron microscopy, electron probe microanalysis and X-ray diffraction. The UAl 3, UAl 4 and Al 20 Mo 2 U phases were identified in the interaction layers of γU(Mo,Pt)/Al and γU(Mo,Zr)/Al diffusion couples. Al 43 Mo 4 U 6 ternary compound was also identified in γU(Mo,Zr)/Al due to the decomposition of γU(Mo,Zr) phase. The U(Al,Si) 3 and U 3 Si 5 phases were identified in the interaction layers of γU(Mo,Pt)/Al A356 and γU(Mo,Zr)/Al A356 diffusion couples. These phases are formed due to the migration of Si to the interaction layer. In the diffusion couple U(Mo,Zr)/Al A356, Zr 5 Al 3 phase was also identified in the interaction layer. The use of synchrotron radiation at Brazilian Synchrotron Light Laboratory (LNLS, CNPq, Campinas, Brazil) was necessary to achieve a complete crystallographic characterization.

  18. Ductile failure in upsetting of a rapid-solidification-processed aluminium alloy

    NARCIS (Netherlands)

    Habraken, F.A.C.M.; Dautzenberg, J.H.

    1993-01-01

    Cold upset-tests have been performed on a Rapid Solidification Processed (RSP) aluminium-alloy, produced by the ‘melt-spun ribbons’-process out of 70% car-scrap and 30% primary scrap. The ribbons are hot extruded, resulting in 29 mm diameter bar. Its properties regarding plastic flow and fracture

  19. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    Science.gov (United States)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  20. Numerical simulation of solute trapping phenomena using phase-field solidification model for dilute binary alloys

    Directory of Open Access Journals (Sweden)

    Henrique Silva Furtado

    2009-09-01

    Full Text Available Numerical simulation of solute trapping during solidification, using two phase-field model for dilute binary alloys developed by Kim et al. [Phys. Rev. E, 60, 7186 (1999] and Ramirez et al. [Phys. Rev. E, 69, 05167 (2004] is presented here. The simulations on dilute Cu-Ni alloy are in good agreement with one dimensional analytic solution of sharp interface model. Simulation conducted under small solidification velocity using solid-liquid interface thickness (2λ of 8 nanometers reproduced the solute (Cu equilibrium partition coefficient. The spurious numerical solute trapping in solid phase, due to the interface thickness was negligible. A parameter used in analytical solute trapping model was determined by isothermal phase-field simulation of Ni-Cu alloy. Its application to Si-As and Si-Bi alloys reproduced results that agree reasonably well with experimental data. A comparison between the three models of solute trapping (Aziz, Sobolev and Galenko [Phys. Rev. E, 76, 031606 (2007] was performed. It resulted in large differences in predicting the solidification velocity for partition-less solidification, indicating the necessity for new and more acute experimental data.

  1. Freezing Range, Melt Quality, and Hot Tearing in Al-Si Alloys

    Science.gov (United States)

    Uludağ, Muhammet; Çetin, Remzi; Dispinar, Derya

    2018-02-01

    In this study, three different aluminum-silicon alloys (A356, A413, and A380) that have different solidification morphology and solidification ranges were examined with an aim to evaluate the hot tearing susceptibility. T-shape mold and Constrained Rod Casting (CRC) mold were used for the characterization. Reduced Pressure Test (RPT) was used to quantify the casting quality by measuring bifilm index. It was found that bifilm index and solidification range have an important role on the hot tearing formation. As it is known, bifilms can cause porosity and in this case, it was shown that porosity formed by bifilms decreased hot tearing tendency. As the freezing range of alloy increases, bifilms find the time to unravel that reduces hot tearing. However, for eutectic alloy (A413), due to zero freezing range, regardless of bifilm content, hot tearing was never observed. A380.1 alloy had the highest tendency for hot tearing due to having the highest freezing range among the alloys investigated in this work.

  2. Laser welding of SSM Cast A356 aluminium alloy processed with CSIR-Rheo technology

    CSIR Research Space (South Africa)

    Akhter, R

    2006-01-01

    Full Text Available Samples of aluminium alloy A356 were manufactured by Semi Solid Metals HPDC technology, developed recently in CSIR, Pretoria. They were butt welded in as cast conditions using as Nd: YAG laser. The best metal and weld microstructure were presented...

  3. Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Osborne, Matthew G. [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100-1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings.

  4. Effect and kinetic mechanism of ultrasonic vibration on solidification of 7050 aluminum alloy

    Directory of Open Access Journals (Sweden)

    Ripeng Jiang

    2014-07-01

    Full Text Available The work described in this paper dealt with the effect of ultrasonic vibration on the solidification of 7050 aluminum alloy. Two experiments were carried out through introducing ultrasound into the semi-continuous direct-chill (DC casting of aluminum alloy and into alloy solidifying in a crucible, respectively. Results show that ultrasonic vibration can refine grains in the whole cross-section of a billet in the first experiment and is able to increase the cooling rate within the temperature range from 625 °C to 590 °C in the other one. The mechanism of particle resonance caused by ultrasonic vibration was illustrated on the basis of theoretical analysis of the kinetics and energy conversion during the solidification. It is demonstrated that the kinetic energy of resonant particles are mainly from the latent heat energy of solidification, which can shorten the cooling time, inhibit the crystal growth and then lead to the grain refinement.

  5. Effects of stress concentration on low-temperature fracture behavior of A356 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Guanghui; Li, Runxia; Li, Rongde

    2016-06-14

    The effect of stress concentration on the dislocation motion, the Si particles and the crack propagation path in A356 alloy at the temperature of 20 °C to −60 °C was analyzed by scanning electron microscope and optical microscope using a series of notched tensile specimens and normal tensile specimens. The results show that the sensitivity of A356 alloy to the stress concentration increases, the tensile strength and yield strength of normal specimens and notched specimens increase, and the elongation shows a decreasing trend with the decrease of test temperature from 20 °C to −60 °C. The yield strength is not affected by the notch, and the tensile strength is sensitive to the stress concentration. Stress concentration leads to a large number of dislocation generation. Local plastic deformation occurred in the stress concentration region during the tensile process firstly. With the stress concentration in the aluminum matrix between the Si phase and the crack further increasing, the distribution of cracks along the Si phase leads to the cracking of aluminum matrix particle.

  6. Effect of solidification rate on the microstructure and microhardness of a melt-spun Al-8Si-1Sb alloy

    International Nuclear Information System (INIS)

    Karakoese, E.; Keskin, M.

    2009-01-01

    The properties of rapidly solidified hypoeutectic Al-8Si-1Sb alloy, produced by melt-spinning technique at a different solidification rates, were investigated using the X-ray diffraction (XRD), the optical microscopy (OM), the scanning electron microscopy (SEM) together with the energy dispersive spectroscopy (EDS), the differential scanning calorimetry (DSC) and the microhardness technique. The properties of rapidly solidified ribbons were then compared with those of the chill-casting alloy. The results show that rapid solidification has influence on the phase constitution of the hypoeutectic Al-8Si-1Sb alloy. The phases present in the hypoeutectic Al-8Si-1Sb ingot alloy were determined to be α-Al, fcc Si and intermetallic AlSb phases whereas only α-Al and fcc Si phases were identified in the melt-spinning alloy. The rapid solidification has a significant effect on the microstructure of the hypoeutectic Al-8Si-1Sb alloy. Particle size in the microstructure of the ribbons is too small to compare with particle size in the microstructure of the ingot alloy. Moreover, the significant change in hardness occurs that is attributed to changes in the microstructure.

  7. Effect of solidification rate on the microstructure and microhardness of a melt-spun Al-8Si-1Sb alloy

    Energy Technology Data Exchange (ETDEWEB)

    Karakoese, E. [Erciyes University, Institute of Science, 38039 Kayseri (Turkey); Keskin, M. [Erciyes University, Institute of Science, 38039 Kayseri (Turkey); Erciyes University, Physics Department, 38039 Kayseri (Turkey)], E-mail: keskin@erciyes.edu.tr

    2009-06-24

    The properties of rapidly solidified hypoeutectic Al-8Si-1Sb alloy, produced by melt-spinning technique at a different solidification rates, were investigated using the X-ray diffraction (XRD), the optical microscopy (OM), the scanning electron microscopy (SEM) together with the energy dispersive spectroscopy (EDS), the differential scanning calorimetry (DSC) and the microhardness technique. The properties of rapidly solidified ribbons were then compared with those of the chill-casting alloy. The results show that rapid solidification has influence on the phase constitution of the hypoeutectic Al-8Si-1Sb alloy. The phases present in the hypoeutectic Al-8Si-1Sb ingot alloy were determined to be {alpha}-Al, fcc Si and intermetallic AlSb phases whereas only {alpha}-Al and fcc Si phases were identified in the melt-spinning alloy. The rapid solidification has a significant effect on the microstructure of the hypoeutectic Al-8Si-1Sb alloy. Particle size in the microstructure of the ribbons is too small to compare with particle size in the microstructure of the ingot alloy. Moreover, the significant change in hardness occurs that is attributed to changes in the microstructure.

  8. Rotary bending fatigue behavior of A356 –T6 aluminum alloys by vacuum pressurizing casting

    Directory of Open Access Journals (Sweden)

    Yong-qin Liu

    2015-09-01

    Full Text Available Vacuum pressurizing casting technique, providing better mould filling and inter-dendritic feeding, can reduce the porosity greatly in cast aluminum alloys, and improve the fatigue properties. The rotary bending fatigue properties of A356-T6 alloys prepared by vacuum pressurizing casting were investigated. The S-N curve and limit strength 90 MPa under fatigue life of 107 cycles were obtained. The analyses on the fatigue fractography and microstructure of specimens showed that the fatigue fracture mainly occurs at the positions with casting defects in the subsurface, especially at porosities regions, which attributed to the crack propagation during the fatigue fracture process. Using the empirical crack propagation law of Pairs-Erdogon, the quantitative relationship among the initial crack size, fatigue life and applied stress was established. The fatigue life decreases with an increase in initial crack size. Two constants in the Pairs-Erdogon equation of aluminum alloy A356-T6 were calculated using the experimental data.

  9. Evaluation of the corrosion behavior of the al-356 alloy in NaCl solutions

    Directory of Open Access Journals (Sweden)

    Mauricio Vásquez Rendón

    2011-01-01

    Full Text Available Cellular metals are a new class of materials with promising applications and a unique combination of physical, chemical and mechanical properties. The Al-356 alloy is used to manufacture metal foams from NaCl preforms. Despite the usefulness of these materials, their performance may be affected by corrosion due to residual salt. This paper reports the study of the behavior of the Al-356 alloy in chloride solutions by electrochemical techniques in rotating disk electrode. The cathodic reaction of oxygen reduction is the crucial stage of process dissolution of the material, which shows that is the oxygen transport which limits the corrosion process.

  10. Solidification structure and dispersoids in rapidly solidified Ti-Al-Sn-Zr-Er-B alloys

    International Nuclear Information System (INIS)

    Rowe, R.G.; Broderick, T.F.; Koch, E.F.; Froes, F.H.

    1986-01-01

    The microstructure of melt extracted and melt spun titanium alloys containing erbium and boron revealed a duplex solidification structure of columnar grains leading to equiaxed and dendritic structures near the free surface of melt extracted and melt spun alloys. The solidification structure was revealed by apparent boride segregation to cellular, interdendritic and grain boundaries. Precipitation of needle or lath-like TiB particles occurred adjacent to Er/sub 2/O/sub 3/ dispesoid particles in as-rapidly solidified ribbon

  11. Influences on Distribution of Solute Atoms in Cu-8Fe Alloy Solidification Process Under Rotating Magnetic Field

    Science.gov (United States)

    Zou, Jin; Zhai, Qi-Jie; Liu, Fang-Yu; Liu, Ke-Ming; Lu, De-Ping

    2018-05-01

    A rotating magnetic field (RMF) was applied in the solidification process of Cu-8Fe alloy. Focus on the mechanism of RMF on the solid solution Fe(Cu) atoms in Cu-8Fe alloy, the influences of RMF on solidification structure, solute distribution, and material properties were discussed. Results show that the solidification behavior of Cu-Fe alloy have influenced through the change of temperature and solute fields in the presence of an applied RMF. The Fe dendrites were refined and transformed to rosettes or spherical grains under forced convection. The solute distribution in Cu-rich phase and Fe-rich phase were changed because of the variation of the supercooling degree and the solidification rate. Further, the variation in solute distribution was impacted the strengthening mechanism and conductive mechanism of the material.

  12. Variations of Microsegregation and Second Phase Fraction of Binary Mg-Al Alloys with Solidification Parameters

    Science.gov (United States)

    Paliwal, Manas; Kang, Dae Hoon; Essadiqi, Elhachmi; Jung, In-Ho

    2014-07-01

    A systematic experimental investigation on microsegregation and second phase fraction of Mg-Al binary alloys (3, 6, and 9 wt pct Al) has been carried out over a wide range of cooling rates (0.05 to 700 K/s) by employing various casting techniques. In order to explain the experimental results, a solidification model that takes into account dendrite tip undercooling, eutectic undercooling, solute back diffusion, and secondary dendrite arm coarsening was also developed in dynamic linkage with an accurate thermodynamic database. From the experimental data and solidification model, it was found that the second phase fraction in the solidified microstructure is not determined only by cooling rate but varied independently with thermal gradient and solidification velocity. Lastly, the second phase fraction maps for Mg-Al alloys were calculated from the solidification model.

  13. A study of aluminum-lithium alloy solidification using acoustic emission techniques. Ph.D. Thesis, 1991

    Science.gov (United States)

    Henkel, Daniel P.

    1992-01-01

    Physical phenomena associated with the solidification of an aluminum lithium alloy was characterized using acoustic emission (AE) techniques. It is shown that repeatable patterns of AE activity may be correlated to microstructural changes that occur during solidification. The influence of the experimental system on generated signals was examined in the time and frequency domains. The analysis was used to show how an AE signal from solidifying aluminum is changed by each component in the detection system to produce a complex waveform. Conventional AE analysis has shown that a period of high AE activity occurs in pure aluminum, an Al-Cu alloy, and the Al-Li alloy, as the last fraction of solid forms. A model attributes this to the internal stresses of grain boundary formation. An additional period of activity occurs as the last fraction of solid forms, but only in the two alloys. A model attributes this to the formation of interdendritic porosity which was not present in the pure aluminum. The AE waveforms were dominated by resonant effects of the waveguide and the transducer.

  14. A scaling analysis of alloy solidification in presence of electromagnetic stirring

    International Nuclear Information System (INIS)

    Kumar, Arvind; Dutta, Pradip

    2006-01-01

    Application of electromagnetic stirring (EMS) during continuous casting shears off the dendrites from the solidification front to produce billets with a non-dendritic microstructure. In the present study, a systematic approach to the scaling analysis of momentum, energy and species conservation equations pertaining to the case of the solidification of a binary alloy in the presence of EMS is outlined. With suitable choices of non-dimensionalizing parameters, the governing equations coupled with appropriate boundary conditions are first scaled, and then the relative significance of various terms appearing in them are analysed. In the physical domain two regions are identified, one where the electromagnetic forces play a dominant role in the momentum equations, and the other where the inertia and viscous effects play major roles. Using the scaling predictions, the influence of various processing parameters on the system variables can be utilized for the selection of appropriate electromagnetic forces to shear off the dendrites from the solidification area. For the sake of assessment of the scaling analysis, the predictions are validated against corresponding computational results

  15. Mechanism of nucleation and growth of hydrogen porosity in solidifying A356 aluminum alloy: an analytical solution

    International Nuclear Information System (INIS)

    Li, K.-D.; Chang, Edward

    2004-01-01

    This study derives an analytical solution for the mechanism of nucleation and growth of hydrogen pore in the solidifying A356 aluminum alloy. A model of initial transient hydrogen redistribution in the growing dendritic grain is used to modify the lever rule for the mechanism of nucleation of pore. The model predicts the fraction of solid at nucleation, the temperature range of nucleation, the radius of hydrogen diffusion cell, and the supersaturation of hydrogen needed for nucleation. The role of solidus velocity in nucleation is explained. The parameters calculated from the model of nucleation are used for analyzing the mechanism of kinetic diffusion-controlled growth of pore, in which the mathematical transformations of variables are introduced. With the transformations, it is argued that the diffusion problem involving the liquid and solid phases during solidification could be treated as a classic problem of precipitation in the single-phase medium treated by Ham or Avrami. The analytical solution for the nucleation of pore is compared with the mechanism of macrosegregation. The predicted volume percent of porosity and radius of pore based on the mechanism of growth of pore is discussed with respect to the thermodynamic solution, the published experimental data, the numerical solutions, and the role of interdendritic fluid flow governed by Darcy's law

  16. Initial stages of solidification of eutectic alloys

    International Nuclear Information System (INIS)

    Lemaignan, Clement

    1980-01-01

    The study of the various initial stages of eutectic solidification - i.e. primary nucleation, eutectic structure formation and stable growth conditions - was undertaken with various techniques including low angle neutron diffusion, in-situ electron microscopy on solidifying alloys and classical metallography. The results obtained allow to discuss the effect of metastable states during primary nucleation, of surface dendrite during eutectic nucleation and also of the crystallographic anisotropy during growth. (author) [fr

  17. Liquid-liquid phase separation and solidification behavior of Al55Bi36Cu9 monotectic alloy with different cooling rates

    Science.gov (United States)

    Bo, Lin; Li, Shanshan; Wang, Lin; Wu, Di; Zuo, Min; Zhao, Degang

    2018-03-01

    The cooling rate has a significant effect on the solidification behavior and microstructure of monotectic alloy. In this study, different cooling rate was designed through casting in the copper mold with different bore diameters. The effects of different cooling rate on the solidification behavior of Al55Bi36Cu9 (at.%) immiscible alloy have been investigated. The liquid-liquid phase separation of Al55Bi36Cu9 immiscible alloy melt was investigated by resistivity test. The solidification microstructure and phase analysis of Al55Bi36Cu9 immiscible alloy were performed by the SEM and XRD, respectively. The results showed that the liquid-liquid phase separation occurred in the solidification of Al55Bi36Cu9 monotectic melt from 917 °C to 653 °C. The monotectic temperature, liquid phase separation temperature and immiscibility zone of Al55Bi36Cu9 monotectic alloy was lower than those of Al-Bi binary monotectic alloy. The solidification morphology of Al55Bi36Cu9 monotectic alloy was very sensitive to the cooling rate. The Al/Bi core-shell structure formed when Al55Bi36Cu9 melt was cast in the copper mold with a 8 mm bore diameter.

  18. Validated thermodynamic prediction of AlP and eutectic (Si) solidification sequence in Al-Si cast alloys

    International Nuclear Information System (INIS)

    Liang, S M; Schmid-Fetzer, R

    2016-01-01

    The eutectic microstructure in hypoeutectic Al-Si cast alloys is strongly influenced by AlP particles which are potent nuclei for the eutectic (Si) phase. The solidification sequence of AlP and (Si) phases is, thus, crucial for the nucleation of eutectic silicon with marked impact on its morphology. This study presents this interdependence between Si- and P-compositions, relevant for Al-Si cast alloys, on the solidification sequence of AlP and (Si). These data are predicted from a series of thermodynamic calculations. The predictions are based on a self-consistent thermodynamic description of the Al-Si-P ternary alloy system developed recently. They are validated by independent experimental studies on microstructure and undercooling in hypoeutectic Al-Si alloys. A constrained Scheil solidification simulation technique is applied to predict the undercooling under clean heterogeneous nucleation conditions, validated by dedicated experimental observations on entrained droplets. These specific undercooling values may be very large and their quantitative dependence on Si and P content of the Al alloy is presented. (paper)

  19. Microstructural evolution in Mg-Zn alloys during solidification: An experimental and simulation study

    Science.gov (United States)

    Paliwal, Manas; Jung, In-Ho

    2014-05-01

    A comprehensive microstructural evolution of Mg-1.5, 4.0 and 5.5 wt% Zn alloys with respect to the solidification parameters such as thermal gradient (G), solidification velocity (V), cooling rate (GV) and solute (Zn) content were investigated in the present study. Solidification techniques such as directional solidification and wedge casting were employed in order to obtain cooling rates between 0.05 and 250 K/s. Microstructural features such as secondary dendrite arm spacing (SDAS), primary dendrite arm spacing (PDAS), microsegregration along the secondary dendrites and secondary phase fractions were experimentally determined. A solidification model that incorporates solute back diffusion, secondary arm coarsening, dendrite tip undercooling and dynamically linked with accurate thermodynamic databases is used to explain the experimental results.

  20. XRMON-GF: A novel facility for solidification of metallic alloys with in situ and time-resolved X-ray radiographic characterization in microgravity conditions

    Science.gov (United States)

    Nguyen-Thi, H.; Reinhart, G.; Salloum Abou Jaoude, G.; Mathiesen, R. H.; Zimmermann, G.; Houltz, Y.; Voss, D.; Verga, A.; Browne, D. J.; Murphy, A. G.

    2013-07-01

    As most of the phenomena involved during the growth of metallic alloys from the melt are dynamic, in situ and time-resolved X-ray imaging should be retained as the method of choice for investigating the solidification front evolution. On Earth, the gravity force is the major source of various disturbing effects (natural convection, buoyancy/sedimentation, and hydrostatic pressure) which can significantly modify or mask certain physical mechanisms. Therefore solidification under microgravity is an efficient way to eliminate such perturbations to provide unique benchmark data for the validation of models and numerical simulations. Up to now, in situ observation during microgravity solidification experiments were limited to the investigations on transparent organic alloys, using optical methods. On the other hand, in situ observation on metallic alloys generally required synchrotron facilities. This paper reports on a novel facility we have designed and developed to investigate directional solidification on metallic alloys in microgravity conditions with in situ X-ray radiography observation. The facility consists of a Bridgman furnace and an X-ray radiography device specifically devoted to the study of Al-based alloys. An unprecedented experiment was recently performed on board a sounding rocket, with a 6 min period of microgravity. Radiographs were successfully recorded during the entire experiment including the melting and solidification phases of the sample, with a Field-of-View of about 5 mm×5 mm, a spatial resolution of about 4 µm and a frequency of 2 frames per second. Some preliminary results are presented on the solidification of the Al-20 wt% Cu sample, which validate the apparatus and confirm the potential of in situ X-ray characterization for the investigation of dynamical phenomena in materials processing, and particularly for the studying of metallic alloys solidification.

  1. The Refining Mechanism of Super Gravity on the Solidification Structure of Al-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Yuhou Yang

    2016-12-01

    Full Text Available There is far less study of the refining effect of super gravity fields on solidification structures of metals than of the effects of electrical currents, magnetic and ultrasonic fields. Moreover, the refining mechanisms of super gravity are far from clear. This study applied a super gravity field to Al-Cu alloys to investigate its effect on refining their structures and the mechanism of interaction. The experimental results showed that the solidification structure of Al-Cu alloys can be greatly refined by a super gravity field. The major refining effect was mainly achieved when super gravity was applied at the initial solidification stage; only slight refinement could be obtained towards the end of solidification. No refinement was obtained by the super gravity treatment on pure liquid or solid stages. The effectiveness of super gravity results from its promoting the multiplication of crystal nuclei, which we call “Heavy Crystal Rain”, thereby greatly strengthening the migration of crystal nuclei within the alloy. Increasing the solute Cu content can increase nucleation density and restrict the growth of crystals, which further increases the refining effect of super gravity. Within this paper, we also discuss the motile behavior of crystals in a field of super gravity.

  2. Experimental and Theoretical Investigations of the Solidification of Eutectic Al-Si Alloy

    Science.gov (United States)

    Sen, S.; Catalina, A. V.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    The eutectic alloys have a wide spectrum of applications due to their good castability and physical and mechanical properties. The interphase spacing resulting during solidification is an important microstructural feature that significantly influences the mechanical behavior of the material. Thus, knowledge of the evolution of the interphase spacing during solidification is necessary in order to properly design the solidification process and optimize the material properties. While the growth of regular eutectics is rather well understood, the irregular eutectics such as Al-Si or Fe-graphite exhibit undercoolings and lamellar spacings much larger than those theoretically predicted. Despite of a considerable amount of experimental and theoretical work a clear understanding of the true mechanism underlying the spacing selection in irregular eutectics is yet to be achieved. A new experimental study of the solidification of the eutectic Al-Si alloy will be reported in this paper. The measured interface undercoolings and lamellar spacing will be compared to those found in the literature in order to get more general information regarding the growth mechanism of irregular eutectics. A modification of the present theory of the eutectic growth is also proposed. The results of the modified mathematical model, accounting for a non-isothermal solid/liquid interface, will be compared to the experimental measurements.

  3. Solidification and casting

    CERN Document Server

    Cantor, Brian

    2002-01-01

    INDUSTRIAL PERSPECTIVEDirect chillcasting of aluminium alloysContinuous casting of aluminium alloysContinuous casting of steelsCastings in the automotive industryCast aluminium-silicon piston alloysMODELLING AND SIMULATIONModelling direct chill castingMold filling simulation of die castingThe ten casting rulesGrain selection in single crystal superalloy castingsDefects in aluminium shape castingPattern formation during solidificationPeritectic solidificationSTRUCTURE AND DEFECTSHetergeneous nucleation in aluminium alloysCo

  4. Phase-field modeling of coring during solidification of Au–Ni alloy using quaternions and CALPHAD input

    International Nuclear Information System (INIS)

    Fattebert, J.-L.; Wickett, M.E.; Turchi, P.E.A.

    2014-01-01

    A numerical method for the simulation of microstructure evolution during the solidification of an alloy is presented. The approach is based on a phase-field model including a phase variable, an orientation variable given by a quaternion, the alloy composition and a uniform temperature field. Energies and diffusion coefficients used in the model rely on thermodynamic and kinetic databases in the framework of the CALPHAD methodology. The numerical approach is based on a finite volume discretization and an implicit time-stepping algorithm. Numerical results for solidification and accompanying coring effect in a Au–Ni alloy are used to illustrate the methodology

  5. The microstructure and composition of equilibrium phases formed in hypoeutectic Te-In alloy during solidification

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Baoguang [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Hu, Jinwu [Center of Failure Analysis, Central Iron and Steel Research Institute, Beijing 100081 (China); Wang, Chongyun; Yang, Wenhui [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Tian, Wenhuai, E-mail: wenhuaitian@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-03-15

    As a key tellurium atoms evaporation source for ultraviolet detection photocathode, the hypoeutectic Te{sub 75}In{sub 25} alloy was prepared by employing a slow solidification speed of about 10{sup −2} K/s. The microstructure and chemical composition of the equilibrium phases formed in the as-prepared alloy were studied in this research work. The experimental results show that the as-prepared Te-In alloy was constituted by primary In{sub 2}Te{sub 5} phase and eutectic In{sub 2}Te{sub 5}/Te phases. The eutectic In{sub 2}Te{sub 5}/Te phases are distributed in the grain boundaries of primary In{sub 2}Te{sub 5} phase. With the slow solidification speed, a pure eutectic Te phase without any excessive indium solute was obtained, where Te content of eutectic Te phase is 100 mass%. Moreover, it can be considered that the stress between the In{sub 2}Te{sub 5} and Te phases plays an important role in reducing the tellurium vapor pressure in Te{sub 75}In{sub 25} alloy. - Highlights: • The microstructure of Te-In alloy as an evaporation source was analyzed. • A pure eutectic Te phase was obtained by using a slow solidification speed method. • The relation between vapor pressure and inner-stress in the alloy was discussed.

  6. Influence of wire EDM parameters on the damping behaviour of A356.2 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Dora Siva, E-mail: dorasivaprasad@gmail.com [Dept of Mechanical Engineering, GITAM University, Visakhapatnam, 530045 (India); Shoba, Chintada [Dept of Industrial Engineering, GITAM University, Visakhapatnam, 530045 (India); Varma, Kalidindi Rahul [Dept of Mechanical Engineering, RAGHU College of Engineering, Visakhapatnam (India); Khurshid, Abdul [M.Tech (CAD/CAM), Dept of Mechanical Engineering, GITAM University, Visakhapatnam, 530045 (India)

    2015-10-15

    The effect of different Wire electrical discharge machining (WEDM) process parameters on the damping behavior of A356.2 aluminum alloy is investigated. In the present investigation pulse on time (T{sub ON}), pulse off time (T{sub OFF}) and peak current (IP) which are considered to be the most significant process parameters from the previous studies are varied using one factor at a time approach, to study the effect on damping behavior of A356.2 aluminum alloy. Damping experiments are performed on a dynamic mechanical analyzer (DMA 8000) at constant strain under dual cantilever mode over a frequency range of 1–100 Hz at room temperature. The scanning electron microscope was used for characterization of the wire EDMed samples. Experimental results reveal that the damping behavior greatly depends on the wire EDM process parameters. The related mechanisms are presented. - Highlights: • Damping capacity increase with the increase in frequency. • Increasing pulse on time increases the damping capacity of aluminum alloy. • The damping capacity was found to decrease with the increase in pulse off time. • No significant change in damping capacity was noticed with varied peak current. • The formation of white layer plays an important role in the damping behavior.

  7. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy.

    Science.gov (United States)

    Dang, B; Zhang, X; Chen, Y Z; Chen, C X; Wang, H T; Liu, F

    2016-08-09

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

  8. Semi-solid A356 alloy slurry for rheocasting prepared by a new process

    Directory of Open Access Journals (Sweden)

    Liu Zheng

    2013-05-01

    Full Text Available To obtain the semi-solid slurry with uniform and fine structure morphology that satisfies the requirement of rheocasting process, a new process for preparing semi-solid Al alloy slurry was developed, in which local chilling was combined with low superheat pouring and slight electromagnetic stirring (LSPSEMS. The morphology and the size of primary α-Al in the A356 alloy slurry prepared with the new process, i.e., LSPSEMS with local chilling, were investigated using MIAPS image analyzing software, and the grain refinement mechanism was discussed. The results indicate that the semi-solid primary phase consists of particle-like or globular-like α-Al, and the morphology and grain size of primary α-Al in the slurry can be markedly improved by the new process. The fine primary α-Al distributes uniformly in the slurry, which satisfies the requirement of rheocasting. Compared with the alloy prepared by LSPSEMS, the average equal-area-circle grain diameter of primary α-Al in semi-solid A356 alloy ingot prepared by the new process is decreased from 85.6 μm to 68.8 μm at the central area, 112.6 μm to 77.6 μm at the transition area and is 84.7 μm in the edge area, respectively. The corresponding shape factor of primary α-Al is increased from 0.78 to 0.83, 0.54 to 0.77 and 0.28 to 0.59, respectively. In addition, the pouring temperature could be suitably raised from 620-630 ℃ of the traditional process to 650 ℃ using this technique, which is convenient for practical operation. The mechanism of grain refinement, in the new process, is that the local chilling quickens up the temperature decrease in the center of the melt. The nuclei could not grow up in a short time so the finer grains are formed in the melt.

  9. Alloy composition dependence of formation of porous Ni prepared by rapid solidification and chemical dealloying

    Energy Technology Data Exchange (ETDEWEB)

    Qi Zhen [Key Laboratory of Liquid Structure and Heredity of Materials, Shandong University, Jingshi Road 73, Jinan 250061 (China); Zhang Zhonghua [Key Laboratory of Liquid Structure and Heredity of Materials, Shandong University, Jingshi Road 73, Jinan 250061 (China)], E-mail: zh_zhang@sdu.edu.cn; Jia Haoling [Key Laboratory of Liquid Structure and Heredity of Materials, Shandong University, Jingshi Road 73, Jinan 250061 (China); Qu Yingjie [Shandong Labor Occupational Technology College, Jingshi Road 388, Jinan 250022 (China); Liu Guodong; Bian Xiufang [Key Laboratory of Liquid Structure and Heredity of Materials, Shandong University, Jingshi Road 73, Jinan 250061 (China)

    2009-03-20

    In this paper, the effect of alloy composition on the formation of porous Ni catalysts prepared by chemical dealloying of rapidly solidified Al-Ni alloys has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis and N{sub 2} adsorption experiments. The experimental results show that rapid solidification and alloy composition have a significant effect on the phase constituent and microstructure of Al-Ni alloys. The melt spun Al-20 at.% Ni alloy consists of {alpha}-Al, NiAl{sub 3} and Ni{sub 2}Al{sub 3}, while the melt spun Al-25 and 31.5 at.% Ni alloys comprise NiAl{sub 3} and Ni{sub 2}Al{sub 3}. Moreover, the formation and microstructure of the porous Ni catalysts are dependent upon the composition of the melt spun Al-Ni alloys. The morphology and size of Ni particles in the Ni catalysts inherit from those of grains in the melt spun Al-Ni alloys. Rapid solidification can extend the alloy composition of Al-Ni alloys suitable for preparation of the Ni catalysts, and obviously accelerate the dealloying process of the Al-Ni alloys.

  10. Densities of Pb-Sn alloys during solidification

    Science.gov (United States)

    Poirier, D. R.

    1988-01-01

    Data for the densities and expansion coefficients of solid and liquid alloys of the Pb-Sn system are consolidated in this paper. More importantly, the data are analyzed with the purpose of expressing either the density of the solid or of the liquid as a function of its composition and temperature. In particular, the densities of the solid and of the liquid during dendritic solidification are derived. Finally, the solutal and thermal coefficients of volume expansion for the liquid are given as functions of temperature and composition.

  11. Microstructure and Mechanical Properties of MWCNTs Reinforced A356 Aluminum Alloys Cast Nanocomposites Fabricated by Using a Combination of Rheocasting and Squeeze Casting Techniques

    Directory of Open Access Journals (Sweden)

    Abou Bakr Elshalakany

    2014-01-01

    Full Text Available A356 hypoeutectic aluminum-silicon alloys matrix composites reinforced by different contents of multiwalled carbon nanotubes (MWCNTs were fabricated using a combination of rheocasting and squeeze casting techniques. A novel approach by adding MWCNTs into A356 aluminum alloy matrix with CNTs has been performed. This method is significant in debundling and preventing flotation of the CNTs within the molten alloy. The microstructures of nanocomposites and the interface between the aluminum alloy matrix and the MWCNTs were examined by using an optical microscopy (OM and scanning electron microscopy (SEM equipped with an energy dispersive X-ray analysis (EDX. This method remarkably facilitated a uniform dispersion of nanotubes within A356 aluminum alloy matrix as well as a refinement of grain size. In addition, the effects of weight fraction (0.5, 1.0, 1.5, 2.0, and 2.5 wt% of the CNT-blended matrix on mechanical properties were evaluated. The results have indicated that a significant improvement in ultimate tensile strength and elongation percentage of nanocomposite occurred at the optimal amount of 1.5 wt% MWCNTs which represents an increase in their values by a ratio of about 50% and 280%, respectively, compared to their corresponding values of monolithic alloy. Hardness of the samples was also significantly increased by the addition of CNTs.

  12. Crystallization characteristics of cast aluminum alloys during a unidirectional solidification process

    Energy Technology Data Exchange (ETDEWEB)

    Okayasu, Mitsuhiro, E-mail: mitsuhiro.okayasu@utoronto.ca; Takeuchi, Shuhei

    2015-05-01

    The crystal orientation characteristics of cast Al–Si, Al–Cu and Al–Mg alloys produced by a unidirectional solidification process are examined. Two distinct crystal orientation patterns are observed: uniform and random formation. A uniform crystal orientation is created by columnar growth of α-Al dendrites in the alloys with low proportions of alloying element, e.g., the Al–Si alloy (with Si <12.6%) and the Al–Cu and Al–Mg alloys (with Cu and Mg <2%). A uniformly organized crystal orientation with [100] direction is created by columnar growth of α-Al dendrites. With increasing proportion of alloying element (>2% Cu or Mg), the uniform crystal orientations collapse in the Al–Cu and Al–Mg alloys, owing to interruption of the columnar α-Al dendrite growth as a result of different dynamics of the alloying atoms and the creation of a core for the eutectic phases. For the hypo-eutectic Al–Si alloys, a uniform crystal orientation is obtained. In contrast, a random orientation can be detected in the hyper-eutectic Al–Si alloy (15% Si), which results from interruption of the growth of the α-Al dendrites due to precipitation of primary Si particles. There is no clear effect of crystal formation on ultimate tensile strength (UTS), whereas crystal orientation does influence the material ductility, with the alloys with a uniform crystal orientation being elongated beyond their UTS points and with necking occurring in the test specimens. In contrast, the alloys with a nonuniform crystal orientation are not elongated beyond their UTS points.

  13. Crystallization characteristics of cast aluminum alloys during a unidirectional solidification process

    International Nuclear Information System (INIS)

    Okayasu, Mitsuhiro; Takeuchi, Shuhei

    2015-01-01

    The crystal orientation characteristics of cast Al–Si, Al–Cu and Al–Mg alloys produced by a unidirectional solidification process are examined. Two distinct crystal orientation patterns are observed: uniform and random formation. A uniform crystal orientation is created by columnar growth of α-Al dendrites in the alloys with low proportions of alloying element, e.g., the Al–Si alloy (with Si <12.6%) and the Al–Cu and Al–Mg alloys (with Cu and Mg <2%). A uniformly organized crystal orientation with [100] direction is created by columnar growth of α-Al dendrites. With increasing proportion of alloying element (>2% Cu or Mg), the uniform crystal orientations collapse in the Al–Cu and Al–Mg alloys, owing to interruption of the columnar α-Al dendrite growth as a result of different dynamics of the alloying atoms and the creation of a core for the eutectic phases. For the hypo-eutectic Al–Si alloys, a uniform crystal orientation is obtained. In contrast, a random orientation can be detected in the hyper-eutectic Al–Si alloy (15% Si), which results from interruption of the growth of the α-Al dendrites due to precipitation of primary Si particles. There is no clear effect of crystal formation on ultimate tensile strength (UTS), whereas crystal orientation does influence the material ductility, with the alloys with a uniform crystal orientation being elongated beyond their UTS points and with necking occurring in the test specimens. In contrast, the alloys with a nonuniform crystal orientation are not elongated beyond their UTS points

  14. Linear Stability of Binary Alloy Solidification for Unsteady Growth Rates

    Science.gov (United States)

    Mazuruk, K.; Volz, M. P.

    2010-01-01

    An extension of the Mullins and Sekerka (MS) linear stability analysis to the unsteady growth rate case is considered for dilute binary alloys. In particular, the stability of the planar interface during the initial solidification transient is studied in detail numerically. The rapid solidification case, when the system is traversing through the unstable region defined by the MS criterion, has also been treated. It has been observed that the onset of instability is quite accurately defined by the "quasi-stationary MS criterion", when the growth rate and other process parameters are taken as constants at a particular time of the growth process. A singular behavior of the governing equations for the perturbed quantities at the constitutional supercooling demarcation line has been observed. However, when the solidification process, during its transient, crosses this demarcation line, a planar interface is stable according to the linear analysis performed.

  15. Effect of alloying elements on solidification of primary austenite in Ni-Mn-Cu cast iron

    Directory of Open Access Journals (Sweden)

    A. Janus

    2011-04-01

    Full Text Available Within the research, determined were direction and intensity of alloying elements influence on solidification way (directional orvolumetric of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu. 50 cast shafts dia. 20 mm were analysed.Chemical composition of the alloy was as follows: 1.7 to 3.3 % C, 1.4 to 3.1 % Si, 2.8 to 9.9 % Ni, 0.4 to 7.7 % Mn, 0 to 4.6 % Cu, 0.14 to0.16 % P and 0.03 to 0.04 % S. The discriminant analysis revealed that carbon influences solidification of primary austenite dendrites most intensively. It clearly increases the tendency to volumetric solidification. Influence of the other elements is much weaker. This means that the solidification way of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu does not differ from that in an unalloyed cast iron.

  16. Phase-Field Simulation of Microstructure Evolution in Industrial A2214 Alloy During Solidification

    Science.gov (United States)

    Wei, Ming; Tang, Ying; Zhang, Lijun; Sun, Weihua; Du, Yong

    2015-07-01

    By linking to the thermodynamic and atomic mobility databases in Al alloys well established in our research group, the microstructure evolution in industrial A2214 alloy (Al-4.5Cu-0.5Mg-1.0Si, in wt pct) during solidification process was studied by means of two-dimensional phase-field simulation via MICRostructure Evolution Simulation Software in the framework of the multi-phase-field formalism. The thermophysical parameters including interfacial energies and interfacial mobilities were carefully chosen for reproducing the experimental features. The solidification sequence due to the present phase-field simulation conforms to both equilibrium calculation and Scheil simulation. The predicted microstructure reproduces the experimental data very well. These facts indicate that a quantitative phase-field simulation was achieved in the present work. Moreover, the mechanisms of characteristic patterns and microstructure formation were revealed with the aid of the phase-field simulation. In addition, the effect of cooling rate on the secondary dendrite arm spacing and microsegregation was also investigated through comprehensive comparison with the experimental data.

  17. Advanced powder metallurgy aluminum alloys via rapid solidification technology

    Science.gov (United States)

    Ray, R.

    1984-01-01

    Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

  18. Relationship between casting modulus and grain size in cast A356 aluminium alloys

    International Nuclear Information System (INIS)

    Niklas, A; Abaunza, U; Fernández-Calvo, A I; Lacaze, J

    2012-01-01

    Microstructure of Al-Si alloy castings depends most generally on melt preparation and on the cooling rate imposed by the thermal modulus of the component. In the case of Al-Si alloys, emphasis is put during melt preparation on refinement of pro-eutectic (Al) grains and on modification of the Al-Si eutectic. Thermal analysis has been used since long to check melt preparation before casting, i.e. by analysis of the cooling curve during solidification of a sample cast in an instrumented cup. The conclusions drawn from such analysis are however valid for the particular cooling conditions of the cups. It thus appeared of interest to investigate how these conclusions could extrapolate to predict microstructure in complicated cast parts showing local changes in the solidification conditions. For that purpose, thermal analysis cups and instrumented sand and die castings with different thermal moduli and thus cooling rates have been made, and the whole set of cooling curves thus recorded has been analysed. A statistical analysis of the characteristic features of the cooling curves related to grain refinement in sand and die castings allowed determining the most significant parameters and expressing the cube of grain size as a polynomial of these parameters. After introduction of a further parameter quantifying melt refining an excellent correlation, with a R 2 factor of 0.99 was obtained.

  19. Effect of solidification parameters on mechanical properties of directionally solidified Al-Rich Al-Cu alloys

    Science.gov (United States)

    Çadırlı, Emin

    2013-05-01

    Al(100-x)-Cux alloys (x=3 wt%, 6 wt%, 15 wt%, 24 wt% and 33 wt%) were prepared using metals of 99.99% high purity in vacuum atmosphere. These alloys were directionally solidified under steady-state conditions by using a Bridgman-type directional solidification furnace. Solidification parameters (G, V and ), microstructure parameters (λ1, λ2 and λE) and mechanical properties (HV, σ) of the Al-Cu alloys were measured. Microstructure parameters were expressed as functions of solidification parameters by using a linear regression analysis. The dependency of HV, σ on the cooling rate, microstructure parameters and composition were determined. According to experimental results, the microhardness and ultimate tensile strength of the solidified samples was increased by increasing the cooling rate and Cu content, but decreased with increasing microstructure parameters. The microscopic fracture surfaces of the different samples were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces showed that the type of fracture significantly changed from ductile to brittle depending on the composition.

  20. Heat transfer and solidification processes of alloy melt with undercooling: I. Experimental results

    International Nuclear Information System (INIS)

    Yoshioka, Hideaki; Tada, Yukio; Kunimine, Kanji; Furuichi, Taira; Hayashi, Yujiro

    2006-01-01

    The solidification process of Pb-Sn and Bi-Sn alloy melts is discussed to obtain a basic understanding of the essential phenomena of solidification with undercooling. First, from macroscopic observations, it is shown that the solidification process consists of the following three stages: (1) free growth with recalescence dissipation of thermal undercooling (2) expansion of crystals with the relaxation of constitutional undercooling or with the recovering process of interrupted quasi-steady heat conduction, and (3) equilibrium solidification. The specific features of free growth under non-uniform undercooling are also shown by comparison with the Lipton, Glicksman, and Kurz model. Next, from microscopic observations, the distribution of the solute concentration and the change of crystal morphology in the solidified materials were investigated quantitatively using scanning electron microscopy and energy-dispersive spectroscopy. Finally, the solidification path during the above three fundamental processes is dynamically represented on phase diagrams

  1. Dynamic and Thermal Properties of Aluminum Alloy A356/Silicon Carbide Hollow Particle Syntactic Foams

    Directory of Open Access Journals (Sweden)

    James Cox

    2014-12-01

    Full Text Available Aluminum alloy A356 matrix syntactic foams filled with SiC hollow particles (SiCHP are studied in the present work. Two compositions of syntactic foams are studied for quasi-static and high strain rate compression. In addition, dynamic mechanical analysis is conducted to study the temperature dependent energy dissipation and damping capabilities of these materials. The thermal characterization includes study of the coefficient of thermal expansion (CTE. A356/SiCHP syntactic foams are not strain rate sensitive as the compressive strength displayed little variation between the tested strain rates of 0.001–2100 s−1. Microscopic analysis of the high strain rate compression tested specimens showed that the fracture is initiated by the failure of hollow particles at the onset of the plastic deformation region. This is followed by plastic deformation of the matrix material and further crushing of particles. The syntactic foams showed decrease in storage modulus with increasing temperature and the trend was nearly linear up to 500 °C. The alloy shows a similar behavior at low temperature but the decrease in storage modulus increases sharply over 375 °C. The loss modulus is very small for the tested materials because of lack of viscoelasticity in metallic materials. The trend in the loss modulus is opposite, where the matrix alloy has lower loss modulus than syntactic foams at low temperature. However, over 250 °C the matrix loss modulus starts to increase rapidly and attains a peak around 460 °C. Syntactic foams have higher damping parameter at low temperatures than the matrix alloy. Incorporation of SiCHP helps in decreasing CTE. Compared to the CTE of the matrix alloy, 23.4 × 10−6 °C−1, syntactic foams showed CTE values as low as 11.67 × 10−6 °C−1.

  2. A three-dimensional cellular automata model coupled with finite element method and thermodynamic database for alloy solidification

    Science.gov (United States)

    Zhao, Y.; Qin, R. S.; Chen, D. F.

    2013-08-01

    A three-dimensional (3D) cellular automata (CA) model has been developed for the simulation of microstructure evolution in alloy solidification. The governing rule for the CA model is associated with the phase transition driving force which is obtained via a thermodynamic database. This determines the migration rate of the non-equilibrium solid-liquid (SL) interface and is calculated according to the local temperature and chemical composition. The curvature of the interface and the anisotropic property of the surface energy are taken into consideration. A 3D finite element (FE) method is applied for the calculation of transient heat and mass transfer. Numerical calculations for the solidification of Fe-1.5 wt% C alloy have been performed. The morphological evolution of dendrites, carbon segregation and temperature distribution in both isothermal and non-isothermal conditions are studied. The parameters affecting the growth of equiaxed and columnar dendrites are discussed. The calculated results are verified using the analytical model and previous experiments. The method provides a sophisticated approach to the solidification of multi-phase and multi-component systems.

  3. Rapid Solidification of a New Generation Aluminum-Lithium Alloy via Electrospark Deposition

    Science.gov (United States)

    Heard, David W.; Boselli, Julien; Gauvin, Raynald; Brochu, Mathieu

    Electrospark deposition (ESD) is a rapid solidification processing technique capable of depositing a metal onto a conductive substrate. The short pulse duration and high pulse frequency, combined with the small amount of material transferred during each pulse, results in high cooling rates being realized, on the order of 105-106 C/sec. This study investigates the ability to induce solute trapping behavior, for a new generation aluminum-lithium alloy, AA2199, using ESD.

  4. Effects of multiple-step thermal ageing treatment on the hardness characteristics of A356.0-type Al-Si-Mg alloy

    International Nuclear Information System (INIS)

    Abdulwahab, M.; Madugu, I.A.; Yaro, S.A.; Hassan, S.B.; Popoola, A.P.I.

    2011-01-01

    The work outlined the hardness characteristics of thermally aged high chromium sodium modified A356.0-type Al-Si-Mg alloy using the multiple-step thermal ageing treatment (MSTAT) approach. This novel approach consists of double thermal ageing (DTAT) and single thermal ageing treatment (STAT). The investigation also includes the development of a new temperature-compensated-time parameter, P, for the studied alloy at different ageing temperatures and time considered. The results obtained in the DTAT developed for the A356.0-type Al-Si-Mg alloy showed an improvement in the precipitation hardening (PH) ability and hardness characteristics as compared to the convectional STAT temper. The observations were evidenced from the X-ray diffractometry (XRD) pattern indicating the possible strengthening phases. Equally, the hardness behavior was correlated with the microstructures using optical microscope (OPM) and scanning electron microscope equipped with energy dispersive spectroscope (SEM-EDS).

  5. Simulating the Effect of Space Vehicle Environments on Directional Solidification of a Binary Alloy

    Science.gov (United States)

    Westra, D. G.; Heinrich, J. C.; Poirier, D. R.

    2003-01-01

    Space microgravity missions are designed to provide a microgravity environment for scientific experiments, but these missions cannot provide a perfect environment, due to vibrations caused by crew activity, on-board experiments, support systems (pumps, fans, etc.), periodic orbital maneuvers, and water dumps. Therefore, it is necessary to predict the impact of these vibrations on space experiments, prior to performing them. Simulations were conducted to study the effect of the vibrations on the directional solidification of a dendritic alloy. Finite element ca!cu!attie?ls were dme with a simd2titcr based on a continuum model of dendritic solidification, using the Fractional Step Method (FSM). The FSM splits the solution of the momentum equation into two steps: the viscous intermediate step, which does not enforce continuity; and the inviscid projection step, which calculates the pressure and enforces continuity. The FSM provides significant computational benefits for predicting flows in a directionally solidified alloy, compared to other methods presently employed, because of the efficiency gains in the uncoupled solution of velocity and pressure. finite differences, arises when the interdendritic liquid reaches the eutectic temperature and concentration. When a node reaches eutectic temperature, it is assumed that the solidification of the eutectic liquid continues at constant temperature until all the eutectic is solidified. With this approach, solidification is not achieved continuously across an element; rather, the element is not considered solidified until the eutectic isotherm overtakes the top nodes. For microgravity simulations, where the convection is driven by shrinkage, it introduces large variations in the fluid velocity. When the eutectic isotherm reaches a node, all the eutectic must be solidified in a short period, causing an abrupt increase in velocity. To overcome this difficulty, we employed a scheme to numerically predict a more accurate value

  6. A statistical analysis on erosion wear behaviour of A356 alloy reinforced with in situ formed TiB2 particles

    International Nuclear Information System (INIS)

    Kumar, S.; Subramanya Sarma, V.; Murty, B.S.

    2008-01-01

    Solid particle erosion wear behaviour of A356 and A356/TiB 2 in situ composites has been studied. A356 alloy reinforced with in situ TiB 2 particles was fabricated by the reaction of halide salts with aluminium melt and the formation of Al 3 Ti brittle phase is completely suppressed. The composites show good grain refinement of α-Al and modification of eutectic Si. These in situ composites show high hardness and better erosion resistance than the base alloy. Though the sizes of in situ formed TiB 2 reinforcement particles are smaller than the erodent SiC particles, TiB 2 particles are able to effectively resist the erodent particles. Design of experiment has been used to run the solid particle erosion experiment. An attempt has also been made to develop a mathematical model by using regression analysis. Analysis of variance (ANOVA) technique is applied to check the validity of the developed model. Student's t-test is utilized to find out the significance of factors. The wear mechanism has been studied by analyzing the surface of the worn specimen using scanning electron microscopy and energy dispersive X-ray microanalysis

  7. Origin of grain orientation during solidification of an aluminum alloy

    International Nuclear Information System (INIS)

    Wei, H.L.; Elmer, J.W.; DebRoy, T.

    2016-01-01

    The evolution of grain morphology during solidification of a moving aluminum alloy pool is simulated by considering heat transfer, flow of liquid metal in the molten pool and solidification parameters. The computationally efficient model consists of a 3D coupled heat transfer and fluid flow simulation to predict the molten pool shape and temperature field, and a 2D model of grain formation in the molten pool. The results demonstrate that columnar grains grow in a curved pattern rather than along straight lines from the fusion boundary towards the center of the molten pool. The calculated results are validated with independent experimental data. The computed ratio of local temperature gradient to solidification rate, G/R, is used to model the columnar to equiaxed transition during solidification. The simulated results show that only curved columnar grains are formed when the scanning speed is low (2.0 mm/s). In contrast, a transition from curved columnar to equiaxed morphologies occurs at the higher scanning speeds of 8.0 mm/s and 11.5 mm/s, with higher equiaxed grain fraction at higher speed. The similarities between the physical processes governing fusion welding and additive manufacturing (AM) make the model capable of predicting grain orientation in both processes.

  8. Effects of heat pipe cooling on permanent mold castings of aluminum alloys

    International Nuclear Information System (INIS)

    Zhang, C.; Mucciardi, F.; Gruzleski, J.E.

    2002-01-01

    The temperature distribution within molds is a critical parameter in determining the ultimate casting quality in permanent mold casting processes, so there is a considerable incentive to develop a more effective method of mold cooling. Based on this consideration, a novel, effective and controllable heat pipe has been successfully developed and used as a new method of permanent mold cooling. Symmetric step casting of A356 alloy have been produced in an experimental permanent mold made of H13 tool steel, which is cooled by such heat pipes. The experimental results show that heat pipes can provide extremely high cooling rates in permanent mold castings of aluminum. The dendrite arm spacing of A356 alloy is refined considerably, and porosity and shrinkage of the castings are redistributed by the heat pipe cooling. Moreover, the heat pipe can be used to determine the time when the air gap forms at the interface between the mold and the casting. The effect of heat pipe cooling on solidification time of castings of A356 alloy with different coating types is also discussed in this paper. (author)

  9. Investigation of solidification behavior of the Sn-rich ternary Sn–Bi–Zn alloys

    Directory of Open Access Journals (Sweden)

    S Mladenović

    2017-03-01

    Full Text Available Solidification properties and microstructure of six as-cast Sn–Bi–Zn alloys with 80 at.% of Sn and variable contents of Bi and Zn were experimentally investigated using the scanning electron microscopy (SEM with energy-dispersive X-ray spectroscopy (EDS and differential scanning calorimetry (DSC. The experimentally obtained results were compared with predicted phase equilibria according to the calculation of phase diagram (CALPHAD method and by the Scheil solidification simulation.

  10. The effect of the solidification mode on eutectic structure in Fe-C-V alloys

    International Nuclear Information System (INIS)

    Fras, E.; Guzik, E.

    1980-01-01

    The aim of the study was to determine such a chemical composition of Fe-C-V alloys which would ensure the formation of perfectly eutectic structures as well as to investigate the eutectic morphology of these alloys when undergoing bulk and directional solidification. Attempts have been done to get in situ composites from Fe-C-V alloys. The adopted testing methods as well as obtained results are described in detail. (H.M.)

  11. The Effect of Applied Pressure During Feeding of Critical Cast Aluminum Alloy Components With Particular Reference to Fatigue Resistance

    Energy Technology Data Exchange (ETDEWEB)

    J.T. Berry; R. Luck; B. Zhang; R.P. Taylor

    2003-06-30

    the medium to long freezing range alloys of aluminum such as A356, A357, A206, 319 for example are known to exhibit dispersed porosity, which is recognized as a factor affecting ductility, fracture toughness, and fatigue resistance of light alloy castings. The local thermal environment, for example, temperature gradient and freezing from velocity, affect the mode of solidification which, along with alloy composition, heat treatment, oxide film occlusion, hydrogen content, and the extent to which the alloy contracts on solidification, combine to exert strong effects on the porosity formation in such alloys. In addition to such factors, the availability of liquid metal and its ability to flow through the partially solidified casting, which will be affect by the pressure in the liquid metal, must also be considered. The supply of molten metal will thus be controlled by the volume of the riser available for feeding the particular casting location, its solidification time, and its location together with any external pressure that might be applied at the riser.

  12. Microstructural and mechanical properties of gravity-die-cast A356 alloy inoculated with yttrium and Al-Ti-B grain refiner simultaneously

    Directory of Open Access Journals (Sweden)

    Y.P. Lim

    2011-10-01

    Full Text Available In the present work, the effect of inoculating yttrium and Al-5Ti-1B simultaneously on A356 aluminum alloy has been studied. Gravity die casting process is used to cast the ASTM tensile test specimens for analysis. In each experiment, the Ti and B contents were maintained constantly at 0.1 and 0.02 wt% respectively. The addition of yttrium was manipulated at the amount of 0, 0.1, 0.2, 0.3, 0.4 and 0.5 wt%. Microstructural characterization of the as-cast A356 alloy was investigated by means of optical microscope and its phases are detected by XRD. The mechanical properties tested are tensile strength and hardness. The inoculation of yttrium was found to enhance the grain refinement effect of Al-5Ti-1B grain refiner and improve the mechanical properties. The optimal weight percentage of yttrium was found to be 0.3. The grain refining efficiency of combining yttrium and Al-5Ti-1B on A356 aluminum alloy was mainly attributed to the heterogeneous nucleation of TiB2 and TiAl3 particles which were dispersed more evenly in the presence of yttrium and the grain growth restriction effected by the accumulation of Al-Y compound at grain boundaries.

  13. Effect of Fe content, cooling rate and porosity on the tensile properties of cast 319 and 356 aluminum alloys

    International Nuclear Information System (INIS)

    Ma, Z.; Samuel, A.M.; Samuel, F.H.; Doty, H.W.; Valtierra, S.

    2002-01-01

    The present study was carried out to investigate the effects of Fe content, cooling rate and porosity on the tensile properties of cast 319 and 356 alloys. Both experimental and industrial 319 alloys (containing 0.1 and 0.4 wt% Mg) and industrial 356 alloys were used, with 200-300 ppm strontium additions to study the modification effect. The Fe content was varied from 0.2 to 0.8 wt% in the 319 alloys, and from 0.1 to 0.6 wt% in the 356 alloy in keeping with Fe levels observed in industry. An end-chilled mold was employed to obtain directionally solidified castings, where the cooling rate varied with the height of the casting. Tensile and microstructural samples were sectioned at heights corresponding to dendrite arm spacings of ∼23 to ∼83 μm. The microstructures were examined using optical- and scanning electron microscopy. The effect of Fe content and cooling rate was investigated through measurements of the β-Al 5 FeSi platelets, using image analysis. Porosity measurements were also made. Phase identification was done using EPMA, EDX and XRD. The results show that the β-Al 5 FeSi platelet size has a significant effect on ductility and tensile strength up to sizes of ∼100 μm in the 319 alloys and ∼70 μm in the 356 alloy, but has no significant effect on the yield strength. While tensile properties are interpreted by means of UTS vs. log Elongation plots (after the Quality index concept of Drouzy et al. (5)), in the present study, the properties for all sample conditions were best interpreted by means of log UTS vs. log Elongation plots, where the properties increased linearly within low cooling rate-high Fe and high cooling rate-low Fe condition extremities. The results are explained in terms of the β-Al 5 FeSi platelet size and porosity values obtained. (author)

  14. Solidification microstructures in a short fiber reinforced alloy composite containing different fiber fractions

    Directory of Open Access Journals (Sweden)

    JING Qing-xiu

    2006-02-01

    Full Text Available The solidification microstructures and micro-segregation of a fiber reinforced Al-9 Cu alloy, containing different volume fractions of Al2O3 short fibers about 6 μm diameter and made by squeeze casting have been studied. The results indicate that as volume fraction of fiber Vf increases, the size of final grains becomes finer in the matrix. If λf /λ>1, the fibers have almost no influence on the solidification behavior of the matrix, so the final grains grow coarse, where λf is the average inter-fiber spacing and λ is the secondary dendrite arm spacing. While if λf /λ<1, the growth of crystals in the matrix is affected significantly by the fibers and the grain size is reduced to the value of the inter-fiber spacing. The fibers influence the average length of a solidification volume element L of the matrix and also influence the solidification time θt of the matrix. As a result of fibers influencing L and θt, the micro-segregation in the matrix is improved when the composite contains more fibers, although the level of the improvement is slight. The Clyne-Kurz model can be used to semi-quantitatively analyze the relationship between Vf and the volume fraction fe of the micro-segregation eutectic structure.

  15. A Comparative study of solidification of Al-Cu alloy under flow of cylindrical radial heat and the unidirectional vertically

    Directory of Open Access Journals (Sweden)

    Jean Robert P. Rodrigues

    2014-09-01

    Full Text Available In spite of technological importance of solidification of metallic alloys under radial heat flow, relatively few studies have been carried out in this area. In this work the solidification of Al 4.5 wt% Cu cylinders against a steel massive mold is analyzed and compared with unidirectional solidification against a cooled mold. Initially temperature variations at different positions in the casting and in the mold were measured during solidification using a data acquisition system. These temperature variations were introduced in a numerical method in order to determine the variation of heat transfer coefficient at metal/mold interface by inverse method. The primary and secondary dendrite arm spacing variations were measured through optical microscopy. Comparisons carried out between experimental and numerical data showed that the numerical method describes well the solidification processes under radial heat flux.

  16. Effect of cooling rate during solidification of Sn-9Zn lead-free solder alloy on its microstructure, tensile strength and ductile-brittle transition temperature

    Energy Technology Data Exchange (ETDEWEB)

    Prabhu, K.N., E-mail: prabhukn_2002@yahoo.co.in [Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore 575 025 (India); Deshapande, Parashuram; Satyanarayan [Department of Metallurgical and Materials Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore 575 025 (India)

    2012-01-30

    Highlights: Black-Right-Pointing-Pointer Effect of cooling rate on tensile and impact properties of Sn-9Zn alloy was assessed. Black-Right-Pointing-Pointer Both DBTT and UTS of the solder alloy increased with increase in cooling rate. Black-Right-Pointing-Pointer An optimum cooling rate during solidification would minimize DBTT and maximize UTS. - Abstract: Solidification rate is an important variable during processing of materials, including soldering, involving solidification. The rate of solidification controls the metallurgical microstructure at the solder joint and hence the mechanical properties. A high tensile strength and a lower ductile-brittle transition temperature are necessary for reliability of solder joints in electronic circuits. Hence in the present work, the effect of cooling rate during solidification on microstructure, impact and tensile properties of Sn-9Zn lead-free solder alloy was investigated. Four different cooling media (copper and stainless steel moulds, air and furnace cooling) were used for solidification to achieve different cooling rates. Solder alloy solidified in copper mould exhibited higher cooling rate as compared to other cooling media. The microstructure is refined as the cooling rate was increased from 0.03 to 25 Degree-Sign C/s. With increase in cooling rate it was observed that the size of Zn flakes became finer and distributed uniformly throughout the matrix. Ductile-to-brittle transition temperature (DBTT) of the solder alloy increased with increase in cooling rate. Fractured surfaces of impact test specimens showed cleavage like appearance and river like pattern at very low temperatures and dimple like appearance at higher temperatures. The tensile strength of the solder alloy solidified in Cu and stainless moulds were higher as compared to air and furnace cooled samples. It is therefore suggested that the cooling rate during solidification of the solder alloy should be optimum to maximize the strength and minimize the

  17. Effect of cooling rate during solidification of Sn–9Zn lead-free solder alloy on its microstructure, tensile strength and ductile–brittle transition temperature

    International Nuclear Information System (INIS)

    Prabhu, K.N.; Deshapande, Parashuram; Satyanarayan

    2012-01-01

    Highlights: ► Effect of cooling rate on tensile and impact properties of Sn–9Zn alloy was assessed. ► Both DBTT and UTS of the solder alloy increased with increase in cooling rate. ► An optimum cooling rate during solidification would minimize DBTT and maximize UTS. - Abstract: Solidification rate is an important variable during processing of materials, including soldering, involving solidification. The rate of solidification controls the metallurgical microstructure at the solder joint and hence the mechanical properties. A high tensile strength and a lower ductile–brittle transition temperature are necessary for reliability of solder joints in electronic circuits. Hence in the present work, the effect of cooling rate during solidification on microstructure, impact and tensile properties of Sn–9Zn lead-free solder alloy was investigated. Four different cooling media (copper and stainless steel moulds, air and furnace cooling) were used for solidification to achieve different cooling rates. Solder alloy solidified in copper mould exhibited higher cooling rate as compared to other cooling media. The microstructure is refined as the cooling rate was increased from 0.03 to 25 °C/s. With increase in cooling rate it was observed that the size of Zn flakes became finer and distributed uniformly throughout the matrix. Ductile-to-brittle transition temperature (DBTT) of the solder alloy increased with increase in cooling rate. Fractured surfaces of impact test specimens showed cleavage like appearance and river like pattern at very low temperatures and dimple like appearance at higher temperatures. The tensile strength of the solder alloy solidified in Cu and stainless moulds were higher as compared to air and furnace cooled samples. It is therefore suggested that the cooling rate during solidification of the solder alloy should be optimum to maximize the strength and minimize the DBTT.

  18. Lamellar boundary alignment of DS-processed TiAl-W alloys by a solidification procedure

    Science.gov (United States)

    Jung, In-Soo; Oh, Myung-Hoon; Park, No-Jin; Kumar, K. Sharvan; Wee, Dang-Moon

    2007-12-01

    In this study, a β solidification procedure was used to align the lamellae in a Ti-47Al-2W (at.%) alloy parallel to the growth direction. The Bridgman technique and the floating zone process were used for directional solidification. The mechanical properties of the directionally solidified alloy were evaluated in tension at room temperature and at 800°C. At a growth rate of 30 mm/h (with the floating zone approach), the lamellae were well aligned parallel to the growth direction. The aligned lamellae yielded excellent room temperature tensile ductility. The tensile yield strength at 800°C was similar to that at room temperature. The orientation of the γ lamellar laths in the directionally solidified ingots, which were manufactured by means of a floating zone process, was identified with the aid of electron backscattered diffraction analysis. On the basis of this analysis, the preferred growth direction of the bcc-β dendrites that formed at high temperatures close to the melting point was inferred to be [001]β at a growth rate of 30 mm/h and [111]β at a growth rate of 90 mm/h.

  19. Increased corrosion resistance of the AZ80 magnesium alloy by rapid solidification.

    Science.gov (United States)

    Aghion, E; Jan, L; Meshi, L; Goldman, J

    2015-11-01

    Magnesium (Mg) and Mg-alloys are being considered as implantable biometals. Despite their excellent biocompatibility and good mechanical properties, their rapid corrosion is a major impediment precluding their widespread acceptance as implantable biomaterials. Here, we investigate the potential for rapid solidification to increase the corrosion resistance of Mg alloys. To this end, the effect of rapid solidification on the environmental and stress corrosion behavior of the AZ80 Mg alloy vs. its conventionally cast counterpart was evaluated in simulated physiological electrolytes. The microstructural characteristics were examined by optical microscopy, SEM, TEM, and X-ray diffraction analysis. The corrosion behavior was evaluated by immersion, salt spraying, and potentiodynamic polarization. Stress corrosion resistance was assessed by Slow Strain Rate Testing. The results indicate that the corrosion resistance of rapidly solidified ribbons is significantly improved relative to the conventional cast alloy due to the increased Al content dissolved in the α-Mg matrix and the correspondingly reduced presence of the β-phase (Mg17 Al12 ). Unfortunately, extrusion consolidated solidified ribbons exhibited a substantial reduction in the environmental performance and stress corrosion resistance. This was mainly attributed to the detrimental effect of the extrusion process, which enriched the iron impurities and increased the internal stresses by imposing a higher dislocation density. In terms of immersion tests, the average corrosion rate of the rapidly solidified ribbons was <0.4 mm/year compared with ∼2 mm/year for the conventionally cast alloy and 26 mm/year for the rapidly solidified extruded ribbons. © 2014 Wiley Periodicals, Inc.

  20. Comparative study on laser welding and TIG welding of semi-solid high pressure die cast A356 aluminium alloy

    CSIR Research Space (South Africa)

    Govender, G

    2007-07-01

    Full Text Available components. The low porosity levels in SSM high pressure die castings (HPDC) improves the weldability of these components. The aim of the current research was to perform a comparative study of laser and TIG welding of SSM HPDC aluminium alloy A356. SSM...

  1. From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

    Science.gov (United States)

    Tourret, D.; Mertens, J. C. E.; Lieberman, E.; Imhoff, S. D.; Gibbs, J. W.; Henderson, K.; Fezzaa, K.; Deriy, A. L.; Sun, T.; Lebensohn, R. A.; Patterson, B. M.; Clarke, A. J.

    2017-11-01

    We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure, supported by quantitative simulations of microstructure formation and its mechanical behavior.

  2. L2 droplet interaction with α-Al during solidification of hypermonotectic Al-8 wt.% Bi alloys

    International Nuclear Information System (INIS)

    Schaffer, P.L.; Mathiesen, R.H.; Arnberg, L.

    2009-01-01

    Studies of Al-based hypermonotectics have so far focused mainly on droplet motion and coagulation dynamics, with limited attention given to the interaction between droplets and the advancing solidification front which is decisive for the final distribution of the second phase within the α-Al matrix. The current work presents results from directional solidification experiments with Al-8 wt.% Bi alloys. It was found that droplets with large radii were frequently pushed and small droplets were engulfed. This is contradictory to the many models that have been proposed to explain pushing/engulfment of solid particles and can in part be ascribed to the fact that while solid-particle models only consider single, non-interacting particles that remain unaffected by solutal gradients ahead of the advancing solidification front, droplet-droplet interaction and local solute gradients have been found to be critical for droplet pushing/engulfment behaviour in hypermonotectic alloys.

  3. GPU-accelerated 3D phase-field simulations of dendrite competitive growth during directional solidification of binary alloy

    International Nuclear Information System (INIS)

    Sakane, S; Takaki, T; Ohno, M; Shimokawabe, T; Aoki, T

    2015-01-01

    Phase-field method has emerged as the most powerful numerical scheme to simulate dendrite growth. However, most phase-field simulations of dendrite growth performed so far are limited to two-dimension or single dendrite in three-dimension because of the large computational cost involved. To express actual solidification microstructures, multiple dendrites with different preferred growth directions should be computed at the same time. In this study, in order to enable large-scale phase-field dendrite growth simulations, we developed a phase-field code using multiple graphics processing units in which a quantitative phase-field method for binary alloy solidification and moving frame algorithm for directional solidification were employed. First, we performed strong and weak scaling tests for the developed parallel code. Then, dendrite competitive growth simulations in three-dimensional binary alloy bicrystal were performed and the dendrite interactions in three-dimensional space were investigated. (paper)

  4. Fluid flow solidification simulation of molten alloys

    International Nuclear Information System (INIS)

    Kaschnitz, E.

    1997-01-01

    In an effort to minimize costs and to obtain optimum designs, computer simulation of shape casting processes is more and more used as a development tool. Accurate predictions are possible by means of three dimensional fluid flow and solidification modelling. The bases of the model are the transient laminar Navier-Stokes-equations for a Newtonian fluid including the tracking of the free surface. They are describing the melt flow pattern during the mold filling sequence. Simultaneously, the temperature development in the alloy and mold is calculated using Fourier's heat transfer equation. At OEGI, a commercial software package (MAGMAsoft) with a finite difference equation solver is used for improvement of casting processes. Different examples of industrial applications will be shown. (author)

  5. Characterization of age-hardening behavior of eutectic region in squeeze-cast A356-T5 alloy using nanoindenter and atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Youn, S.W. [Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564 (Japan)]. E-mail: youn.sung-won@aist.go.jp; Kang, C.G. [National Laboratory of Thixo/Rheo Forming, School of Mechanical Engineering, Pusan National University, Busan (Korea, Republic of)]. E-mail: cgkang@pusan.ac.kr

    2006-06-15

    The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy parts were investigated using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at 150 deg. C for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness (H {sub V}) and indentation (H {sub IT}) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

  6. Evaluation of thermophysical properties of Al–Sn–Si alloys based on computational thermodynamics and validation by numerical and experimental simulation of solidification

    International Nuclear Information System (INIS)

    Bertelli, Felipe; Cheung, Noé; Ferreira, Ivaldo L.; Garcia, Amauri

    2016-01-01

    Highlights: • A numerical routine coupled to a computational thermodynamics software is proposed to calculate thermophysical properties. • The approach encompasses numerical and experimental simulation of solidification. • Al–Sn–Si alloys thermophysical properties are validated by experimental/numerical cooling rate results. - Abstract: Modelling of manufacturing processes of multicomponent Al-based alloys products, such as casting, requires thermophysical properties that are rarely found in the literature. It is extremely important to use reliable values of such properties, as they can influence critically on simulated output results. In the present study, a numerical routine is developed and connected in real runtime execution to a computational thermodynamic software with a view to permitting thermophysical properties such as: latent heats; specific heats; temperatures and heats of transformation; phase fractions and composition and density of Al–Sn–Si alloys as a function of temperature, to be determined. A numerical solidification model is used to run solidification simulations of ternary Al-based alloys using the appropriate calculated thermophysical properties. Directional solidification experiments are carried out with two Al–Sn–Si alloys compositions to provide experimental cooling rates profiles along the length of the castings, which are compared with numerical simulations in order to validate the calculated thermophysical data. For both cases a good agreement can be observed, indicating the relevance of applicability of the proposed approach.

  7. Superior metallic alloys through rapid solidification processing (RSP) by design

    Energy Technology Data Exchange (ETDEWEB)

    Flinn, J.E. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)

    1995-05-01

    Rapid solidification processing using powder atomization methods and the control of minor elements such as oxygen, nitrogen, and carbon can provide metallic alloys with superior properties and performance compared to conventionally processing alloys. Previous studies on nickel- and iron-base superalloys have provided the baseline information to properly couple RSP with alloy composition, and, therefore, enable alloys to be designed for performance improvements. The RSP approach produces powders, which need to be consolidated into suitable monolithic forms. This normally involves canning, consolidation, and decanning of the powders. Canning/decanning is expensive and raises the fabrication cost significantly above that of conventional, ingot metallurgy production methods. The cost differential can be offset by the superior performance of the RSP metallic alloys. However, without the performance database, it is difficult to convince potential users to adopt the RSP approach. Spray casting of the atomized molten droplets into suitable preforms for subsequent fabrication can be cost competitive with conventional processing. If the fine and stable microstructural features observed for the RSP approach are preserved during spray casing, a cost competitive product can be obtained that has superior properties and performance that cannot be obtained by conventional methods.

  8. Rapid Solidification of AB{sub 5} Hydrogen Storage Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gulbrandsen-Dahl, Sverre

    2002-01-01

    This doctoral thesis is concerned with rapid solidification of AB{sub 5} materials suitable for electrochemical hydrogen storage. The primary objective of the work has been to characterise the microstructure and crystal structure of the produced AB{sub 5} materials as a function of the process parameters, e.g. the cooling rate during rapid solidification, the determination of which has been paid special attention to. The thesis is divided into 6 parts, of which Part I is a literature review, starting with a short presentation of energy storage alternatives. Then a general review of metal hydrides and their utilisation as energy carriers is presented. This part also includes more detailed descriptions of the crystal structure, the chemical composition and the hydrogen storage properties of AB{sub 5} materials. Furthermore, a description of the chill-block melt spinning process and the gas atomisation process is given. In Part II of the thesis a digital photo calorimetric technique has been developed and applied for obtaining in situ temperature measurements during chill-block melt spinning of a Mm(NiCoMnA1){sub 5} hydride forming alloy (Mm = Mischmetal of rare earths). Compared with conventional colour transmission temperature measurements, this technique offers a special advantage in terms of a high temperature resolutional and positional accuracy, which under the prevailing experimental conditions were found to be {+-}29 K and {+-} 0.1 mm, respectively. Moreover, it is shown that the cooling rate in solid state is approximately 2.5 times higher than that observed during solidification, indicating that the solid ribbon stayed in intimate contact with the wheel surface down to very low metal temperatures before the bond was broken. During this contact period the cooling regime shifted from near ideal in the melt puddle to near Newtonian towards the end, when the heat transfer from the solid ribbon to the wheel became the rate controlling step. In Part III of the

  9. The Production of Material with Ultrafine Grain Structure in Al-Zn Alloy in the Process of Rapid Solidification

    Directory of Open Access Journals (Sweden)

    Szymaneka M.

    2014-06-01

    Full Text Available In the aluminium alloy family, Al-Zn materials with non-standard chemical composition containing Mg and Cu are a new group of alloys, mainly owing to their high strength properties. Proper choice of alloying elements, and of the method of molten metal treatment and casting enable further shaping of the properties. One of the modern methods to produce materials with submicron structure is a method of Rapid Solidification. The ribbon cast in a melt spinning device is an intermediate product for further plastic working. Using the technique of Rapid Solidification it is not possible to directly produce a solid structural material of the required shape and length. Therefore, the ribbon of an ultrafine grain or nanometric structure must be subjected to the operations of fragmentation, compaction, consolidation and hot extrusion.

  10. Characterization of age-hardening behavior of eutectic surface on rheo-cast A356-T5 alloy by using nano/micro-indentation, scratching and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Youn, S.W. [Department of Precision and Mechanical Engineering, Pusan National University, Pusan 609-735 (Korea, Republic of)]. E-mail: youn.sung-won@aist.go.jp; Kang, C.G. [National Research Laboratory of Thixo/Rheo Forming, School of Mechanical Engineering, Pusan National University, JangJun-Dong, Gumjung-Gu, Pusan 609-735 (Korea, Republic of)]. E-mail: cgkang@pusan.ac.kr

    2006-11-10

    This study investigates the nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in rheo-cast A356 alloy parts using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. The aging responses of the eutectic regions in the rheo-cast A356 alloys aged at 150 deg. C for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. Both Vickers hardness and indentation test results showed a similar trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

  11. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    Science.gov (United States)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  12. Solidification Sequence of Spray-Formed Steels

    Science.gov (United States)

    Zepon, Guilherme; Ellendt, Nils; Uhlenwinkel, Volker; Bolfarini, Claudemiro

    2016-02-01

    Solidification in spray-forming is still an open discussion in the atomization and deposition area. This paper proposes a solidification model based on the equilibrium solidification path of alloys. The main assumptions of the model are that the deposition zone temperature must be above the alloy's solidus temperature and that the equilibrium liquid fraction at this temperature is reached, which involves partial remelting and/or redissolution of completely solidified droplets. When the deposition zone is cooled, solidification of the remaining liquid takes place under near equilibrium conditions. Scanning electron microscopy (SEM) and optical microscopy (OM) were used to analyze the microstructures of two different spray-formed steel grades: (1) boron modified supermartensitic stainless steel (SMSS) and (2) D2 tool steel. The microstructures were analyzed to determine the sequence of phase formation during solidification. In both cases, the solidification model proposed was validated.

  13. Investigation of the T4 and T6 heat treatment cycles of semi-solid processed aluminium alloy A356

    CSIR Research Space (South Africa)

    Moller, H

    2008-01-01

    Full Text Available of the solution treatment time at 540 C from 6 hours to 1 hour does not alter the T4 or T6 tensile properties of the SSM processed A356 alloy. Slightly better impact properties are obtained with the shorter solution treatment. This could lead to time and energy...

  14. Grain Floatation During Equiaxed Solidification of an Al-Cu Alloy in a Side-Cooled Cavity: Part II—Numerical Studies

    Science.gov (United States)

    Kumar, Arvind; Walker, Mike J.; Sundarraj, Suresh; Dutta, Pradip

    2011-08-01

    In this article, a single-phase, one-domain macroscopic model is developed for studying binary alloy solidification with moving equiaxed solid phase, along with the associated transport phenomena. In this model, issues such as thermosolutal convection, motion of solid phase relative to liquid and viscosity variations of the solid-liquid mixture with solid fraction in the mobile zone are taken into account. Using the model, the associated transport phenomena during solidification of Al-Cu alloys in a rectangular cavity are predicted. The results for temperature variation, segregation patterns, and eutectic fraction distribution are compared with data from in-house experiments. The model predictions compare well with the experimental results. To highlight the influence of solid phase movement on convection and final macrosegregation, the results of the current model are also compared with those obtained from the conventional solidification model with stationary solid phase. By including the independent movement of the solid phase into the fluid transport model, better predictions of macrosegregation, microstructure, and even shrinkage locations were obtained. Mechanical property prediction models based on microstructure will benefit from the improved accuracy of this model.

  15. In Situ Study of Microstructure Evolution in Solidification of Hypereutectic Al-Si Alloys with Application of Thermal Analysis and Neutron Diffraction

    Science.gov (United States)

    Sediako, Dimitry G.; Kasprzak, Wojciech

    2015-09-01

    Understanding of the kinetics of solid-phase evolution in solidification of hypereutectic aluminum alloys is a key to control their as-cast microstructure and resultant mechanical properties, and in turn, to enhance the service characteristics of actual components. This study was performed to evaluate the solidification kinetics for three P-modified hypereutectic Al-19 pct Si alloys: namely, Al-Si binary alloy and with the subsequent addition of 2.8 pct Cu and 2.8 pct Cu + 0.7 pct Mg. Metallurgical evaluation included thermodynamic calculations of the solidification process using the FactSage™ 6.2 software package, as well as experimental thermal analysis, and in situ neutron diffraction. The study revealed kinetics of solid α-Al, solid Si, Al2Cu, and Mg2Si evolution, as well as the individual effects of Cu and Mg alloying additions on the solidification path of the Al-Si system. Various techniques applied in this study resulted in some discrepancies in the results. For example, the FactSage computations, in general, resulted in 281 K to 286 K (8 °C to 13 °C) higher Al-Si eutectic temperatures than the ones recorded in the thermal analysis, which are also ~278 K (~5 °C) higher than those observed in the in situ neutron diffraction. None of the techniques can provide a definite value for the solidus temperature, as this is affected by the chosen calculation path [283 K to 303 K (10 °C to 30 °C) higher for equilibrium solidification vs non-equilibrium] for the FactSage analysis; and further complicated by evolution of secondary Al-Cu and Mg-Si phases that commenced at the end of solidification. An explanation of the discrepancies observed and complications associated with every technique applied is offered in the paper.

  16. Stress-strain time-dependent behavior of A356.0 aluminum alloy subjected to cyclic thermal and mechanical loadings

    Science.gov (United States)

    Farrahi, G. H.; Ghodrati, M.; Azadi, M.; Rezvani Rad, M.

    2014-08-01

    This article presents the cyclic behavior of the A356.0 aluminum alloy under low-cycle fatigue (or isothermal) and thermo-mechanical fatigue loadings. Since the thermo-mechanical fatigue (TMF) test is time consuming and has high costs in comparison to low-cycle fatigue (LCF) tests, the purpose of this research is to use LCF test results to predict the TMF behavior of the material. A time-independent model, considering the combined nonlinear isotropic/kinematic hardening law, was used to predict the TMF behavior of the material. Material constants of this model were calibrated based on room-temperature and high-temperature low-cycle fatigue tests. The nonlinear isotropic/kinematic hardening law could accurately estimate the stress-strain hysteresis loop for the LCF condition; however, for the out-of-phase TMF, the condition could not predict properly the stress value due to the strain rate effect. Therefore, a two-layer visco-plastic model and also the Johnson-Cook law were applied to improve the estimation of the stress-strain hysteresis loop. Related finite element results based on the two-layer visco-plastic model demonstrated a good agreement with experimental TMF data of the A356.0 alloy.

  17. Purification in the interaction between yttria mould and Nb-silicide-based alloy during directional solidification: A novel effect of yttrium

    International Nuclear Information System (INIS)

    Ma, Limin; Tang, Xiaoxia; Wang, Bin; Jia, Lina; Yuan, Sainan; Zhang, Hu

    2012-01-01

    Nb-silicide-based alloys were directionally solidified in yttria moulds. As a result of thermal dissociation of yttria, the alloys were slightly contaminated with oxygen, which caused a competitive oxidation between yttrium and hafnium. The addition of 0.15 at.% yttrium reduced the oxygen increment by 42%, because the buoyant inclusions concentrated around the top surface. The yttrium addition caused a significant purification of the interaction between the yttria mould and the Nb-silicide-based alloys during the directional solidification.

  18. On the transition from short-range diffusion-limited to collision-limited growth in alloy solidification

    International Nuclear Information System (INIS)

    Aziz, M.J.; Boettinger, W.J.

    1994-01-01

    Short-range diffusion-limited growth, collision-limited growth, and the transition between the two regimes are explained as natural consequences of a single model for the kinetics of alloy solidification. Analytical expressions are developed for the velocity-undercooling function of a planar interface during dilute alloy solidification, using Turnbull's collision-limited growth model and the Continuous Growth Solute Trapping Model of Aziz and Kaplan both with and without a solute drag effect. The interface mobility, -dv/dT, is shown to be very high (proportional to the speed of sound) if the alloy is sufficiently dilute or if the growth rate is sufficiently rapid for nearly complete solute trapping. The interface mobility is reduced by the three orders of magnitude (becoming proportional to the diffusive speed) at intermediate growth rates where partial solute trapping occurs. Differences in low velocity predictions of the models with and without solute drag are also discussed. Comparison of the results of the analytical expressions to numerical solutions of the non-dilute kinetic model for Al-Be alloys shows that the dilute approximation breaks down at melt compositions on the order of 10 at.%. Similar variations in the interface mobility are shown for the disorder-trapping model of Boettinger and Aziz

  19. Wear behavior of A356/M{sub 7}C{sub 3} and A356/SiC particulate metal matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Turhan, H. [Univ. of Firat, Dept. of Metallurgy, Elazig (Turkey); Yilmaz, O. [Univ. of Firat, Dept. of Metallurgical Engineering, Elazig (Turkey)

    2002-06-01

    The stability of M{sub 7}C{sub 3} carbides as reinforcement for A356 materials for tribological applications has been investigated. For this purpose, A356/M{sub 7}C{sub 3}, A356/SiC and A356/M{sub 7}C{sub 3}/SiC composites were prepared by powder metallurgy and tested at room temperature against SAE 4620 steel ring and AISI 304 stainless steel counterfaces under loads of 10 - 150 N. For comparison, also unreinforced A356 specimens were processed and tested under the same conditions. The tribological behavior was evaluated by microstructural examination of the wear-effected zones and by weight loss measurements of the specimens and counterfaces. The wear behavior of A356/M{sub 7}C{sub 3} composite gave an excellent result as function of the applied load because the M{sub 7}C{sub 3} particles act as load-bearing elements due to their excellent bonding to the Al matrix, and their interfaces withtood the wear stresses even at the highest applied load. Moreover, the M{sub 7}C{sub 3} particles limited the incorporation of wear debris into the Al matrix and reduced the wear damage occasioned to the steel counterfaces compared to that of A356 Al alloy. (orig.)

  20. Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

    Science.gov (United States)

    Stein, Frank; Philips, Noah

    2018-03-01

    High-melting Nb-based alloys hold significant promise for the development of novel high-temperature materials for structural applications. In order to understand the effect of alloying elements Al and Fe, the Nb-rich part of the ternary Nb-Al-Fe system was investigated. A series of Nb-rich ternary alloys were synthesized from high-purity Nb, Al, and Fe metals by arc melting. Solidification paths were identified and the liquidus surface of the Nb corner of the ternary system was established by analysis of the as-melted microstructures and thermal analysis. Complementary analysis of heat-treated samples yielded isothermal sections at 1723 K and 1873 K (1450 °C and 1600 °C).

  1. In situ synchrotron x-ray characterization of microstructure formation in solidification processing of Al-based metallic alloys

    International Nuclear Information System (INIS)

    Billia, Bernard; Nguyen-Thi, Henri; Mangelinck-Noel, Nathalie

    2010-01-01

    The microstructure formed during the solidification step has a major influence on the properties of materials processed by major techniques (casting, welding ...). In situ and real-time characterization by synchrotron X-ray imaging is the method of choice to unveil the dynamical formation of the solidification microstructure in metallic alloys, and thus provide precise data for the critical validation of the theoretical predictions that is needed for sound advancement of modeling and numerical simulation. After a description of the experimental procedure used at the European Synchrotron Radiation Facility (ESRF), dynamical phenomena in the formation of the grain structure and dendritic or equiaxed solidification microstructure in Al-based alloys are presented. Beyond fluid flow interaction, earth gravity induces stresses, deformation and fragmentation in the dendritic mush. Settling of dendrite arms and equiaxed grains thus occurs, in particular in the columnar to equiaxed transition. Other types of stresses and strains are caused by the mere formation of the solidification microstructure itself. In white-beam X-ray topography, stresses and strains are manifested by specific contrasts and breaking of the Laue images into several pieces. Finally, quantitative analysis of the grey level in radiographs enables the analysis of solute segregation, which noticeably results in solutal poisoning of growth when equiaxed grains are interacting. (author)

  2. Precipitation in as-solidified undercooled Ni-Si hypoeutectic alloy: Effect of non-equilibrium solidification

    Energy Technology Data Exchange (ETDEWEB)

    Fan Kai [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Liu Feng, E-mail: liufeng@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Yang Gencang; Zhou Yaohe [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China)

    2011-08-25

    Highlights: {yields} The solid solubility of Si atom in {alpha}-Ni matrix increased with undercooling in the as-solidified sample. {yields} The effect of non-equilibrium solidification on precipitation has been theoretically described. {yields} The nucleation density, the real-time particle size and the precipitation rate are all increased upon annealing. {yields} The precipitate process can be artificially controlled by modifying the initial melt undercooling and the annealing time. - Abstract: Applying glass fluxing and cyclic superheating, high undercooling up to {approx}350 K was achieved for Ni-Si hypoeutectic alloy melt. By isothermally annealing the as-solidified alloy subjected to different undercoolings, precipitation behavior of Ni{sub 3}Si particle, at 973 K, was systematically studied. It was found that, the nucleation density and the real-time particle size, as well as the precipitation rate, were all increased, provided the sample was solidified subjected to higher undercooling. This was ascribed mainly to the increased solid solubility of Si atom in {alpha}-Ni matrix upon non-equilibrium solidification. On this basis, the non-equilibrium dendrite growth upon solidification and the soft impingement prevailing upon solid-state precipitation have been quantitatively connected. As such, the effect of liquid/solid transformation on subsequent precipitation was described.

  3. Precipitation in as-solidified undercooled Ni-Si hypoeutectic alloy: Effect of non-equilibrium solidification

    International Nuclear Information System (INIS)

    Fan Kai; Liu Feng; Yang Gencang; Zhou Yaohe

    2011-01-01

    Highlights: → The solid solubility of Si atom in α-Ni matrix increased with undercooling in the as-solidified sample. → The effect of non-equilibrium solidification on precipitation has been theoretically described. → The nucleation density, the real-time particle size and the precipitation rate are all increased upon annealing. → The precipitate process can be artificially controlled by modifying the initial melt undercooling and the annealing time. - Abstract: Applying glass fluxing and cyclic superheating, high undercooling up to ∼350 K was achieved for Ni-Si hypoeutectic alloy melt. By isothermally annealing the as-solidified alloy subjected to different undercoolings, precipitation behavior of Ni 3 Si particle, at 973 K, was systematically studied. It was found that, the nucleation density and the real-time particle size, as well as the precipitation rate, were all increased, provided the sample was solidified subjected to higher undercooling. This was ascribed mainly to the increased solid solubility of Si atom in α-Ni matrix upon non-equilibrium solidification. On this basis, the non-equilibrium dendrite growth upon solidification and the soft impingement prevailing upon solid-state precipitation have been quantitatively connected. As such, the effect of liquid/solid transformation on subsequent precipitation was described.

  4. Modeling solute segregation during the solidification of γ-phase U-Mo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Steiner, M.A., E-mail: mas4cw@virginia.edu [University of Virginia, Material Science and Engineering, 395 McCormick Rd, Charlottesville, VA 22904 (United States); Garlea, E. [Y-12 National Security Complex, Oak Ridge, TN 37831 (United States); Agnew, S.R. [University of Virginia, Material Science and Engineering, 395 McCormick Rd, Charlottesville, VA 22904 (United States)

    2016-06-15

    Using first principles calculations, it is demonstrated that solute segregation during U-Mo solidification can be modeled using the classic Brody-Fleming limited diffusion framework. The necessary supporting equations specific to the U-Mo alloy, along with careful verification of the assumptions underpinning the Brody-Fleming model are developed, allowing for concentration profile predictions as a function of alloy composition and cooling rate. The resulting model is compared to experimental solute concentration profiles, showing excellent agreement. Combined with complementary modeling of dendritic feature sizes, the solute segregation model can be used to predict the complete microstructural state of individual U-Mo volume elements based upon cooling rates, informing ideal processing routes.

  5. Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

    International Nuclear Information System (INIS)

    Gorny, Anton; Manickaraj, Jeyakumar; Cai, Zhonghou; Shankar, Sumanth

    2013-01-01

    Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al 13 Fe 4 , τ 5 -Al 8 Fe 2 Si and τ 6 -Al 9 Fe 2 Si 2 phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s −1 . Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ 5 -Al 8 SiFe 2 and τ 6 -Al 9 Fe 2 Si 2 . The τ 5 -Al 8 SiFe 2 phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ 6 -Al 9 Fe 2 Si 2 through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al 13 Fe 4 binary phase precludes the evolution of the τ 5 during solidification and subsequently transforms into the τ 6 phase during solidification. These observations are anomalous to the publications as prior art and simulation predictions of thermodynamic phase diagrams of these alloys, wherein, only one intermetallic phases in the

  6. Aluminum alloy weldability. Identification of weld solidification cracking mechanisms through novel experimental technique and model development

    Energy Technology Data Exchange (ETDEWEB)

    Coniglio, Nicolas

    2008-07-01

    The objective of the present thesis is to make advancements in understanding solidification crack formation in aluminum welds, by investigating in particular the aluminum 6060/4043 system. Alloy 6060 is typical of a family of Al-Mg-Si extrusion alloys, which are considered weldable only when using an appropriate filler alloy such as 4043 (Al-5Si). The effect of 4043 filler dilution (i.e. weld metal silicon content) on cracking sensitivity and solidification path of Alloy 6060 welds are investigated. Afterwards, cracking models are developed to propose mechanisms for solidification crack initiation and growth. Cracking Sensitivity. Building upon the concept that silicon improves weldability and that weldability can be defined by a critical strain rate, strain rate-composition combinations required for solidification crack formation in the Al- 6060/4043 system were determined using the newly developed Controlled Tensile Weldability (CTW) test utilizing local strain extensometer measurements. Results, presented in a critical strain rate - dilution map, show a crack - no crack boundary which reveals that higher local strain rates require higher 4043 filler dilution to avoid solidification cracking when arc welding Alloy 6060. Using the established crack - no crack boundary as a line of reference, additional parameters were examined and their influence on cracking characterized. These parameter influences have included studies of weld travel speed, weld pool contaminants (Fe, O, and H), and grain refiner additions (TiAl{sub 3} + Boron). Each parameter has been independently varied and its effect on cracking susceptibility quantified in terms of strain rate - composition combinations. Solidification Path. Solidification path of the Al-6060/4043 system was characterized using thermal analysis and phase identification. Increasing 4043 filler dilution from 0 to 16% in Alloy 6060 arc welds resulted in little effect on thermal arrests and microstructure, no effect on

  7. Solidification of AM and AZ magnesium alloys characterized by heat-transfer modeled thermal and calorimetric analysis and microsegregation study of directionally solidified microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Mirkovic, Djordje

    2008-05-09

    The micro-scale solidification of commercial Mg alloys of the AZ and AM series is in the focus of the present thesis. Two approaches of investigating solidification are implemented, complementary regarding temperature gradient and solidification rate, and also with respect to the generated microstructure. The first approach considers solidification under a negligible spatial temperature gradient. Here the solidification curves, i.e. fraction solid versus temperature, were determined by developing an improved heat-transfer modeling applicable on both differential thermal analysis (DTA) and differential scanning calorimetry (DSC) signals. The correlation between solidification enthalpy and fraction solid during solidification was tested in detail. A better evaluation of the measured DTA and DSC signals is attained through an independent measurement of the time constant as function of temperature for the applied equipment. A further improvement is achieved through a more impartial interpretation of the measured curves. Both improvements enable a better desmearing of measured signals and reduce the error induced by the operator. The novel tantalum encapsulation enabled appropriate handling of challenging Mg-alloys. The viability and limitations of thermal analysis in general to determine start and end of solidification of AZ magnesium alloys was also studied. The second approach is based on directional solidification in a high temperature gradient and at constant solidification rate, achieved by the Bridgman technique. The resulting dendritic microstructure and inherent microsegregation are studied in this work. The solute profiles, i.e. solute content versus solid phase fraction during solidification, are determined by an advanced treatment of the EPMA data. Problems that are demonstrated in this work are Al-loss and melt pollution due to reaction with typical sample container material made of unprotected steel. The development of an optimized boron nitride (BN

  8. Developments of high strength Bi-containing Sn0.7Cu lead-free solder alloys prepared by directional solidification

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiaowu, E-mail: xwhmaterials@aliyun.com [School of Mechanical Electrical Engineering, Nanchang University, Nanchang 330031 (China); Li, Yulong [School of Mechanical Electrical Engineering, Nanchang University, Nanchang 330031 (China); Liu, Yi [School of Materials Science and Engineering, Nanchang University, Nanchang 330031 (China); Min, Zhixian [China Electronics Technology Group Corporation No. 38 Research Institute, Hefei 230088 (China)

    2015-03-15

    Highlights: • The Sn0.7Cu–xBi solder alloys were directionally solidified. • Both spacing and diameter of fibers decreased with increasing solidification rate. • The UTS and YS first increased with increased solidification rate, then decreased. • The UTS and YS of Sn0.7Cu–xBi first increased with increased Bi content. - Abstract: Bi-containing Sn0.7Cu (SC) eutectic solder alloys were prepared and subjected to directional solidification, through which new types of fiber reinforced eutectic composites were generated. The influences of Bi addition on the microstructures and tensile properties of directionally solidified (DS) Bi-containing eutectic SC lead-free solder alloys have been investigated by using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and a tensile testing machine. The experimental results showed that addition of Bi could effectively reduce both the melting temperature and undercooling of SC solder alloy. The microstructures of DS SC–xBi solder alloys were composed of Sn-rich phase (β) and Cu{sub 6}Sn{sub 5} fiber. No other intermetallic compounds (IMCs) with Bi content were observed in the solder matrix for SC solder alloys with various Bi contents. Both fiber spacing and diameter all decreased gradually with increasing growth rate and/or Bi content. Besides, the regularity of Cu{sub 6}Sn{sub 5} fibers alignment also decreased with increasing growth rate, too. The tensile strengths of the SC–xBi eutectic solder alloys varied parabolically with growth rate (R). When R was 60 μm/s, maximum tensile strengths of 43.8, 55.2 and 56.37 MPa were reached for SC, SC0.7Bi and SC1.3Bi solder alloys. A comparison of tensile strength of SC, SC0.7Bi and SC1.3Bi with the same R indicated that the tensile strength increased with increasing Bi content, which was attributed to the presence of Bi and its role in refining microstructure and solid solution strengthening.

  9. Rheologic behaviors of A356 aluminum alloy billet produced by semisolid continuous casting process

    Directory of Open Access Journals (Sweden)

    Shuming XING

    2004-08-01

    Full Text Available The experiments for rheologic behaviors of semisolid continous casting billets of A356 alloy in semisolid state has been carried out with a multifunctional rheometer. The results show that the deformation rate increases with loading time, the maximum strain reaches 120% (which is one time larger than that of traditional casting billet and the strain can be rapidly eliminated to 10% after unloading. Moreover, there is a critic stress for billet deformation even in semisolid state, which is named as critic shear stress. This stress increases with the decreasing of heating time. The rheologic behaviors can be expressed by five elements mechanical model and can be modified with the increasing of heating time.

  10. Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

    Energy Technology Data Exchange (ETDEWEB)

    Gorny, Anton; Manickaraj, Jeyakumar [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada); Cai, Zhonghou [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Shankar, Sumanth, E-mail: shankar@mcmaster.ca [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada)

    2013-11-15

    Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al{sub 13}Fe{sub 4}, τ{sub 5}-Al{sub 8}Fe{sub 2}Si and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s{sup −1}. Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ{sub 5}-Al{sub 8}SiFe{sub 2} and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2}. The τ{sub 5}-Al{sub 8}SiFe{sub 2} phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al{sub 13}Fe{sub 4} binary phase precludes the evolution of the τ{sub 5} during solidification and subsequently transforms into the τ{sub 6} phase during solidification. These observations are anomalous to the publications as prior art and

  11. Microstructure and corrosion properties of as sub-rapid solidification Mg-Zn-Y-Nd alloy in dynamic simulated body fluid for vascular stent application.

    Science.gov (United States)

    Wang, Jun; Wang, Liguo; Guan, Shaokang; Zhu, Shijie; Ren, Chenxing; Hou, Shusen

    2010-07-01

    Magnesium alloy stent has been employed in animal and clinical experiment in recent years. It has been verified to be biocompatible and degradable due to corrosion after being implanted into blood vessel. Mg-Y-Gd-Nd alloy is usually used to construct an absorbable magnesium alloy stent. However, the corrosion resistant of as cast Mg-Y-Gd-Nd alloy is poor relatively and the control of corrosion rate is difficult. Aiming at the requirement of endovascular stent in clinic, a new biomedical Mg-Zn-Y-Nd alloy with low Zn and Y content (Zn/Y atom ratio 6) was designed, which exists quasicrystals to improve its corrosion resistance. Additionally, sub-rapid solidification processing was applied for preparation of corrosion-resisting Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys. Compared with the as cast sample, the corrosion behavior of alloys in dynamic simulated body fluid (SBF) (the speed of body fluid: 16 ml/800 ml min(-1)) was investigated. The results show that as sub-rapid solidification Mg-Zn-Y-Nd alloy has the better corrosion resistance in dynamic SBF due to grain refinement and fine dispersion distribution of the quasicrystals and intermetallic compounds in alpha-Mg matrix. In the as cast sample, both Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys exhibit poor corrosion resistance. Mg-Zn-Y-Nd alloy by sub-rapid solidification processing provides excellent corrosion resistance in dynamic SBF, which open a new window for biomedical materials design, especially for vascular stent application.

  12. In situ observations of solidification processes in γ-TiAl alloys by synchrotron radiation

    International Nuclear Information System (INIS)

    Shuleshova, Olga; Holland-Moritz, Dirk; Loeser, Wolfgang; Voss, Andrea; Hartmann, Helena; Hecht, Ulrike; Witusiewicz, Victor T.; Herlach, Dieter M.; Buechner, Bernd

    2010-01-01

    In situ observations of phase transformations involving melts are performed using energy-dispersive diffraction of synchrotron X-rays on electromagnetically levitated γ-TiAl alloys containing Nb. The determined primary solidification modes, confirmed by microstructure analysis, delivered new reliable data about the boundary of the α(Ti) solidification domain, which differs in the various Ti-Al-Nb phase diagram descriptions. These data have been used for a reassessment of the thermodynamic database of the ternary Ti-Al-Nb system. The new description realistically reflects the experimental findings. Liquidus and solidus temperatures determined by the pyrometric method agree fairly well with the calculated values. Direct experimental information on the nature of the reactions along the univariant lines is provided.

  13. The Effect of Ultrasonic Melt Treatment on the Microstructure and Mechanical Properties of Al-7Si-0.35Mg Casting Alloys

    International Nuclear Information System (INIS)

    Kim, Soo-Bae; Cho, Young-Hee; Lee, Jung-Moo; Jung, Jae-Gil; Lim, Su Gun

    2017-01-01

    The effect of ultrasonic melt treatment (UST) on the microstructure and mechanical properties of Al-7Si-0.35Mg (A356) casting alloys was investigated. The particular aim of this study was to analyze the mechanism involved in the strengthening of the A356 alloys when fabricated by UST. The UST had little effect on the sizes of the α-Al grain and eutectic Si at a melt temperature of 750 ℃, and the yield strength of the A356 alloy was increased by UST by approximately 16%. After T6 heat treatment, however, both alloys prepared with and without UST had similar levels of yield strength. These results are possibly associated with a change in the type and the volume fraction of intermetallics due to UST. UST greatly reduced the volume fractions of the intermetallics which were formed upon solidification, resulting in alloys with predominantly β-Al_5FeSi instead of π-Al_8FeMg_3Si_6. However, T6 heat treatment, especially a solid solution treatment at 530 ℃ for 8 hours, led to the dissolving of intermetallics such as Mg_2Si and π -Al_8FeMg_3Si_6 and as a result their volume fractions were further reduced to similar levels in both alloys with and without UST.

  14. The Effect of Ultrasonic Melt Treatment on the Microstructure and Mechanical Properties of Al-7Si-0.35Mg Casting Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Soo-Bae; Cho, Young-Hee; Lee, Jung-Moo; Jung, Jae-Gil [Korea Institute of Materials Science, Changwon (Korea, Republic of); Lim, Su Gun [Gyeongsang National University, Jinju (Korea, Republic of)

    2017-04-15

    The effect of ultrasonic melt treatment (UST) on the microstructure and mechanical properties of Al-7Si-0.35Mg (A356) casting alloys was investigated. The particular aim of this study was to analyze the mechanism involved in the strengthening of the A356 alloys when fabricated by UST. The UST had little effect on the sizes of the α-Al grain and eutectic Si at a melt temperature of 750 ℃, and the yield strength of the A356 alloy was increased by UST by approximately 16%. After T6 heat treatment, however, both alloys prepared with and without UST had similar levels of yield strength. These results are possibly associated with a change in the type and the volume fraction of intermetallics due to UST. UST greatly reduced the volume fractions of the intermetallics which were formed upon solidification, resulting in alloys with predominantly β-Al{sub 5}FeSi instead of π-Al{sub 8}FeMg{sub 3}Si{sub 6}. However, T6 heat treatment, especially a solid solution treatment at 530 ℃ for 8 hours, led to the dissolving of intermetallics such as Mg{sub 2}Si and π -Al{sub 8}FeMg{sub 3}Si{sub 6} and as a result their volume fractions were further reduced to similar levels in both alloys with and without UST.

  15. Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam.

    Science.gov (United States)

    Kang, Minjung; Han, Heung Nam; Kim, Cheolhee

    2018-04-23

    Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility.

  16. Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam

    Directory of Open Access Journals (Sweden)

    Minjung Kang

    2018-04-01

    Full Text Available Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility.

  17. On the stable eutectic solidification of iron–carbon–silicon alloys

    International Nuclear Information System (INIS)

    Stefanescu, Doru M.; Alonso, Gorka; Larrañaga, Pello; Suarez, Ramon

    2016-01-01

    Extensive effort was expanded to elucidate the growth and morphology of the stable eutectic grains during early solidification of continuous cooled Fe–C–Si alloys. To this purpose, quenching experiments at successive stages during solidification have been carried out on five cast irons with various magnesium and titanium levels designed to produce graphite morphologies ranging from lamellar to mixed compacted–spheroidal. The graphite shape factors were measured on the metallographic samples, and their evolution as a function of the chemical composition and the solid fraction was analyzed. Extensive scanning electron microscopy was carried on to evaluate the change in graphite shape during early solidification, to establish the fraction of solid at which the transition from spheroidal-to-compacted-to-lamellar graphite occurs, and to outline the early morphology of the eutectic grains. It was confirmed that solidification of Mg containing irons started with the development of spheroidal graphite even at Mg levels as low as 0.013 mass%. Then, as solidification proceeds, when some spheroids developed one or more tails (tadpole graphite), the spheroidal-to-compacted graphite transition occurs. The new findings were then integrated in previous knowledge to produce an understanding of the eutectic solidification of these materials. It was concluded that in hypoeutectic lamellar graphite iron austenite/graphite eutectic grains can nucleate at the austenite/liquid interface or in the bulk of the liquid, depending on the sulfur content and on the cooling rate. When graphite nucleation occurs on the primary austenite, several eutectic grains can nucleate and grow on the same dendrite. The primary austenite continues growing as eutectic austenite and therefore the two have the same crystallographic orientation. Thus, a final austenite grain may include several eutectic grains. In eutectic irons the eutectic grains nucleate and grow mostly in the liquid. The eutectic

  18. Macrosegregation Resulting from Directional Solidification Through an Abrupt Change in Cross-Sections

    Science.gov (United States)

    Lauer, M.; Poirier, D. R.; Ghods, M.; Tewari, S. N.; Grugel, R. N.

    2017-01-01

    Simulations of the directional solidification of two hypoeutectic alloys (Al-7Si alloy and Al-19Cu) and resulting macrosegregation patterns are presented. The casting geometries include abrupt changes in cross-section from a larger width of 9.5 mm to a narrower 3.2 mm width then through an expansion back to a width of 9.5 mm. The alloys were chosen as model alloys because they have similar solidification shrinkages, but the effect of Cu on changing the density of the liquid alloy is about an order of magnitude greater than that of Si. The simulations compare well with experimental castings that were directionally solidified in a graphite mold in a Bridgman furnace. In addition to the simulations of the directional solidification in graphite molds, some simulations were effected for solidification in an alumina mold. This study showed that the mold must be included in numerical simulations of directional solidification because of its effect on the temperature field and solidification. For the model alloys used for the study, the simulations clearly show the interaction of the convection field with the solidifying alloys to produce a macrosegregation pattern known as "steepling" in sections with a uniform width. Details of the complex convection- and segregation-patterns at both the contraction and expansion of the cross-sectional area are revealed by the computer simulations. The convection and solidification through the expansions suggest a possible mechanism for the formation of stray grains. The computer simulations and the experimental castings have been part of on-going ground-based research with the goal of providing necessary background for eventual experiments aboard the ISS. For casting practitioners, the results of the simulations demonstrate that computer simulations should be applied to reveal interactions between alloy solidification properties, solidification conditions, and mold geometries on macrosegregation. The simulations also presents the

  19. Effect of turning parameters on surface roughness of A356/5% SiC composite produced by electromagnetic stir casting

    Energy Technology Data Exchange (ETDEWEB)

    Dwivedi, S. P.; Kumar, Sudhir; Kumar, Ajay [Noida Institute of Engineering Technology, U.P (India)

    2012-12-15

    In the present investigation, A356 alloy 5 wt% SiC composite is fabricated by electromagnetic stir casting process. An attempt has been made to investigate the effect of CNC lathe process parameters like cutting speed, depth of cut, and feed rate on surface roughness during machining of A356 alloy 5 wt% SiC particulate metal-matrix composites in dry condition. Response surface methodology (Box Behnken Method) is chosen to design the experiments. The results reveal that cutting speed increases surface roughness decreases, whereas depth of cut and feed increase surface roughness increase. Optimum values of speed (190 m/min), feed (0.14 mm/rev) and depth of cut (0.20 mm) during turning of A356 alloy 5 wt% SiC composites to minimize the surface roughness (3.15>m) have been find out. The mechanical properties of A356 alloy 5 wt% SiC were also analyzed.

  20. Microstructural characterisation of Al-Si cast alloys containing rare earth additions

    Science.gov (United States)

    Elgallad, E. M.; Ibrahim, M. F.; Doty, H. W.; Samuel, F. H.

    2018-05-01

    This paper presents a thorough study on the effect of rare earth elements, specifically La and Ce, on the microstructure characteristics of non-modified and Sr-modified A356 and A413 alloys. Several alloys were prepared by adding 1% La and 1% Ce either individually or in combination. Microstructural characterisation was carried out using optical microscopy, scanning electron microscopy and electron probe microanalysis as well as differential scanning calorimetry (DSC) analysis. The results showed that the individual and combined additions of La and Ce did not bring about any modification or even refinement in the eutectic Si structure. Moreover, these additions were found to negate the modification effect of Sr, particularly in the presence of La. The A356 and A413 alloys containing La and/or Ce displayed high phase volume fractions owing to the formation of Al-Si-La/Ce/(La,Ce) and Al-Ti-La/Ce intermetallic phases. DSC analysis revealed that the formation temperatures of these phases varied from 560 to 568 °C and 568 to 574 °C, respectively. This analysis also showed that the addition of La and Ce whether individually or in combination resulted in a depression in the eutectic temperature and a considerable increase in the solidification range, particularly for the A413 alloy.

  1. Study of the microstructural evolution and rheological behavior by semisolid compression between parallel plate of the alloy A356 solidified under a continuously rotating magnetic field

    International Nuclear Information System (INIS)

    Leiva L, Ricardo; Sanchez V, Cristian; Mannheim C, Rodolfo; Bustos C, Oscar

    2004-01-01

    This work presents a study of the rheological behavior of the alloy A356, with and without continuous magnetic agitation during its solidification, in semisolid state. The evaluation was performed using a parallel plate compression rheometer with the digital recording of position and time data. The microstructural evolution was also studied at the start and end of the semisolid compression test. The procedure involved tests of short cylinders extracted from billets with a non dendritic microstructure cast under a continuously rotating magnetic field. These pieces were tested in different solid fractions, at constant charges and at constant deformation velocities. When the test is carried out at a constant charge the equation can be determined that governs the rheological behavior of the material in semisolid state following a power grade of two Ostwald-de-Waele parameters. But when the test is done at a constant deformation speed the flow behavior of the material can be described in the semisolid shaping process. The results obtained show that the morphology of the phases present in the microstructure is highly relevant to its rheological behavior. A globular coalesced rosette to rosette type microstructure was found to have the typical behavior of a fluid when shaped in a semisolid state but a cast dendritic structure did not behave this way. Also the Arrhenius type dependence of viscosity with temperature was established (CW)

  2. A Real Time Investigation of Morphological Evolution During Solidification of Different Alloy Systems

    Science.gov (United States)

    Sen, S.; Kaukler, W. F.; Curreri, P. A.

    1999-01-01

    Solidification phenomenon which occur at the solid/liquid (s/I) interface play a major role in the determination of structure and hence the technologically important properties of a casting. However, metals being opaque, conclusions related to several important phenomenon such as boundary layer thickness, morphological evolution, and eutectic and cell spacing are deduced from quenching experiments and subsequent post solidification metallographic analysis. Consequently, limited information is obtained about the dynamics of the process. This paper will discuss the recent efforts at the Space Science Laboratory, NASA Marshall Space Flight Center, to view and quantify in-situ and in real time the dynamics of the solidification process and to measure interfacial undercooling. First, a high resolution x-ray transmission microscope (XTM) has been developed to monitor fundamental interfacial phenomena during directional solidification of metals and alloys. The XTM operates in the range of 10-100 KeV and through projection is capable of achieving magnification of up to 16OX. Secondly, an innovative collapsible furnace has been designed to quantify interfacial undercooling by measuring the temperature of a moving s/I interface in reference to a fixed s/l interface. This measurement technique is non-intrusive in nature and is based on the Seebeck principle. In this paper real time results obtained to characterize the dynamics of irregular eutectic spacing will be presented. As an example fiber to lamella or plate transition in the Al-Al2Au eutectic system will be discussed. Further, a resolution limit of 25 micron has permitted viewing in real time morphological instability and cellular growth in Al-Au and Al-Ag systems. Simultaneously, a systematic investigation has been carried out to measure interfacial undercooling for Pb-1 wt.% Sn at and near the marginal stability regime. In conjunction with the XTM observations this study attempts to validate existing relationships

  3. Study of the thermal and kinetic parameters during directional solidification of zinc-aluminum eutectic alloys

    International Nuclear Information System (INIS)

    Gueijman, Sergio Fabian; Ares, Alicia Esther; Schvezov, Carlos Enrique

    2008-01-01

    Much work has been done recently on investigating zinc-based binary alloys, with different aluminum content, and modified or not with small amounts of other alloying elements. Some of these alloys have interesting properties, such as, the ZA alloys that have properties similar to some bronzes that are used in applications that require pieces with enough resistance to mechanical stresses. The longitudinal thermal gradients, the minimal gradients, the velocities of the liquid interphases, the velocities of the solid interphases and the accelerations of both interphases as a function of time and position were determined for each diluted alloy of the eutectic concentration considered (Zn-5%Al, % in weight), solidified horizontally with caloric extraction from both ends of the test pieces. The values obtained from the horizontal solidification with two directions of predominant caloric extraction are compared to previous values obtained for the same vertically solidified alloy system with a predominantly caloric extraction direction

  4. Direct numerical simulation of solidification microstructures affected by fluid flow

    International Nuclear Information System (INIS)

    Juric, D.

    1997-12-01

    The effects of fluid flow on the solidification morphology of pure materials and solute microsegregation patterns of binary alloys are studied using a computational methodology based on a front tracking/finite difference method. A general single field formulation is presented for the full coupling of phase change, fluid flow, heat and solute transport. This formulation accounts for interfacial rejection/absorption of latent heat and solute, interfacial anisotropies, discontinuities in material properties between the liquid and solid phases, shrinkage/expansion upon solidification and motion and deformation of the solid. Numerical results are presented for the two dimensional dendritic solidification of pure succinonitrile and the solidification of globulitic grains of a plutonium-gallium alloy. For both problems, comparisons are made between solidification without fluid flow and solidification within a shear flow

  5. Efficient estimation of diffusion during dendritic solidification

    Science.gov (United States)

    Yeum, K. S.; Poirier, D. R.; Laxmanan, V.

    1989-01-01

    A very efficient finite difference method has been developed to estimate the solute redistribution during solidification with diffusion in the solid. This method is validated by comparing the computed results with the results of an analytical solution derived by Kobayashi (1988) for the assumptions of a constant diffusion coefficient, a constant equilibrium partition ratio, and a parabolic rate of the advancement of the solid/liquid interface. The flexibility of the method is demonstrated by applying it to the dendritic solidification of a Pb-15 wt pct Sn alloy, for which the equilibrium partition ratio and diffusion coefficient vary substantially during solidification. The fraction eutectic at the end of solidification is also obtained by estimating the fraction solid, in greater resolution, where the concentration of solute in the interdendritic liquid reaches the eutectic composition of the alloy.

  6. Evolution of solidification texture during additive manufacturing

    Science.gov (United States)

    Wei, H. L.; Mazumder, J.; DebRoy, T.

    2015-01-01

    Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components. PMID:26553246

  7. Dual-scale phase-field simulation of Mg-Al alloy solidification

    International Nuclear Information System (INIS)

    Monas, A; Shchyglo, O; Tegeler, M; Steinbach, I; Höche, D

    2015-01-01

    Phase-field simulations of the nucleation and growth of primary α-Mg phase as well as secondary, β-phase of a Mg-Al alloy are presented. The nucleation model for α- and β-Mg phases is based on the “free growth model” by Greer et al.. After the α-Mg phase solidification we study a divorced eutectic growth of α- and β-Mg phases in a zoomed in melt channel between α-phase dendrites. The simulated cooling curves and final microstructures of α-grains are compared with experiments. In order to further enhance the resolution of the interdendritic region a high-performance computing approach has been used allowing significant simulation speed gain when using supercomputing facilities. (paper)

  8. Combined effect of non-equilibrium solidification and thermal annealing on microstructure evolution and hardness behavior of AZ91 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Z.Z.; Yang, W., E-mail: weiyang@mail.nwpu.edu.cn; Chen, S.H.; Yu, H.; Xu, Z.F.

    2014-06-15

    Non-equilibrium solidification of commercial AZ91 magnesium alloy was performed by copper mold spray-casting technique and the thermal stability property of as-formed meta-stable microstructure was investigated by subsequent annealing at different temperatures and times. Remarkable grain refinement appears with increasing cooling rate during solidification process, which is accompanied by a visible cellular/dendrite transition for the grain morphology of primary phase. Moreover, the non-equilibrium solidified alloy exhibits obvious precipitation hardening effect upon annealing at 200 °C, and the precipitation mode of β-Mg{sub 17}Al{sub 12} phase changes from discontinuous to continuous with extending isothermal time from 4 h to 16 h, which generates an increase of resultant micro-hardness value. After solid solution treatment at the elevated temperature of 420 °C, the volume fraction of β-Mg{sub 17}Al{sub 12} phase decreases and a notable grain growth phenomenon occurs, which give rise to a reduction of hardness in comparison with that of as-quenched alloy.

  9. Columnar and Equiaxed Solidification of Al-7 wt.% Si Alloys in Reduced Gravity in the Framework of the CETSOL Project

    Science.gov (United States)

    Zimmermann, G.; Sturz, L.; Nguyen-Thi, H.; Mangelinck-Noel, N.; Li, Y. Z.; Gandin, C.-A.; Fleurisson, R.; Guillemot, G.; McFadden, S.; Mooney, R. P.; Voorhees, P.; Roosz, A.; Ronaföldi, A.; Beckermann, C.; Karma, A.; Chen, C.-H.; Warnken, N.; Saad, A.; Grün, G.-U.; Grohn, M.; Poitrault, I.; Pehl, T.; Nagy, I.; Todt, D.; Minster, O.; Sillekens, W.

    2017-08-01

    During casting, often a dendritic microstructure is formed, resulting in a columnar or an equiaxed grain structure, or leading to a transition from columnar to equiaxed growth (CET). The detailed knowledge of the critical parameters for the CET is important because the microstructure affects materials properties. To provide unique data for testing of fundamental theories of grain and microstructure formation, solidification experiments in microgravity environment were performed within the European Space Agency Microgravity Application Promotion (ESA MAP) project Columnar-to-Equiaxed Transition in SOLidification Processing (CETSOL). Reduced gravity allows for purely diffusive solidification conditions, i.e., suppressing melt flow and sedimentation and floatation effects. On-board the International Space Station, Al-7 wt.% Si alloys with and without grain refiners were solidified in different temperature gradients and with different cooling conditions. Detailed analysis of the microstructure and the grain structure showed purely columnar growth for nonrefined alloys. The CET was detected only for refined alloys, either as a sharp CET in the case of a sudden increase in the solidification velocity or as a progressive CET in the case of a continuous decrease of the temperature gradient. The present experimental data were used for numerical modeling of the CET with three different approaches: (1) a front tracking model using an equiaxed growth model, (2) a three-dimensional (3D) cellular automaton-finite element model, and (3) a 3D dendrite needle network method. Each model allows for predicting the columnar dendrite tip undercooling and the growth rate with respect to time. Furthermore, the positions of CET and the spatial extent of the CET, being sharp or progressive, are in reasonably good quantitative agreement with experimental measurements.

  10. Multiscale modeling of alloy solidification using a database approach

    Science.gov (United States)

    Tan, Lijian; Zabaras, Nicholas

    2007-11-01

    A two-scale model based on a database approach is presented to investigate alloy solidification. Appropriate assumptions are introduced to describe the behavior of macroscopic temperature, macroscopic concentration, liquid volume fraction and microstructure features. These assumptions lead to a macroscale model with two unknown functions: liquid volume fraction and microstructure features. These functions are computed using information from microscale solutions of selected problems. This work addresses the selection of sample problems relevant to the interested problem and the utilization of data from the microscale solution of the selected sample problems. A computationally efficient model, which is different from the microscale and macroscale models, is utilized to find relevant sample problems. In this work, the computationally efficient model is a sharp interface solidification model of a pure material. Similarities between the sample problems and the problem of interest are explored by assuming that the liquid volume fraction and microstructure features are functions of solution features extracted from the solution of the computationally efficient model. The solution features of the computationally efficient model are selected as the interface velocity and thermal gradient in the liquid at the time the sharp solid-liquid interface passes through. An analytical solution of the computationally efficient model is utilized to select sample problems relevant to solution features obtained at any location of the domain of the problem of interest. The microscale solution of selected sample problems is then utilized to evaluate the two unknown functions (liquid volume fraction and microstructure features) in the macroscale model. The temperature solution of the macroscale model is further used to improve the estimation of the liquid volume fraction and microstructure features. Interpolation is utilized in the feature space to greatly reduce the number of required

  11. Progress on Numerical Modeling of the Dispersion of Ceramic Nanoparticles During Ultrasonic Processing and Solidification of Al-Based Nanocomposites

    Science.gov (United States)

    Zhang, Daojie; Nastac, Laurentiu

    2016-12-01

    In present study, 6061- and A356-based nano-composites are fabricated by using the ultrasonic stirring technology (UST) in a coreless induction furnace. SiC nanoparticles are used as the reinforcement. Nanoparticles are added into the molten metal and then dispersed by ultrasonic cavitation and acoustic streaming assisted by electromagnetic stirring. The applied UST parameters in the current experiments are used to validate a recently developed magneto-hydro-dynamics (MHD) model, which is capable of modeling the cavitation and nanoparticle dispersion during UST processing. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, and electromagnetic field, as well as the complex interaction between the nanoparticles and both the molten and solidified alloys by using ANSYS Maxwell and ANSYS Fluent. Molecular dynamics (MD) simulations are conducted to analyze the complex interactions between the nanoparticle and the liquid/solid interface. The current modeling results demonstrate that a strong flow can disperse the nanoparticles relatively well during molten metal and solidification processes. MD simulation results prove that ultrafine particles (10 nm) will be engulfed by the solidification front instead of being pushed, which is beneficial for nano-dispersion.

  12. Multiscale modelling of solidification microstructures, including microsegregation and microporosity, in an Al-Si-Cu alloy

    International Nuclear Information System (INIS)

    Lee, P.D.; Chirazi, A.; Atwood, R.C.; Wang, W.

    2004-01-01

    Phase transition phenomena in metallic alloys involve complex physical processes occurring over a wide range of temporal, spatial and energy scales. Multiscale modelling is a powerful methodology for understanding these complex systems. In this paper, a multiscale model of grain and pore formation is presented during solidification. At the microscale, a combined stochastic-deterministic approach based on the cellular automata method is used to solve multicomponent diffusion in a three-phase system (liquid, solid and gas), simulating the nucleation and growth of both grains and pores. The impingement of the growing pores upon the developing solid is also solved to predict the tortuous shape of the porosity, a critical factor for fatigue properties. The micromodel is coupled with a finite element method (FEM) solution of the macroscale heat transfer and fluid flow in industrial castings through the temperature and pressure fields. The result model was used to investigate the influence of local solidification time, hydrogen content, local metallostatic pressure and alloy composition upon the predicted grain structure and pore morphology. Comparison of the model predictions to both laboratory and industrial scale castings are presented

  13. Microstructures and mechanical responses of powder metallurgy non-combustive magnesium extruded alloy by rapid solidification process in mass production

    International Nuclear Information System (INIS)

    Kondoh, Katsuyoshi; Hamada, EL-Sayed Ayman; Imai, Hisashi; Umeda, Junko; Jones, Tyrone

    2010-01-01

    Spinning Water Atomization Process (SWAP), which was one of the rapid solidification processes, promised to produce coarse non-combustible magnesium alloy powder with 1-4 mm length, having fine α-Mg grains and Al 2 Ca intermetallic compounds. It had economical and safe benefits in producing coarse Mg alloy powders with very fine microstructures in the mass production process due to its extreme high solidification rate compared to the conventional atomization process. AMX602 (Mg-6%Al-0.5%Mn-2%Ca) powders were compacted at room temperature. Their green compacts with a relative density of about 85% were heated at 573-673 K for 300 s in Ar gas atmosphere, and immediately consolidated by hot extrusion. Microstructure observation and evaluation of mechanical properties of the extruded AMX602 alloys were carried out. The uniform and fine microstructures with grains less than 0.45-0.8 μm via dynamic recrystallization during hot extrusion were observed, and were much small compared to the extruded AMX602 alloy fabricated by using cast ingot. The extremely fine intermetallic compounds 200-500 nm diameter were uniformly distributed in the matrix of powder metallurgy (P/M) extruded alloys. These microstructures caused excellent mechanical properties of the wrought alloys. For example, in the case of AMX602 alloys extruded at 573 K, the tensile strength (TS) of 447 MPa, yield stress (YS) of 425 MPa and 9.6% elongation were obtained.

  14. Determination of Systems Suitable for Study as Monotectic Binary Metallic Alloy Solidification Models

    Science.gov (United States)

    Smith, J. E., Jr.

    1983-01-01

    Succinonitrile-water and diethylene glycol-ethyl salicylate are two transparent systems which have been studied as monotectic binary metallic alloy solidification models. Being transparent, these systems allow for the direct observations of phase transformations and solidification reactions. The objective was to develop a screening technique to find systems of interest and then experimentally measure those systems. The succinonitrile-water system was used to check the procedures. To simulate the phase diagram of the system, two computer programs which determine solid-liquid and liquid-liquid equilibria were obtained. These programs use the UNIFAC method to determine activity coefficients and together with several other programs were used to predict the phase diagram. An experimental apparatus was developed and the succinonitrile-water phase diagram measured. The diagram was compared to both the simulation and literature data. Substantial differences were found in the comparisons which serve to demonstrate the need for this procedure.

  15. Effect of natural aging on the properties of heat-treated A356 aluminum alloy

    International Nuclear Information System (INIS)

    Hernandez-Paz, J.F.; Paray, F.; Gruzleski, J.E.; Emadi, D.

    2002-01-01

    During the heat treatment of aluminum alloys, there is usually a delay time between quenching and the final artificial aging. This delay is called natural aging or preaging at room temperature. This research was conducted in order to study the effect of various natural aging times (0, 6, 12 and 20 hours) on the properties of unmodified and strontium modified A356 aluminum alloys solution heat-treated 4 hours at 540 o C, water quenched and artificially aged 6 hours at 155 o C and 170 o C. The samples were tested for electrical conductivity, microhardness, and tensile properties. In the case of the samples artificially aged at 155 o C from the results it can be seen a decrease in the microhardness and yield strength with natural aging. Regarding the samples aged at 170 o C it is noticed that natural aging at 12 hours will result in the lowest electrical conductivity, yield strength and microhardness. However, there is evidence of recovery of those properties at 20 hours of natural aging. Regarding the elongation, natural aging seems to have a positive effect when artificial aging is carried out at 155 o C, but at 170 o C an optimum elongation is obtained only at 12 hours. (author)

  16. Study of the influence of gravity on the thermodynamic equilibrium of a liquid alloy, and on its solidification: application to eutectic Al-Ge and monotectic Al-In alloys

    International Nuclear Information System (INIS)

    Vinet, Bernard

    1981-01-01

    After having recalled the meaning of gravity, this research thesis addresses the study of movements within the Earth gravity field to assess accelerations for a centrifuged system, and to describe conditions which create weightlessness. The various actions of gravity on fluid phases are analysed by highlighting phenomena of convection and segregation. In a second part, the author addresses the issue of local order. The third part addresses the influence of gravity conditions on the distribution of components of a binary liquid alloy in thermodynamic equilibrium. The fourth part addresses experimental means. The next parts address the eutectic Al-Ge alloy and the monotectic Al-In alloy. Results obtained for liquid alloy are presented, and the author analyse segregations which appeared during solidification in gravity conditions between 40 and 100 g. The influence of these conditions of the structure of both alloys is then studied

  17. Effect of steady and time-harmonic magnetic fields on macrosegragation in alloy solidification

    Energy Technology Data Exchange (ETDEWEB)

    Incropera, F.P.; Prescott, P.J. [Purdue Univ., West Lafayette, IN (United States)

    1995-12-31

    Buoyancy-induced convection during the solidification of alloys can contribute significantly to the redistribution of alloy constituents, thereby creating large composition gradients in the final ingot. Termed macrosegregation, the condition diminishes the quality of the casting and, in the extreme, may require that the casting be remelted. The deleterious effects of buoyancy-driven flows may be suppressed through application of an external magnetic field, and in this study the effects of both steady and time-harmonic fields have been considered. For a steady magnetic field, extremely large field strengths would be required to effectively dampen convection patterns that contribute to macrosegregation. However, by reducing spatial variations in temperature and composition, turbulent mixing induced by a time-harmonic field reduces the number and severity of segregates in the final casting.

  18. Room Temperature Mechanical Properties of A356 Alloy with Ni Additions from 0.5 Wt to 2 Wt %

    Directory of Open Access Journals (Sweden)

    Lucia Lattanzi

    2018-03-01

    Full Text Available In recent years, the influence of Ni on high-temperature mechanical properties of casting Al alloys has been extensively examined in the literature. In the present study, room temperature mechanical properties of an A356 alloy with Ni additions from 0.5 to 2 wt % were investigated. The role of Ni-based compounds and eutectic Si particles in reinforcing the Al matrix was studied with image analysis and was then related to tensile properties and microhardness. In the as-cast condition, the formation of the 3D network is not sufficient to determine an increase of mechanical properties of the alloys since fracture propagates by cleavage through eutectic Si particles and Ni aluminides or by the debonding of brittle phases from the aluminum matrix. After T6 heat treatment the increasing amount of Ni aluminides, due to further addition of Ni to the alloy, together with their brittle behavior, leads to a decrease of yield strength, ultimate tensile strength, and Vickers microhardness. Despite the fact that Ni addition up to 2 wt % hinders spheroidization of eutectic Si particles during T6 heat treatment, it also promotes the formation of a higher number of brittle Ni-based compounds that easily promote fracture propagation.

  19. Acoustic emission from a solidifying aluminum-lithium alloy

    Science.gov (United States)

    Henkel, D. P.; Wood, J. D.

    1992-01-01

    Physical phenomena associated with the solidification of an AA2090 Al-Li alloy have been characterized by AE methods. Repeatable patterns of AE activity as a function of solidification time are recorded and explained for ultrahigh-purity (UHP) aluminum and an Al-4.7 wt pct Cu binary alloy, in addition to the AA2090 Al-Li alloy, by the complementary utilization of thermal, AE, and metallographic methods. One result shows that the solidification of UHP aluminum produces one discrete period of high AE activity as the last 10 percent of solid forms.

  20. Phase-field simulation of solidification in multicomponent alloys coupled with thermodynamic and diffusion mobility databases

    International Nuclear Information System (INIS)

    Zhang Ruijie; Jing Tao; Jie Wanqi; Liu Baicheng

    2006-01-01

    To simulate quantitatively the microstructural evolution in the solidification process of multicomponent alloys, we extend the phase-field model for binary alloys to multicomponent alloys with consideration of the solute interactions between different species. These interactions have a great influence not only on the phase equilibria but also on the solute diffusion behaviors. In the model, the interface region is assumed to be a mixture of solid and liquid with the same chemical potential, but with different compositions. The simulation presented is coupled with thermodynamic and diffusion mobility databases, which can accurately predict the phase equilibria and the solute diffusion transportation in the whole system. The phase equilibria in the interface and other thermodynamic quantities are obtained using Thermo-Calc through the TQ interface. As an example, two-dimensional computations for the dendritic growth in Al-Cu-Mg ternary alloy are performed. The quantitative solute distributions and diffusion matrix are obtained in both solid and liquid phases

  1. Morphological variants of carbides of solidification origin in the rapidly solidified powder particles of hypereutectic iron alloy

    International Nuclear Information System (INIS)

    Kusy, M.; Grgac, P.; Behulova, M.; Vyrostkova, A.; Miglierini, M.

    2004-01-01

    The paper deals with the analysis of the morphological variants of solidification microstructures and vanadium rich M 4 C 3 carbide phases in the rapidly solidified (RS) powder particles from hypereutectic Fe-C-Cr-V alloy prepared by the nitrogen gas atomisation. Five main types of solidification microstructures were identified in RS particles: microstructure with globular carbides, microstructure with globular and star-like carbides, microstructure with primary carbides in the centres of eutectic colonies, microstructure with eutectic colonies without primary carbides and microstructure with eutectic spherulites. Based on the morphological features of carbide phases and the thermal history of RS particles, the microstructures were divided into two groups - microstructures morphologically affected and non-affected during the post-recalescence period of solidification. Thermophysical reasons for the morphologically different M 4 C 3 carbide phases development in the RS powder particles are discussed

  2. Probing liquation cracking and solidification through modeling of momentum, heat, and solute transport during welding of aluminum alloys

    International Nuclear Information System (INIS)

    Mishra, S.; Chakraborty, S.; DebRoy, T.

    2005-01-01

    A transport phenomena-based mathematical model is developed to understand liquation cracking in weldments during fusion welding. Equations of conservation of mass, momentum, heat, and solute transport are numerically solved considering nonequilibrium solidification and filler metal addition to determine the solid and liquid phase fractions in the solidifying region and the solute distribution in the weld pool. An effective partition coefficient that considers the local interface velocity and the undercooling is used to simulate solidification during welding. The calculations show that convection plays a dominant role in the solute transport inside the weld pool. The predicted weld-metal solute content agreed well with the independent experimental observations. The liquation cracking susceptibility in Al-Cu alloy weldments could be reliably predicted by the model based on the computed solidifying weld-metal composition and solid fraction considering nonequilibrium solidification

  3. The solidification and structure of Al-17wt.%Si alloy modified with intermetallic phases containing Ti and Fe

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2011-10-01

    Full Text Available The article describes the process of casting and solidification of Al-17wt.%Si alloy that have been modified with composite powdercontaining the intermetallic phases of Ti and Fe. The chemical and phase composition of the applied modifier was described with thefollowingformula:FeAlx–TiAlx–Al2O3. Applying the method of thermal analysis ATD, the characteristic parameters of the solidificationprocess were determined, and exo-and endothermic effects of the modifying powder on the run of the silumin solidification curves wereobserved. By the methods of light, scanning, and X-ray microscopy, the structure of alloy and the chemical composition of the dispersionhardening precipitates were examined. A change in the morphology of Al-Si eutectic from the lamellar to fibrous type was reportedtogether with changes in the form of complex eutectics of an Al-Si-Ti and Al-Si-Fe type and size reduction of primary silicon crystals.

  4. Solidification with back-diffusion of irregular eutectics

    Directory of Open Access Journals (Sweden)

    M. Trepczyńska-Łent

    2008-10-01

    Full Text Available The definition of the α - parameter back-diffusion has been introduced in the work. The alternative models of solidification were describedtaking into consideration back-diffusion process. The possibility of using those models for eutectic alloys solidification is worthyof interest.

  5. Comparative study of solute trapping and Gibbs free energy changes at the phase interface during alloy solidification under local nonequilibrium conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sobolev, S. L., E-mail: sobolev@icp.ac.ru [Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)

    2017-03-15

    An analytical model has been developed to describe the influence of solute trapping during rapid alloy solidification on the components of the Gibbs free energy change at the phase interface with emphasis on the solute drag energy. For relatively low interface velocity V < V{sub D}, where V{sub D} is the characteristic diffusion velocity, all the components, namely mixing part, local nonequilibrium part, and solute drag, significantly depend on solute diffusion and partitioning. When V ≥ V{sub D}, the local nonequilibrium effects lead to a sharp transition to diffusionless solidification. The transition is accompanied by complete solute trapping and vanishing solute drag energy, i.e. partitionless and “dragless” solidification.

  6. Formation of bands of ultrafine beryllium particles during rapid solidification of Al-Be alloys: Modeling and direct observations

    International Nuclear Information System (INIS)

    Elmer, J.W.; Tanner, L.E.; Smith, P.M.; Wall, M.A.; Aziz, M.J.

    1994-01-01

    Rapid solidification of dilute hyper-eutectic and monotectic alloys sometimes produces a dispersion of ultrafine randomly-oriented particles that lie in arrays parallel to the advancing solidification front. The authors characterize this effect in Al-Be where Be-rich particles with diameters on the order of 10 nm form in arrays spaced approximately 25 nm apart, and they present a model of macroscopically steady state but microscopically oscillatory motion of the solidification front to explain this unusual microstructure. The proposed mechanism involves; (i) the build-up of rejected solute in a diffusional boundary layer which slows down the growing crystal matrix, (2) the boundary layer composition entering a metastable liquid miscibility gap, (3) homogeneous nucleation of solute rich liquid droplets in the boundary layer, and crystallization of these droplets, and (4) growth of the matrix past the droplets and its reformation into a planar interface. The size of the Be-rich particles is limited by the beryllium supersaturation in the diffusional boundary layer. A numerical model was developed to investigate this solidification mechanism, and the results of the model are in good agreement with experimental observations of rapidly solidified Al-5 at.% Be

  7. Matemathical description of solidification cooling curves of pure metals

    Directory of Open Access Journals (Sweden)

    Arno Müller

    1998-10-01

    Full Text Available The introduction of an "incubation time" to the Schwarz classical mathematical description of metals solidification, resulted in a new model called Modified Schwarz Model. By doing so it was possible to identify and quantify the "delay time" that separates the two heat waves traveling independently in a casting during the solidification: the Supercooled / Superheated Liquid and the Solid / Liquid. The thermal shock produced in the initial stage of the undercooling generation process, can be used as an important parameter in the forecasting of the solidification's behavior of pure metals and alloys, when changing mold's materials, pouring and ambient temperatures. The hypercooling proneness degree of metals and alloys, can also be calculated.

  8. Susceptibility of ternary aluminum alloys to cracking during solidification

    International Nuclear Information System (INIS)

    Liu, Jiangwei; Kou, Sindo

    2017-01-01

    The crack susceptibility map of a ternary Al alloy system provides useful information about which alloy compositions are most susceptible to cracking and thus should be avoided by using a filler metal with a significantly different composition. In the present study the crack susceptibility maps of ternary Al alloy systems were calculated based on the maximum |dT/d(f S ) 1/2 | as an index for the crack susceptibility, where T is temperature and f S fraction solid. Due to the complexity associated with ternary alloy solidification, commercial thermodynamic software Pandat and Al database PanAluminum, instead of analytical equations, were used to calculate f S as a function of T and hence the maximum |dT/d(f S ) 1/2 | for ternary Al-Mg-Si, Al-Cu-Mg and Al-Cu-Si alloy systems. A crack susceptibility map covering 121 alloy compositions was constructed for each of the three ternary alloy systems at each of the following three levels of back diffusion: no back diffusion, back diffusion under a 100 °C/s cooling rate, and back diffusion under 20° C/s. The location of the region of high crack susceptibility, which is the most important part of the map, was shown in each of the nine calculated maps. These locations were compared with those observed in crack susceptibility tests by previous investigators. With back diffusion considered, either under 20 or 100 °C/s, the agreement between the calculated and observed maps was good especially for Al-Mg-Si and Al-Cu-Mg. Thus, the maximum |dT/d(f S ) 1/2 | can be used as a crack susceptibility index to construct crack susceptibility maps for ternary Al alloys and to evaluate the effect of back diffusion on their crack susceptibility. - Graphical abstract: The crack susceptibility map of a ternary alloy system indicates the composition range most susceptible to cracking, which should be avoided in welding or casting. The crack susceptibility maps of ternary Al alloy systems Al-Mg-Si, Al-Cu-Mg and Al-Cu-Si were calculated based

  9. Multi-scale Modeling of Dendritic Alloy Solidification

    OpenAIRE

    Dagner, Johannes

    2009-01-01

    Solidification of metallic melts is one of the most important processes in material science. The microstructure, which is formed during freezing, determines the mechanical properties of the final product largely. Many physical phenomena influence the solidification process and hence the resulting microstructure. One important parameter is influence of melt flow, which may modify heat and species transport on a large range of length- and time-scales. On the micro-scale, it influences the conce...

  10. Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part I. Microstructural Characterization of Rapidly Solidified Solders

    Science.gov (United States)

    Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

    2016-12-01

    Particles of Cu x Al y in Sn-Cu-Al solders have previously been shown to nucleate the Cu6Sn5 phase during solidification. In this study, the number and size of Cu6Sn5 nucleation sites were controlled through the particle size refinement of Cu x Al y via rapid solidification processing and controlled cooling in a differential scanning calorimeter. Cooling rates spanning eight orders of magnitude were used to refine the average Cu x Al y and Cu6Sn5 particle sizes down to submicron ranges. The average particle sizes, particle size distributions, and morphologies in the microstructures were analyzed as a function of alloy composition and cooling rate. Deep etching of the samples revealed the three-dimensional microstructures and illuminated the epitaxial and morphological relationships between the Cu x Al y and Cu6Sn5 phases. Transitions in the Cu6Sn5 particle morphologies from faceted rods to nonfaceted, equiaxed particles were observed as a function of both cooling rate and composition. Initial solidification cooling rates within the range of 103 to 104 °C/s were found to be optimal for realizing particle size refinement and maintaining the Cu x Al y /Cu6Sn5 nucleant relationship. In addition, little evidence of the formation or decomposition of the ternary- β phase in the solidified alloys was noted. Solidification pathways omitting the formation of the ternary- β phase agreed well with observed room temperature microstructures.

  11. Real-time synchrotron x-ray observations of equiaxed solidification of aluminium alloys and implications for modelling

    Science.gov (United States)

    Prasad, A.; Liotti, E.; McDonald, S. D.; Nogita, K.; Yasuda, H.; Grant, P. S.; StJohn, D. H.

    2015-06-01

    Recently, in-situ observations were carried out by synchrotron X-ray radiography to observe the nucleation and growth in Al alloys during solidification. The nucleation and grain formation of a range of Al-Si and Al-Cu binary alloys were studied. When grain refiner was added to the alloys, the location of the nucleation events was readily observed. Once nucleation began it continued to occur in a wave of events with the movement of the temperature gradient across the field of view due to cooling. Other features observed were the settling of the primary phase grains in the Al-Si alloys and floating in the Al-Cu alloys, the effects of convection with marked fluctuation of the growth rate of the solid-liquid interface in the Al-Si alloys, and an absence of fragmentation. The microstructures are typical of those produced in the equiaxed zone of actual castings. These observations are compared with predictions arising from the Interdependence model. The results from this comparison have implications for further refinement of the model and simulation and modelling approaches in general. These implications will be discussed.

  12. Thermodynamic database of multi-component Mg alloys and its application to solidification and heat treatment

    Directory of Open Access Journals (Sweden)

    Guanglong Xu

    2016-12-01

    Full Text Available An overview about one thermodynamic database of multi-component Mg alloys is given in this work. This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-component (Mg–Ag–Al–Ca–Ce–Cu–Fe–Gd–K–La–Li–Mn–Na–Nd–Ni–Pr–Si–Sn–Sr–Th–Y–Zn–Zr system. First, the major computational and experimental tools to establish the thermodynamic database of Mg alloys are briefly described. Subsequently, among the investigated binary and ternary systems, representative binary and ternary systems are shown to demonstrate the major feature of the database. Finally, application of the thermodynamic database to solidification simulation and selection of heat treatment schedule is described.

  13. Mesoscopic simulation of dendritic growth observed in x-ray video microscopy during directional solidification of Al-Cu alloys

    International Nuclear Information System (INIS)

    Delaleau, Pierre; Beckermann, Christoph; Mathiesen, Ragnvald H.; Arnberg, Lars

    2010-01-01

    A mesoscopic model is developed to simulate microstructures observed in situ by X-ray video microscopy during directional solidification of Al-Cu alloys in a Hele-Shaw cell. In the model, a volume-averaged species conservation equation is solved to obtain the solute concentration and solid fraction fields, and an analytical stagnant film model is used to predict the motion of the dendrite envelopes. The model is carefully validated in several test cases. Then, the model is applied to simulate the columnar dendritic microstructures observed in the X-ray video microscopy experiments for two different alloy compositions. Reasonable agreement is found between the measured and predicted dendrite envelope shapes, solid fractions, and solute concentration fields. The predicted size of the mushy zone and the extent of the undercooled melt region ahead of the columnar front agree well with the in situ experimental observations. The simulation results show quantitative agreement with the internal solid fraction variations measured from the radiographs. The present model is also able to realistically simulate a primary dendrite trunk spacing adjustment that was observed in one of the experiments. Overall, the present study represents the first successful validation of a solidification model using real time, in situ data from an experiment with a metallic alloy. Considerable additional research is needed to account in the model for the effect of gravity driven melt convection. (author)

  14. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    Science.gov (United States)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  15. Interplay among solidification, microstructure, residual strain and hot tearing in B206 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    D’Elia, F., E-mail: f.delia10@gmail.com [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. East, Toronto, Ontario, Canada M5B 2K3 (Canada); Ravindran, C. [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard St. East, Toronto, Ontario, Canada M5B 2K3 (Canada); Sediako, D. [Canadian Neutron Beam Centre, Chalk River Laboratories, Chalk River, Ontario, Canada K0J 1J0 (Canada)

    2015-01-29

    Hot tearing is a complex phenomenon attributed to alloy solidification, microstructure and stress/strain development within a casting. In this research, the conditions associated with the formation of hot tears in B206 aluminum alloy were investigated. Neutron diffraction strain mapping was carried out on three B206 castings with varying levels of titanium (i.e. unrefined, 0.02 and 0.05 wt%). Titanium additions effectively reduced grain size and transformed grain morphology from coarse dendrites to fine globular grains. Further, thermal analysis suggested that grain refinement delayed the onset of dendrite coherency in B206 and therefore enhanced the duration of bulk liquid metal feeding for the refined casting conditions. As a result, the interactive effects of such factors resulted in a more uniform distribution of strain, and subsequent higher resistance to hot tearing for the grain refined castings.

  16. Microstructure, corrosion behavior and cytotoxicity of biodegradable Mg-Sn implant alloys prepared by sub-rapid solidification.

    Science.gov (United States)

    Zhao, Chaoyong; Pan, Fusheng; Zhao, Shuang; Pan, Hucheng; Song, Kai; Tang, Aitao

    2015-09-01

    In this study, biodegradable Mg-Sn alloys were fabricated by sub-rapid solidification, and their microstructure, corrosion behavior and cytotoxicity were investigated by using optical microscopy, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, X-ray diffraction, immersion test, potentiodynamic polarization test and cytotoxicity test. The results showed that the microstructure of Mg-1Sn alloy was almost equiaxed grain, while the Mg-Sn alloys with higher Sn content (Sn≥3 wt.%) displayed α-Mg dendrites, and the secondary dendrite arm spacing of the primary α-Mg decreased significantly with increasing Sn content. The Mg-Sn alloys consisted of primary α-Mg matrix, Sn-rich segregation and Mg2Sn phase, and the amount of Mg2Sn phases increased with increasing Sn content. Potentiodynamic polarization and immersion tests revealed that the corrosion rates of Mg-Sn alloys increased with increasing Sn content. Cytotoxicity test showed that Mg-1Sn and Mg-3Sn alloys were harmless to MG63 cells. These results of the present study indicated that Mg-1Sn and Mg-3Sn alloys were promising to be used as biodegradable implants. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Physical and welding metallurgy of Gd-enriched austenitic alloys for spent nuclear fuel applications. Part II, nickel base alloys

    International Nuclear Information System (INIS)

    Mizia, Ronald E.; Michael, Joseph Richard; Williams, David Brian; Dupont, John Neuman; Robino, Charles Victor

    2004-01-01

    The physical and welding a metallurgy of gadolinium- (Gd-) enriched Ni-based alloys has been examined using a combination of differential thermal analysis, hot ductility testing. Varestraint testing, and various microstructural characterization techniques. Three different matrix compositions were chosen that were similar to commercial Ni-Cr-Mo base alloys (UNS N06455, N06022, and N06059). A ternary Ni-Cr-Gd alloy was also examined. The Gd level of each alloy was ∼2 wt-%. All the alloys initiated solidification by formation of primary austenite and terminated solidification by a Liquid γ + Ni 5 Gd eutectic-type reaction at ∼1270 C. The solidification temperature ranges of the alloys varied from ∼100 to 130 C (depending on alloy composition). This is a substantial reduction compared to the solidification temperature range to Gd-enriched stainless steels (360 to 400 C) that terminate solidification by a peritectic reaction at ∼1060 C. The higher-temperature eutectic reaction that occurs in the Ni-based alloys is accompanied by significant improvements in hot ductility and solidification cracking resistance. The results of this research demonstrate that Gd-enriched Ni-based alloys are excellent candidate materials for nuclear criticality control in spent nuclear fuel storage applications that require production and fabrication of large amounts of material through conventional ingot metallurgy and fusion welding techniques

  18. Relationship Between Solidification Microstructure and Hot Cracking Susceptibility for Continuous Casting of Low-Carbon and High-Strength Low-Alloyed Steels: A Phase-Field Study

    Science.gov (United States)

    Böttger, B.; Apel, M.; Santillana, B.; Eskin, D. G.

    2013-08-01

    Hot cracking is one of the major defects in continuous casting of steels, frequently limiting the productivity. To understand the factors leading to this defect, microstructure formation is simulated for a low-carbon and two high-strength low-alloyed steels. 2D simulation of the initial stage of solidification is performed in a moving slice of the slab using proprietary multiphase-field software and taking into account all elements which are expected to have a relevant effect on the mechanical properties and structure formation during solidification. To account for the correct thermodynamic and kinetic properties of the multicomponent alloy grades, the simulation software is online coupled to commercial thermodynamic and mobility databases. A moving-frame boundary condition allows traveling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. From the simulation results, significant microstructure differences between the steel grades are quantitatively evaluated and correlated with their hot cracking behavior according to the Rappaz-Drezet-Gremaud (RDG) hot cracking criterion. The possible role of the microalloying elements in hot cracking, in particular of traces of Ti, is analyzed. With the assumption that TiN precipitates trigger coalescence of the primary dendrites, quantitative evaluation of the critical strain rates leads to a full agreement with the observed hot cracking behavior.

  19. Effect of carbon content on solidification behaviors and morphological characteristics of the constituent phases in Cr-Fe-C alloys

    International Nuclear Information System (INIS)

    Lin, Chi-Ming; Lai, Hsuan-Han; Kuo, Jui-Chao; Wu, Weite

    2011-01-01

    A combination of transmission electron microscopy, electron backscatter diffraction and wavelength dispersive spectrum has been used to identify crystal structure, grain boundary characteristic and chemical composition of the constituent phases in Cr-Fe-C alloys with three different carbon concentrations. Depending on the three different carbon concentrations, the solidification structures are found to consist of primary α-phase and [α + (Cr,Fe) 23 C 6 ] eutectic in Cr-18.4Fe-2.3 C alloy; primary (Cr,Fe) 23 C 6 and [α + (Cr,Fe) 23 C 6 ] eutectic in Cr-24.5Fe-3.8 C alloy and primary (Cr,Fe) 7 C 3 and [α + (Cr,Fe) 7 C 3 ] eutectic in Cr-21.1Fe-5.9 C alloy, respectively. The grain boundary analysis is useful to understand growth mechanism of the primary phase. The morphologies of primary (Cr,Fe) 23 C 6 and (Cr,Fe) 7 C 3 carbides are faceted structures with polygonal shapes, different from primary α-phase with dendritic shape. The primary (Cr,Fe) 23 C 6 and (Cr,Fe) 7 C 3 carbides with strong texture exist a single crystal structure and contain a slight low angle boundary, resulting in the polygonal growth mechanism. Nevertheless, the primary α-phase with relative random orientation exhibits a polycrystalline structure and comprises a massive high-angle boundary, caused by the dendritic growth mechanism. - Highlights: ► Microstructures of the as-clad Cr-based alloys are characterized by TEM. ► EBSD technique has been use to characterize the grain boundary of primary phases. ► We examine transitions in morphology about the primary phases. ► Morphologies of primary carbides are polygonal different from primary α-phase. ► Solidification structures rely on C concentrations in Cr-Fe-C alloy.

  20. Phase-field modeling of microstructural pattern formation during directional solidification of peritectic alloys without morphological instability

    International Nuclear Information System (INIS)

    Shing Lo, Tak; Karma, Alain; Plapp, Mathis

    2001-01-01

    During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio (G/v p ), one solid phase usually outgrows and covers the other phase, leading to a cellular-dendritic array structure closely analogous to the one formed during monophase solidification of a dilute binary alloy. In contrast, when G/v p is large enough for both phases to be morphologically stable, the formation of the microstructure becomes controlled by a subtle interplay between the nucleation and growth of the two solid phases. The structures that have been observed in this regime (in small samples where convection effects are suppressed) include alternate layers (bands) of the parent and peritectic phases perpendicular to the growth direction, which are formed by alternate nucleation and lateral spreading of one phase onto the other as proposed in a recent model [R. Trivedi, Metall. Mater. Trans. A 26, 1 (1995)], as well as partially filled bands (islands), where the peritectic phase does not fully cover the parent phase which grows continuously. We develop a phase-field model of peritectic solidification that incorporates nucleation processes in order to explore the formation of these structures. Simulations of this model shed light on the morphology transition from islands to bands, the dynamics of spreading of the peritectic phase on the parent phase following nucleation, which turns out to be characterized by a remarkably constant acceleration, and the types of growth morphology that one might expect to observe in large samples under purely diffusive growth conditions

  1. Application of the thermodynamic extremal principle to phase-field modeling of non-equilibrium solidification in multi-component alloys

    International Nuclear Information System (INIS)

    Zhang, Xiao; Wang, Haifeng; Kuang, Wangwang; Zhang, Jianbao

    2017-01-01

    Modeling of non-equilibrium solidification in multi-component alloys is of singular importance in microstructure control, which however owing to the complex systems with complex additional constraints is still an open problem. In this work, the thermodynamic extremal principle was applied to solve the complex additional constraints self-consistently in thermodynamics. Consequently, short-range solute redistribution and long-range solute diffusion that share the same mobility are integrated naturally into the solute diffusion equations, thus avoiding the introduction of additional kinetic coefficients (e.g. interface permeability) to describe solute redistribution. Application to the non-equilibrium solidification of Al-Si-Cu alloys shows that anomalous solute trapping and anomalous solute profiles within the diffuse interface could occur, thus highlighting the important effect of the interaction among the component elements on the interface kinetics. The current phase-field model might be preferred for simulations not only because of its simplest form of evolution equations but also its feasibility to increase the simulation efficiency by the “thin interface limit” analysis.

  2. effect of pre effect of pre-ageing thermal conditions on the corrosion

    African Journals Online (AJOL)

    eobe

    solution heat treatment and ageing) and Double thermal ageing treatmen ... Corrosion of aluminium alloys lead to impairment of ... of passive protection by coating or by means of active ... The Al-Si-Mg alloy with the chemical composition as .... Heat. Transfer and Solidification Behavior of Modified A356 alloy. Journal of ...

  3. Directional solidification of filamentary shapes of Pb--Cd and Pb--Sn eutectic alloys

    International Nuclear Information System (INIS)

    Dhindaw, B.K.; Verhoeven, J.D.; Spencer, C.R.; Gibson, E.D.

    1978-01-01

    Eutectic alloys of Pb--Cd and Pb--Sn were directionally solidified as thin filamentary strips contained in stainless steel and quartz capillaries. As the solidification rate increased the filament width, w, had to be reduced to maintain complete alignment of the lamellae clear across the filament. It was determined that in order to achieve complete alignment the ratio of filament width to lamellar spacing, w/lambda had to be less than about 30. Experiments were carried out at rates of 2-400 μm/s and at temperature gradients of 130 and 320 0 C/cm

  4. Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hosch, Timothy [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  5. Application of shortened heat treatment cycles on A356 automotive brake calipers with respective globular and dendritic microstructures

    CSIR Research Space (South Africa)

    Moller, H

    2010-09-01

    Full Text Available The conventional casting alloy A356 is probably one of the most popular alloys used for semi-solid metal (SSM) forming. This is due to its high fluidity and good castability. This alloy can be heat treated alternatively to the T4, T5 or T6 temper...

  6. Strain Measurement in Aluminium Alloy during the Solidification Process Using Embedded Fibre Bragg Gratings.

    Science.gov (United States)

    Weraneck, Klaus; Heilmeier, Florian; Lindner, Markus; Graf, Moritz; Jakobi, Martin; Volk, Wolfram; Roths, Johannes; Koch, Alexander W

    2016-11-04

    In recent years, the observation of the behaviour of components during the production process and over their life cycle is of increasing importance. Structural health monitoring, for example of carbon composites, is state-of-the-art research. The usage of Fibre Bragg Gratings (FBGs) in this field is of major advantage. Another possible area of application is in foundries. The internal state of melts during the solidification process is of particular interest. By using embedded FBGs, temperature and stress can be monitored during the process. In this work, FBGs were embedded in aluminium alloys in order to observe the occurring strain. Two different FBG positions were chosen in the mould in order to compare its dependence. It was shown that FBGs can withstand the solidification process, although a compression in the range of one percent was measured, which is in agreement with the literature value. Furthermore, different lengths of the gratings were applied, and it was shown that shorter gratings result in more accurate measurements. The obtained results prove that FBGs are applicable as sensors for temperatures up to 740 °C.

  7. Simulation of microstructural evolution in directional solidification of Ti-45at.%Al alloy using cellular automaton method

    Directory of Open Access Journals (Sweden)

    Wang Kuangfei

    2010-02-01

    Full Text Available The microstructural evolution of Ti-45 at.%Al alloy during directional solidification was simulated by applying a solute diffusion controlled solidification model. The obtained results have shown that under high thermal gradients the stable primary spacing can be adjusted via branching or competitive growth. For dendritic structures formed under a high thermal gradient, the secondary dendrite arms are developed not very well in many cases due to the branching mechanism under a constrained dendritic growth condition. Furthermore, it has been observed that, with increasing pulling velocity, there exists a cell/dendrite transition region consisting of cells and dendrites, which varies with the thermal gradient in a contradicting way, i.e. increase of the thermal gradient leading to the decrease of the range of the transition region. The simulations agree reasonably well with experiment results.

  8. Calculation of solidification microstructure maps for the system Al-Fe-Si

    International Nuclear Information System (INIS)

    Gilgien, P.

    1996-01-01

    Computer programs have been developed in order to calculate solidification microstructure maps for binary and ternary alloys. These programs are based on recent analytical models for the constrained growth of dendrites and eutectics. Due to the importance of phase diagrams data, programs for the calculation of growth kinetics are coupled with ThermoCalc, a commercial software for phase diagram calculations. These programs have been used to calculate a solidification microstructure map for the Al-Fe system from 0 to 4 at%Fe. Comparison of the calculated results with an experimental solidification microstructure map from the literature shows that all microstructure transitions were predicted. Nevertheless there remain significant discrepancies between some calculated and experimental transition velocities. The programs were also used to calculate solidification microstructure maps in the Al-rich corner of the Al-Fe-Si system (0 to 8 at% Fe and 0 to 8 at% Si). In this case also, calculated results were in satisfactory agreement with experimental solidification microstructure maps, although the comparison was only partial since experimental ternary microstructure maps are less complete than for the binary system, and because the available thermodynamic database does not, as yet, include metastable phases. Laser surface remelting experiments were carried out on an Al-4 at% Fe alloy in order to link results from the literature, obtained at high solidification rates by laser surface remelting and at low solidification rates by Bridman experiments. Finally, Bridman experiments were carried out with an Al-2.63 wt% Fe alloy in order to determine the critical velocity at which a planar Al-Al 13 Fe 4 eutectic front is destabilised in a cellular eutectic by a small amount of Si. The critical solidification velocity thus obtained was in agreement with a criterion of constitutional undercooling. (author) figs., tabs., refs

  9. Optimisation of the T6 heat treatment of rheocast alloy A356

    CSIR Research Space (South Africa)

    Moller, H

    2007-11-01

    Full Text Available popular solution heat treatment employed for SSM processed A356 is 6 hours at 540oC (i.e. similar to that used for permanent mould cast A356)6,7,9. Only limited work has been performed on the optimisation of the solution heat treatment of SSM processed... was not adequately studied by either Dewhirst8 or Rosso and Actis Grande5. The optimum artificial aging heat treatment proposed in both papers5,8 is 180oC for 4 hours. This was also confirmed in this work, but importantly, this applies only when natural aging...

  10. Effect of Rapid Solidification and Addition of Cu3P on the Mechanical Properties of Hypereutectic Al-Si Alloys

    OpenAIRE

    Suárez-Rosales,Miguel Ángel; Pinto-Segura,Raúl; Palacios-Beas,Elia Guadalupe; Hernández-Herrera,Alfredo; Chávez-Alcalá,José Federico

    2016-01-01

    The combined processes; rapid solidification, addition of Cu3P compound and heat treatments to improve the mechanical properties of the hypereutectic Al-13Si, Al-20Si and Al-20Si-1.5Fe-0.7Mn alloys (in wt. %) was studied. Optical microscopy and scanning electron microscopy were used to characterize the microstructures. The mechanical properties were evaluated by tensile tests. It was found that the cooling rate (20-50°C/s) used to solidify the alloys plus the addition of Cu3P compound favored...

  11. Relation between feeding mechanisms and solidification mode in 380 aluminium alloy with different iron contents

    International Nuclear Information System (INIS)

    Tovio, D. O.; Gonzalez, A.C.; Mugica, G. W.; Cuyas, J. C.

    2003-01-01

    In the present work the effect of iron (0.15, 0.42 and 0.86%) content in feeding mechanisms for 380 aluminium alloy has been studied. The feeding capacity has been evaluated by a device that produces a barrier removable to allowing the movement of the inter dendritic liquid. The results show the flow of different quantity of liquid, it depends of the temperature of operating the device and of the iron content. For minimum and maximum iron content, the inter dendritic and bursts feeding mechanisms are fundamentally involved, for 0.42% of iron the feeding mechanisms was the inter dendritic. The authors establish this behavior by the solidification mode of alloy, which promotes the presence of particles of Si or plates of b-Al 3 FeDi phase, in the inter dendritic channels and produce the different feeding mechanisms. (Author) 15 refs

  12. Solidification in Multicomponent Multiphase Systems (SIMMS)

    Science.gov (United States)

    Rex, S.; Hecht, U.

    2005-06-01

    The multiphase microstructures that evolve during the solidification of multicomponent alloys are attracting widespread interest for industrial applications and fundamental research.Thermodynamic databases are now well-established for many alloy systems. Thermodynamic calculations provide all the required information about phase equilibria, forming an integral part of both dedicated and comprehensive microstructure models. Among the latter, phase-field modelling has emerged as the method of choice. Solidification experiments are intended to trigger model development or to serve as benchmarks for model validation. For benchmarking, microgravity conditions offer a unique opportunity for avoiding buoyancy-induced convection and buoyancy forces in bulk samples. However, diffusion and the free-energy of interfaces and its anisotropy need to be determined.The measurement of chemical diffusivities in the liquid state can equally benefit from microgravity experiments.

  13. Effect of thermodiffusion on the fluid flow, heat transfer, and solidification of molten metal alloys

    Directory of Open Access Journals (Sweden)

    E. Jafar-Salehi

    2016-03-01

    Full Text Available In this paper, a transient Finite Element (FE method has been employed to solve the transport equations to investigate the heat transfer and fluid flow and the effect of thermodiffusion on vertical solidification of a binary molten metal alloy, forming a rod. The binary system considered in this study is SnBi composed of 65% Sn and 35% Bi subjected to bottom cooling. It is found that the flow of molten metal at the boundary of the mushy region plays an important role in the shape and geometry of the zone. The presence of thermodiffusion shows considerable difference in the composition of the solidified rod, compared with the one without considering the effect of thermodiffusion. Thermodiffusion also causes a faster solidification and a more uniform concentration distribution. The results of this study may be extended to similar binary and multicomponent systems in which a temperature gradient exists and the Soret coefficient is large enough so as to affect the fluid flow and concentration of the species.

  14. Erosion-corrosion and surface protection of A356 Al/ZrO2 composites produced by vortex and squeeze casting

    International Nuclear Information System (INIS)

    El-Khair, M.T. Abou; Aal, A. Abdel

    2007-01-01

    Erosive-corrosive wear behavior of Al-Si-Mg (A356 Al) alloy and its composite reinforced by ZrO 2 and produced by vortex and squeeze techniques has been studied in water containing 40% sand slurry. The worn surfaces of investigated alloys have been studied and the mechanism of material removal from the specimen surface was examined to be associated with number of subsequent and repetitive stages. The possibility of Ni coating for Al composites by electrochemical deposition is investigated. The surface layer was characterized by microhardness measurements, optical microscope, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) analysis. The electrochemical results obtained from polarization studies for Ni-coated, A356 Al alloy and composites in 3.5% sodium chloride solution indicated higher protection exhibited by Ni coatings due to the nickel properties. The squeezed cast composite is characterized by high corrosion and wear resistance comparing the composite produced by vortex process. This study revealed that the Ni-coated materials provide higher abrasive resistance and therefore a longer service life compared to A356 Al-ZrO 2

  15. Formation of Al15Mn3Si2 Phase During Solidification of a Novel Al-12%Si-4%Cu-1.2%Mn Heat-Resistant Alloy and Its Thermal Stability

    Science.gov (United States)

    Suo, Xiaojing; Liao, Hengcheng; Hu, Yiyun; Dixit, Uday S.; Petrov, Pavel

    2018-02-01

    The formation of Al15Mn3Si2 phase in Al-12Si-4Cu-1.2Mn (wt.%) alloy during solidification was investigated by adopting CALPHAD method and microstructural observation by optical microscopy, SEM-EDS, TEM-EDS/SAD and XRD analysis; SEM fixed-point observation method was applied to evaluate its thermal stability. As-cast microstructural observation consistently demonstrates the solidification sequence of the studied alloy predicted by phase diagram calculation. Based on the phase diagram calculation, SEM-EDS, TEM-EDS/SAD and XRD analysis, as well as evidences on Al-Si-Mn-Fe compounds from the literature, the primary and eutectic Mn-rich phases with different morphologies in the studied alloy are identified to be Al15Mn3Si2 that has a body-centered cubic (BCC) structure with a lattice constant of a = 1.352 nm. SEM fixed-point observation and XRD analysis indicate that Al15Mn3Si2 phase has more excellent thermal stability at high temperature than that of CuAl2 phase and can serve as the major strengthening phase in heat-resistant aluminum alloy that has to face a high-temperature working environment. Results of tension test show that addition of Mn can improve the strength of Al-Si-Cu alloy, especially at elevated temperature.

  16. Solidification microstructure of centrifugally cast Inconel 625

    Directory of Open Access Journals (Sweden)

    Silvia Barella

    2017-07-01

    Full Text Available Centrifugal casting is a foundry process allowing the production of near net-shaped axially symmetrical components. The present study focuses on the microstructural characterization of centrifugally cast alloys featuring different chemical compositions for the construction of spheres applied in valves made of alloy IN625 for operation at high pressure. Control of the solidification microstructure is needed to assure the reliability of the castings. Actually, a Ni-base superalloy such as this one should have an outstanding combination of mechanical properties, high temperature stability and corrosion resistance. Alloys such as IN625 are characterised by a large amount of alloying elements and a wide solidification range, so they can be affected by micro-porosity defects, related to the shrinkage difference between the matrix and the secondary reinforcing phases (Nb-rich carbides and Laves phase. In this study, the microstructure characterization was performed as a function of the applied heat treatments and it was coupled with a calorimetric analysis in order to understand the mechanism ruling the formation of micro-porosities that can assure alloy soundness. The obtained results show that the presence of micro-porosities is governed by morphology and by the size of the secondary phases, and the presence of the observed secondary phases is detrimental to corrosion resistance.

  17. Effect of Y additions on the solidification behavior of a copper mold cast CuZrAl alloy with high oxygen content

    International Nuclear Information System (INIS)

    Coury, F.G.; Batalha, W.; Botta, W.J.; Bolfarini, C.; Kiminami, C.S.

    2014-01-01

    Bulk glassy samples of the CuAlZr system were produced by copper mold casting in the form of wedges with different amounts of yttrium (0 , 0.3 and 2 at%) , the processing conditions led to high oxygen contents on the samples (1000ppm). A reportedly good glass-former composition was chosen as the base alloy, it’s nominal composition is Cu47Zr45Al8. This study aimed to understand the influence of oxygen and yttrium in the solidification of these alloys. The samples were analyzed by scanning and transmission electron microscopy, differential scanning calorimetry and X-Ray diffraction. The sequence of formation of crystalline phases in these alloys was determined as a function of the different cooling rates inherent in the process. It was observed that the formation of CuZr2 phase was inhibited in samples with Y allowing the production of a fully glassy 8mm. (author)

  18. Influence of Alloy and Solidification Parameters on Grain Refinement in Aluminum Weld Metal due to Inoculation

    Energy Technology Data Exchange (ETDEWEB)

    Schempp, Philipp [BAM, Germany; Tang, Z. [BIAS, Germany; Cross, Carl E. [Los Alamos National Laboratory; Seefeld, T. [BIAS, Germany; Pittner, A. [BAM, Germany; Rethmeier, M. [BAM, Germany

    2012-06-28

    The goals are: (1) Establish how much Ti/B grain refiner is need to completely refine aluminum weld metal for different alloys and different welding conditions; (2) Characterize how alloy composition and solidification parameters affect weld metal grain refinement; and (3) Apply relevant theory to understand observed behavior. Conclusions are: (1) additions of Ti/B grain refiner to weld metal in Alloys 1050, 5083, and 6082 resulted in significant grain refinement; (2) grain refinement was more effective in GTAW than LBW, resulting in finer grains at lower Ti content - reason is limited time available for equiaxed grain growth in LBW (inability to occlude columnar grain growth); (3) welding travel speed did not markedly affect grain size within GTAW and LBW clusters; and (4) application of Hunt CET analysis showed experimental G to be on the order of the critical G{sub CET}; G{sub CET} was consistently higher for GTAW than for LBW.

  19. Microstructural investigation of D2 tool steel during rapid solidification

    Science.gov (United States)

    Delshad Khatibi, Pooya

    Solidification is considered as a key processing step in developing the microstructure of most metallic materials. It is, therefore, important that the solidification process can be designed and controlled in such a way so as to obtain the desirable properties in the final product. Rapid solidification refers to the system's high undercooling and high cooling rate, which can yield a microstructure with unique chemical composition and mechanical properties. An area of interest in rapid solidification application is high-chromium, high-carbon tool steels which experience considerable segregation of alloying elements during their solidification in a casting process. In this dissertation, the effect of rapid solidification (undercooling and cooling rate) of D2 tool steel on the microstructure and carbide precipitation during annealing was explored. A methodology is described to estimate the eutectic and primary phase undercooling of solidifying droplets. The estimate of primary phase undercooling was confirmed using an online measurement device that measured the radiation energy of the droplets. The results showed that with increasing primary phase and eutectic undercooling and higher cooling rate, the amount of supersaturation of alloying element in metastable retained austenite phase also increases. In the case of powders, the optimum hardness after heat treatment is achieved at different temperatures for constant periods of time. Higher supersaturation of austenite results in obtaining secondary hardness at higher annealing temperature. D2 steel ingots generated using spray deposition have high eutectic undercooling and, as a result, high supersaturation of alloying elements. This can yield near net shape D2 tool steel components with good mechanical properties (specifically hardness). The data developed in this work would assist in better understanding and development of near net shape D2 steel spray deposit products with good mechanical properties.

  20. Directional solidification and characterization of the Al Nb2 - Al3 Nb eutectic system

    International Nuclear Information System (INIS)

    Trevisan, Eduardo A.O.; Andreotti, Fabio; Caram, Rubens

    1996-01-01

    The manufacturing of components to operate at high temperatures requires the use of metallic materials which can keep satisfactory mechanical and chemical properties, even at temperatures beyond 1000 deg C. An interesting alternative is the use of directionally solidified eutectic alloys. The eutectic alloy solidification makes possible the production of 'in situ' composite. A potentially useful system for manufacturing structural materials is the Al-Nb eutectic system. The aim of this work is to present the directional solidification of the Al-Nb eutectic alloy. (author)

  1. Directional Solidification and Liquidus Projection of the Sn-Co-Cu System

    Science.gov (United States)

    Chen, Sinn-Wen; Chang, Jui-Shen; Pan, Kevin; Hsu, Chia-Ming; Hsu, Che-Wei

    2013-04-01

    This study investigates the Sn-Co-Cu ternary system, which is of interest to the electronics industry. Ternary Sn-Co-Cu alloys were prepared, their as-solidified microstructures were examined, and their primary solidification phases were determined. The primary solidification phases observed were Cu, Co, Co3Sn2, CoSn, CoSn2, Cu6Sn5, Co3Sn2, γ, and β phases. Although there are ternary compounds reported in this ternary system, no ternary compound was found as the primary solidification phase. The directional solidification technique was applied when difficulties were encountered using the conventional quenching method to distinguish the primary solidification phases, such as Cu6Sn5, Cu3Sn, and γ phases. Of all the primary solidification phases, the Co3Sn2 and Co phases have the largest compositional regimes in which alloys display them as the primary solidification phases. There are four class II reactions and four class III reactions. The reactions with the highest and lowest reaction temperatures are both class III reactions, and are L + CoSn2 + Cu6Sn5 = CoSn3 at 621.5 K (348.3 °C) and L + Co3Sn2 + CoSn = Cu6Sn5 at 1157.8 K (884.6 °C), respectively.

  2. Effect of alloying elements on the isothermal solidification during TLP bonding of SS 410 and SS 321 using a BNi-2 interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Arafin, M.A. [Department of Mechanical and Industrial Engineering, Concordia University, Montreal, H3G 1M8 (Canada)], E-mail: ma_arafi@encs.concordia.ca; Medraj, M. [Department of Mechanical and Industrial Engineering, Concordia University, Montreal, H3G 1M8 (Canada)], E-mail: mmedraj@encs.concordia.ca; Turner, D.P. [Metallurgical Planning, Pratt and Whitney Canada, Longueuil, Que., J4G 1A1 (Canada)], E-mail: Daniel.P.Turner@pwc.ca; Bocher, P. [Department de Genie Mecanique, Ecole de Technologie Superieure, Montreal, H3C 1K3 (Canada)], E-mail: Philippe.Bocher@etsmtl.ca

    2007-11-15

    The random diffusion of solute atoms during transient liquid phase (TLP) bonding of SS 410 and 321 with nickel-based brazing filler alloy BNi-2 have been modeled using Random Walk Modeling technique. Cumulative probability distributions and probability density functions of isothermal solidification times have been calculated for different process conditions and verified with experimental data. The solubility limit of boron has been found to have decreased from 0.3 at.% at higher temperature bonding operations (1358-1394 K) because of substantial iron-rich base metal dissolution when SS 410 was used as base metals; whereas it remained unchanged for SS 321/BNi-2 combination because of high concentrations of nickel and chromium in the base metal. Silicon diffusion model, based on the EDS analysis, also predicted the isothermal solidification times reasonably well.

  3. The effect of the melt spinning processing parameters on the solidification structures in Ti-30 at.% Ni-20 at.% Cu shape memory alloys

    International Nuclear Information System (INIS)

    Kim, Yeon-wook; Yun, Young-mok; Nam, Tae-hyun

    2006-01-01

    Solidification structures and shape memory characteristics of Ti-30 at.% Ni-20 at.% Cu alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change the ejection temperature of the melt from 1350 to 1500 deg. C and the velocity of cooling wheel from 33 to 55 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on solidification structures and martensitic transformation behaviors is discussed

  4. Controlled Directional Solidification of Aluminum - 7 wt Percent Silicon Alloys: Comparison Between Samples Processed on Earth and in the Microgravity Environment Aboard the International Space Station

    Science.gov (United States)

    Grugel, Richard N.; Tewari, Surendra N.; Erdman, Robert G.; Poirier, David R.

    2012-01-01

    An overview of the international "MIcrostructure Formation in CASTing of Technical Alloys" (MICAST) program is given. Directional solidification processing of metals and alloys is described, and why experiments conducted in the microgravity environment aboard the International Space Station (ISS) are expected to promote our understanding of this commercially relevant practice. Microstructural differences observed when comparing the aluminum - 7 wt% silicon alloys directionally solidified on Earth to those aboard the ISS are presented and discussed.

  5. Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 1: Formulation and analysis

    Science.gov (United States)

    Maples, A. L.; Poirier, D. R.

    1980-01-01

    The physical and numerical formulation of a model for the horizontal solidification of a binary alloy is described. It can be applied in an ingot. The major purpose of the model is to calculate macrosegregation in a casting ingot which results from flow of interdendritic liquid during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, was modeled as flow through a porous medium. The symbols used are defined. The physical formulation of the problem leading to a set of equations which can be used to obtain: (1) the pressure field; (2) the velocity field: (3) mass flow and (4) solute flow in the solid plus liquid zone during solidification is presented. With these established, the model calculates macrosegregation after solidification is complete. The numerical techniques used to obtain solution on a computational grid are presented. Results, evaluation of the results, and recommendations for future development of the model are given. The macrosegregation and flow field predictions for tin-lead, aluminum-copper, and tin-bismuth alloys are included as well as comparisons of some of the predictions with published predictions or with empirical data.

  6. Atomic mobility in liquid and fcc Al-Si-Mg-RE (RE = Ce, Sc) alloys and its application to the simulation of solidification processes in RE-containing A357 alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zhao; Zhang, Lijun [Central South Univ., Changsha (China). State Key Lab of Powder Metallurgy; Tang, Ying [Thermo-Calc Software AB, Solna (Sweden)

    2017-06-15

    This paper first provides a critical review of experimental and theoretically-predicted diffusivities in both liquid and fcc Al-Si-Mg-RE (RE = Ce, Sc) alloys as-reported by previous researchers. The modified Sutherland equation is then employed to predict self- and impurity diffusivities in Al-Si-Mg-RE melts. The self-diffusivity of metastable fcc Sc is evaluated via the first-principles computed activation energy and semi-empirical relations. Based on the critically-reviewed and presently evaluated diffusivity information, atomic mobility descriptions for liquid and fcc phases in the Al-Si-Mg-RE systems are established by means of the Diffusion-Controlled TRAnsformation (DICTRA) software package. Comprehensive comparisons show that most of the measured and theoretically-predicted diffusivities can be reasonably reproduced by the present atomic mobility descriptions. The atomic mobility descriptions for liquid and fcc Al-Si-Mg-RE alloys are further validated by comparing the model-predicted differential scanning calorimetry curves for RE-containing A357 alloys during solidification against experimental data. Detailed analysis of the curves and microstructures in RE-free and RE-containing A357 alloys indicates that both Ce and Sc can serve as the grain refiner for A357 alloys, and that the grain refinement efficiency of Sc is much higher.

  7. Atomic mobility in liquid and fcc Al-Si-Mg-RE (RE = Ce, Sc) alloys and its application to the simulation of solidification processes in RE-containing A357 alloys

    International Nuclear Information System (INIS)

    Lu, Zhao; Zhang, Lijun

    2017-01-01

    This paper first provides a critical review of experimental and theoretically-predicted diffusivities in both liquid and fcc Al-Si-Mg-RE (RE = Ce, Sc) alloys as-reported by previous researchers. The modified Sutherland equation is then employed to predict self- and impurity diffusivities in Al-Si-Mg-RE melts. The self-diffusivity of metastable fcc Sc is evaluated via the first-principles computed activation energy and semi-empirical relations. Based on the critically-reviewed and presently evaluated diffusivity information, atomic mobility descriptions for liquid and fcc phases in the Al-Si-Mg-RE systems are established by means of the Diffusion-Controlled TRAnsformation (DICTRA) software package. Comprehensive comparisons show that most of the measured and theoretically-predicted diffusivities can be reasonably reproduced by the present atomic mobility descriptions. The atomic mobility descriptions for liquid and fcc Al-Si-Mg-RE alloys are further validated by comparing the model-predicted differential scanning calorimetry curves for RE-containing A357 alloys during solidification against experimental data. Detailed analysis of the curves and microstructures in RE-free and RE-containing A357 alloys indicates that both Ce and Sc can serve as the grain refiner for A357 alloys, and that the grain refinement efficiency of Sc is much higher.

  8. Phase selection and microstructure in directional solidification of glass forming Pd-Si-Cu alloys

    Science.gov (United States)

    Huo, Yang

    Phase selection and microstructure formation during the rapid solidification of alloy melts has been a topic of substantial interest over the last several decades, attributed mainly to the access to novel structures involving metastable crystalline and non-crystalline phases. In this work, Bridgeman type directional solidification was conducted in Pd-Si-Cu glass forming system to study such cooling rate dependent phase transition and microstructure formation. The equilibrium state for Pd-Si-Cu ternary system was investigated through three different works. First of all, phase stabilities for Pd-Si binary system was accessed with respects of first-principles and experiments, showing Pd5Si, Pd9Si2, Pd3Si and Pd 2Si phase are stable all way to zero Kevin while PdSi phase is a high temperature stable phase, and Pd2Si phase with Fe2P is a non-stoichiometry phase. A thermodynamic database was developed for Pd-Si system. Second, crystal structures for compounds with ternary compositions were studied by XRD, SEM and TEM, showing ordered and disordered B2/bcc phases are stable in Pd-rich part. At last, based on many phase equilibria and phase transitions data, a comprehensive thermodynamic discrption for Pd-Si-Cu ternary system was first time to be developed, from which different phase diagrams and driving force for kinetics can be calculated. Phase selection and microstructure formation in directional solidification of the best glass forming composition, Pd 77.5Si16.5Cu6, in this system with growth velocities from 0.005 to 7.5mm/s was systematically studied and the solidification pathways at different conditions were interpreted from thermodynamic simulation. The results show that for growth velocities are smaller than 0.1mm/s Pd 3Si phase is primary phase and Pd9Si2 phase is secondary phase, the difficulty for Pd9Si2 phase nucleation gives rise to the formation of two different eutectic structure. For growth velocities between 0.4 and 1mm/s, instead of Pd3Si phase, Pd9Si2

  9. Welding Metallurgy of Alloy HR-160

    International Nuclear Information System (INIS)

    DuPont, J.N.; Michael, J.R.; Newbury, B.D.

    1999-01-01

    The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in alloy HR-160 was investigated by Varestraint testing, differential thermal analysis, and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 degC and initiated solidification by a primary L - γ reaction in which Ni, Si, and Ti segregated to the interdendritic liquid and Co segregated to the γ dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at ∼ 1162 degC by a eutectic-type L - [γ+ (Ni,Co) 16 (Ti,Cr) 6 Si 7 ] reaction. The (Ni,Co) 16 (Ti,Cr) 6 Si 7 phase is found to be analogous to the G phase which forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found to exist between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [γ +(Ni,Co) l6 (Ti,Cr) 6 Si 7 ] eutectic-typr constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 degC and the presence of 2 to 5 vol% solute rich interdendritic liquid which preferentially wets the grain boundaries and interdendritic regions

  10. Solidification paths in modified Inconel 625 weld overlay material

    DEFF Research Database (Denmark)

    Chandrasekaran, Karthik; Tiedje, Niels Skat; Hald, John

    2009-01-01

    Inconel 625 is commonly used for overlay welding to protect the base metal against high temperature corrosion. The efficiency of corrosion protection depends on effective mixing of the overlay weld with the base metal and the subsequent segregation of alloy elements during solidification....... Metallographic analysis of solidified samples of Inconel 625 with addition of selected elements is compared with thermodynamic modelling of segregation during solidification. The influence of changes in the melt chemistry on the formation of intermetallic phases during solidification is shown. In particular...

  11. Convection Effects During Bulk Transparent Alloy Solidification in DECLIC-DSI and Phase-Field Simulations in Diffusive Conditions

    Science.gov (United States)

    Mota, F. L.; Song, Y.; Pereda, J.; Billia, B.; Tourret, D.; Debierre, J.-M.; Trivedi, R.; Karma, A.; Bergeon, N.

    2017-08-01

    To study the dynamical formation and evolution of cellular and dendritic arrays under diffusive growth conditions, three-dimensional (3D) directional solidification experiments were conducted in microgravity on a model transparent alloy onboard the International Space Station using the Directional Solidification Insert in the DEvice for the study of Critical LIquids and Crystallization. Selected experiments were repeated on Earth under gravity-driven fluid flow to evidence convection effects. Both radial and axial macrosegregation resulting from convection are observed in ground experiments, and primary spacings measured on Earth and microgravity experiments are noticeably different. The microgravity experiments provide unique benchmark data for numerical simulations of spatially extended pattern formation under diffusive growth conditions. The results of 3D phase-field simulations highlight the importance of accurately modeling thermal conditions that strongly influence the front recoil of the interface and the selection of the primary spacing. The modeling predictions are in good quantitative agreements with the microgravity experiments.

  12. Thermosolutal convection during dendritic solidification

    Science.gov (United States)

    Heinrich, J. C.; Nandapurkar, P.; Poirier, D. R.; Felicelli, S.

    1989-01-01

    This paper presents a mathematical model for directional solidification of a binary alloy including a dendritic region underlying an all-liquid region. It is assumed initially that there exists a nonconvecting state with planar isotherms and isoconcentrates solidifying at a constant velocity. The stability of this system has been analyzed and nonlinear calculations are performed that show the effect of convection in the solidification process when the system is unstable. Results of calculations for various cases defined by the initial temperature gradient at the dendrite tips and varying strength of the gravitational field are presented for systems involving lead-tin alloys. The results show that the systems are stable for a gravitational constant of 0.0001 g(0) and that convection can be suppressed by appropriate choice of the container's size for higher values of the gravitational constant. It is also concluded that for the lead-tin systems considered, convection in the mushy zone is not significant below the upper 20 percent of the dendritic zone, if al all.

  13. Study on segregation of aluminium-uranium alloys

    International Nuclear Information System (INIS)

    Lima, Rui Marques de

    1979-01-01

    The relations between alloy solidification and solute segregation were considered. The solidification structure and the solute redistribution during the solidification of alloys with dendritic micro morphology were studied. The macro and micro segregation theories were reviewed. The mechanisms that could change the solidification structure were taken into account in the context of more homogeneous alloy production. Aluminum alloys solidification structures and segregation were studied experimentally in the 13 to 45% uranium range, usually considering solidification in static molds. The uranium alloys with up to 20% uranium were studied both for solidification in ingot molds and for controlled directional solidification. It was verified that these alloy compositions had structures similar to those of hipoeutectic alloys, showing an a phase with dendritic morphology and inter dendritic eutectic. For the alloys with more than 25% uranium, it was observed the formation of UAl 3 and UAl 4 phases with dendritic morphology. The dendritic UAl 3 , phase morphology was affected both by the solute concentration in the alloy and by the growth rate. The dendritic UAl 3 phase non-singular aspect could be destroyed with decrease of the alloy solute concentration. In the alloys obtained with higher cooling rates it was found a tendency for the formation of substantial quantities of equi axial crystals of the solute enriched phases in the central regions of the ingot upper half. In the more external regions it was observed dendritic growth of these phases, for alloy compositions with over 25% uranium. An adequate reduction in the cooling rate changed the solidification structure form and distribution, as well as the segregation type and intensity. The uranium content in the solidified macro structures is presented as a function of: cooling rate, superheating, mold size, mold form and its temperature, number of remelting and time for the melt homogenization and agitation. It was

  14. The effect of hot isostatic pressing on the microstructure and tensile properties of an unmodified A356-T6 cast aluminum alloy

    International Nuclear Information System (INIS)

    Ran Guang; Zhou Jingen; Wang, Q.G.

    2006-01-01

    In this paper, the effect of HIPping process on the microstructure and tensile properties of an unmodified sand cast A356-T6 aluminum alloy was studied. The microstructure and tensile fracture surfaces of the alloy were examined by transmission electron microscope (TEM), scanning electron microscope (SEM) and optical microscope. The results show that sub-grain boundaries are formed by HIPping process, and some silicon precipitates are formed at the sub-grain boundaries during aging hardening. The needle-shape precipitates are Mg 2 Si particles according to SED pattern analysis. The lattice misfit between Mg 2 Si and aluminum matrix is about 0.256% for [111] Al //[410] Mg 2 Si HIPping process significantly reduces porosity volume fraction and pore sizes and thus improves ductility. However, the tensile strength is improved very marginally due to the brittle nature of the unmodified coarse microstructure. The sub-grain boundary formed in the HIPping process has not shown significant influence on the tensile properties. For the studied alloy with large secondary dendrite arm spacing (SDAS) (above 80μm), the tensile fracture exhibits a transgranular mode (along the cell boundaries) with quasi-cleavage feature

  15. Direct observation of spatially isothermal equiaxed solidification of an Al-Cu alloy in microgravity on board the MASER 13 sounding rocket

    Science.gov (United States)

    Murphy, A. G.; Mathiesen, R. H.; Houltz, Y.; Li, J.; Lockowandt, C.; Henriksson, K.; Melville, N.; Browne, D. J.

    2016-11-01

    For the first time, isothermal equiaxed solidification of a metallic alloy has been observed in situ in space, providing unique benchmark experimental data. The experiment was completed on board the MASER 13 sounding rocket, launched in December 2015, using a newly developed isothermal solidification furnace. A grain-refined Al-20 wt%Cu sample was fully melted and solidified during 360 s of microgravity and the solidification sequence was recorded using time-resolved X-radiography. Equiaxed nucleation, dendritic growth, solutal impingement, and eutectic transformation were thus observed in a gravity-free environment. Equiaxed nucleation was promoted through application of a controlled cooling rate of -0.05 K/s producing a 1D grain density of 6.5 mm-1, uniformly distributed throughout the field of view (FOV). Primary growth slowed to a visually imperceptible level at an estimated undercooling of 7 K, after which the cooling rate was increased to -1.0 K/s for the remainder of solidification and eutectic transformation, ensuring the sample was fully solidified inside the microgravity time window. The eutectic transformation commenced at the centre of the FOV proceeding radially outwards covering the entire FOV in 3 s Microgravity-based solidification is compared to an identical pre-flight ground-based experiment using the same sample and experiment timeline. The ground experiment was designed to minimise gravity effects, by choice of a horizontal orientation for the sample, so that any differences would be subtle. The first equiaxed nucleation occurred at an apparent undercooling of 0.6 K less than the equivalent event during microgravity. During primary equiaxed solidification, as expected, no buoyant grain motion was observed during microgravity, compared to modest grain rotation and reorientation observed during terrestrial-based solidification. However, when the cooling rate was increased from -0.05 K/s to -1.0 K/s during the latter stages of solidification, in

  16. Effect of high-intensity ultrasonic irradiation on the modification of solidification microstructure in a Si-rich hypoeutectic Al-Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Das, A., E-mail: A.Das@swansea.ac.uk [Materials Research Centre, School of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom); Kotadia, H.R. [Brunel Centre for Advanced Solidification Technology, Brunel University, Uxbridge, UB8 3PH (United Kingdom)

    2011-02-15

    Effect of high-intensity ultrasound irradiation in modifying complex solidification microstructure is explored in a high Si containing Al-Si alloy and the origin of microstructural changes explained on the basis of nucleation and growth behaviour. Complete suppression of dendritic growth and dramatic refinement to globular morphology were observed for primary {alpha}-Al grains. Strong supportive evidence is presented towards enhanced and prolonged heterogeneous nucleation triggered by cavitation induced increase in the equilibrium melting point and effective dissipation of latent heat at the solidification front. Morphological evolution of eutectic Si and intermetallic particles is found to be dominated by coarsening and spherodisation from strong fluid flow in areas of intense cavitation near the ultrasonic radiator. Outside the region of direct energy transfer, Si particle morphology appears to be controlled predominantly by the imposed cooling conditions. Extremely fine and short Si-platelets observed in the intergranular spaces near the radiator are explained on the basis of probable rapid cooling of final liquid pockets of small volume and large surface area, rather than refinement through ultrasound.

  17. Effect of Chemical Composition on Susceptibility to Weld Solidification Cracking in Austenitic Weld Metal

    Science.gov (United States)

    Kadoi, Kota; Shinozaki, Kenji

    2017-12-01

    The influence of the chemical composition, especially the niobium content, chromium equivalent Creq, and nickel equivalent Nieq, on the weld solidification cracking susceptibility in the austenite single-phase region in the Schaeffler diagram was investigated. Specimens were fabricated using the hot-wire laser welding process with widely different compositions of Creq, Nieq, and niobium in the region. The distributions of the susceptibility, such as the crack length and brittle temperature range (BTR), in the Schaeffler diagram revealed a region with high susceptibility to solidification cracking. Addition of niobium enhanced the susceptibility and changed the distribution of the susceptibility in the diagram. The BTR distribution was in good agreement with the distribution of the temperature range of solidification (Δ T) calculated by solidification simulation based on Scheil model. Δ T increased with increasing content of alloying elements such as niobium. The distribution of Δ T was dependent on the type of alloying element owing to the change of the partitioning behavior. Thus, the solidification cracking susceptibility in the austenite single-phase region depends on whether the alloy contains elements. The distribution of the susceptibility in the region is controlled by the change in Δ T and the segregation behavior of niobium with the chemical composition.

  18. Solidification of Undercooled Melts of Al-Based Alloys on Earth and in Space

    Science.gov (United States)

    Herlach, Dieter M.; Burggraf, Stefan; Galenko, Peter; Gandin, Charles-André; Garcia-Escorial, Asuncion; Henein, Hani; Karrasch, Christian; Mullis, Andrew; Rettenmayr, Markus; Valloton, Jonas

    2017-08-01

    Containerless processing of droplets and drops by atomization and electromagnetic levitation are applied to undercool metallic melts and alloys prior to solidification. Heterogeneous nucleation on crucible walls is completely avoided giving access to large undercoolings. Experiments are performed both under terrestrial (1 g) conditions and in reduced gravity ( µg) as well. Microgravity conditions are realized by the free fall of small droplets during atomization of a spray of droplets, individual drops in a drop tube and by electromagnetic levitation of drops during parabolic flights, sounding rocket missions, and using the electro-magnetic levitator multi-user facility on board the International Space Station. The comparison of both sets of experiments in 1 g and µg leads to an estimation of the influence of forced convection on dendrite growth kinetics and microstructure evolution.

  19. The Influence of Alloy Composition on the Hot Tear Susceptibility of the Al-Zn-Mg-Cu Alloy System

    International Nuclear Information System (INIS)

    Kim, Jee-Hun; Jo, Jae-Sub; Sim, Woo-Jeong; Im, Hang-Joon

    2012-01-01

    Hot tearing was the most significant casting defect when the castability evaluation of the Al- Zn-Mg-Cu alloy system was conducted. It was related to the solidification range of the alloy. Therefore, the hot tear susceptibility of the AA7075 alloy, whose solidification range is the widest, was evaluated. The hot tear susceptibility was evaluated by using a mold for a hot tearing test designed to create the condition for the occurrence of hot tear in 8 steps. According to the tearing location and shape, a hot tear susceptibility index (HTS) score was measured. The solidification range of each alloy and hot tear susceptibility was compared and thereafter the microstructure of a near tear defect was observed. As a result, the HTS of the AA7075 alloy was found to be 67. Also, the HTS in relation to a change in Zn, Mg, Cu composition showed a difference of about 6-11% compared to the AA7075 alloy.

  20. Inverse thermal analysis method to study solidification in cast iron

    DEFF Research Database (Denmark)

    Dioszegi, Atilla; Hattel, Jesper

    2004-01-01

    Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... inverse thermal analysis was tested on both experimental and simulated data....

  1. Dry Sliding Wear Behavior of A356 Alloy/Mg2Sip Functionally Graded in-situ Composites: Effect of Processing Conditions

    Directory of Open Access Journals (Sweden)

    S.C. Ram

    2016-09-01

    Full Text Available In present study, the effect of dry sliding wear conditions of A356 alloy/Mg2Sip functionally graded in-situ composites developed by centrifugal casting method has been studied. A pure commercial A356 alloy (Al–7.5Si–0.3Mg was selected to be the matrix of the composites and primary Mg2Sip reinforcing particles were formed by in-situ chemical reaction with an average grain size of 40-47.8 µm. The Al–(Mg2Sip functionally graded metal matrix composites (FGMMC’s were synthesized by centrifugal casting technique with radial geometry, using two different mould rotating speeds ( 1200 and 1600 rpm. The X-ray diffraction (XRD characterization technique was carried out to confirm the in-situ formed Mg2Si particles in composites. Optical microscopy examination was carried out to reveals the grain refinement of Al-rich grains due to in-situ formed Mg2Si particles. Scanning electron microscope (SEM and Energy dispersive X-ray spectroscopy (EDS techniques were carried out to reveal the distribution of phases, morphological characteristics and confirmation of primary Mg2Si particles in the matrix. The sliding wear behavior was studied using a Pin-on-Disc set-up machine with sliding wear parameters: effect of loads (N, effect of sliding distances (m and effect of Mg on wear at room temperature with a high-carbon chromium steel disc (HRC-64 as counter surfaces. A good correlation was evidenced between the dry sliding behaviour of functionally graded in-situ composites and the distribution of Mg2Si reinforcing particles. Beside the above processing conditions, the dominant wear mechanisms of functionally graded in-situ composites have been correlated with the microstructures. The hardness and wear resistance properties of these composites increase with increasing volume percent of reinforced primary Si/Mg2Si particles toward inner zone of cast cylindrical shapes. The objective of this works was to study the tribological characteristics under dry sliding

  2. Effect Of Natural Convection On Directional Solidification Of Pure Metal

    Directory of Open Access Journals (Sweden)

    Skrzypczak T.

    2015-06-01

    Full Text Available The paper is focused on the modeling of the directional solidification process of pure metal. During the process the solidification front is sharp in the shape of the surface separating liquid from solid in three dimensional space or a curve in 2D. The position and shape of the solid-liquid interface change according to time. The local velocity of the interface depends on the values of heat fluxes on the solid and liquid sides. Sharp interface solidification belongs to the phase transition problems which occur due to temperature changes, pressure, etc. Transition from one state to another is discontinuous from the mathematical point of view. Such process can be identified during water freezing, evaporation, melting and solidification of metals and alloys, etc.

  3. Micromechanical modeling of stress-induced strain in polycrystalline Ni–Mn–Ga by directional solidification

    International Nuclear Information System (INIS)

    Zhu, Yuping; Shi, Tao; Teng, Yao

    2015-01-01

    Highlights: • A micromechanical model of directional solidification Ni–Mn–Ga is developed. • The stress–strain curves in different directions are tested. • The martensite Young’s moduli in different directions are predicted. • The macro reorientation strains in different directions are investigated. - Abstract: Polycrystalline ferromagnetic shape memory alloy Ni–Mn–Ga produced by directional solidification possess unique properties. Its compressive stress–strain behaviors in loading–unloading cycle show nonlinear and anisotropic. Based on the self-consistent theory and thermodynamics principle, a micromechanical constitutive model of polycrystalline Ni–Mn–Ga by directional solidification is developed considering the generating mechanism of the macroscopic strain and anisotropy. Then, the stress induced strains at different angles to solidification direction are calculated, and the results agree well with the experimental data. The predictive curves of martensite Young’s modulus and macro reorientation strain in different directions are investigated. It may provide theoretical guidance for the design and use of ferromagnetic shape memory alloy

  4. The Effect of Water Mist Cooling of Casting Die on the Solidification, Microstructure and Properties of AlSi20 Alloy

    Directory of Open Access Journals (Sweden)

    Władysiak R.

    2017-03-01

    Full Text Available Unmodified AlSi20 alloy were casted at the research station, allowing for sequential multipoint cooling using a dedicated computer- controlled program. This method allows for the formation of the microstructure of hypereutectic AlSi20 alloy and also increases hardness. Primary silicon dendrites were found in the microstructure of cooled samples. Based on these dendrites, the formation of primary silicon particles is explained. Cooling of casting die with a water mist stream causes changes in solidification, which leads to expansion of the boundary layer with columnar crystals and shrinkage of the core zone with equiaxed crystals. It also causes more regular hardness distribution around pre-eutectic Si crystals, which can lead to tensile strength and machinability improvement.

  5. Rate of solidification of aluminium casting in varying wall thickness of cylindrical metallic moulds

    Directory of Open Access Journals (Sweden)

    Katsina Christopher BALA

    2014-02-01

    Full Text Available The quality of final casting mainly depends on the rate of solidification as rapid solidification produces fine grains structures with better mechanical properties. The analysis of heat transfer during the casting and solidification of aluminium alloy as well as the experimental investigation of the rate of solidification in varying thicknesses of cylindrical metallic mould was carried out. The temperature variation with time of the casting was recorded from which cooling curves were obtained for the determination of solidification time of the cast. The results showed that as the cylindrical mould thickness increases the solidification time decreases due to the chilling effect of the mould.

  6. Three-dimensional phase-field simulations of directional solidification

    Science.gov (United States)

    Plapp, Mathis

    2007-05-01

    The phase-field method has become the method of choice for simulating microstructural pattern formation during solidification. One of its main advantages is that time-dependent three-dimensional simulations become feasible, which makes it possible to address long-standing questions of pattern stability and pattern selection. Here, a brief introduction to the phase-field model and its implementation is given, and its capabilities are illustrated by examples taken from the directional solidification of binary alloys. In particular, the morphological stability of hexagonal cellular arrays and of eutectic lamellar patterns is investigated.

  7. Effect of grain refiner on intermetallic phase formation in directional solidification of 6xxx series wrought Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sha, G.; O' Reilly, K.; Cantor, B. [Oxford Univ. (United Kingdom). Centre for Adv. Mat. and Composites; Hamerton, R.; Worth, J.

    2000-07-01

    The effect of a grain refiner on the formation of intermetallic phases in a directionally solidified (Bridgman grown) model 6xxx series wrought Al alloy has been investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). A base alloy with and without Al-Ti-B grain refiner was directionally solidified in a Bridgman furnace at growth velocities in the range of 5-120 mm/min. In both cases, the Fe-containing intermetallic phases present were found to be mainly {alpha}-AlFeSi and {beta}-AlFeSi. However, in the alloy with grain refiner solidified at 5mm/min, Al{sub 13}Fe{sub 4} was also observed. Quantitative XRD results indicated that the addition of Al-Ti-B grain refiner has a strong influence on the relative quantities of intermetallic phases forming during solidification at different growth velocities, which was also confirmed by TEM observations. TEM observations also show that depending on where the {beta}-AlFeSi particles solidified e.g. grain boundaries or triple grain junctions, the size and morphology of the particles may change dramatically. TiB{sub 2} particles were observed to nucleate {beta}-AlFeSi at low and high growth velocities in the 6xxx series Al alloys. (orig.)

  8. Phase formation in multicomponent monotectic aluminium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mirkovic, Djordje; Groebner, Joachim; Schmid-Fetzer, Rainer [Institute of Metallurgy, Clausthal University of Technology (Germany)

    2008-07-01

    Alloys with a miscibility gap in the liquid state are potential materials for advanced bearings in automotive and other applications. While binary alloys, such as Al-Pb or Al-Bi, are well known, the information available for ternary monotectic Al-alloys is scarce. However, the phase formation in multicomponent alloys is not only more challenging from a scientific aspect, it is also a prerequisite for a focused development of advanced alloys. This motivated our detailed study of monotectic Al-Bi-Cu-Sn alloys including both experimental and computational thermodynamic methods. Based on the initially established systematic classification of monotectic ternary Al-alloys, the first promising monotectic reaction was observed in the ternary Al-Bi-Zn system. Further ternary systems Al-Cu-Sn, Al-Bi-Sn, Al-Bi-Cu and Bi-Cu-Sn were investigated as basis for quaternary Al-Bi-Cu-Sn alloys. Experimental investigations of phase equilibria, enthalpies and solidification microstructures were combined with thermodynamic modeling. The results demonstrate that the developed precise thermodynamic description is vital to reveal the distinct multicomponent monotectic features of pertinent phase diagrams. The solidification paths of ternary monotectic alloy systems, Al-Bi-Zn, Al-Sn-Cu and Al-Bi-Cu, were also studied using thermodynamic calculations, revealing specific details of phase formation during solidification of selected alloys.

  9. Microstructural Development in Al-Si Powder During Rapid Solidification

    Energy Technology Data Exchange (ETDEWEB)

    Genau, Amber Lynn [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

  10. Vacuum brazing of aluminium metal matrix composite (55 vol.% SiC{sub p}/A356) using aluminium-based filler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Jitai, E-mail: niujitai@163.com [Harbin Institute of Technology (China); Zhengzhou University (China); Luo, Xiangwei; Tian, Hao [Zhengzhou University (China); Brnic, Josip [University of Rijka (Croatia)

    2012-11-20

    Highlights: Black-Right-Pointing-Pointer The proper filler metal has been developed, especially for contents of Mg and Si. Black-Right-Pointing-Pointer The pressure device has been designed for specimen in vacuum brazing process. Black-Right-Pointing-Pointer The accurate measurement method for shear strength of lap joint has been found. Black-Right-Pointing-Pointer The brazing temperature of 560 Degree-Sign C has been optimised. Black-Right-Pointing-Pointer The micro-mechanism has been discussed for SiC{sub p}/Al composites' brazing joint. - Abstract: Aluminium matrix composites with high volume fractions of SiC particles, as the reinforcements, are potentially suitable materials for electronic packaging. These composites, due to their poor weldability, however, have very limited applications. The microstructure and shear strengths of the bonds made in 55 vol.% SiC{sub p}/A356 composite, using an aluminium based filler alloy containing Cu, Si, Mg and Ni, were investigated in this paper. The brazing temperature had a clear effect on the bond integrity, and the samples brazed at 560 Degree-Sign C demonstrated good bonding between the filler alloy and the SiC particles. The maximum shear strength achieved in this work was 102 MPa.

  11. The effect of strontium on the microstructure, porosity and tensile properties of A356-10%B4C cast composite

    International Nuclear Information System (INIS)

    Lashgari, H.R.; Emamy, M.; Razaghian, A.; Najimi, A.A.

    2009-01-01

    This study was undertaken to investigate the effect of different concentrations of strontium (0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 1%) on the microstructure, porosity content and tensile properties of A356-10%B 4 C particulate metal matrix composite. In this work, the matrix alloy and composite were characterized by optical microscope, scanning electron microscope equipped with EDS and XRD. The composite ingots were made by stir casting process. The results showed that the addition of 0.03%Sr strongly modified silicon eutectic phase in A356 monolithic alloy, but 0.5%Sr was needed to complete the modification of A356-10%B 4 C composite. Results also demonstrated that Sr addition increases shrinkage porosity and generates new intermetallics in the microstructure. Further investigations on tensile tests revealed optimum strontium levels for improving tensile properties. In the point of fracture behavior of the composite, modified specimens with 0.2%Sr showed broken B 4 C particles and acceptable cohesion between B 4 C and matrix.

  12. Solidification at the micro-scale

    International Nuclear Information System (INIS)

    Howe, A.

    2003-01-01

    The experimental determination and computer simulation of the micro-segregation accompanying the solidification of alloys continues to be a subject of much academic and industrial interest. Both are subject to progressively more sophisticated analyses, and a discussion is offered regarding the development and practical use of such studies. Simple steels are particularly difficult targets for such work: solidification does not end conveniently in a eutectic, the rapid diffusion particularly in the delta-ferrite phase obscures most evidence of what had occurred at the micro-scale during solidification, and one or more subsequent solid state phase transformations further obscure such details. Also, solidification at the micro-scale is inherently variable: the usual, dendrite morphologies encountered are, after all, instabilities in growth behaviour, and therefore such variability should be expected. For questions such as the relative susceptibility of different grades to particular problems, it is the average, typical behaviour that is of interest, whereas for other questions such as the on-set of macro-segregation, the local variability is paramount. Depending on the question being asked, and indeed the accuracy with which validatory data are available, simple pseudo-analytical equations employing various limiting assumptions, or sophisticated models which remove the need for most such limitations, could be appropriate. This paper highlights the contribution to such studies of various collaborative research forums within the European Union with which the author is involved. (orig.) [de

  13. Real-time X-ray transmission microscopy for fundamental studies solidification: Al-Al2Au eutectic

    International Nuclear Information System (INIS)

    Curreri, Peter A.; Kaukler, William F.; Sen, Subhayu

    1998-01-01

    High resolution real-time X-ray Transmission Microscopy, XTM, has been applied to obtain information fundamental to solidification of optically opaque metallic systems. We have previously reported the measurement of the solute profile in the liquid, phase growth, and detailed solid-liquid interfacial morphology of aluminum based alloys with exposure times less than 2 seconds. Recent advances in XTM furnace design have provided an increase in real-time magnification (during solidification) for the XTM from 40X to 160X. The increased magnification has enabled for the first time the XTM imaging of real-time growth of fibers and particles with diameters of 5 μm. We have previously applied this system to study the kinetics of formation and morphological evolution of secondary fibers and particles in Al-Bi monotectic alloys. In this paper we present the preliminary results of the first real-time observations of fiber morphology evolution in optically opaque bulk metal sample of Aluminum-Gold eutectic alloy. These studies show that the XTM can be applied to study the fundamentals of eutectic and monotectic solidification. We are currently attempting to apply this technology in the fundamentals of solidification in microgravity

  14. Macrosegregation and Grain Formation Caused by Convection Associated with Directional Solidification Through Cross-Section Increase

    Science.gov (United States)

    Ghods, Masoud; Lauer, Mark; Tewari, Surendra; Poirier, David; Grugel, Richard

    2016-01-01

    Cylindrical Al-7 wt% Silicon, Al-19 wt% Copper and Lead-6 wt% Antimony alloy samples were directionally solidified (DS) with liquid above, solid below, and gravity pointing down, in graphite crucibles having an abrupt cross-sectional increase. These alloys have similar solidification shrinkage but are expected to have different degrees of thermosolutal convection during solidification. Microstructures in the DS samples in the vicinity of the section change have been studied in order to examine the effect of convection associated with the combined influence of thermosolutal effects and solidification shrinkage. Extensive radial and axial macrosegregation associated with cross-section change is observed. It also appears that steepling and local primary alpha-phase remelting resulting from convection are responsible for stray grain formation at the reentrant corners. Preliminary results from a numerical model, which includes solidification shrinkage and thermosolutal convection in the mushy zone, indicate that these regions are prone to solutal remelting of dendrites.

  15. Solidification and solid state phenomena during TLP bonding of IN718 superalloy using Ni–Si–B ternary filler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Pouranvari, M., E-mail: mpouranvari@yahoo.com [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-11155 (Iran, Islamic Republic of); Ekrami, A.; Kokabi, A.H. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-11155 (Iran, Islamic Republic of)

    2013-06-25

    Highlights: ► Microstructure evolution during TLP bonding of IN718 using Ni–Si–B filler. ► Athermal solidification path is influenced by severe segregation of B and Si in residual liquid. ► High hardness of ASZ microconstituents necessitates designing a PBHT to avert brittleness. ► Diffusion induced Cr–Mo–Nb based boride precipitation was observed in DAZ. ► Boride precipitates in DAZ influence the corrosion resistance and aging behavior. -- Abstract: This paper addresses solidification and solid state precipitation phenomena during transient liquid phase (TLP) bonding of wrought IN718 nickel base superalloy using Ni–4.5Si–3.2B (wt.%) ternary filler alloy. The solidification sequence of the residual liquid in the joint centerline was found to be (1) formation of proeutectic γ, followed by (2) γ/Ni{sub 3}B eutectic reaction, followed by (3) ternary eutectic of γ/Ni{sub 3}B/Ni{sub 6}Si{sub 2}B. Extensive fine Ni{sub 3}Si formed within the eutectic-γ via solid state precipitation during cooling. Extensive Cr–Mo–Nb rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during bonding process. The implications of the phase transformations on the mechanical properties, corrosion resistance and aging behavior of the joint, which are pertinent to the development of an optimum post bond heat treatment, are highlighted.

  16. Solidification and solid state phenomena during TLP bonding of IN718 superalloy using Ni–Si–B ternary filler alloy

    International Nuclear Information System (INIS)

    Pouranvari, M.; Ekrami, A.; Kokabi, A.H.

    2013-01-01

    Highlights: ► Microstructure evolution during TLP bonding of IN718 using Ni–Si–B filler. ► Athermal solidification path is influenced by severe segregation of B and Si in residual liquid. ► High hardness of ASZ microconstituents necessitates designing a PBHT to avert brittleness. ► Diffusion induced Cr–Mo–Nb based boride precipitation was observed in DAZ. ► Boride precipitates in DAZ influence the corrosion resistance and aging behavior. -- Abstract: This paper addresses solidification and solid state precipitation phenomena during transient liquid phase (TLP) bonding of wrought IN718 nickel base superalloy using Ni–4.5Si–3.2B (wt.%) ternary filler alloy. The solidification sequence of the residual liquid in the joint centerline was found to be (1) formation of proeutectic γ, followed by (2) γ/Ni 3 B eutectic reaction, followed by (3) ternary eutectic of γ/Ni 3 B/Ni 6 Si 2 B. Extensive fine Ni 3 Si formed within the eutectic-γ via solid state precipitation during cooling. Extensive Cr–Mo–Nb rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during bonding process. The implications of the phase transformations on the mechanical properties, corrosion resistance and aging behavior of the joint, which are pertinent to the development of an optimum post bond heat treatment, are highlighted

  17. Sadhana | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Sadhana. SAKENDRA KUMAR. Articles written in Sadhana. Volume 41 Issue 10 October 2016 pp 1203-1208. Evaluation of microstructure of A356 aluminum alloy casting prepared under vibratory conditions during the solidification · SAKENDRA KUMAR S P TEWARI · More Details Abstract Fulltext PDF.

  18. Homogeneous nucleation ahead of the solid-liquid interface during rapid solidification of binary alloys

    International Nuclear Information System (INIS)

    Smith, P.M.; Elmer, J.W.

    1996-01-01

    In recent rapid solidification experiments on Al-5%Be alloys, a Liquid Phase Nucleation (LPN) model was developed to explain the formation of periodic arrays of randomly-oriented Be-rich particles in an Al-rich matrix. In the LPN model, Be droplets were assumed to nucleate in the liquid ahead of the solid-liquid interface, but no justification for this was given. Here the authors present a model which considers the geometric constraints (imposed by proximity to the interface) on the number of solute atoms available to form a nucleus. Calculations based on this model predict that nucleation of second-phase particles can be most likely a short distance ahead of the interface in immiscible binary systems such as Al-Be. As part of the nucleation calculations, a semi-empirical method of calculating solid-liquid surface tensions in binary systems was developed, and is presented in the Appendix

  19. Ternary equilibria in bismuth--indium--lead alloys

    International Nuclear Information System (INIS)

    Liao, K.C.; Johnson, D.L.; Nelson, R.C.

    1975-01-01

    The liquidus surface is characterized by three binary equilibria. One binary extends from the Pb--Bi peritectic to the Pb--In peritectic. The other two extend from In--Bi eutectics, merge at 50 at. percent Bi and 30 at. percent Pb, and end at the Bi--Pb eutectic. Based on analysis of ternary liquidus contours and vertical sections, it is suggested that solidification for high lead and very high indium alloys occurs from two-phase equilibria. Solidification from all other alloys occurs from three-phase equilibria. Four-phase solidification does not occur in this system

  20. A dendritic solidification experiment under large gravity - implications for the Earth's inner core solidification regime.

    Science.gov (United States)

    Deguen, R.; Alboussière, T.; Brito, D.; La Rizza, P.; Masson, J.

    2009-05-01

    The Earth's inner core solidification regime is usually thought to be dendritic, which should results in the formation of a mushy layer at the inner core boundary, possibly extending deep in the inner core. The release of latent heat and solute associated with crystallization provides an important boyancy source to drive thermo- chemical convection in the core. In the laboratory, two modes of convection associated with the crystallization of mushy layers have been observed. One is a boundary layer mode originating from the destabilisation of the chemical boundary layer present at the mush-liquid interface; the second is the so-called 'mushy layer mode' which involves the whole mushy layer. In the mushy layer mode, convection usually takes the form of narrow plumes rising through crystal free conduits called chimneys. One particularity of inner core crystallization is its extremely small solidification rate compared to typical outer core convective timescales. We have designed and build an experiment devoted to the study of crystallization under a large gravity field, using a centrifuge, of an aqueous solution of ammonium chloride, which is a good analogue to metallic alloys. The large gravity field allows to reach Rayleigh numbers much larger than in typical solidification experiments. Under large gravity fields, we observe the disappearance of chimney convection and show that the large gravity field promotes the boundary layer convection mode at the expent of the mushy layer mode. As the gravitationnal forcing is increased, convective heat and solute transport are significantly enhanced, which results in larger solid fraction directly below the mush-liquid interface. The increase in solid fraction results in a dramatic decrease of the permeability in the mushy layer, which eventually becomes subcritical in respect to the mushy layer mode. Because of the very slow solidification rate of the inner core, convective transport of heat and solute from the ICB is

  1. Solidification at the High and Low Rate Extreme

    Energy Technology Data Exchange (ETDEWEB)

    Meco, Halim [Iowa State Univ., Ames, IA (United States)

    2004-12-19

    The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the low growth rates can be utilized for the study of the intrinsic growth behavior of a certain phase growing from the melt. Although the length scales associated with certain processes, such as capillarity, and the diffusion of heat and solute, are different at low and high rate extremes, the phenomena that govern the selection of a certain microstructural length scale or a growth mode are the same. Consequently, one can analyze the solidification phenomena at both high and low rates by using the same governing principles. In this study, we examined the microstructural control at both low and high extremes. For the high rate extreme, the formation of crystalline products and factors that control the microstructure during rapid solidification by free-jet melt spinning are examined in Fe-Si-B system. Particular attention was given to the behavior of the melt pool at different quench-wheel speeds. Since the solidification process takes place within the melt-pool that forms on the rotating quench-wheel, we examined the influence of melt-pool dynamics on nucleation and growth of crystalline solidification products and glass formation. High-speed imaging of the melt-pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt-spinning rates for which nucleation can be avoided, and fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt

  2. A study on the microstructural characteristics of rapidly solidified Al-Fe alloys(I)

    International Nuclear Information System (INIS)

    Kim, D.H.; Lee, H.I.

    1991-01-01

    Solidification microstructures and phases in rapidly solidified Al-5, 10wt% Fe alloys have been investigated by TEM bright field and dark field imaging techniques and electron and x-ray diffraction techniques. Rapid solidification of Al-5, 10wt%Fe alloys produces various metastable and stable phases, such as Al m Fe, Al 6 Fe and Al 13 Fe 4 . In addition to these phases, clusters of randomly oriented few nm scale particles exist in the form of fine cellular network with α-Al or primary spherical particles. Solidification microstructures of the rapidly solidified Al-5, 10wt%Fe alloys consist of various combination of primary phases such as Al 13 Fe 4 , Al m Fe and cluster of nm scale particles, and cellular/dendritic structures such as fine cellular network structure of nm scale particle clusters and α-Al and cellular structure of Al m Fe and α-Al, depending upon alloy compositions and local cooling rates. (Author)

  3. Low gravity containerless processing of immiscible gold rhodium alloys

    Science.gov (United States)

    Andrews, J. Barry

    1986-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

  4. Altering the cooling rate dependence of phase formation during rapid solidification in the Nd{sub 2}Fe{sub 14}B system

    Energy Technology Data Exchange (ETDEWEB)

    Branagan, D.J. [USDOE, Ames, IA (United States). Ames Lab.]|[Iowa State Univ. of Science and Technology, Ames, IA (United States). Dept. of Materials Science and Engineering; McCallum, R.W. [USDOE, Ames, IA (United States). Ames Lab.]|[Iowa State Univ. of Science and Technology, Ames, IA (United States). Dept. of Materials Science and Engineering

    1995-04-26

    In order to evaluate the effects of additions on the solidification behavior of Nd{sub 2}Fe{sub 14}B, a stoichiometric alloy was modified with elemental additions of Ti or C and a compound addition of Ti with C. For each alloy, a series of wheel speed runs was undertaken, from which the optimum wheel speeds and optimum energy products were determined. On the BH{sub max} versus wheel speed plots, regions were identified in order to analyze the changes with cooling rates leading to phase formation brought about by the alloy modifications. The compilation of the regional data of the modified alloys showed their effects on altering the cooling rate dependence of phase formation. It was found that the regions of properitectic iron formation, glass formation, and the optimum cooling rate can be changed by more than a factor of two through appropriate alloying additions. The effects of the alloy modifications can be visualized in a convenient fashion through the use of a model continuous cooling transformation (CCT) diagram which represents phase formation during the solidification process under continuous cooling conditions for a wide range of cooling rates from rapid solidification to equilibrium cooling. ((orig.)).

  5. Pore structure and mechanical properties of directionally solidified porous aluminum alloys

    Directory of Open Access Journals (Sweden)

    Komissarchuk Olga

    2014-01-01

    Full Text Available Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the final pore structure and the solidification pressure, as well as the influences of Mg quantity on the pore size, porosity and mechanical properties of Al-Mg alloy were investigated. The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.

  6. Segregation and convection in dendritic alloys

    Science.gov (United States)

    Poirier, D. R.

    1990-01-01

    Microsegregation in dentritic alloys is discussed, including solidification with and without thermal gradient, the convection of interdendritic liquid. The conservation of momentum, energy, and solute is considered. Directional solidification and thermosolutal convection are discussed.

  7. Microstructure selection in thin-sample directional solidification of an Al-Cu alloy: In situ X-ray imaging and phase-field simulations

    International Nuclear Information System (INIS)

    Clarke, A. J.; Tourret, D.; Song, Y.; Imhoff, S. D.; Gibbs, P. J.

    2017-01-01

    We study microstructure selection during during directional solidification of a thin metallic sample. We combine in situ X-ray radiography of a dilute Al-Cu alloy solidification experiments with three-dimensional phase-field simulations. Here we explore a range of temperature gradient G and growth velocity V and build a microstructure selection map for this alloy. We investigate the selection of the primary dendritic spacing Λ and tip radius ρ. While ρ shows a good agreement between experimental measurements and dendrite growth theory, with ρ~V"-"1"/"2, Λ is observed to increase with V (∂Λ/∂V > 0), in apparent disagreement with classical scaling laws for primary dendritic spacing, which predict that ∂Λ/∂V<0. We show through simulations that this trend inversion for Λ(V) is due to liquid convection in our experiments, despite the thin sample configuration. We use a classical diffusion boundary-layer approximation to semi-quantitatively incorporate the effect of liquid convection into phase-field simulations. This approximation is implemented by assuming complete solute mixing outside a purely diffusive zone of constant thickness that surrounds the solid-liquid interface. This simple method enables us to quantitatively match experimental measurements of the planar morphological instability threshold and primary spacings over an order of magnitude in V. Lastly, we explain the observed inversion of ∂Λ/∂V by a combination of slow transient dynamics of microstructural homogenization and the influence of the sample thickness.

  8. Vertical solidification of dendritic binary alloys

    Science.gov (United States)

    Heinrich, J. C.; Felicelli, S.; Poirier, D. R.

    1991-01-01

    Three numerical techniques are employed to analyze the influence of thermosolutal convection on defect formation in directionally solidified (DS) alloys. The finite-element models are based on the Boussinesq approximation and include the plane-front model and two plane-front models incorporating special dendritic regions. In the second model the dendritic region has a time-independent volume fraction of liquid, and in the last model the dendritic region evolves as local conditions dictate. The finite-element models permit the description of nonlinear thermosolutal convection by treating the dendritic regions as porous media with variable porosities. The models are applied to lead-tin alloys including DS alloys, and severe segregation phenomena such as freckles and channels are found to develop in the DS alloys. The present calculations and the permeability functions selected are shown to predict behavior in the dendritic regions that qualitatively matches that observed experimentally.

  9. The Effect of Rotation Stirring on Macrosegregation in Bi-Sn Alloy

    OpenAIRE

    Zulaida Yeni Muriani; Afrizal Riyan; Suryana Suryana

    2017-01-01

    Macrosegregation is a defect that difficult to avoid in a metal alloy made by casting method. Macrosegregation can cause decreasing in mechanical properties of casting products. It will reduce their performance in industrial application. Macrosegregation is convinced occur during solidification time in liquid alloy. In the early solidified, The solids move upward/downward in liquid alloy during solidification are considered to contribute on macrosegregation formation. This movement occur due ...

  10. Dendritic solidification in undercooled Ni-Zr-Al melts: Experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Galenko, P.K., E-mail: Peter.Galenko@dlr.de [Institut fuer Materialsphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), D-51170 Koeln (Germany); Reutzel, S.; Herlach, D.M. [Institut fuer Materialsphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), D-51170 Koeln (Germany); Fries, S.G. [ICAMS, Ruhr-Universitaet Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany)] [SGF Scientific Consultancy, Arndtstr 9, D-52064 Aachen (Germany); Steinbach, I. [ICAMS, Ruhr-Universitaet Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany); Apel, M. [ACCESS eV, Intzestrasse 5, D-52072 Aachen (Germany)

    2009-12-15

    The kinetics of dendritic solidification in a ternary Ni{sub 98}Zr{sub 1}Al{sub 1} alloy is investigated experimentally in a range of melt undercoolings 40K{<=}{Delta}T{<=}320K. The growth velocity is measured for samples processed by the electromagnetic levitation technique using a high-speed video camera. With {Delta}T{<=}220K the measured growth rates are the same as those of a binary Ni{sub 99}Zr{sub 1} alloy. In the regime of rapid solidification, especially within the regime of thermal dendritic growth at {Delta}T{>=}220K, growth rates are decreased. Sharp-interface modeling predicts growth rates over the whole range of undercooling. Phase-field simulations give quantitative predictions for the dendritic growth velocity in the solute-controlled growth regime. Results show that the composition and temperature dependency of the thermodynamic data, e.g. liquidus slope and solute partition coefficient, are important for describing the alloys. Our findings give improved sharp-interface model predictions compared to calculations based on an approximation of the thermodynamic data derived from binary phase diagrams.

  11. Design of a braze alloy for fast epitaxial brazing of superalloys

    Science.gov (United States)

    Piegert, S.; Laux, B.; Rösier, J.

    2012-07-01

    For the repair of directionally solidified turbine components made of nickel-based superalloys, a new high-temperature brazing method has been developed. Utilising heterogeneous nucleation on the crack surface, the microstructure of the base material can be reproduced, i.e. single crystallinity can be maintained. In contrast to commonly used eutectic braze alloys, such as nickel-boron or nickel-silicon systems, the process is not diffusion controlled but works with a consolute binary base system. The currently applied epitaxial brazing methods rely on isothermal solidification diffusing the melting point depressants into the base material until their concentration is reduced so that the liquid braze solidifies. Contrary, the identified Ni-Mn consolute system enables a temperature driven epitaxial solidification resulting in substantially reduced process duration. The development of the braze alloys was assisted using the CALPHAD software Thermo-Calc. The solidification behaviour was estimated by kinetic calculations with realistic boundary conditions. Finally, the complete system, including braze alloy as well as substrate material, was modelled by means of DICTRA. Subsequently, the thermodynamic properties of the braze alloys were experimentally analysed by DSC measurements. For brazing experiments 300 μm wide parallel gaps were used. Complete epitaxial solidification, i.e. the absence of high-angle grain boundaries, could be achieved within brazing times being up to two orders of magnitude shorter compared to diffusion brazing processes. Theoretically and experimentally evaluated process windows reveal similar shapes. However, a distinct shift has to be stated which can be ascribed to the limited accuracy of the underlying thermodynamic databases.

  12. Experimental Observation and Analytical Modeling of Melting and Solidification during Aluminum Alloy Repair by Turbulence Flow Casting

    Directory of Open Access Journals (Sweden)

    Muki Satya Permana

    2015-10-01

    Full Text Available This paper presents an overview on the state of the art of applicable casting technology for applications in the field of repairing aluminum alloy components. Repair process on the Al alloy sample using similar metal has been carried out to investigate the micro-structural effect. Joining occurs as a result of convection heat transfer of molten flow into the sand mold which melts the existing base metal inside the mold and subsequent solidification. The analytical model has been developed to describe aluminum alloy component repair by turbulence flow casting. The model is designed based on heat transfer principle that can handle the phenomena of heat flow. The experimental result and analytical model analyses pointed out that joint quality are greatly affected by parameters of preheating temperature and duration of molten metal flow in the mold. To obtain a desired metallurgical sound at the joint, the optimum temperature and time were adjusted in order to obtain a similarity of microstructure between filler and base metal. This model is aimed to predict the use of the process parameter ranges in order to have the optimum parameters when it is applied to the experiment. The fixed parameters are flow rate, sand ratio, and pouring temperature. The process parameters are preheating temperature and pouring time. It is concluded that analytical modeling has good agreement with the experimental result.

  13. Irradiation response of rapidly solidified Path A type prime candidate alloys

    International Nuclear Information System (INIS)

    Imeson, E.; Tong, C.; Lee, M.; Vander Sande, J.B.; Harling, O.K.

    1981-01-01

    The objective of this study is to present a first assessment of the microstructural response to neutron irradiation shown by Path A alloys prepared by rapid solidification processing. To more fully demonstrate the potential of the method, alloys with increased titanium and carbon content have been used in addition to the Path A prime candidate alloy

  14. Solidification process of a tool steel with niobium

    International Nuclear Information System (INIS)

    Makray, E.T.; Bresciani Filho, E.; Martinez Nazar, A.M.

    1984-01-01

    The solidification process of M2 high speed steel where tungsten was totally substituted by niobium was analysed. It occurs through a eutectic type reaction, in four steps. It was verified that one can apply the Coupled Zone Concept to explain the solification mechanism of this alloy: there is a primary phase (NbC), which is envolved by the other phase (ferrite) as a halo in order to send the composition back to the coupled growth region, where the binary eutectic forms. The last step is the formation of other compounds at the grain boundary. (Author) [pt

  15. Ensemble averaged multi-phase Eulerian model for columnar/equiaxed solidification of a binary alloy: II. Simulation of the columnar-to-equiaxed transition (CET)

    International Nuclear Information System (INIS)

    Ciobanas, A I; Fautrelle, Y

    2007-01-01

    A new multi-phase Eulerian model for the columnar and equiaxed dendritic solidification has been developed. In this paper we first focus on the numerical simulation of quasi-steady solidification experiments in order to obtain corresponding CET maps. We have identified three main zones on the CET map: the pure columnar, the pure equiaxed zone and finally the mixed columnar+equiaxed zone. The mixed c/e zone was further quantified by means of a columnar fraction ε c which quantifies in a rigorous way the two coexisting structures. Since it intrinsically includes the solutal and the mechanical blocking effects, the new ensemble model unifies the semi-empirical Hunt's approach (pure mechanical blocking mechanism) and the Martorano et al approach (pure solutal blocking mechanism). Secondly the present model was used to simulate unidirectional solidification experiments. It was found that the columnar front evolved in a quasi-steady state until a time very close to the critical CET moment. It is also found that the equiaxed nucleation undercooling is close to the maximum columnar dendrite tip undercooling and that the CET is virtually independent of the equiaxed zone ahead of the columnar front. If the equiaxed zone is not taken into account it is observed that the columnar front velocity exhibits a sudden increase at the beginning of the solidification followed by a quasi-plateau corresponding to a quasi-state at the columnar tips and finally, above a critical time, an oscillatory evolution. The beginning of the oscillatory evolution of the columnar front was well correlated with the CET position measured in the experiments. We also find that this oscillatory evolution of the columnar front is very favourable for the fragmentation of the columnar dendrites and thus for the CET. In this respect, it seems that the unsteady regime of the columnar front with respect to the local cooling conditions represents the main cause for the CET phenomena, at least for the non

  16. Modelling Eutectic Growth in Unmodified and Modified Near-Eutectic Al-Si Alloy

    DEFF Research Database (Denmark)

    Tiedje, Niels Skat; Hattel, Jesper Henri; Taylor, John A.

    2013-01-01

    growth parameters from the literature that depend on the type of modification (unmodified, Na-modified or Sr-modified) are used to describe differences in growth of the alloys. Modelling results are compared with solidification experiments where an Al-12.5wt%Si alloy was cast in unmodified, Na modified......A numerical model that describes solidification of primary aluminium grains and nucleation and growth of eutectic cells is used to analyse the solidification of an Al-12.5wt% Si alloy. Nucleation of eutectic cells is modelled using an Oldfield-type nucleation model where the number of nuclei...... and Sr modified forms. The model confirms experimental observations of how modification and alloy composition influence nucleation, growth and finally the size of eutectic cells in the alloys. Modelling results are used to explain how cooling conditions in the casting act together with the nuclei density...

  17. Bubble Induced Disruption of a Planar Solid-Liquid Interface During Controlled Directional Solidification in a Microgravity Environment

    Science.gov (United States)

    Grugel, Richard N.; Brush, Lucien N.; Anilkumar, Amrutur V.

    2013-01-01

    Pore Formation and Mobility Investigation (PFMI) experiments were conducted in the microgravity environment aboard the International Space Station with the intent of better understanding the role entrained porosity/bubbles play during controlled directional solidification. The planar interface in a slowing growing succinonitrile - 0.24 wt% water alloy was being observed when a nitrogen bubble traversed the mushy zone and remained at the solid-liquid interface. Breakdown of the interface to shallow cells subsequently occurred, and was later evaluated using down-linked data from a nearby thermocouple. These results and other detrimental effects due to the presence of bubbles during solidification processing in a microgravity environment are presented and discussed.

  18. Three-dimensional granular model of semi-solid metallic alloys undergoing solidification: Fluid flow and localization of feeding

    International Nuclear Information System (INIS)

    Sistaninia, M.; Phillion, A.B.; Drezet, J.-M.; Rappaz, M.

    2012-01-01

    A three-dimensional (3-D) granular model which simulates fluid flow within solidifying alloys with a globular microstructure, such as that found in grain refined Al alloys, is presented. The model geometry within a representative volume element (RVE) consists of a set of prismatic triangular elements representing the intergranular liquid channels. The pressure field within the liquid channels is calculated using a finite elements (FEs) method assuming a Poiseuille flow within each channel and flow conservation at triple lines. The fluid flow is induced by solidification shrinkage and openings at grain boundaries due to deformation of the coherent solid. The granular model predictions are validated against bulk data calculated with averaging techniques. The results show that a fluid flow simulation of globular semi-solid materials is able to reproduce both a map of the 3-D intergranular pressure and the localization of feeding within the mushy zone. A new hot cracking sensitivity coefficient is then proposed. Based on a mass balance performed over a solidifying isothermal volume element, this coefficient accounts for tensile deformation of the semi-solid domain and for the induced intergranular liquid feeding. The fluid flow model is then used to calculate the pressure drop in the mushy zone during the direct chill casting of aluminum alloy billets. The predicted pressure demonstrates that deep in the mushy zone where the permeability is low the local pressure can be significantly lower than the pressure predicted by averaging techniques.

  19. Optimization design of a gating system for sand casting aluminium A356 using a Taguchi method and multi-objective culture-based QPSO algorithm

    Directory of Open Access Journals (Sweden)

    Wen-Jong Chen

    2016-04-01

    Full Text Available This article combined Taguchi method and analysis of variance with the culture-based quantum-behaved particle swarm optimization to determine the optimal models of gating system for aluminium (Al A356 sand casting part. First, the Taguchi method and analysis of variance were, respectively, applied to establish an L27(38 orthogonal array and determine significant process parameters, including riser diameter, pouring temperature, pouring speed, riser position and gating diameter. Subsequently, a response surface methodology was used to construct a second-order regression model, including filling time, solidification time and oxide ratio. Finally, the culture-based quantum-behaved particle swarm optimization was used to determine the multi-objective Pareto optimal solutions and identify corresponding process conditions. The results showed that the proposed method, compared with initial casting model, enabled reducing the filling time, solidification time and oxide ratio by 68.14%, 50.56% and 20.20%, respectively. A confirmation experiment was verified to be able to effectively reduce the defect of casting and improve the casting quality.

  20. A review on hot tearing of magnesium alloys

    Directory of Open Access Journals (Sweden)

    Jiangfeng Song

    2016-09-01

    Full Text Available Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products. Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood, it is of great importance to investigate the hot tearing behaviour of magnesium alloys. This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades. The hot tearing criteria including recently developed Kou's criterion are summarized and compared. The numeric simulation and assessing methods of hot tearing, factors influencing hot tearing, and hot tearing susceptibility (HTS of magnesium alloys are discussed.

  1. The effect of major alloying elements on the size of the secondary dendrite arm spacing in the as-cast Al-Si-Cu alloys

    Directory of Open Access Journals (Sweden)

    M. B. Djurdjevič

    2012-01-01

    Full Text Available A comprehensive understanding of melt quality is of paramount importance for the control and prediction of actual casting characteristics. Among many phenomenons that occur during the solidification of castings, there are four that control structure and consequently mechanical properties: chemical composition, liquid metal treatment, cooling rate and temperature gradient. The cooling rate and alloy composition are among them most important. This paper investigates the effect of some major alloying elements (silicon and copper of Al-Si-Cu alloys on the size of the secondary dendrite arm spacing. It has been shown that both alloying elements have reasonable influence on the refinement of this solidification parameter.

  2. Modeling the effects of cooling rate, hydrogen content, grain refiner and modifier on microporosity formation in Al A356 alloys

    Energy Technology Data Exchange (ETDEWEB)

    Conley, J.G.; Huang, J.; Asada, J.; Akiba, K. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

    2000-06-15

    Cast Aluminum-Silicon alloys are used in numerous automotive and industrial weight sensitive applications because of their low density and excellent castability. The presence of trapped gas and or shrinkage pores in certain locations within castings has been shown to influence fatigue life. These micromechanical defects can be found most anywhere in a casting depending on processing conditions. A large amount of porosity located in the center of the cast material thickness may have no effect on mechanical properties or fatigue performance. A smaller, isolated pore near a surface may have a significant impact on mechanical properties. Hence, it is important to develop a comprehensive model to predict the size, location and distribution of microporosity in castings. In this work, we model the effect of various casting process parameters on microporosity formation for aluminum A356 alloy castings. The process parameters include cooling rate, hydrogen content, grain refiner and modifier. The proposed two-dimensional model predicts the size, morphology and distribution of microporosity at a given location in the casting. The method couples a mathematical model of porosity evolution with a probabilistic grain structure prediction model. The porosity evolution model is based on the simultaneous solution of the continuity and momentum equations for the metal and the mass conservation equation for the dissolved gas. The nucleation and growth of grains are simulated with a probabilistic method that uses the information from a heat transfer simulation, i.e. temperature and solid fraction, to determine the transition rules for grain evolution. The simulation results correlate well with experimental observation of porosity in cast structures. (orig.)

  3. Rapid solidification for preparation of high Tc superconductors

    International Nuclear Information System (INIS)

    Yavari, A.R.

    1988-01-01

    High Tc superconducting oxides are prepared in two different ways using rapid solidification: by oxidation of microcrystalline or amorphous tapes obtained by quenching the liquid alloy and via crystallisation of the amorphous oxide obtained by rapid quenching of the oxide melt. This technique is applied for the first time to the BiCaSrCuO family [fr

  4. On the hot cracking susceptibility of a semisolid aluminium 6061 weld: Application of a coupled solidification- thermomechanical model

    International Nuclear Information System (INIS)

    Rajani, H R Zareie; Phillion, A B

    2015-01-01

    A coupled solidification-thermomechanical model is presented that investigates the hot tearing susceptibility of an aluminium 6061 semisolid weld. Two key phenomena are considered: excessive deformation of the semisolid weld, initiating a hot tear, and the ability of the semisolid weld to heal the hot tear by circulation of the molten metal. The model consists of two major modules: weld solidification and thermomechanical analysis. 1) By means of a multi-scale model of solidification, the microstructural evolution of the semisolid weld is simulated in 3D. The semisolid structure, which varies as a function of welding parameters, is composed of solidifying grains and a network of micro liquid channels. The weld solidification module is utilized to obtain the solidification shrinkage. The size of the micro liquid channels is used as an indicator to assess the healing ability of the semisolid weld. 2) Using the finite element method, the mechanical interaction between the weld pool and the base metal is simulated to capture the transient force field deforming the semisolid weld. Thermomechanical stresses and shrinkage stresses are both considered in the analysis; the solidification contractions are extracted from the weld solidification module and applied to the deformation simulation as boundary conditions. Such an analysis enables characterization of the potential for excessive deformation of the weld. The outputs of the model are used to study the effect of welding parameters including welding current and speed, and also welding constraint on the hot cracking susceptibility of an aluminium alloy 6061 semisolid weld. (paper)

  5. Influence of the thermal history of a particle during atomization on the morphology of carbides in a hypereutectic iron based alloy

    International Nuclear Information System (INIS)

    Kusý, M.; Behúlová, M.; Grgač, P.

    2012-01-01

    Highlights: ► Identification of solidification microstructures in RS powder from iron based alloy. ► Microstructures affected and nonaffected during the post-recalescence period. ► Thermokinetic newtonian model of rapid solidification of a droplet in gas atomization. ► Droplet thermal history and conditions for the microstructure development. ► Parameters influencing development of different solidification microstructures. - Abstract: Basic principles and consequences of the rapid solidification processing of melts have been successfully exploited in several progressive technologies of material production. In the paper, the solidification microstructures developed in the hypereutectic iron based alloy with the chemical composition of 3% C–3% Cr–12% V (wt.%) prepared by nitrogen gas atomization are presented and analysed. Several main types of solidification microstructures were identified in the rapidly solidified powder particles. According to the morphological features of carbide phases and computed thermal history of rapidly solidified particles, the microstructures were divided into two groups – microstructures morphologically non-affected during the post-recalescence period of solidification, and microstructures with morphological transitions occurring during the quasi-isothermal period of structure development. Based on the thermokinetic newtonian model of rapid solidification of a spherical droplet in the process of atomization, the thermal history of droplets with diameter from 20 μm to 400 μm rapidly solidified from different nucleation temperatures was studied. The thermo-physical conditions necessary for the development of variable microstructures in single rapidly solidified powder particles are predicted and discussed. The nucleation temperature, recalescence temperature and duration of quasi-isothermal plateau are supposed to be the most important parameters influencing the microstructure development in the rapidly solidified

  6. Formation of AlFeSi phase in AlSi12 alloy with Ce addition

    Directory of Open Access Journals (Sweden)

    S. Kores

    2012-04-01

    Full Text Available The influence of cerium addition on the solidification sequence and microstructure constituents of the Al-Si alloys with 12,6 mass % Si was examined. The solidification was analyzed by a simple thermal analysis. The microstructures were examined with conventional light and scanning electron microscopy. Ternary AlSiCe phase was formed in the Al-Si alloys with added cerium during the solidification process. AlSiCe and β-AlFeSi phases solidified together in the region that solidified the last. Cerium addition influenced on the morphology of the α-AlFeSi phase solidification.

  7. Joining of superalloy Inconel 600 by diffusion induced isothermal solidification of a liquated insert metal

    International Nuclear Information System (INIS)

    Egbewande, A.T.; Chukwukaeme, C.; Ojo, O.A.

    2008-01-01

    The effect of process variables on the microstructure of transient liquid phase bonded IN 600 using a commercial filler alloy was studied. Microstructural examination of bonded specimens showed that isothermal solidification of the liquated insert occurred during holding at the joining temperatures. In cases where the holding time was insufficient for complete isothermal solidification, the residual liquid transformed on cooling into a centerline eutectic product. The width of the eutectic decreased with increased holding time and an increase in initial gap width resulted in thicker eutectic width in specimens bonded at the same temperature and for equivalent holding times. In addition to the centerline eutectic microconstituent, precipitation of boron-rich particles was observed within the base metal region adjacent to the substrate-joint interface. Formation of these particles appeared to have influenced the rate of solidification of the liquated interlayer during bonding. In contrast to the conventional expectation of an increase in the rate of isothermal solidification with an increase in temperature, a decrease in the rate was observed with an increase in temperatures above 1160 deg. C. This could be related to a decrease in solubility of boron in nickel above the Ni-B eutectic temperature

  8. Matching time and spatial scales of rapid solidification: dynamic TEM experiments coupled to CALPHAD-informed phase-field simulations

    Science.gov (United States)

    Perron, Aurelien; Roehling, John D.; Turchi, Patrice E. A.; Fattebert, Jean-Luc; McKeown, Joseph T.

    2018-01-01

    A combination of dynamic transmission electron microscopy (DTEM) experiments and CALPHAD-informed phase-field simulations was used to study rapid solidification in Cu-Ni thin-film alloys. Experiments—conducted in the DTEM—consisted of in situ laser melting and determination of the solidification kinetics by monitoring the solid-liquid interface and the overall microstructure evolution (time-resolved measurements) during the solidification process. Modelling of the Cu-Ni alloy microstructure evolution was based on a phase-field model that included realistic Gibbs energies and diffusion coefficients from the CALPHAD framework (thermodynamic and mobility databases). DTEM and post mortem experiments highlighted the formation of microsegregation-free columnar grains with interface velocities varying from ˜0.1 to ˜0.6 m s-1. After an ‘incubation’ time, the velocity of the planar solid-liquid interface accelerated until solidification was complete. In addition, a decrease of the temperature gradient induced a decrease in the interface velocity. The modelling strategy permitted the simulation (in 1D and 2D) of the solidification process from the initially diffusion-controlled to the nearly partitionless regimes. Finally, results of DTEM experiments and phase-field simulations (grain morphology, solute distribution, and solid-liquid interface velocity) were consistent at similar time (μs) and spatial scales (μm).

  9. A Stochastic mesoscopic model for predicting the globular grain structure and solute redistribution in cast alloys at low superheat

    International Nuclear Information System (INIS)

    Nastac, Laurentiu; El Kaddah, Nagy

    2012-01-01

    It is well known that casting at low superheat has a strong influence on the solidification morphology and macro- and microstructures of the cast alloy. This paper describes a stochastic mesoscopic solidification model for predicting the grain structure and segregation in cast alloy at low superheat. This model was applied to predict the globular solidification morphology and size as well as solute redistribution of Al in cast Mg AZ31B alloy at superheat of 5°C produced by the Magnetic Suspension Melting (MSM) process, which is an integrated containerless induction melting and casting process. The castings produced at this low superheat have fine globular grain structure, with an average grain size of 80 μm, which is about 3 times smaller than that obtained by conventional casting techniques. The stochastic model was found to reasonably predict the observed grain structure and Al microsegregation. This makes the model a useful tool for controlling the structure of cast magnesium alloys.

  10. Dimensional analysis of the transition from columnar to equiaxial structure in aluminium-copper and lead-tin alloys

    International Nuclear Information System (INIS)

    Gueijman, Sergio Fabian; Ares, Alicia Esther; Schvezov, Carlos E

    2004-01-01

    The importance of directional solidification studies is well known from systematic scientific research undertaken to understand the characteristics of the solidification of alloys. Such studies offer much information about the morphology of the interphase and the distribution of solute during solidification. Most alloys grow while attaining dendritic interphases. So considerable effort has been expended to understand the dendritic growth characteristics under controlled solidification conditions. A treatment that can quantitatively explain all the available test data and that correctly includes the physics of the problem is not yet available. This work carries out a theoretical analysis of columnar and equiaxial growth and of dendritic spacing under different conditions of solidification of the test pieces. The basic parameters that are used characterize a given alloy system. Next, we define non-dimensional parameters, that are used to formulate the final result of our problem regardless of the specific alloy being studied. We present the important functional relationships of our study, including the physical interpretation of the results obtained in the first work (CW)

  11. Toward Understanding Pore Formation and Mobility during Controlled Directional Solidification in a Microgravity Environment Investigation (PFMI)

    Science.gov (United States)

    Grugel, Richard N.; Anilkumar, A. V.; Luz, Paul; Jeter, Linda; Volz, Martin P.; Spivey, Reggie; Smith, G.

    2003-01-01

    The generation and inclusion of detrimental porosity, e.g., pipes and rattails can occur during controlled directional solidification processing. The origin of these defects is generally attributed to gas evolution and entrapment during solidification of the melt. On Earth, owing to buoyancy, an initiated bubble can rapidly rise through the liquid melt and pop at the surface; this is obviously not ensured in a low gravity or microgravity environment. Clearly, porosity generation and inclusion is detrimental to conducting any meaningful solidification-science studies in microgravity. Thus it is essential that model experiments be conducted in microgravity, to understand the details of the generation and mobility of porosity, so that methods can be found to eliminate it. In hindsight, this is particularly relevant given the results of the previous directional solidification experiments conducted in Space. The current International Space Station (ISS) Microgravity Science Glovebox (MSG) investigation addresses the central issue of porosity formation and mobility during controlled directional solidification processing in microgravity. The study will be done using a transparent metal-analogue material, succinonitrile (SCN) and succinonitrile-water 'alloys', so that direct observation and recording of pore generation and mobility can be made during the experiments. Succinonitrile is particularly well suited for the proposed investigation because it is transparent, it solidifies in a manner analogous to most metals, it has a convenient melting point, its material properties are well characterized and, it has been successfully used in previous microgravity experiments. The PFMI experiment will be launched on the UF-2, STS-111 flight. Highlighting the porosity development problem in metal alloys during microgravity processing, the poster will describe: (i) the intent of the proposed experiments, (ii) the theoretical rationale behind using SCN as the study material for

  12. Evolution of morphology in solidifying aluminium alloys

    NARCIS (Netherlands)

    Dijkstra, W.O.

    2007-01-01

    In the thesis two different models of solidification of aluminum alloys are presented and analyzed. The first 1--D solidification model is derived from the conservation of solute, heat and mass. With numerical experiments it is shown that simulations with the Finite Difference discretization must

  13. Reduction in secondary dendrite arm spacing in cast eutectic Al-Si piston alloys by cerium addition

    Science.gov (United States)

    Ahmad, R.; Asmael, M. B. A.; Shahizan, N. R.; Gandouz, S.

    2017-01-01

    The effects of Ce on the secondary dendrite arm spacing (SDAS) and mechanical behavior of Al-Si-Cu-Mg alloys were investigated. The reduction of SDAS at different Ce concentrations was evaluated in a directional solidification experiment via computer-aided cooling curve thermal analysis (CA‒CCTA). The results showed that 0.1wt%-1.0wt% Ce addition resulted in a rapid solidification time, Δ t s, and low solidification temperature, Δ T S, whereas 0.1wt% Ce resulted in a fast solidification time, Δ t a-Al, of the α-Al phase. Furthermore, Ce addition refined the SDAS, which was reduced to approximately 36%. The mechanical properties of the alloys with and without Ce were investigated using tensile and hardness tests. The quality index ( Q) and ultimate tensile strength of (UTS) Al-Si-Cu-Mg alloys significantly improved with the addition of 0.1wt% Ce. Moreover, the base alloy hardness was improved with increasing Ce concentration.

  14. Quasicrystal-reinforced Mg alloys.

    Science.gov (United States)

    Kyun Kim, Young; Tae Kim, Won; Hyang Kim, Do

    2014-04-01

    The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg-Zn-Y and Mg-Zn-Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α -Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg-Zn-Y alloys, the co-presence of I and Ca 2 Mg 6 Zn 3 phases by addition of Ca can significantly enhance formability, while in Mg-Zn-Al alloys, the co-presence of the I-phase and Mg 2 Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg-Zn-Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg-Zn-Al-Sn alloys is attributed to the presence of finely distributed Mg 2 Sn and I-phase particles embedded in the α -Mg matrix.

  15. Cellular Automaton Study of Hydrogen Porosity Evolution Coupled with Dendrite Growth During Solidification in the Molten Pool of Al-Cu Alloys

    Science.gov (United States)

    Gu, Cheng; Wei, Yanhong; Yu, Fengyi; Liu, Xiangbo; She, Lvbo

    2017-09-01

    Welding porosity defects significantly reduce the mechanical properties of welded joints. In this paper, the hydrogen porosity evolution coupled with dendrite growth during solidification in the molten pool of Al-4.0 wt pct Cu alloy was modeled and simulated. Three phases, including a liquid phase, a solid phase, and a gas phase, were considered in this model. The growth of dendrites and hydrogen gas pores was reproduced using a cellular automaton (CA) approach. The diffusion of solute and hydrogen was calculated using the finite difference method (FDM). Columnar and equiaxed dendrite growth with porosity evolution were simulated. Competitive growth between different dendrites and porosities was observed. Dendrite morphology was influenced by porosity formation near dendrites. After solidification, when the porosities were surrounded by dendrites, they could not escape from the liquid, and they made pores that existed in the welded joints. With the increase in the cooling rate, the average diameter of porosities decreased, and the average number of porosities increased. The average diameter of porosities and the number of porosities in the simulation results had the same trend as the experimental results.

  16. PREPARATION OF ACTINIDE-ALUMINUM ALLOYS

    Science.gov (United States)

    Moore, R.H.

    1962-09-01

    BS>A process is given for preparing alloys of aluminum with plutonium, uranium, and/or thorium by chlorinating actinide oxide dissolved in molten alkali metal chloride with hydrochloric acid, chlorine, and/or phosgene, adding aluminum metal, and passing air and/or water vapor through the mass. Actinide metal is formed and alloyed with the aluminum. After cooling to solidification, the alloy is separated from the salt. (AEC)

  17. The influence of Ta on the solidification microstructure and segregation behavior of γ(Ni)/γ′(Ni3Al)–δ(Ni3Nb) eutectic Ni-base superalloys

    International Nuclear Information System (INIS)

    Xie, M.; Helmink, R.; Tin, S.

    2013-01-01

    Highlights: ► Ta and Nb have a nominally identical influence on equilibrium δ volume fraction. ► Ta and Nb impact the sequence and segregation differently during solidification. ► Microstructure varies with both overall Ta + Nb level and Ta/Nb ratio. ► Pandat (PanNi7) is unable to predict trends quantitatively in this system. -- Abstract: Polycrystalline γ/γ′–δ eutectic Ni-base superalloys based on the Ni–Al–Nb alloy system were recently demonstrated to possess excellent high temperature strength and creep resistance. Investigations aimed to establish the fundamental relationships between alloy chemistry, solidification behavior and cast microstructure in these novel Ni–Al–Nb γ/γ′–δ alloy systems are currently underway. This particular study is focused on understanding the influence of Ta additions on the solidification sequence, phase volume fraction, distribution coefficient and solid state partitioning parameter of this eutectic alloy system by systematically investigating a series of experimental alloys with nominally constant overall levels of Ta + Nb content but varying Ta/Nb ratios. Although many of the tendencies observed in these multi-component γ/γ′–δ eutectic alloys are in agreement with trends observed in lower order model alloy systems, Ta additions were found to significantly modify solidification characteristics of the alloys. The experimental observations were also used to critically assess the predictive capability of thermodynamic database calculations. Despite the qualitative agreement observed between the experimental results and predictions for relatively simple quaternary and quinary model alloys, comparison of the results for higher order, multi-component γ/γ′–δ eutectic alloys reveals notable differences

  18. Constituent phase diagrams of the Al-Cu-Fe-Mg-Ni-Si system and their application to the analysis of aluminium piston alloys

    Energy Technology Data Exchange (ETDEWEB)

    Belov, N.A. [Moscow Institute of Steel and Alloys, Leninsky prosp. 4, Moscow 119049 (Russian Federation); Eskin, D.G. [Netherlands Institute for Metals Research, Rotterdamseweg 137, 2628AL Delft (Netherlands)]. E-mail: deskin@nimr.nl; Avxentieva, N.N. [Moscow Institute of Steel and Alloys, Leninsky prosp. 4, Moscow 119049 (Russian Federation)

    2005-10-15

    The evaluation of phase equilibria in quinary systems that constitute the commercially important Al-Cu-Fe-Mg-Ni-Si alloying system is performed in the compositional range of casting alloys by means of metallography, electron probe microanalysis, X-ray diffractometry, differential scanning calorimetry, and by the analysis of phase equilibria in the constituent systems of lesser dimensionality. Suggested phase equilibria are illustrated by bi-, mono- and invariant solidification reactions, polythermal diagrams of solidification, distributions of phase fields in the solid state, and isothermal and polythermal sections. Phase composition of as-cast alloys is analyzed in terms of non-equilibrium solidification. It is shown that the increase in copper concentration in piston Al-Si alloys results in the decrease in the equilibrium solidus from 540 to 505 deg C. Under non-equilibrium solidification conditions, piston alloys finish solidification at {approx}505 deg C. Iron is bound in the quaternary Al{sub 8}FeMg{sub 3}Si{sub 6} phase in low-iron alloys and in the ternary Al{sub 9}FeNi and Al{sub 5}FeSi phases in high-iron alloys.

  19. A mesoscale granular model for the mechanical behavior of alloys during solidification

    Energy Technology Data Exchange (ETDEWEB)

    Vernede, Stephane [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland); Alcan Centre de Recherches de Voreppe, ZI Centr' Alp, 725 rue Aristide Berges, BP 27, Voreppe FR-38341 (France)], E-mail: stephane.vernede@alcan.com; Dantzig, Jonathan A. [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland); Department of Mechanical Science and Engineering, University of Illinois, 1206 West Green Street Urbana, IL 61801 (United States); Rappaz, Michel [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland)

    2009-03-15

    We present a two-dimensional granular model for the mechanical behavior of an ensemble of globular grains during solidification. The grain structure is produced by a Voronoi tessellation based on an array of predefined nuclei. We consider the fluid flow caused by grain movement and solidification shrinkage in the network of channels that is formed by the faces of the grains in the tessellation. We develop the governing equations for the flow rate and pressure drop across each channel when the grains are allowed to move, and we then assemble the equations into a global expression that conserves mass and force in the system. We show that the formulation is consistent with dissipative formulations of non-equilibrium thermodynamics. Several example problems are presented to illustrate the effect of tensile strains and the availability of liquid to feed the deforming microstructure. For solid fractions below g{sub s}=0.97, we find that the fluid is able to feed the deformation at low strain, even if external feeding is not permitted. For solid fractions above g{sub s}=0.97, clusters of grains with 'dry' boundaries form and fluid flow becomes highly localized.

  20. Structural investigations of mechanical properties of Al based rapidly solidified alloys

    International Nuclear Information System (INIS)

    Karakoese, Ercan; Keskin, Mustafa

    2011-01-01

    Highlights: → Rapid solidification processing (RSP) involves exceptionally high cooling rates. → We correlate the microstructure of the intermetallic Al 3 Fe, Al 2 Cu and Al 3 Ni phases with the cooling rate. → The solidification rate is high enough to retain most of alloying elements in the Al matrix. → The rapid solidification has effect on the phase constitution. -- Abstract: In this study, Al based Al-3 wt.%Fe, Al-3 wt.%Cu and Al-3 wt.%Ni alloys were prepared by conventional casting. They were further processed using the melt-spinning technique and characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) together with energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), differential scanning calorimetry (DSC) and the Vickers microhardness tester. The rapidly solidified (RS) binary alloys were composed of supersaturated α-Al solid solution and finely dispersed intermetallic phases. Experimental results showed that the mechanical properties of RS alloys were enhanced, which can be attributed to significant changes in the microstructure. RS samples were measured using a microhardness test device. The dependence of microhardness H V on the solidification rate (V) was analysed. These results showed that with the increasing values of V, the values of H V increased. The enthalpies of fusion for the same alloys were determined by DSC.

  1. Search for a solute-drag effect in dendritic solidification

    International Nuclear Information System (INIS)

    Eckler, K.; Herlach, D.M.; Aziz, M.J.

    1994-01-01

    The authors report the results of an indirect experimental test for the solute-drag effect in alloy solidification by fitting the data of Eckler et.al. for Ni-B dendrite tip velocities vs undercooling to models in several ways. The unknown equilibrium partition coefficient, k e , was varied as a fitting parameter. When they combine the dendrite growth model of Boettinger et al. with the Continuous Growth Model (CGM) of Aziz and Kaplan with solute drag, they cannot fit the data for any value of k e . When they combine dendrite growth theory with the CGM without solute drag, they obtain a reasonable fit to the data for k e = 4 x 10 -6 . When they combine dendrite growth theory with a new partial-solute-drag interpolation between the with-solute-drag and the without-solute-drag versions of the CGM, they obtain a still better fit to the data for k e = 2.8 x 10 - 4. This result points out the possibility of partial solute-drag during solidification and the importance of an independent determination of k e in order to distinguish between models

  2. Direct chill casting of aluminium alloys under electromagnetic interaction by permanent magnet assembly

    Science.gov (United States)

    Bojarevičs, Andris; Kaldre, Imants; Milgrāvis, Mikus; Beinerts, Toms

    2018-05-01

    Direct chill casting is one of the methods used in industry to obtain good microstructure and properties of aluminium alloys. Nevertheless, for some alloys grain structure is not optimal. In this study, we offer the use of electromagnetic interaction to modify melt convection near the solidification interface. Solidification under various electromagnetic interactions has been widely studied, but usually at low solidification velocity and high thermal gradient. This type of interaction may succeed fragmentation of dendrite arms and transport of solidification nuclei thus leading to improved material structure and properties. Realization of experimental small-scale crystallizer and electromagnetic system has been described in this article.

  3. Investigation of columnar-to-equiaxed transition in solidification processing of AlSi alloys in microgravity – The CETSOL project

    International Nuclear Information System (INIS)

    Zimmermann, G; Sturz, L; Billia, B; Mangelinck-Noël, N; Thi, H Nguyen; Gandin, Ch- A; Browne, D J; Mirihanage, W U

    2011-01-01

    Grain structures observed in most casting processes of metallic alloys are the result of a competition between the growth of several arrays of dendrites that develop under constrained and unconstrained conditions. Often this leads to a transition from columnar to equiaxed grain growth during solidification (CET). A microgravity environment results in suppression of buoyancy-driven melt flow and so enables growth of equiaxed grains free of sedimentation and buoyancy effects. This contribution presents first results obtained in experiments on-board the International Space Station (ISS), which were performed in the frame of the ESA-MAP programme CETSOL. Hypoeutectic aluminium-silicon alloys with and without grain refiners were processed successfully in a low gradient furnace (MSL-LGF). First analysis shows that in the non grain refined samples columnar dendritic growth exists, whereas CET is observed in the grain refined samples. From analysis of the thermal data and the grain structure the critical parameters for the temperature gradient and the cooling rate describing CET are determined. These data are used for initial numerical simulations to predict the position of the columnar-to-equiaxed transition and will form a unique database for calibration and further development of numerical CET-modeling.

  4. A computational/directional solidification method to establish saddle points on the Mg-Al-Ca liquidus

    International Nuclear Information System (INIS)

    Cao Hongbo; Zhang Chuan; Zhu Jun; Cao Guoping; Kou Sindo; Schmid-Fetzer, Rainer; Chang, Y. Austin

    2008-01-01

    We established two saddle point maxima, L + α(Mg) + C14 and L + α(Mg) + C36, on the monovariant liquidus, calculated from a previously presented thermodynamic description, by characterizing the microstructures of several directionally solidified alloys in the near-solidification front zone, the mushy zone, and the steady-state zone using optical microscopy, scanning electron microscopy and transmission electron microscopy

  5. Molecular Dynamics Simulation of Solidification of Pd-Ni Clusters with Different Nickel Content

    Directory of Open Access Journals (Sweden)

    Chen Gang

    2014-01-01

    Full Text Available Molecular dynamics simulation has been performed for investigating the glass transition of Pd-Ni alloy nanoparticles in the solidification process. The results showed that the Pd-Ni nanoparticles with composition far from pure metal should form amorphous structure more easily, which is in accordance with the results of the thermodynamic calculation. There are some regular and distorted fivefold symmetry in the amorphous Pd-Ni alloy nanoparticles. The nanoclusters with bigger difference value between formation enthalpies of solutions and glasses will transform to glass more easily than the other Pd-Ni alloy nanoclusters.

  6. Characterization of aluminium alloys rapidly solidified

    International Nuclear Information System (INIS)

    Monteiro, W.A.

    1988-01-01

    This paper discussed the investigation of the microstructural and mechanical properties of the aluminium alloys (3003; 7050; Al-9% Mg) rapidly solidified by melt spinning process (cooling rate 10 4 - 10 6 K/s). The rapidly solidification process of the studied aluminium alloys brought a microcrystallinity, a minimum presence of coarse precipitation and, also, better mechanical properties of them comparing to the same alloys using ingot process. (author) [pt

  7. Microstructure and property of directionally solidified Ni-Si hypereutectic alloy

    Science.gov (United States)

    Cui, Chunjuan; Tian, Lulu; Zhang, Jun; Yu, Shengnan; Liu, Lin; Fu, Hengzhi

    2016-03-01

    This paper investigates the influence of the solidification rate on the microstructure, solid/liquid interface, and micro-hardness of the directionally solidified Ni-Si hypereutectic alloy. Microstructure of the Ni-Si hypereutectic alloy is refined with the increase of the solidification rate. The Ni-Si hypereutectic composite is mainly composed of α-Ni matrix, Ni-Ni3Si eutectic phase, and metastable Ni31Si12 phase. The solid/liquid interface always keeps planar interface no matter how high the solidification rate is increased. This is proved by the calculation in terms of M-S interface stability criterion. Moreover, the Ni-Si hypereutectic composites present higher micro-hardness as compared with that of the pure Ni3Si compound. This is caused by the formation of the metastable Ni31Si12 phase and NiSi phase during the directional solidification process.

  8. 9 CFR 3.56 - Sanitation.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Sanitation. 3.56 Section 3.56 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE ANIMAL... Animal Health and Husbandry Standards § 3.56 Sanitation. (a) Cleaning of primary enclosures. (1) Primary...

  9. 19 CFR 356.20 - Discovery.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Discovery. 356.20 Section 356.20 Customs Duties... § 356.20 Discovery. (a) Voluntary discovery. All parties are encouraged to engage in voluntary discovery... sanctions proceeding. (b) Limitations on discovery. The administrative law judge shall place such limits...

  10. 19 CFR 356.23 - Hearing.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Hearing. 356.23 Section 356.23 Customs Duties... § 356.23 Hearing. (a) Scheduling of hearing. The administrative law judge will schedule the hearing at a... parties adequately to prepare for the hearing and the importance of expeditiously resolving the matter. (b...

  11. Rapid Solidification of Sn-Cu-Al Alloys for High-Reliability, Lead-Free Solder: Part II. Intermetallic Coarsening Behavior of Rapidly Solidified Solders After Multiple Reflows

    Science.gov (United States)

    Reeve, Kathlene N.; Choquette, Stephanie M.; Anderson, Iver E.; Handwerker, Carol A.

    2016-12-01

    Controlling the size, dispersion, and stability of intermetallic compounds in lead-free solder alloys is vital to creating reliable solder joints regardless of how many times the solder joints are melted and resolidified (reflowed) during circuit board assembly. In this article, the coarsening behavior of Cu x Al y and Cu6Sn5 in two Sn-Cu-Al alloys, a Sn-2.59Cu-0.43Al at. pct alloy produced via drip atomization and a Sn-5.39Cu-1.69Al at. pct alloy produced via melt spinning at a 5-m/s wheel speed, was characterized after multiple (1-5) reflow cycles via differential scanning calorimetry between the temperatures of 293 K and 523 K (20 °C and 250 °C). Little-to-no coarsening of the Cu x Al y particles was observed for either composition; however, clustering of Cu x Al y particles was observed. For Cu6Sn5 particle growth, a bimodal size distribution was observed for the drip atomized alloy, with large, faceted growth of Cu6Sn5 observed, while in the melt spun alloy, Cu6Sn5 particles displayed no significant increase in the average particle size, with irregularly shaped, nonfaceted Cu6Sn5 particles observed after reflow, which is consistent with shapes observed in the as-solidified alloys. The link between original alloy composition, reflow undercooling, and subsequent intermetallic coarsening behavior was discussed by using calculated solidification paths. The reflowed microstructures suggested that the heteroepitaxial relationship previously observed between the Cu x Al y and the Cu6Sn5 was maintained for both alloys.

  12. Structure of nanocomposites of Al–Fe alloys prepared by ...

    Indian Academy of Sciences (India)

    Wintec

    This difference in the product structure can be attributed to the difference in alloying mechanisms in MA and RSP. Keywords. Nanocomposites; Al–Fe; mechanical alloying; rapid solidification; quasicrystalline. 1. Introduction. Al–Fe alloys are attractive for applications at temperatures beyond those normally associated with ...

  13. Solidification of Magnesium (AM50A) / vol%. SiCp composite

    International Nuclear Information System (INIS)

    Zhang, X; Hu, H

    2012-01-01

    Magnesium matrix composite is one of the advanced lightweight materials with high potential to be used in automotive and aircraft industries due to its low density and high specific mechanical properties. The magnesium composites can be fabricated by adding the reinforcements of fibers or/and particles. In the previous literature, extensive studies have been performed on the development of matrix grain structure of aluminum-based metal matrix composites. However, there is limited information available on the development of grain structure during the solidification of particulate-reinforced magnesium. In this work, a 5 vol.% SiC p particulate-reinforced magnesium (AM50A) matrix composite (AM50A/SiC p ) was prepared by stir casting. The solidification behavior of the cast AM50A/SiC p composite was investigated by computer-based thermal analysis. Optical and scanning electron microscopies (SEM) were employed to examine the occurrence of nucleation and grain refinement involved. The results indicate that the addition of SiC p particulates leads to a finer grain structure in the composite compared with the matrix alloy. The refinement of grain structure should be attributed to both the heterogeneous nucleation and the restricted primary crystal growth.

  14. Grain refinement of Al wrought alloys with newly developed AlTiC master alloys; Kornfeinung von Al-Knetlegierungen mit neu entwickelten AlTiC-Vorlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, W. [Vereinigte Aluminium-Werke AG, Bonn (Germany). Forschung und Entwicklung

    2000-10-01

    AlTiC master alloys are a new grain refiner type to produce an equiaxed grain structure of cast extrusion and rolling ingots. These master alloys contain Ti carbides which act as nucleants of the {alpha} solid solution during solidification. The TiC content is lower than the TiB{sub 2} content of the industrial proved AlTiB master alloys. Benefits of the AlTiC master alloys are the low agglomeration tendency of the Ti carbides in the melt and that no Zr poisoning takes place. Despite of the low Ti carbide content the grain refinement performance can be very efficient, if low melt temperatures during casting will be used and as result of this a sufficient constitutional supercooling at the solidification front is achieved. (orig.)

  15. Phase transformation and liquid density redistribution during solidification of Ni-based superalloy Inconel 718

    Directory of Open Access Journals (Sweden)

    Wang Ling

    2012-08-01

    Full Text Available The influences of chemical segregation and phase transformation on liquid density variation during solidification of Ni-based supperalloy Inconel 718 were investigated using SEM and EDS. It was found that significant segregation in liquid prompts high Nb phase to precipitate directly from liquid, which results in the redistribution of alloy elements and liquid density in their vicinity. The term “inter-precipitate liquid density” is therefore proposed and this concept should be applied to determine the solidification behavior of superalloy Inconel 718.

  16. In situ investigation of SnAgCu solder alloy microstructure

    International Nuclear Information System (INIS)

    Pietrikova, Alena; Bednarcik, Jozef; Durisin, Juraj

    2011-01-01

    Research highlights: → In situ X-ray diffraction investigation enabled detailed analysis of the melting and solidification process of the SAC305 alloy. → It was found that the SAC305 solder melts at 230 deg. C. When cooling from 240 deg. C the SAC305 alloy solidifies at the temperature of 214 deg. C. During solidification β-Sn and Cu 6 Sn 5 is also formed. Formation of Ag 3 Sn occurs at 206 deg. C and the remaining amount of alloy crystallizes approximately at 160 deg. C. → Furthermore, observation of the thermal expansion behaviour of the β-Sn tetragonal unit cell revealed linear dependence of the unit cell volume on temperature. The unit cell parameters a and c also increase linearly with the temperature. Despite the fact that the c parameter is substantially smaller than parameter a, it exhibits a significantly higher linear thermal expansion coefficient. Comparison between data obtained during heating and cooling indicates that the thermal expansion coefficient is slightly greater in the case of cooling. - Abstract: In situ X-ray diffraction experiments, using synchrotron radiation, were employed to analyze microstructure evolution of the 96.5Sn3Ag0.5Cu (wt.%)-SAC305 lead-free solder alloy during heating (30-240 deg. C), isothermal dwell (240 deg. C) and cooling (240-30 deg. C). The special emphasis was placed on the study of the melting and solidification processes, explaining formation, distribution and the order of crystallization of the crystal phases (β-Sn, intermetallic compounds) in the solder alloy. Furthermore, thermal expansion behaviour of the main constituent phase β-Sn was analyzed prior to melting and after the consequent solidification.

  17. Effect of grain refiner on the tensile and impact properties of Al–Si–Mg cast alloys

    International Nuclear Information System (INIS)

    Samuel, E.; Golbahar, B.; Samuel, A.M.; Doty, H.W.; Valtierra, S.; Samuel, F.H.

    2014-01-01

    The present study aims to investigate the influence of the addition of Ti and B in the form of five different grain refiners/aluminium master alloys (Al–10%Ti, Al–5%Ti–1%B, Al–2.5%Ti–2.5%B, Al–1.7%Ti–1.4%B and Al–4%B) in conjunction with that of Sr (as modifier) added in the form of Al–10%Sr master alloy to A356.2 alloy. Grain refinement of an A356.2 alloy with Ti and B additions in the ranges of 0.02–0.5% and 0.01–0.5%, respectively, was examined using these different types of grain refiners. Strontium additions of 30 and 200 ppm were made. All alloys were T6-heat treated before mechanical testing. Tensile and impact tests were conducted to evaluate the influence of the interaction between grain refiner and modifier on the mechanical properties. The properties were determined for both the as-cast and heat-treated conditions. - Highlights: • Grain refining of 356 alloys using five types of grain refiners. • Interaction between the added grain refiner and amount of modifier used (i.e. 30 or 200ppm Sr). • Role of the added amount of Ti and/or B on the eutectic Si particle characteristics. • Role of Ti/B on the impact toughness of 356 alloys modified with Sr (30 or 200ppm)

  18. The influence of cooling rate on the microstructure of stainless steel alloys

    Energy Technology Data Exchange (ETDEWEB)

    Elmer, J.W.

    1988-09-01

    The emergence of high energy density welding, laser surface modification and rapid solidification as commonly used metallurgical processing techniques has greatly increased the range of cooling rates that can be accessed during the solidification of metals and alloys. The microstructures which develop during these rapid cooling conditions may be significantly different from those which develop during low cooling rate conditions as the result of access to new metastable phases with the additional kinetic limitations that accompany rapid solidification. This investigation explores the influence of cooling rate on a series of seven ternary alloys which span the line of two-fold saturation in the Fe-Ni-Cr system. High speed electron beam surface melting was used to resolidify these alloys at scan speeds up to 5 m/s. The resulting cooling rates were estimated from dendrite arm spacing measurements and were confirmed by heat flow modeling to vary from 7 /times/ 10/sup 0/ /degree/C/s to 8 /times/ 10/sup 6/ /degree/C/s. The microstructures that developed from each solidification condition were examined using optical metallography, electron microprobe analysis, scanning electron microscopy and a vibrating sample magnetometer. These results were used to create diagrams to predict the primary mode of solidification, the ferrite content and the complex microstructural morphologies which develop as a function of interface velocity and composition. 158 refs., 90 figs., 45 tabs.

  19. Elevated temperature mechanical properties of a rapidly solidified A1-Fe-V-Si alloy

    International Nuclear Information System (INIS)

    Mitra, S.

    1992-01-01

    Dispersion strengthened Al alloys based on the Al-Fe-V-Si quartenary system have recently been developed using rapid solidification techniques. Rapid solidification techniques which resulted in the above mentioned alloys have also been used to manufacture another commercial alloy, FVS 1212, with 37 volume % of dispersoid. The alloy has shown excellent resistance to coarsening at high temperatures and to creep deformation. Elevated temperature exposure of FVS 1212, for times up to 100 hours, resulted in a significant loss in room temperature mechanical properties only beyond 500 degrees C while 1000 hours at 425 degrees C did not result in any degradation of mechanical but no detailed study of the tensile behavior of FVS 1212 at slow strain rates and elevated temperatures has been reported to date. This paper reports that the present study was undertaken to investigate the tensile behavior of FVS 1212 from room temperature to 400 degrees C at strain rates of 6.56 x 10 - 5/sec and 6.56 x 10 -6 /sec. The study focussed on dynamic strain aging effects and strain hardening behavior, while the effect of strain rate on the flow behavior at elevated temperatures was also evaluated

  20. Multiphase Model of Semisolid Slurry Generation and Isothermal Holding During Cooling Slope Rheoprocessing of A356 Al Alloy

    Science.gov (United States)

    Das, Prosenjit; Samanta, Sudip K.; Mondal, Biswanath; Dutta, Pradip

    2018-04-01

    In the present paper, we present an experimentally validated 3D multiphase and multiscale solidification model to understand the transport processes involved during slurry generation with a cooling slope. In this process, superheated liquid alloy is poured at the top of the cooling slope and allowed to flow along the slope under the influence of gravity. As the melt flows down the slope, it progressively loses its superheat, starts solidifying at the melt/slope interface with formation of solid crystals, and eventually exits the slope as semisolid slurry. In the present simulation, the three phases considered are the parent melt as the primary phase, and the solid grains and air as secondary phases. The air phase forms a definable air/liquid melt interface as the free surface. After exiting the slope, the slurry fills an isothermal holding bath maintained at the slope exit temperature, which promotes further globularization of microstructure. The outcomes of the present model include prediction of volume fractions of the three different phases considered, grain evolution, grain growth, size, sphericity and distribution of solid grains, temperature field, velocity field, macrosegregation and microsegregation. In addition, the model is found to be capable of making predictions of morphological evolution of primary grains at the onset of isothermal coarsening. The results obtained from the present simulations are validated by performing quantitative image analysis of micrographs of the rapidly oil-quenched semisolid slurry samples, collected from strategic locations along the slope and from the isothermal slurry holding bath.

  1. The sequence of intermetallic formation and solidification pathway of an Al–13Mg–7Si–2Cu in-situ composite

    Energy Technology Data Exchange (ETDEWEB)

    Farahany, Saeed, E-mail: saeedfarahany@gmail.com [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Johor Bahru (Malaysia); Nordin, Nur Azmah; Ourdjini, Ali; Abu Bakar, TutyAsma; Hamzah, Esah; Idris, Mohd Hasbullah [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Johor Bahru (Malaysia); Hekmat-Ardakan, Alireza [École Polytechnique de Montréal, Dép. de Génie Chimique, P.O. Box 6079, Centre-ville, Montreal, Quebec H3C 3A7 (Canada)

    2014-12-15

    The phase transformation sequence and solidification behaviour of an Al–13Mg–7Si–2Cu in-situ composite was examined using a combination of computer-aided cooling curve thermal analysis and interrupted quenching techniques. Five different phases were identified by analysing the derivative cooling curves, the X-ray diffraction profile, optical and scanning electron microscopy images and the corresponding energy dispersive spectroscopy. It has been found that the solidification of this alloy begins with primary Mg{sub 2}Si precipitation and continues with the formation of eutectic Al–Mg{sub 2}Si, followed by Al{sub 5}FeSi and simultaneous precipitation of Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 2}Cu complex intermetallic phases. The formation of the last three intermetallic compounds changes the solidification behaviour of these composites remarkably due to their complex eutectic formation reactions. The solidification of the alloy, calculated using the Factsage thermochemical analysis software, has demonstrated a good agreement with the experiments in terms of compound prediction, their weight fractions and reaction temperatures. - Highlights: • Solidification path of a commercial Al-13Mg-7Si-2Cu composite was characterized. • Five different phases were identified and then confirmed with EDS and XRD results. • Mg{sub 2}Si, Al-Mg{sub 2}Si,Al{sub 5}FeSi (β),Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) and Al{sub 2}Cu(θ) precipitated respectively. • Solidification was predicted using the Factsage thermochemical analysis software.

  2. Method of preparing a negative electrode including lithium alloy for use within a secondary electrochemical cell

    Science.gov (United States)

    Tomczuk, Zygmunt; Olszanski, Theodore W.; Battles, James E.

    1977-03-08

    A negative electrode that includes a lithium alloy as active material is prepared by briefly submerging a porous, electrically conductive substrate within a melt of the alloy. Prior to solidification, excess melt can be removed by vibrating or otherwise manipulating the filled substrate to expose interstitial surfaces. Electrodes of such as solid lithium-aluminum filled within a substrate of metal foam are provided.

  3. Thermodynamic assessment of liquid composition change during solidification and its effect on freckle formation in superalloys

    International Nuclear Information System (INIS)

    Long Zhengdong; Liu Xingbo; Yang Wanhong; Chang, K.-M.; Barbero, Ever

    2004-01-01

    The solidification macrosegregation, i.e. freckle, becomes more and more concerned with ever increasing demand for the large ingot size of superalloys. The evaluation of freckle formation is very difficult because of the less understanding of freckle formation mechanism and complex solidification behaviors of multi-component superalloys. The macrostructure of typical Nb-bearing and Ti-bearing superalloys in horizontally directional solidification and vacuum arc remelting (VAR) ingots were investigated to clarify the freckle formation mechanism. The thermodynamic approach was proposed to simulate the solidification behaviors. The relative Ra numbers, a reliable criterion, of freckle formation for some alloys were obtained based on the results of thermodynamic calculations. This thermodynamic approach was evaluated through comparison of the calculations from semi-experimental results. The Ra numbers obtained by thermodynamic approach are in good agreement with the ingot size capability of the industry melting shops, which is limited mainly by freckle defects

  4. Superplastic forming of rapid solidification processed Al-4Li-0.2Zr

    International Nuclear Information System (INIS)

    Meschter, P.J.; Lederich, R.J.; Sastry, S.M.L.

    1987-01-01

    Aluminum-4 wt pct lithium alloys are attractive as structural materials because they are 13 to 14 pct less dense and have 25 pct larger elastic moduli than high-strength 2XXX-and 7XXX-series aluminum alloys. These low-density alloys can be produced only by rapid solidification processing (RSP). Successful RSP of Al-4Li-0.2Zr, Al-4Li-1Mg-0.2Zr, and Al-4Li-1Cu-0.2Zr alloys with strengths similar to that of 7075-T76 has recently been demonstrated. Net-shaped processing techniques such as superplastic forming are capable of producing complex structural elements while minimizing usage of expensive material; thus, these techniques are particularly applicable to Al-Li alloys. The purpose of this study was to determine the conditions of strain rate and temperature under which RSP Al-4Li alloys could be superplastically formed

  5. Solidification of cast iron - A study on the effect of microalloy elements on cast iron

    DEFF Research Database (Denmark)

    Moumeni, Elham

    The present thesis deals with the heat transfer and solidification of ductile and microalloyed grey cast iron. Heterogeneous nucleation of nodular graphite at inclusions in ductile iron during eutectic solidification has been investigated. A series of ductile iron samples with two different...... of the austenite, in the last region to solidify. The superfine graphite which forms in this type of irons is short (10-20µm) and stubby. The microstructure of this kind of graphite flakes in titanium alloyed cast iron is studied using electron microscopy techniques. The methods to prepare samples of cast iron...... for comprehensive transmission electron microscopy of graphite and the surrounding iron matrix have been developed and explained. Dual beam microscopes are used for sample preparation. A TEM study has been carried out on graphite flakes in grey cast iron using selected area electron diffraction (SAED). Based...

  6. Influence of trace boron addition on the directional solidification characteristics of Ti-6Al-4V

    International Nuclear Information System (INIS)

    Srinivasan, Raghavan; Tamirisakandala, Sesh

    2010-01-01

    Trace boron addition to several titanium alloys results in a reduction in the as-cast grain size by an order of magnitude. TiB needles are observed along the prior beta grain boundaries and not the grain interior in these alloys, indicating that TiB needles are not sites for the heterogeneous nucleation of beta grains. This study seeks to understand the influence of the growth rate R on microstructure evolution and grain refinement in Ti-6Al-4V-0.1B alloy using directional solidification experiments and microstructural characterization.

  7. Microstructure engineering of TiAl-based refractory intermetallics within power-down directional solidification process

    International Nuclear Information System (INIS)

    Kartavykh, A.V.; Tcherdyntsev, V.V.; Gorshenkov, M.V.; Kaloshkin, S.D.

    2014-01-01

    Highlights: ► VGF power-down technique is suitable for TiAl-based alloys solidification with tailored microstructure. ► Both columnar-dendrite and granular structures are created in Ti–46Al–8Nb ingots. ► Granular microstructure has been refined with TiB 2 addition to the melt. ► TiB 2 re-precipitate into (Ti,Nb)B particles, those acting as point seeds for fine equiaxed grains nucleation. -- Abstract: The work is aimed at the study of the formation and refinement of primary microstructure appearing in the refractory lightweight structural TiAl-based alloy of Ti–46Al–8Nb (at.%) nominal composition. For tailored microstructure development, the Directional Solidification (DS) of pre-synthesized alloy was performed in the vertical multizone resistive electro-furnace by power-down technique in pure argon environment. Both columnar-dendrite, and equiaxed-granular reproducible as-cast microstructures have been produced in DS ingots, basing on Columnar-to-Equiaxed Transition (CET) diagram and experimental exploration. Particular attention was paid further to equiaxed microstructure improvement by combination of modifying doping of alloy with boron grain refiner and DS processing. As a result the perfect inoculated microstructure of Ti–44Al–7Nb–2B (at.%) ingots was produced with 100 μm mean grain diameter, low scattering of dimensional grain characteristics and high tolerance to DS process parameters variation

  8. Application of SEM/EBSD and FEG-TEM/CBED to determine eutectic solidification mechanisms

    International Nuclear Information System (INIS)

    Nogita, K.; Dahle, A.K.; Drennan, J.

    2002-01-01

    Full text: This study shows the application of electron backscatter diffraction (EBSD) in SEM and convergent beam electron diffraction (CBED) in FEG-TEM to determine eutectic nucleation and growth in hypoeutectic Al-Si foundry alloys. Because the eutectic reaction is often the final stage of solidification it can be expected to have a significant impact on the formation of casting defects, particularly porosity. Previous EBSD work by Nogita and Dahle (2001), Dahle et al (2001), has shown that the eutectic nucleates on the primary phase in the unmodified alloy, and eutectic grains are nucleated in the intergranular liquid, instead of filling the dendrite envelopes, when Sr or Sb is added. However, the orientation relationship between silicon and aluminium in the eutectic has so far not been determined because of difficulties with sample preparation for EBSD and also detection limitations of Kikuchi refraction of silicon and aluminium, particularly in modified alloys with a refined eutectic. The combination of the EBSD technique in SEM and CBED in TEM analyses can provide crystallographic orientation relationships between primary aluminium dendrites, eutectic aluminium and silicon, which are important to explicitly define the solidification mode of the eutectic in hypoeutectic Al-Si alloys. These relationships are influenced, and altered, by the addition of certain elements. This paper also describes the sample preparation techniques for SEM and TEM for samples with different eutectic structures. The advantages the techniques are discussed. Copyright (2002) Australian Society for Electron Microscopy Inc

  9. Comparative Evaluation of Cast Aluminum Alloys for Automotive Cylinder Heads: Part II—Mechanical and Thermal Properties

    Science.gov (United States)

    Roy, Shibayan; Allard, Lawrence F.; Rodriguez, Andres; Porter, Wallace D.; Shyam, Amit

    2017-05-01

    The first part of this study documented the as-aged microstructure of five cast aluminum alloys namely, 206, 319, 356, A356, and A356+0.5Cu, that are used for manufacturing automotive cylinder heads (Roy et al. in Metall Mater Trans A, 2016). In the present part, we report the mechanical response of these alloys after they have been subjected to various levels of thermal exposure. In addition, the thermophysical properties of these alloys are also reported over a wide temperature range. The hardness variation due to extended thermal exposure is related to the evolution of the nano-scale strengthening precipitates for different alloy systems (Al-Cu, Al-Si-Cu, and Al-Si). The effect of strengthening precipitates (size and number density) on the mechanical response is most obvious in the as-aged condition, which is quantitatively demonstrated by implementing a strength model. Significant coarsening of precipitates from long-term heat treatment removes the strengthening efficiency of the nano-scale precipitates for all these alloys systems. Thermal conductivity of the alloys evolve in an inverse manner with precipitate coarsening compared to the strength, and the implications of the same for the durability of cylinder heads are noted.

  10. Role of modification and melt thermal treatment processes on the microstructure and tensile properties of Al–Si alloys

    International Nuclear Information System (INIS)

    Samuel, A.M.; Garza-Elizondo, G.H.; Doty, H.W.; Samuel, F.H.

    2015-01-01

    Highlights: • High tensile strength applying the melt thermal treatment process. • Enhanced ductility by changing the Si particle morphology. • Control of the dissolution and precipitation of Mg 2 Si phase. • Establishment of the fracture mechanisms of Al–Si–Mg alloys. - Abstract: The present study was performed on an Al–7%Si–0.35%Mg alloy (A356 alloy) with the primary objective of improving the alloy performance through modification of the microstructure. Ultimate tensile strength (UTS) can be improved by the addition of strontium (Sr), superheating or Sr modified melt thermal treatment. The melt thermal treatment process alone has no apparent influence on the UTS. Both Sr-modified and Sr-modified melt thermal treatment can help to improve the percentage elongation of A356 alloy castings. A higher percentage elongation can be reached at a higher cooling rate. The effect of solution heat treatment on the tensile properties of various A356.2 alloy castings can be summed up as follows: (i) the yield strength of the A356.2 castings is significantly improved after 8 h solution heat treatment due to the precipitation of Mg 2 Si, (ii) the yield strength remains more or less the same with further increase in solution treatment time to 80 h, and (iii) the UTS is greatly improved within the first 8 h of solution heat treatment and continues up to 80 h, where this improvement is attributed to Mg 2 Si precipitation, dissolution of silicon within the Al-matrix and change in the Si particle morphology (spheroidization). The ductility of the A356.2 alloys can also be considerably enhanced with solution heat treatment (e.g. from ∼6% in the non-modified casting in the as-cast condition to ∼10% after 80 h solution treatment)

  11. Detachment of Tertiary Dendrite Arms during Controlled Directional Solidification in Aluminum - 7 wt Percent Silicon Alloys: Observations from Ground-based and Microgravity Processed Samples

    Science.gov (United States)

    Grugel, Richard N.; Erdman, Robert; Van Hoose, James R.; Tewari, Surendra; Poirier, David

    2012-01-01

    Electron Back Scattered Diffraction results from cross-sections of directionally solidified aluminum 7wt% silicon alloys unexpectedly revealed tertiary dendrite arms that were detached and mis-oriented from their parent arm. More surprisingly, the same phenomenon was observed in a sample similarly processed in the quiescent microgravity environment aboard the International Space Station (ISS) in support of the joint US-European MICAST investigation. The work presented here includes a brief introduction to MICAST and the directional solidification facilities, and their capabilities, available aboard the ISS. Results from the ground-based and microgravity processed samples are compared and possible mechanisms for the observed tertiary arm detachment are suggested.

  12. Transformation processes during annealing of Al-amorphous alloys

    International Nuclear Information System (INIS)

    Petrescu, N.; Petrescu, M.; Calin, M.; Jianu, A.D.; Fecioru, M.

    1993-01-01

    As the amorphous aluminum alloys represent the newest achievement in rapid solidification of Al-based high strength heat resistent materials, a study was undertaken on the amorphous alloys in the Al-RE-TM system, the rare-earth metal being a lanthanide mixture and the transition metal a Ni-Fe substitution in definite proportions. The decomposition on heating of the most highly alloyed amorphous alloy in the investigated series is characterized by differential thermal analysis, electron microscopy and X-ray diffraction. (orig.)

  13. Transformation processes during annealing of Al-amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Petrescu, N. (Polytechnic Inst. Bucharest, Faculty Materials Science and Engineering, Bucharest (Romania)); Petrescu, M. (Polytechnic Inst. Bucharest, Faculty Materials Science and Engineering, Bucharest (Romania)); Calin, M. (Polytechnic Inst. Bucharest, Faculty Materials Science and Engineering, Bucharest (Romania)); Jianu, A.D. (Polytechnic Inst. Bucharest, Faculty Materials Science and Engineering, Bucharest (Romania) IFTM-Bucharest (Romania)); Fecioru, M. (Polytechnic Inst. Bucharest, Faculty Materials Science and Engineering, Bucharest (Romania) DACIA Enterprise-Bucharest (Romania))

    1993-11-01

    As the amorphous aluminum alloys represent the newest achievement in rapid solidification of Al-based high strength heat resistent materials, a study was undertaken on the amorphous alloys in the Al-RE-TM system, the rare-earth metal being a lanthanide mixture and the transition metal a Ni-Fe substitution in definite proportions. The decomposition on heating of the most highly alloyed amorphous alloy in the investigated series is characterized by differential thermal analysis, electron microscopy and X-ray diffraction. (orig.).

  14. Evolution of Primary Fe-Rich Compounds in Secondary Al-Si-Cu Alloys

    Science.gov (United States)

    Fabrizi, Alberto; Capuzzi, Stefano; Timelli, Giulio

    Although iron is usually added in die cast Al-Si foundry alloys to prevent die soldering, primary Fe-rich particles are generally considered as "hardspot" inclusions which compromise the mechanical properties of the alloy, namely ductility and toughness. As there is no economical methods to remove the Fe excess in secondary Al-Si alloys at this time, the control of solidification process and chemical composition of the alloy is a common industrial practice to overcome the negative effects connected with the presence of Fe-rich particles. In this work, the size and morphology as well as the nucleation density of primary Fe-rich particles have been studied as function of cooling rate and alloy chemical composition for secondary Al-Si-Cu alloys. The solidification experiments were carried out using differential scanning calorimetry whereas morphology investigations were conducted using optical and scanning electron microscopy. Mcrosegregations and chemical composition of primary Fe-rich particles were examined by energy dispersive spectroscopy.

  15. Porous Nb-Ti based alloy produced from plasma spheroidized powder

    Directory of Open Access Journals (Sweden)

    Qijun Li

    Full Text Available Spherical Nb-Ti based alloy powder was prepared by the combination of plasma spheroidization and mechanical alloying. Phase constituents, microstructure and surface state of the powder, and pore characteristics of the resulting porous alloy were investigated. The results show that the undissolved W and V in the mechanically alloyed powder is fully alloyed after spheroidization, and single β phase is achieved. Particle size of the spheroidized powder is in the range of 20–110 μm. With the decrease of particle size, a transformation from typical dendrite solidification structure to fine cell microstructure occurs. The surface of the spheroidized powder is coated by a layer of oxides consisting mainly of TiO2 and Nb2O5. Probabilities of sinter-neck formation and particle coalescence increases with increasing sintering temperature. Porous skeleton with relatively homogeneous pore distribution and open pore channel is formed after vacuum sintering at 1700 °C, and the porosity is 32%. The sintering kinetic analysis indicates that grain boundary diffusion is the primary mass transport mechanism during sintering process. Keywords: Powder metallurgy, Nb-Ti based alloy, Porous material, Mechanical alloying, Plasma spheroidizing, Solidification microstructure

  16. Copper-base alloys processed by rapid solidification and ion implantation

    International Nuclear Information System (INIS)

    Wood, J.V.; Elvidge, C.J.; Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Henriksen, O.

    1985-01-01

    Alloys of Cu-Sn and Cu-B have been processed by both melt spinning and ion implantation. In some instances (e.g. Cu-Sn alloys) rapidly solidified ribbons have been subjected to further implantation. This paper describes the similarities and differences in structure of materials subjected to a dynamic and contained process. For example in Cu-B alloys (up to 2wt% Boron) extended solubility is found in implanted alloys which is not present to the same degree in rapidly solidified alloys of the same composition. Likewise the range and nature of the reversible martensitic transformation is different in both cases as examined by electron microscopy and differential scanning calorimetry. (orig.)

  17. Compact x-ray microradiograph for in situ imaging of solidification processes: Bringing in situ x-ray micro-imaging from the synchrotron to the laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Rakete, C.; Baumbach, C.; Goldschmidt, A.; Samberg, D.; Schroer, C. G. [Institut fuer Strukturphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany); Breede, F.; Stenzel, C. [Astrium-Space Transportation, Department: TO 611, Claude-Dornier-Strasse, D-88039 Friedrichshafen (Germany); Zimmermann, G.; Pickmann, C. [ACCESS e.V., Intzestrasse 5, D-52072 Aachen (Germany); Houltz, Y.; Lockowandt, C. [Science Services Division, SSC, Box 4207, SE-17104 Solna (Sweden); Svenonius, O.; Wiklund, P. [Scint-X AB, Torshamnsgatan 35, SE-164 40 Kista (Sweden); Mathiesen, R. H. [Inst. for Fysikk, NTNU, N-7491 Trondheim (Norway)

    2011-10-15

    A laboratory based high resolution x-ray radiograph was developed for the investigation of solidification dynamics in alloys. It is based on a low-power microfocus x-ray tube and is potentially appropriate for x-ray diagnostics in space. The x-ray microscope offers a high spatial resolution down to approximately 5 {mu}m. Dynamic processes can be resolved with a frequency of up to 6 Hz. In reference experiments, the setup was optimized to yield a high contrast for AlCu-alloys. With samples of about 150 {mu}m thickness, high quality image sequences of the solidification process were obtained with high resolution in time and space.

  18. Simulation of Microstructure during Laser Rapid Forming Solidification Based on Cellular Automaton

    Directory of Open Access Journals (Sweden)

    Zhi-jian Wang

    2014-01-01

    Full Text Available The grain microstructure of molten pool during the solidification of TC4 titanium alloy in the single point laser cladding was investigated based on the CAFE model which is the cellular automaton (CA coupled with the finite element (FE method. The correct temperature field is the prerequisite for simulating the grain microstructure during the solidification of the molten pool. The model solves the energy equation by the FE method to simulate the temperature distribution in the molten pool of the single point laser cladding. Based on the temperature field, the solidification microstructure of the molten pool is also simulated with the CAFE method. The results show that the maximum temperature in the molten pool increases with the laser power and the scanning rate. The laser power has a larger influence on the temperature distribution of the molten pool than the scanning rate. During the solidification of the molten pool, the heat at the bottom of the molten pool transfers faster than that at the top of the molten pool. The grains rapidly grow into the molten pool, and then the columnar crystals are formed. This study has a very important significance for improving the quality of the structure parts manufactured through the laser cladding forming.

  19. A thermodynamic prediction for microporosity formation in aluminum-rich Al-Cu alloys

    Science.gov (United States)

    Poirier, D. R.; Yeum, K.; Maples, A. L.

    1987-01-01

    A computer model is used to predict the formation and degree of microporosity in a directionally solidified Al-4.5 wt pct Cu alloy, considering the interplay between solidification shrinkage and gas porosity. Macrosegregation theory is used to determine the local pressure within the interdendritic liquid. Results show interdendritic porosity for initial hydrogen contents in the 0.03-1 ppm range, and none below contents of 0.03. An increase in either the thermal gradient or the solidification rate is show to decrease the amount of interdendritic porosity.

  20. Microstructure and Tensile/Corrosion Properties Relationships of Directionally Solidified Al-Cu-Ni Alloys

    Science.gov (United States)

    Rodrigues, Adilson V.; Lima, Thiago S.; Vida, Talita A.; Brito, Crystopher; Garcia, Amauri; Cheung, Noé

    2018-03-01

    Al-Cu-Ni alloys are of scientific and technological interest due to high strength/high temperature applications, based on the reinforcement originated from the interaction between the Al-rich phase and intermetallic composites. The nature, morphology, size, volume fraction and dispersion of IMCs particles throughout the Al-rich matrix are important factors determining the resulting mechanical and chemical properties. The present work aims to evaluate the effect of the addition of 1wt%Ni into Al-5wt%Cu and Al-15wt%Cu alloys on the solidification rate, macrosegregation, microstructure features and the interrelations of such characteristics on tensile and corrosion properties. A directional solidification technique is used permitting a wide range of microstructural scales to be examined. Experimental growth laws relating the primary and secondary dendritic spacings to growth rate and solidification cooling rate are proposed, and Hall-Petch type equations are derived relating the ultimate tensile strength and elongation to the primary dendritic spacing. Considering a compromise between ultimate tensile strength and corrosion resistance of the examined alloys samples from both alloys castings it is shown that the samples having more refined microstructures are associated with the highest values of such properties.

  1. Experimental and thermodynamic assessments of substitutions in the AlFeSi, FeMnSi, FeSiZr and AlCaFeSi systems (65 wt % Si) - solidification simulation

    International Nuclear Information System (INIS)

    Gueneau, C.; Ansara, I.

    1994-01-01

    The substitutions of Al Si, Fe Mn and Fe Zr in some intermetallic compounds of the Al-Fe-Si, Fe-Mn-Si and Fe-Si-Zr systems are modelled in the Si-rich corner using a two sublattice model. The solidification paths of the studied alloys are determined at equilibrium. The ascalculated phase volume fractions of the alloys are compared to the experimental ones. Finally, a solidification simulation using the Gulliver-Scheil's model is performed in order to explain the formation of some precipitates experimentally observed. (authors). 14 figs., 19 refs

  2. Effect of Temperature and Fluid Flow on Dendrite Growth During Solidification of Al-3 Wt Pct Cu Alloy by the Two-Dimensional Cellular Automaton Method

    Science.gov (United States)

    Gu, Cheng; Wei, Yanhong; Liu, Renpei; Yu, Fengyi

    2017-12-01

    A two-dimensional cellular automaton-finite volume model was developed to simulate dendrite growth of Al-3 wt pct Cu alloy during solidification to investigate the effect of temperature and fluid flow on dendrite morphology, solute concentration distribution, and dendrite growth velocity. Different calculation conditions that may influence the results of the simulation, including temperature and flow, were considered. The model was also employed to study the effect of different undercoolings, applied temperature fields, and forced flow velocities on solute segregation and dendrite growth. The initial temperature and fluid flow have a significant impact on the dendrite morphologies and solute profiles during solidification. The release of energy is operated with solidification and results in the increase of temperature. A larger undercooling leads to larger solute concentration near the solid/liquid interface and solute concentration gradient at the same time-step. Solute concentration in the solid region tends to increase with the increase of undercooling. Four vortexes appear under the condition when natural flow exists: the two on the right of the dendrite rotate clockwise, and those on the left of the dendrite rotate counterclockwise. With the increase of forced flow velocity, the rejected solute in the upstream region becomes easier to be washed away and enriched in the downstream region, resulting in acceleration of the growth of the dendrite in the upstream and inhibiting the downstream dendrite growth. The dendrite perpendicular to fluid flow shows a coarser morphology in the upstream region than that of the downstream. Almost no secondary dendrite appears during the calculation process.

  3. PREFACE: Third International Conference on Advances in Solidification Processes (ICASP - 3)

    Science.gov (United States)

    Zimmermann, Gerhard; Ratke, Lorenz

    2012-01-01

    The 3rd International Conference on Advances in Solidification Processes was held in the Rolduc Abbey in the Netherlands a few kilometres away from Aachen. Around 200 scientists from 24 countries come in for the four day meeting. They found a stimulating but also relaxing environment and atmosphere, with beautiful weather and the medieval abbey inviting for walks, discussions, sitting outside and drinking a beer or wine. The contributions given at the conference reflected recent advances in various topics of solidification processes, ranging from fundamental aspects to applied casting technologies. In 20 oral sessions and a large poster session innovative results of segregation phenomena, microstructure evolution, nucleation and growth, phase formation, polyphase solidification, rapid solidification and welding, casting technology, thermophysics of molten alloys, solidification with forced melt flow and growth of single crystals and superalloys together with innovative diagnostic techniques were presented. Thereby, findings from experiments as well as from numerical modeling on different lengths scales were jointly discussed and contribute to new insight in solidification behaviour. The papers presented in this open access proceedings cover about half the oral and poster presentations given. They were carefully reviewed as in classical peer reviewed journals by two independent referees and most of them were revised and thus improved according to the reviewers comments. We think that this collection of papers presented at ICASP-3 gives an impression of the excellent contributions made. The papers embrace both the basic and applied aspects of solidification. We especially wish to express our appreciation for the team around Georg Schmitz and Margret Nienhaus organising this event and giving us their valued advice and support at every stage in preparing the conference. We also thank Lokasenna Lektorat for taking the task of checking all language-associated issues and

  4. Modelling of micro- and macrosegregation for industrial multicomponent aluminium alloys

    International Nuclear Information System (INIS)

    Ellingsen, K; M'Hamdi, M; Mortensen, D

    2015-01-01

    Realistic predictions of macrosegregation formation during casting of aluminium alloys requires an accurate modeling of solute microsegregation accounting for multicomponent phase diagrams and secondary phase formation. In the present work, the stand alone Alstruc model, a microsegregation model for industrial multicomponent aluminium alloys, is coupled with the continuum model ALSIM which calculates the macroscopic transport of mass, enthalpy, momentum, and solutes as well as stresses and deformation during solidification of aluminium. Alstruc deals with multicomponent alloys accounting for temperature dependent partition coefficients, liquidus slopes and the precipitation of secondary phases. The challenge associated with computation of microsegregation for multicomponent alloys is solved in Alstruc by approximating the phase diagram data by simple, analytical expressions which allows for a CPU-time efficient coupling with the macroscopic transport model. In the present work, the coupled model has been applied in a study of macrosegregation including thermal and solutal convection, solidification shrinkage and surface exudation on an industrial DC-cast billet. (paper)

  5. A thermodynamically consistent model of shape-memory alloys

    Czech Academy of Sciences Publication Activity Database

    Benešová, Barbora

    2011-01-01

    Roč. 11, č. 1 (2011), s. 355-356 ISSN 1617-7061 R&D Projects: GA ČR GAP201/10/0357 Institutional research plan: CEZ:AV0Z20760514 Keywords : slape memory alloys * model based on relaxation * thermomechanic coupling Subject RIV: BA - General Mathematics http://onlinelibrary.wiley.com/doi/10.1002/pamm.201110169/abstract

  6. Temperature and Pressure Evolution during Al Alloy Solidification at Different Squeeze Pressures

    International Nuclear Information System (INIS)

    Li, Junwen; Zhao, Haidong; Chen, Zhenming

    2015-01-01

    Squeeze casting is an advanced and near net-shape casting process, in which external high pressure is applied to solidifying castings. The castings are characterized with fine grains and good mechanical properties. In this study, a series of experiments were carried out to measure the temperature and pressure histories in cavity of Al-Si-Mg direct squeeze castings with different applied solidification pressures of 0.1, 50, 75, and 100 MPa. The evolution of the measured temperatures and pressures was compared and discussed. The effect of pressure change on formation of shrinkage defects was analyzed. Further the friction between the castings and dies during solidification was calculated. It is shown that the applied squeeze pressure has significant influence on the friction at die and casting interfaces, which affects the pressure evolution and transmission. The results could provide some benchmark data for future thermal-mechanics coupled modeling of squeeze castings. (paper)

  7. The Influence of Cr on the Solidification Behavior of Polycrystalline γ(Ni)/ γ'(Ni3Al)- δ(Ni3Nb) Eutectic Ni-Base Superalloys

    Science.gov (United States)

    Xie, Mengtao; Helmink, Randolph; Tin, Sammy

    2012-04-01

    In the current investigation, the effect of Cr on the solidification characteristics and as-cast microstructure of pseudobinary γ- δ eutectic alloys based on a near-eutectic composition (Ni-5.5Al-13.5Nb at. pct) was investigated. It was found that Cr additions promote the formation of a higher volume fraction of γ- δ eutectic microstructure in the interdendritic region. Increasing levels of Cr also triggered morphological changes in the γ- δ eutectic and the formation of γ- γ'- δ ternary eutectic during the last stage of solidification. A detailed characterization of the as-cast alloys also revealed that Cr additions suppressed the liquidus, solidus, and γ' precipitation temperature of these γ/ γ'- δ eutectic alloys. A comparison of the experimental results with thermodynamic calculations using the CompuTherm Pandat database (CompuTherm LLC, Madison, WI) showed qualitative agreement.

  8. Microstructure, SDAS and Mechanical Properties of A356 alloy Castings Made in Sand and Granulated Blast Furnace Slag Moulds

    Directory of Open Access Journals (Sweden)

    Jinugu B. R.

    2017-03-01

    Full Text Available Investigations were carried out to ensure the granulated blast furnace (GBF slag as an alternative mould material in foundry industry by assessing the cast products structure property correlations. Sodium silicate-CO2 process was adopted for preparing the moulds. Three types of moulds were made with slag, silica sand individually and combination of these two with 10% sodium silicate and 20 seconds CO2 gassing time. A356 alloy castings were performed on these newly developed slag moulds. The cast products were investigated for its metallography and mechanical properties. Results reveal that cast products with good surface finish and without any defects were produced. Faster heat transfers in slag moulds enabled the cast products with fine and refined grain structured; and also, lower Secondary Dendrite Arm Spacing (SDAS values were observed than sand mould. Slag mould casting shows improved mechanical properties like hardness, compression, tensile and impact strength compared to sand mould castings. Two types of tensile fracture modes, namely cleavage pattern with flat surfaces representing Al−Si eutectic zone and the areas of broken Fe-rich intermetallic compounds which appear as flower-like morphology was observed in sand mould castings. In contrast, GBF slag mould castings exhibit majority in dimple fracture morphology with traces of cleavage fracture. Charpy impact fractured surfaces of sand mould castings shows both transgranular and intergranular fracture modes. Only intergranular fracture mode was noticed in both GBF slag and mixed mould castings.

  9. High temperature diffusion induced liquid phase joining of a heat resistant alloy

    International Nuclear Information System (INIS)

    Wikstrom, N.P.; Egbewande, A.T.; Ojo, O.A.

    2008-01-01

    Transient liquid phase bonding (TLP) of a nickel base superalloy, Waspaloy, was performed to study the influence of holding time and temperature on the joint microstructure. Insufficient holding time for complete isothermal solidification of liquated insert caused formation of eutectic-type microconstituent along the joint centerline region in the alloy. In agreement with prediction by conventional TLP diffusion models, an increase in bonding temperature for a constant gap size, resulted in decrease in the time, t f, required to form a eutectic-free joint by complete isothermal solidification. However, a significant deviation from these models was observed in specimens bonded at and above 1175 deg. C. A reduction in isothermal solidification rate with increased temperature was observed in these specimens, such that a eutectic-free joint could not be achieved by holding for a time period that produced complete isothermal solidification at lower temperatures. Boron-rich particles were observed within the eutectic that formed in the joints prepared at the higher temperatures. An overriding effect of decrease in boron solubility relative to increase in its diffusivity with increase in temperature, is a plausible important factor responsible for the reduction in isothermal solidification rate at the higher bonding temperatures

  10. Radioactive gas solidification apparatus

    International Nuclear Information System (INIS)

    Kobayashi, Yoshihiro; Seki, Eiji; Yabu, Tomohiko; Matsunaga, Hiroyuki.

    1990-01-01

    Handling of a solidification container from the completion for the solidifying processing to the storage of radioactive gases by a remote control equipment such as a manipulator requires a great cost and is difficult to realize. In a radioactive gas solidification device for injection and solidification in accumulated layers of sputtered metals by glow discharge, radiation shieldings are disposed surrounding the entire container, and cooling water is supplied to a cooling vessel formed between the container and the shielding materials. The shielding materials are divided into upper and lower shielding materials, so that solidification container can be taken out from the shielding materials. As a result, the solidification container after the solidification of radioactive gases can be handled with ease. Further, after-heat can be removed effectively from the ion injection electrode upon solidifying treatment upon storage, to attain a radioactive gas solidifying processing apparatus which is safe, economical and highly reliable. (N.H.)

  11. Sulfide phase in the Fe-Ti-S and Fe-C-Ti-S alloys

    International Nuclear Information System (INIS)

    Malinochka, Ya.N.; Balakina, N.A.; Shmelev, Yu.S.

    1976-01-01

    The nature of the sulfide phases in Fe-Ti-S and Fe-C-Ti-S alloys was studied. The carbide and the sulfide phase were identified the aid of X-ray spectral microanalysis. It was established that for a small content of titanium and sulfur in ternary Fe-Ti-S alloys the solidification of the γ-solution on the boundaries of dendritic branches is accompanied, along with the precipitation of a sulfide rich in iron of the (Fe, Ti) S type where a small quantity of titanium is dissolved, by the formation of a titanium-bearing sulfide eutectic γ + TiS. The amount of the sulfide eutectic increases with the contents of titanium and sulfur until a purely eutectic alloy is formed. Both carbides and sulfides may be formed in the solidification of quaternary alloys Fe-C-Ti-S

  12. Pseudobinary eutectics in Cu–Ag–Ge alloy droplets under containerless condition

    International Nuclear Information System (INIS)

    Ruan, Y.; Wang, X.J.; Lu, X.Y.

    2013-01-01

    Highlights: ► Two pseudobinary eutectics form in Cu–Ag–Ge alloy. ► It is influenced by thermodynamic and kinetic factors of the alloy in the drop tube. ► As droplet size reduces, anomalous → lamellar → anomalous transition happens in (Ag + ζ). ► (Ag + ε 2 ) is a product of both peri-eutectic and pseudobinary eutectic transitions. -- Abstract: Pseudobinary eutectic generated by pseudobinary eutectic transition or peri-eutectic transition is a crucial structure in ternary alloy systems. Its formation mechanism strongly influences mechanical properties of these metallic materials. However, it was customarily neglected. In this paper, two pseudobinary eutectics, i.e. (Ag + ζ) and (Ag + ε 2 ), were investigated during the rapid solidification of Cu–Ag–Ge ternary alloy in a 3 m-drop tube. The sharp temperature variations and dramatic kinetic activities of the falling alloy droplets before solidification cause special microstructural characteristics. (Ag) dendrite is the heterogeneous nucleus for anomalous (Ag + ζ) pseudobinary eutectic in large droplets. Lamellar (Ag + ζ) pseudobinary eutectic grain forms independently on condition that primary (Ag) dendrite cannot form and its eutectic morphology becomes anomalous with the decrease of droplet size. Nanoscaled (Ag + ε 2 ) pseudobinary eutectic generating at the last stage of solidification is the product of both peri-eutectic and pseudobinary eutectic transitions. It distributes in the gaps of (Ag + ζ) pseudobinary eutectic grains and its morphology remains lamellar regardless of droplet size

  13. Thermal description of hypoeutectic Al-Si-Cu alloys using silicon equivalency

    Directory of Open Access Journals (Sweden)

    Mile B. Đurđević

    2012-01-01

    Full Text Available The modeling of casting processes has remained a topic of active interest for several decades, and availability of numerous software packages on the market is a good indication of the interest that the casting industry has in this field. Most of the data used in these software packages are read or estimated from the binary or multi-component phase diagrams. Unfortunately, except for binary diagrams, many of ternary or higher order phase diagrams are still not accurate enough. Having in mind that most of the aluminum binary systems are very well established, it has been tried to transfer a multi-component system into one well known Al-Xi pseudo binary system (in this case the Al-Si phase diagram was chosen as a reference system. The new Silicon Equivalency (SiEQ algorithm expresses the amounts of major and minor alloying elements in the aluminum melts through an 'equivalent' amount of silicon. Such a system could be used to calculate several thermo-physical and solidification characteristics of multi component as cast aluminum alloys. This lends the model the ability to make predictions of solidification characteristics of cast parts, where cooling rates are slow and the solidification process has to be known in great detail in order to avoid problems in the casting. This work demonstrates how the SiEQ algorithm can be used to calculate characteristic solidification temperatures of the multi-component hypoeutectic Al-Si-Cu alloys as well as their latent heats. SA statistical analysis of the results obtained for a wide range of alloy chemical compositions shows a very good correlation with the experimental data and the SiEQ calculations.

  14. Solidification structure and abrasion resistance of high chromium white irons

    Science.gov (United States)

    Doğan, Ö. N.; Hawk, J. A.; Laird, G.

    1997-06-01

    Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.

  15. Grain Refinement and Texture Mitigation in Low Boron Containing TiAl-Alloys

    Science.gov (United States)

    Hecht, Ulrike; Witusiewicz, Victor T.

    2017-12-01

    Controlling the grain size and texture of lamellar TiAl-alloys is essential for well-balanced creep and fatigue properties. Excellent refinement and texture mitigation are achieved in aluminum lean alloys by low boron additions of 0.2 at.%. This amount is sufficient to promote in situ formation of ultrafine borides during the last stages of body centered cubic (BCC) solidification. The borides subsequently serve as nucleation sites for hexagonal close packed (HCP) during the BCC-HCP phase transformation. Bridgman solidification experiments with alloy Ti-43Al-8Nb-0.2C-0.2B were performed under a different growth velocity, i.e., cooling rate, to evaluate the HCP grain size distribution and texture. For slow-to-moderate cooling rates, about 65% of HCP grains are randomly oriented, despite the pronounced texture of the parent BCC phase resulting from directional solidification. For high cooling rates, obtained by quenching, texture mitigation is less pronounced. Only 28% of the HCP grains are randomly oriented, the majority being crystallographic variants of the Burgers orientation relationship.

  16. Prediction of mechanical properties of Al alloys with change of cooling rate

    Directory of Open Access Journals (Sweden)

    Quan-Zhi Dong

    2012-11-01

    Full Text Available The solidification process significantly affects the mechanical properties and there are lots of factors that affect the solidification process. Much progress has been made in the research on the effect of solidification on mechanical properties. Among them, the PF (Phase Field model and CA (Cellular Automata model are widely used as simulation methods which can predict nucleation and its growth, and the size and morphology of the grains during solidification. Although they can give accurate calculation results, it needs too much computational memory and calculation time. So it is difficult to apply the simulation to the real production process. In this study, a more practical simulation approach which can predict the mechanical properties of real aluminum alloys is proposed, by identifying through experiment the relationship between cooling rate and SDAS (Secondary Dendrite Arm Spacing and mechanical properties. The experimentally measured values and the values predicted by simulation have relatively small differences and the mechanical properties of a variety of Al alloys are expected to be predicted before casting through use of the simulation.

  17. Study of the oxidation effects on isothermal solidification based high temperature stable Pt/In/Au and Pt/In/Ag thick film interconnections on LTCC substrate

    International Nuclear Information System (INIS)

    Kumar, Duguta Suresh; Khanna, P. K.; Suri, Nikhil; Sharma, R. P.

    2016-01-01

    The objective of the presented paper is to determine the oxidized phase compositions of indium lead-free solders during solidification at 190 ° C under room environment with the help of X-ray diffraction (XRD) and Energy dispersive spectroscopy (EDX). Many lead-free solders alloys available oxidizes and have poor wetting properties. The oxidation of pure indium solder foil, Au, Pt, and Ag alloys were identified and investigated, in the process of isothermal solidification based solder joints construction at room environment and humidity. Both EDX and XRD characterization techniques were performed to trace out the amount of oxide levels and variety of oxide formations at solder interface respectively. The paper also aims to report the isothermal solidification technique to provide interconnections to pads on Low temperature co-fired ceramic (LTCC) substrate. It also elaborates advantages of isothermal solidification over the other methods of interconnection. Scanning electron microscope (SEM) used to identify the oxidized spots on the surface of Pt, Ag substrates and In solder. The identified oxides were reported.

  18. High-temperature electrochemical performance of low-cost La–Ni–Fe based hydrogen storage alloys with different preparation methods

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiannan [Department of Advanced Energy Materials, College of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Zhu, Ding [Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065 (China); Zhou, Wanhai; Zhong, Chenglin; Wu, Chaoling [Department of Advanced Energy Materials, College of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Chen, Yungui, E-mail: ygchen60@aliyun.com [Department of Advanced Energy Materials, College of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065 (China)

    2016-04-15

    Highlights: • Effects of four different preparation processes were studied at 20/60 °C. • All NS + HT, RS and RS + HT processes can optimize the thermodynamic performance. • The HT process can provoke the precipitation of A{sub 2}B{sub 7} and leads to a poor cycling life. • Al exhibits the most remarkable dissolution for all the alloys, especially at 60 °C. - Abstract: In order to optimize the microstructure and high temperature electrochemical performances of low-cost AB{sub 5}-type Ml(NiMnAl){sub 4.2}Co{sub 0.3}Fe{sub 0.5} hydrogen storage electrode alloys, four different preparation methods including normal solidification (NS), normal solidification and 900 °C heat treatment (NS + HT), rapid solidification (RS), rapid solidification and 900 °C heat treatment (RS + HT) were adopted in this work. All alloys exhibit CaCu{sub 5} type hexagonal structure and there is a small amount of A{sub 2}B{sub 7} phase in NS + HT and RS + HT alloys. It is found the using of HT process can decrease the hydrogen equilibrium plateau pressure, the plateau slope and hysteresis at 40, 60 and 80 °C. The NS + HT and RS + HT alloys also possess better activation, high rate discharge performance, larger discharge capacity, but poor cycling performance due to the existence of A{sub 2}B{sub 7} phase which can accelerate dissolution of Ni, Mn and Fe elements in KOH alkaline electrolyte. The RS process can make alloy exhibit the best cycling performance especially at 60 °C.

  19. Compositional Approach to Designing Fcc High-Entropy Alloys that Have an Enlarged Equiaxed Zone

    Directory of Open Access Journals (Sweden)

    Minju Kang

    2018-01-01

    Full Text Available A compositional approach to designing alloys that have an enlarged equiaxed zone is suggested in this study. The partitioning of elements during the solidification of CoCrFeMnNi high-entropy alloy (HEA was confirmed through a directional solidification quenching experiment. Several HEAs were designed to maximize the effects of constitutional and thermal undercooling by considering factors including solute enrichment at the columnar front and the melting temperatures and thermal conductivities of the individual elements. The newly designed HEAs were shown to have successfully enlarged equiaxed zones, and improved anisotropic properties.

  20. A Study on Development of High Strength Al-Zn Based alloy for Die Casting Ⅲ

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sang-Soo; Park, Ik-Min [Pusan National University, Busan (Korea, Republic of); Yeom, Gil-Young; Lim, Kyoung-Mook [Korea Institute of Industrial Technology, Incheon (Korea, Republic of); Son, Hyun-Jin [Oh-Sung Co. Ltd., Siheung (Korea, Republic of)

    2015-09-15

    In this study, the microstructural evolution and various characteristics of Al-20⁓45wt%Zn alloys were investigated. In terms of microstructure, as the amount of Zn addition to the alloys increased, the α-phase size decreased and the α+η non-equilibrium solidification phase fraction increased. Also, increasing Zn content improved the wear resistance of the alloys, but reduced the damping capacity and toughness of the alloys. Their physical properties of the Al-Zn alloy with high Zn content, specifically the wear resistance and toughness, were superior to those of commercial ALDC12 alloys for die-casting. Based on these results, we considered the possibility of application of the developed Al-Zn alloy as a structural material.

  1. A Study on Development of High Strength Al-Zn Based alloy for Die Casting Ⅲ

    International Nuclear Information System (INIS)

    Shin, Sang-Soo; Park, Ik-Min; Yeom, Gil-Young; Lim, Kyoung-Mook; Son, Hyun-Jin

    2015-01-01

    In this study, the microstructural evolution and various characteristics of Al-20⁓45wt%Zn alloys were investigated. In terms of microstructure, as the amount of Zn addition to the alloys increased, the α-phase size decreased and the α+η non-equilibrium solidification phase fraction increased. Also, increasing Zn content improved the wear resistance of the alloys, but reduced the damping capacity and toughness of the alloys. Their physical properties of the Al-Zn alloy with high Zn content, specifically the wear resistance and toughness, were superior to those of commercial ALDC12 alloys for die-casting. Based on these results, we considered the possibility of application of the developed Al-Zn alloy as a structural material.

  2. Directional Solidification of Pure Succinonitrile and a Succinonitrile-Acetone Alloy

    Science.gov (United States)

    Simpson, James E.; deGroh, Henry C., III; Garimella, Suresh V.

    2000-01-01

    An experimental study of the horizontal Bridgman growth of pure succinonitrile (SCN) and of a succinonitrile-1.0 mol% acetone alloy (SCN-1.0 mol.% ACE) has been performed. Experiments involving both a stationary thermal field (no-growth case) and a translating thermal field (growth case) were conducted. Growth rates of 2 and 40 micrometers/sec were investigated. For the pure SCN experiments, the velocity field in the melt was estimated using video images of seed particles in the melt. Observations of the seed particles indicate that a primary longitudinal convective cell is formed. The maximum velocity of two different particles which traveled along similar paths was the same and equal to 1.49 +/- 0.01 mm/s. The general accuracy of velocity measurements is estimated to be +/-0.08 mm/s, though the data shows consistency to within +/- 0.02 mm/s. The shape of the solid/liquid interface was also quantitatively determined. The solid/liquid interface was stable (non-dendritic and non-cellular) but not flat: rather it was significantly distorted by the influence of connection in the melt and, for the growth case, by the moving temperature boundary conditions along the ampoule. It was found that the interface shape and position were highly dependent on the alignment of the ampoule in the apparatus. Consequently, the ampoule was carefully aligned for all experiments. The values for front location agree with those determined in previous experiments. For the alloy experiments, the solid/liquid interface was determined to be unstable at growth rates greater than 2.8 micrometers/sec, but stable for the cases of no-growth and growth at 2 micrometers/sec. When compared to the shape of the pure SCN interface, the alloy interface forms closer to the cold zone, indicating that the melting temperature decreased due to the alloying element. Extensive temperature measurements were performed on the outside of the ampoule containing pure SCN. The resulting thermal profiles are presented

  3. 40 CFR 51.356 - Vehicle coverage.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

  4. Viscosity of Industrially Important Zn-Al Alloys Part II: Alloys with Higher Contents of Al and Si

    Science.gov (United States)

    Nunes, V. M. B.; Queirós, C. S. G. P.; Lourenço, M. J. V.; Santos, F. J. V.; Nieto de Castro, C. A.

    2018-05-01

    The viscosity of Zn-Al alloys melts, with industrial interest, was measured for temperatures between 693 K and 915 K, with an oscillating cup viscometer, and estimated expanded uncertainties between 3 and 5 %, depending on the alloy. The influence of minor components, such as Si, Mg and Ce + La, on the viscosity of the alloys is discussed. An increase in the amount of Mg triggers complex melt/solidification processes while the addition of Ce and La renders alloys viscosity almost temperature independent. Furthermore, increases in Al and Si contents decrease melts viscosity and lead to an Arrhenius type behavior. This paper complements a previous study describing the viscosity of Zn-Al alloys with quasi-eutectic compositions.

  5. X-Ray Radiographic Observation of Directional Solidification Under Microgravity: XRMON-GF Experiments on MASER12 Sounding Rocket Mission

    Science.gov (United States)

    Reinhart, G.; NguyenThi, H.; Bogno, A.; Billia, B.; Houltz, Y.; Loth, K.; Voss, D.; Verga, A.; dePascale, F.; Mathiesen, R. H.; hide

    2012-01-01

    The European Space Agency (ESA) - Microgravity Application Promotion (MAP) programme entitled XRMON (In situ X-Ray MONitoring of advanced metallurgical processes under microgravity and terrestrial conditions) aims to develop and perform in situ X-ray radiography observations of metallurgical processes in microgravity and terrestrial environments. The use of X-ray imaging methods makes it possible to study alloy solidification processes with spatio-temporal resolutions at the scales of relevance for microstructure formation. XRMON has been selected for MASER 12 sounding rocket experiment, scheduled in autumn 2011. Although the microgravity duration is typically six minutes, this short time is sufficient to investigate a solidification experiment with X-ray radiography. This communication will report on the preliminary results obtained with the experimental set-up developed by SSC (Swedish Space Corporation). Presented results dealing with directional solidification of Al-Cu confirm the great interest of performing in situ characterization to analyse dynamical phenomena during solidification processes.

  6. Corrosion Inhibition Study of Al-Cu-Ni Alloy in Simulated Sea-Water ...

    African Journals Online (AJOL)

    Akorede

    ABSTRACT: A study on the inhibition of Al-Cu-Ni alloy in simulated ... which the percentage of Copper, and Nickel were kept .... proceed based on equation of reaction in eqn (4). Al .... Sodium-Modified A356.0-Type Al-Si-Mg Alloy in Simulated.

  7. Control of segregation in squeeze cast Al-4.5Cu binary alloy

    Energy Technology Data Exchange (ETDEWEB)

    Durrant, G. [Oxford Univ. (United Kingdom). Dept. of Materials; Gallerneault, M. [Alcan International Ltd., Kingston, ON (Canada); Cantor, B. [Oxford Univ. (United Kingdom). Dept. of Materials

    1997-10-01

    The high pressure applied in squeeze casting allows Al alloys of wrought composition to be cast to near net-shape, although their long freezing range leads to the segregation of alloying elements. In this paper we present results on the squeeze casting and gravity casting of a model Al-4.5 wt%Cu alloy. Squeeze cast Al-4.5Cu has a normal segregation pattern with eutectic macrosegregates towards the centre of the billet, whereas gravity cast material has a typical inverse segregation pattern. Normal segregation in squeeze cast Al-4.5Cu is due to large temperature gradients during solidification. Segregation can be minimized by releasing the applied pressure during solidification to allow backflow of the interdendritic fluid, or by the addition of grain refiner to remove the large columnar dendritic growth structure. (orig.)

  8. Radioactive gas solidification treatment device

    International Nuclear Information System (INIS)

    Igarashi, Ryokichi; Watanabe, Yu; Seki, Eiji.

    1992-01-01

    In a radioactive gas solidification treatment device by using sputtering, spiral pipelines are disposed with a gap therebetween for cooling an ion injection electrode by passing cooling water during operation of the solidification treatment. During the operation of the solidification treatment, cooling water is passed in the pipelines to cool the ion injection electrode. During storage, a solidification vessel is cooled by natural heat dissipation from an exposed portion at the surface of the solidification vessel. Accordingly, after-heat of radioactive gas solidified in a metal accumulation layer can be removed efficiently, safely and economically to improve the reliability. (N.H.)

  9. Inspection method for solidification product of radioactive waste and method of preparing solidification product of radiation waste

    International Nuclear Information System (INIS)

    Izumida, Tatsuo; Tamada, Shin; Matsuda, Masami; Kamata, Shoji; Kikuchi, Makoto.

    1993-01-01

    A powerful X-ray generation device using an electron-ray accelerator is used for inspecting presence or absence of inner voids in solidification products of radioactive wastes during or after solidification. By installing the X-ray CT system and the radioactive waste solidifying facility together, CT imaging for solidification products is conducted in a not-yet cured state of solidifying materials during or just after the injection. If a defect that deteriorates the durability of the solidification products should be detected, the solidification products are repaired, for example, by applying vibrations to the not-yet cured solidification products. Thus, since voids or cracks in the radioactive wastes solidification products, which were difficult to be measured so far, can be measured in a short period of time accurately thereby enabling to judge adaptability to the disposal standards, inspection cost for the radioactive waste solidification product can be saved remarkably. Further, the inside of the radioactive waste solidification products can be evaluated correctly and visually, so that safety in the ground disposal storage of the radioactive solidification products can be improved remarkably. (N.H.)

  10. Interface Pattern Selection Criterion for Cellular Structures in Directional Solidification

    Science.gov (United States)

    Trivedi, R.; Tewari, S. N.; Kurtze, D.

    1999-01-01

    The aim of this investigation is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. We shall first address scientific concepts that are crucial in the selection of interface patterns. Next, the results of ground-based experimental studies in the Al-4.0 wt % Cu system will be described. Both experimental studies and theoretical calculations will be presented to establish the need for microgravity experiments.

  11. New insight on glass-forming ability and designing Cu-based bulk metallic glasses: The solidification range perspective

    International Nuclear Information System (INIS)

    Wu, Jili; Pan, Ye; Li, Xingzhou; Wang, Xianfei

    2014-01-01

    Highlights: • The equation, T rg = T g /T l , was rotationally modified to T rg = κ(T m /T l ) + C/T l . • The newly generalized equation suggests a way for describing glass-forming ability. • Several new Cu-based bulk metallic glasses were discovered by solidification range. - Abstract: In this paper, a new equation was rationally generalized from the reduced glass transition temperature. This equation indicates that solidification range can be used for describing glass-forming ability, which can be calculated with the aid of computational thermodynamic approach. Based on this scenario, several new Cu-based bulk metallic glasses in the ternary Cu–Zr–Ti alloy system were discovered. The as-cast samples were characterized by X-ray diffraction and transmission electronic microscopy. The results indicate that as-cast samples have monolithic amorphous nature. Thermal analysis validates that the smaller solidification range is closely related to the higher glass-forming ability, which is contributed to the effect of solidification time on the formation of bulk metallic glasses. This work also suggests that solidus can influence glass formation

  12. Influence of Laser Welding Speed on the Morphology and Phases Occurring in Spray-Compacted Hypereutectic Al-Si-Alloys

    Directory of Open Access Journals (Sweden)

    Thomas Gietzelt

    2016-11-01

    Full Text Available Normally, the weldability of aluminum alloys is ruled by the temperature range of solidification of an alloy according to its composition by the formation of hot cracks due to thermal shrinkage. However, for materials at nonequilibrium conditions, advantage can be taken by multiple phase formation, leading to an annihilation of temperature stress at the microscopic scale, preventing hot cracks even for alloys with extreme melting range. In this paper, several spray-compacted hypereutectic aluminum alloys were laser welded. Besides different silicon contents, additional alloying elements like copper, iron and nickel were present in some alloys, affecting the microstructure. The microstructure was investigated at the delivery state of spray-compacted material as well as for a wide range of welding speeds ranging from 0.5 to 10 m/min, respectively. The impact of speed on phase composition and morphology was studied at different disequilibrium solidification conditions. At high welding velocity, a close-meshed network of eutectic Al-Si-composition was observed, whereas the matrix is filled with nearly pure aluminum, helping to diminish the thermal stress during accelerated solidification. Primary solidified silicon was found, however, containing considerable amounts of aluminum, which was not expected from phase diagrams obtained at the thermodynamic equilibrium.

  13. Solidification method of radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Tsutomu; Chino, Koichi; Sasahira, Akira; Ikeda, Takashi

    1992-07-24

    Metal solidification material can completely seal radioactive wastes and it has high sealing effect even if a trace amount of evaporation should be caused. In addition, the solidification operation can be conducted safely by using a metal having a melting point of lower than that of the decomposition temperature of the radioactive wastes. Further, the radioactive wastes having a possibility of evaporation and scattering along with oxidation can be solidified in a stable form by putting the solidification system under an inert gas atmosphere. Then in the present invention, a metal is selected as a solidification material for radioactive wastes, and a metal, for example, lead or tin having a melting point of lower than that of the decomposition temperature of the wastes is used in order to prevent the release of the wastes during the solidification operation. Radioactive wastes which are unstable in air and scatter easily, for example, Ru or the like can be converted into a stable solidification product by conducting the solidification processing under an inert gas atmosphere. (T.M.).

  14. Nucleation and Growth of Cu-Al Intermetallics in Al-Modified Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys

    Science.gov (United States)

    Reeve, Kathlene N.; Anderson, Iver E.; Handwerker, Carol A.

    2015-03-01

    Lead-free solder alloys Sn-Cu (SC) and Sn-Ag-Cu (SAC) are widely used by the microelectronics industry, but enhanced control of the microstructure is needed to improve solder performance. For such control, nucleation and stability of Cu-Al intermetallic compound (IMC) solidification catalysts were investigated by variation of the Cu (0.7-3.0 wt.%) and Al (0.0-0.4 wt.%) content of SC + Al and SAC + Al alloys, and of SAC + Al ball-grid array (BGA) solder joints. All of the Al-modified alloys produced Cu-Al IMC particles with different morphologies and phases (occasionally non-equilibrium phases). A trend of increasing Cu-Al IMC volume fraction with increasing Al content was established. Because of solidification of non-equilibrium phases in wire alloy structures, differential scanning calorimetry (DSC) experiments revealed delayed, non-equilibrium melting at high temperatures related to quenched-in Cu-Al phases; a final liquidus of 960-1200°C was recorded. During cooling from 1200°C, the DSC samples had the solidification behavior expected from thermodynamic equilibrium calculations. Solidification of the ternary alloys commenced with formation of ternary β and Cu-Al δ phases at 450-550°C; this was followed by β-Sn, and, finally, Cu6Sn5 and Cu-Al γ1. Because of the presence of the retained, high-temperature phases in the alloys, particle size and volume fraction of the room temperature Cu-Al IMC phases were observed to increase when the alloy casting temperature was reduced from 1200°C to 800°C, even though both temperatures are above the calculated liquidus temperature of the alloys. Preliminary electron backscatter diffraction results seemed to show Sn grain refinement in the SAC + Al BGA alloy.

  15. Effect of Additions of Ceramic Nanoparticles and Gas-Dynamic Treatment on Al Casting Alloys

    Directory of Open Access Journals (Sweden)

    Konstantin Borodianskiy

    2015-12-01

    Full Text Available In recent years, improving the mechanical properties of metals has become the main challenge in the modern materials and metallurgical industry. An alloying process is usually used to achieve advanced performance of metals. This paper, however, describes an alternative approach. Modification with ceramic nanoparticles, gas-dynamic treatment (GDT and a combined treatment were investigated on a hypoeutectic Al-Si A356 alloy. Microstructural studies revealed the refinement of coarse α-Al grains and the formation of distributed eutectic Si particles. Subsequent testing of the mechanical properties revealed improvement after applying each of the treatments. The best results were obtained after modification with TiCN nanoparticles followed by GDT; the tensile strength and elongation of the A356 alloys increased by 18% and 19%, respectively.

  16. 3D printing of high-strength aluminium alloys.

    Science.gov (United States)

    Martin, John H; Yahata, Brennan D; Hundley, Jacob M; Mayer, Justin A; Schaedler, Tobias A; Pollock, Tresa M

    2017-09-20

    Metal-based additive manufacturing, or three-dimensional (3D) printing, is a potentially disruptive technology across multiple industries, including the aerospace, biomedical and automotive industries. Building up metal components layer by layer increases design freedom and manufacturing flexibility, thereby enabling complex geometries, increased product customization and shorter time to market, while eliminating traditional economy-of-scale constraints. However, currently only a few alloys, the most relevant being AlSi10Mg, TiAl6V4, CoCr and Inconel 718, can be reliably printed; the vast majority of the more than 5,500 alloys in use today cannot be additively manufactured because the melting and solidification dynamics during the printing process lead to intolerable microstructures with large columnar grains and periodic cracks. Here we demonstrate that these issues can be resolved by introducing nanoparticles of nucleants that control solidification during additive manufacturing. We selected the nucleants on the basis of crystallographic information and assembled them onto 7075 and 6061 series aluminium alloy powders. After functionalization with the nucleants, we found that these high-strength aluminium alloys, which were previously incompatible with additive manufacturing, could be processed successfully using selective laser melting. Crack-free, equiaxed (that is, with grains roughly equal in length, width and height), fine-grained microstructures were achieved, resulting in material strengths comparable to that of wrought material. Our approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines. It thus provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting, and will enable additive manufacturing of other alloy systems, such as non-weldable nickel

  17. 3D printing of high-strength aluminium alloys

    Science.gov (United States)

    Martin, John H.; Yahata, Brennan D.; Hundley, Jacob M.; Mayer, Justin A.; Schaedler, Tobias A.; Pollock, Tresa M.

    2017-09-01

    Metal-based additive manufacturing, or three-dimensional (3D) printing, is a potentially disruptive technology across multiple industries, including the aerospace, biomedical and automotive industries. Building up metal components layer by layer increases design freedom and manufacturing flexibility, thereby enabling complex geometries, increased product customization and shorter time to market, while eliminating traditional economy-of-scale constraints. However, currently only a few alloys, the most relevant being AlSi10Mg, TiAl6V4, CoCr and Inconel 718, can be reliably printed; the vast majority of the more than 5,500 alloys in use today cannot be additively manufactured because the melting and solidification dynamics during the printing process lead to intolerable microstructures with large columnar grains and periodic cracks. Here we demonstrate that these issues can be resolved by introducing nanoparticles of nucleants that control solidification during additive manufacturing. We selected the nucleants on the basis of crystallographic information and assembled them onto 7075 and 6061 series aluminium alloy powders. After functionalization with the nucleants, we found that these high-strength aluminium alloys, which were previously incompatible with additive manufacturing, could be processed successfully using selective laser melting. Crack-free, equiaxed (that is, with grains roughly equal in length, width and height), fine-grained microstructures were achieved, resulting in material strengths comparable to that of wrought material. Our approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines. It thus provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting, and will enable additive manufacturing of other alloy systems, such as non-weldable nickel

  18. Dispersion strengthening of precipitation hardened Al-Cu-Mg alloys prepared by rapid solidification and mechanical alloying

    Science.gov (United States)

    Gilman, P. S.; Sankaran, K. K.

    1988-01-01

    Several Al-4Cu-1Mg-1.5Fe-0.75Ce alloys have been processed from either rapidly solidified or mechanically alloyed powder using various vacuum degassing parameters and consolidation techniques. Strengthening by the fine subgrains, grains, and the dispersoids individually or in combination is more effective when the alloys contain shearable precipitates; consequently, the strength of the alloys is higher in the naturally aged rather than the artificially aged condition. The strengths of the mechanically alloyed variants are greater than those produced from prealloyed powder. Properties and microstructural features of these dispersion strengthened alloys are discussed in regards to their processing histories.

  19. Density of Ni-Cr Alloy in the Mushy State

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy.The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy.The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.

  20. Description of hypo eutectic Al-Si-Cu alloys based on their known chemical compositions

    International Nuclear Information System (INIS)

    Djurdjevic, M. B.; Vicario, I.

    2013-01-01

    The modeling of casting processes has remained a topic of active interest for several decades, and the availability of numerous software packages on the market is a good indication of the interest that the casting industry has in this field. Most of the data used in these software packages are directly read or estimated from the binary or multi-component phase diagrams. Unfortunately, except for binary diagrams, many of ternary or higher order phase diagrams are still not accurate enough. Having in mind that most of the aluminum binary systems are very well established, it has been tried to transfer multi-component system into one well known Al-Xi pseudo binary system (in this case the Al-Si phase diagram was chosen as a reference system). The new Silicon Equivalency (SiEQ) algorithm expresses the amounts of major and minor alloying elements in the aluminum melts through an equivalent amount of silicon. Such a system could be used to calculate several thermo-physical and solidification characteristics of multi component as cast aluminum alloys. This provides to the model the capacity to predict the solidification characteristics of cast parts, where cooling rates are slow and the solidification process has to be known in great detail in order to avoid quality problems in the casting. This work demonstrates how the SiEQ algorithm can be used to calculate the characteristic solidification temperatures of the multicomponent Al-Si alloys as well as their latent heats and growth restriction factor. Statistical analysis of the results obtained for a wide range of alloy chemical compositions shows a very good correlation with the experimental data and the SiEQ calculations. The same mathematical approach might be applied for other metallic systems such as iron and magnesium, using carbon equivalency for ferrous systems and aluminum equivalency for magnesium multi-component alloys. (Author)

  1. Fabrication of a Porous Metal via Selective Phase Dissolution in Al-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Juan Vargas-Martínez

    2018-05-01

    Full Text Available Through free corrosion, a new low cost porous material was successfully fabricated by removing a single phase of a binary aluminum-copper alloy. This selective phase dissolution was carried out an Al-Al2Cu eutectic alloy of the Al-Cu binary system and additionally for two hypereutectic compositions. The porosity of the material depends on the microstructure formed upon solidification. For this reason, several solidification methods were studied to define the most convenient in terms of uniformity and refinement of the average pore and ligament sizes. The samples were corroded in a 10% v/v NaOH aqueous solution, which demonstrated to be the most convenient in terms of time involved and resulting porosity conditions after the corrosion process. The porosity was measured through analysis of secondary electron images. The effectiveness of the process was verified using X-ray diffraction, which showed that, under the proposed methodology, there was complete removal of one of the phases, namely the aluminum one.

  2. The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites

    Science.gov (United States)

    Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.

    1990-01-01

    Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or siliconcarbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.

  3. Effect of Fe content and microstructural features on the tensile and fatigue properties of the Al–Si10–Cu2 alloy

    International Nuclear Information System (INIS)

    Ceschini, Lorella; Boromei, Iuri; Morri, Alessandro; Seifeddine, Salem; Svensson, Ingvar L.

    2012-01-01

    Highlights: ► The effect of different amounts of Fe and Mn on fatigue behaviour of the Al–Si10–Cu2 alloy was studied. ► Fatigue specimens were subjected to HIP to eliminate the internal pores. ► The effect of microstructural features on the fatigue propagation was studied. ► The presence of β-Al 5 FeSi induced only a slight increase on the fatigue resistance. ► The presence of the α-Al 15 (Fe,Mn) 3 Si increased the fatigue resistance of the alloy. -- Abstract: As the automotive industry has to meet the requirements of fuel efficiency and environmental concerns, the use of aluminium alloys is steadily increasing. A number of papers have been published about the correlation between microstructure and mechanical properties of the widely used A356/A357 aluminium alloys, while relatively few data are available on others hypoeutectic Al–Si alloys, such as Al–Si–Cu alloys with higher Si content. In this work the effect of different amounts of Fe and Mn on the tensile and fatigue behaviour of the Al–Si10–Cu2 casting alloy was studied. The reason of this study comes from the fact that cast components are mostly made by secondary Al alloys that inevitably contain Fe, which in turn forms intermetallic compounds, negatively affecting the mechanical behaviour of the alloy. Fatigue specimens were subjected to hot isostatic pressing (HIP) before tests, in order to eliminate the internal pores (gas pores and interdendritic shrinkages) and therefore to solely investigate the effect of microstructural features, rather than solidification defects, on the fatigue propagation stage. The microstructural characterisation of the alloy was carried out by optical and scanning electron microscopy. Proof and ultimate tensile strength, as well as fatigue life of the investigated alloy were greatly enhanced by high Fe and Mn content, which reduced the micro-crack propagation rate; on the contrary Fe, without Mn, negatively affected the elongation to failure.

  4. Integrated System of Thermal/Dimensional Analysis for Quality Control of Metallic Melt and Ductile Iron Casting Solidification

    Science.gov (United States)

    Stan, Stelian; Chisamera, Mihai; Riposan, Iulian; Neacsu, Loredana; Cojocaru, Ana Maria; Stan, Iuliana

    2018-03-01

    The main objective of the present work is to introduce a specific experimental instrument and technique for simultaneously evaluating cooling curves and expansion or contraction of cast metals during solidification. Contraction/expansion analysis illustrates the solidification parameters progression, according to the molten cast iron characteristics, which are dependent on the melting procedure and applied metallurgical treatments, mold media rigidity and thermal behavior [heat transfer parameters]. The first part of the paper summarizes the performance of this two-mold device. Its function is illustrated by representative shrinkage tendency results in ductile cast iron as affected by mold rigidity (green sand and furan resin sand molds) and inoculant type (FeSi-based alloys), published in part previously. The second part of the paper illustrates an application of this equipment adapted for commercial foundry use. It conducts thermal analysis and volume change measurements in a single ceramic cup so that mold media as well as solidification conditions are constants, with cast iron quality as the variable. Experiments compared gray and ductile cast iron solidification patterns. Gray iron castings are characterized by higher undercooling at the beginning and at the end of solidification and lower graphitic expansion. Typically, ductile cast iron exhibits higher graphitic, initial expansion, conducive for shrinkage formation in soft molds.

  5. Prediction of as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal conditions

    International Nuclear Information System (INIS)

    Du, Qiang; Li, Yanjun

    2015-01-01

    In this paper, a multi-scale as-cast grain size prediction model is proposed to predict as-cast grain size of inoculated aluminum alloys melt solidified under non-isothermal condition, i.e., the existence of temperature gradient. Given melt composition, inoculation and heat extraction boundary conditions, the model is able to predict maximum nucleation undercooling, cooling curve, primary phase solidification path and final as-cast grain size of binary alloys. The proposed model has been applied to two Al-Mg alloys, and comparison with laboratory and industrial solidification experimental results have been carried out. The preliminary conclusion is that the proposed model is a promising suitable microscopic model used within the multi-scale casting simulation modelling framework. (paper)

  6. 7 CFR 35.6 - Shipment.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Shipment. 35.6 Section 35.6 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... country regardless of the number of consignees, receivers, or ports of destination in that country. [41 FR...

  7. Effect of directional solidification rate on the microstructure and properties of deformation-processed Cu–7Cr–0.1Ag in situ composites

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Keming [Jiangxi Key Laboratory for Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Jiang, Zhengyi; Zhao, Jingwei [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Zou, Jin; Chen, Zhibao [Jiangxi Key Laboratory for Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); Lu, Deping, E-mail: llludp@163.com [Jiangxi Key Laboratory for Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China)

    2014-11-05

    Highlights: • Effect of directional solidification (DS) rate on a Cu–Cr–Ag in situ composite. • The microstructure and properties of the DS in situ composite were investigated. • The second-phase Cr grains were parallel to drawing direction, and were finer. • The tensile strength was higher and the combination of properties was better. - Abstract: The influence of directional solidification rate on the microstructure, mechanical properties and conductivity of deformation-processed Cu–7Cr–0.1Ag in situ composites produced by thermo-mechanical processing was systematically investigated. The microstructure was analyzed by optical microscopy and scanning electronic microscopy. The mechanical properties and conductivity were evaluated by tensile-testing machine and micro-ohmmeter, respectively. The results indicate that the size, shape and distribution of second-phase Cr grains are significantly different in the Cu–7Cr–0.1Ag alloys with different growth rates. At a growth rate of 200 μm s{sup −1}, the Cr grains transform into fine Cr fiber-like grains parallel to the pulling direction from the Cr dendrites. The tensile strength of the Cu–7Cr–0.1Ag in situ composites from the directional solidification (DS) alloys is significantly higher than that from the as-cast alloy, while the conductivity of the in situ composites from the DS alloys is slightly lower than that from the as-cast alloy. The following combinations of tensile strength, elongation to fracture and conductivity of the Cu–7Cr–0.1Ag in situ composites from the DS alloy with a growth rate of 200 μm s{sup −1} and a cumulative cold deformation strain of 8 after isochronic aging treatment for 1 h can be obtained respectively as: (i) 1067 MPa, 2.9% and 74.9% IACS; or (ii) 1018 MPa, 3.0%, and 76.0% IACS or (iii) 906 MPa, 3.3% and 77.6% IACS.

  8. 42 CFR 438.356 - State contract options.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false State contract options. 438.356 Section 438.356 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL ASSISTANCE PROGRAMS MANAGED CARE External Quality Review § 438.356 State contract options...

  9. Fabricating method of hydrogen absorbing alloy for alkali storage battery; Arukari chikudenchiyo suiso kyuzo gokin no seizo hoho

    Energy Technology Data Exchange (ETDEWEB)

    Tadokoro, M.

    1996-03-08

    There are many grain boundaries in spherical hydrogen absorbing alloy particles prepared by rapid solidification methods such as centrifugal spraying method and gas atomizing method, and heterogeneous strains are produced at boundaries. When hydrogen absorbing alloy with large heterogeneous strain is used for preparing electrodes, many cracks are produced in hydrogen absorbing alloy to cause pulverization in the charge and discharge cycles. This invention relates to heat treatment of hydrogen absorbing alloys having spherical shape, cannon ball shape, and egg-like shape prepared by rapid solidification method in moving conditions. By this heat treatment, mutual sintering of hydrogen absorbing alloy particles can be prevented. The methods for moving hydrogen absorbing alloy are vibration or rotation of the heat treatment container in which hydrogen absorbing alloy is held and agitation of hydrogen absorbing alloy powder. Furthermore, mutual sintering of hydrogen absorbing alloy is restricted to reduce homogeneous strain by heat treatment in the range from 700{degree}C to 1,100{degree}C. 3 figs., 6 tabs.

  10. Low-level radwaste solidification

    International Nuclear Information System (INIS)

    Naughton, M.D.; Miller, C.C.; Nelson, R.A.; Tucker, R.F.

    1983-01-01

    This paper reports on a study of ''Advanced Low-Level Radioactive Waste Treatment Systems'' conducted under an EPRI contract. The object of the study is to identify advanced lowlevel radwaste treatment systems that are commercially available or are expected to be in the near future. The current state-ofthe-art in radwaste solidification technology is presented. Related processing technologies, such as the compaction of dry active waste (DAW), containers available for radwaste disposal, and the regulatory aspects of radwaste transportation and solidification, are described. The chemical and physical properties of the currently acceptable solidification agents, as identified in the Barnwell radwaste burial site license, are examined. The solidification agents investigated are hydraulic cements, thermoplastic polymers, and thermosetting polymers. It is concluded that solidification processes are complex and depend not only on the chemical and physical properties of the binder material and the waste, but also on how these materials are mixed

  11. Effect of scandium on structure and hardening of Al–Ca eutectic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Belov, N.A., E-mail: nikolay-belov@yandex.ru [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); Naumova, E.A. [Bauman Moscow State Technical University, 5, 2 ul. Baumanskaya, Moscow, 105005 (Russian Federation); Alabin, A.N. [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation); Matveeva, I.A. [UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation)

    2015-10-15

    The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al{sub 4}Ca and Al{sub 3}Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al{sub 4}Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °C on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °C, which was due to the precipitation of Al{sub 3}Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al{sub 4}Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting. - Highlights: • Al–Ca–Sc phase diagram in aluminum corner. • Formation of Al{sub 3}Sc nanoparticles in eutectic (Al) + Al{sub 4}Ca during heating at 300–450 °C. • Hardening and thermal stability of proposed (Al–Ca–Sc) and commercial (Al–Si–Mg, 356 type) eutectic alloys.

  12. Mechanisms of the porosity formation during the fiber laser lap welding of aluminium alloy

    Directory of Open Access Journals (Sweden)

    J. Wang

    2015-10-01

    Full Text Available When joining the aluminum alloys, one of the biggest challenges is the formation of porosity, which deteriorates mechanical properties of welds. In this study, the lap welding was conducted on an aluminum alloy 5754 metal sheets with a thickness of 2 mm. The effects of various laser welding parameters on the weld quality were investigated. The porosity content was measured by X-ray inspections. The key is to control the solidification duration of molten pool. When the solidification duration of molten pool is large enough, more bubbles can escape from the molten pool and less remain as porosity.

  13. Immobilization of carbon 14 contained in spent fuel hulls through melting-solidification treatment

    International Nuclear Information System (INIS)

    Mizuno, T.; Maeda, T.; Nakayama, S.; Banba, T.

    2004-01-01

    The melting-solidification treatment of spent nuclear fuel hulls is a potential technique to improve immobilization/stabilization of carbon-14 which is mobile in the environment due to its weakly absorbing properties. Carbon-14 can be immobilized in a solid during the treatment under an inert gas atmosphere, where carbon is not oxidized to gaseous form and remains in the solid. A series of laboratory scale experiments on retention of carbon into an alloy waste form was conducted. Metallic zirconium was melted with metallic copper (Zr/Cu=8/2 in weight) at 1200 deg C under an argon atmosphere. Almost all of the carbon remained in the resulting zirconium-copper alloy. (authors)

  14. Formation of Nitrogen Bubbles During Solidification of Duplex Stainless Steels

    Science.gov (United States)

    Dai, Kaiju; Wang, Bo; Xue, Fei; Liu, Shanshan; Huang, Junkai; Zhang, Jieyu

    2018-04-01

    The nucleation and growth of nitrogen bubbles for duplex stainless steels are of great significance for the formation mechanism of bubbles during solidification. In the current study, numerical method and theoretical analysis of formula derivation were used to study the formation of nitrogen bubbles during solidification. The critical sizes of the bubble for homogeneous nucleation and heterogeneous nucleation at the solid-liquid interface during solidification were derived theoretically by the classical nucleation theory. The results show that the calculated values for the solubility of nitrogen in duplex stainless steel are in good agreement with the experimental values which are quoted by references: for example, when the temperature T = 1823 K and the nitrogen partial pressure P_{{N2 }} = 40P^{Θ} , the calculated value (0.8042 wt pct) for the solubility of Fe-12Cr alloy nitrogen in molten steel is close to the experimental value (0.780 wt pct). Moreover, the critical radii for homogeneous nucleation and heterogeneous nucleation are identical during solidification. On the one hand, with the increasing temperature or the melt depth, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. On the other hand, with the decreasing initial content of nitrogen or the cooling rate, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. Furthermore, when the melt depth is greater than the critical depth, which is determined by the technological conditions, the change in the Gibbs free energy for the nucleation is not conducive enough to form new bubbles.

  15. The Effect of Rotation Stirring on Macrosegregation in Bi-Sn Alloy

    Directory of Open Access Journals (Sweden)

    Zulaida Yeni Muriani

    2017-01-01

    Full Text Available Macrosegregation is a defect that difficult to avoid in a metal alloy made by casting method. Macrosegregation can cause decreasing in mechanical properties of casting products. It will reduce their performance in industrial application. Macrosegregation is convinced occur during solidification time in liquid alloy. In the early solidified, The solids move upward/downward in liquid alloy during solidification are considered to contribute on macrosegregation formation. This movement occur due to the density differences between the solid and the surrounding liquid. This research want to observe the effect of stirring on macrosegregation formation for interfering on the movement of initial solidified solid. Stiring with rotation method is applied in this experiment at certain temperature. The temperature and the rotation speed of stirring are varied to observe the effect of rotation stirring on macrosegregation formation. The mold is covered by insulation jacket and kept the bottom part opened in order to obtain the directionally solidification. The result shows that the rotation stirring can change the macrostructure of casting but in case of composition distribution, the macrosegregation still appear. Increasing the rotation stirring will rise solid crystals up and the macrosegregation become more uniform and the treatment is better if conducting at lower temperature.

  16. Effect of microstructural evolution and elevated temperature on the mechanical properties of Ni–Cr–Mo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karaköse, Ercan, E-mail: ekarakose@karatekin.edu.tr [Karatekin University, Faculty of Sciences, Department of Physics, 18100 Çankırı (Turkey); Keskin, Mustafa [Erciyes University, Faculty of Sciences, Department of Physics, 38039 Kayseri (Turkey)

    2015-01-15

    Highlights: • A ternary Ni–Cr–Mo alloy is the crucial for many industrial applications. • Microstructure of Ni–25Cr–18Mo alloy mostly depends upon the undercooling rate. • Increasing the applied undercooling range the average dendrite arm thickness decreases from 5 to 0.5 μm. - Abstract: This paper characterizes the impact of solidification rate on the morphology and type of microstructural and mechanical properties of a nickel-based superalloy with a nominal composition of Ni–25Cr–18Mo (at.%) in a wide cooling range (5–100 K/s). The microstructures of the alloys were identified by scanning electron microscopy (SEM) and the phase composition was examined by X-ray diffractometry (XRD). The phase transitions during the solidification process were investigated by differential thermal analysis (DTA) under an Ar atmosphere. It was found that the final microstructure of Ni–25Cr–18Mo alloy mostly depends upon the solidification rate; the microstructures evolve from a coarse dendritic structure to a refined dendritic structure. The mechanical properties of Ni–25Cr–18Mo alloys were examined by using Vickers and Rockwell hardness tests at room temperature and at elevated temperatures from 400 °C to 800 °C. It was found that the hardness values of the samples were connected with the cooling rate and test temperatures.

  17. Effect of microstructural evolution and elevated temperature on the mechanical properties of Ni–Cr–Mo alloys

    International Nuclear Information System (INIS)

    Karaköse, Ercan; Keskin, Mustafa

    2015-01-01

    Highlights: • A ternary Ni–Cr–Mo alloy is the crucial for many industrial applications. • Microstructure of Ni–25Cr–18Mo alloy mostly depends upon the undercooling rate. • Increasing the applied undercooling range the average dendrite arm thickness decreases from 5 to 0.5 μm. - Abstract: This paper characterizes the impact of solidification rate on the morphology and type of microstructural and mechanical properties of a nickel-based superalloy with a nominal composition of Ni–25Cr–18Mo (at.%) in a wide cooling range (5–100 K/s). The microstructures of the alloys were identified by scanning electron microscopy (SEM) and the phase composition was examined by X-ray diffractometry (XRD). The phase transitions during the solidification process were investigated by differential thermal analysis (DTA) under an Ar atmosphere. It was found that the final microstructure of Ni–25Cr–18Mo alloy mostly depends upon the solidification rate; the microstructures evolve from a coarse dendritic structure to a refined dendritic structure. The mechanical properties of Ni–25Cr–18Mo alloys were examined by using Vickers and Rockwell hardness tests at room temperature and at elevated temperatures from 400 °C to 800 °C. It was found that the hardness values of the samples were connected with the cooling rate and test temperatures

  18. Solidification behaviors of a single-crystal superalloy under lateral constraints

    International Nuclear Information System (INIS)

    Zhuangqi Hu; Huaming Wang

    1993-01-01

    The effect of lateral constraints ahead of solidification interface on the solidification behaviors of a newly developed hot corrosion resistant single-crystal nickel-base superalloy was investigated under commercial single-crystal production conditions. The lateral constraints or section variations ahead of solidification front were found to have drastic influences both on the modes of solidification and the profiles of solute segregation. As lateral constraints were imposed ahead of the directionally solidifying interface, the solidification microstructure of the single-crystal superalloy changed suddenly, through a γ/γ' eutectic-free zone which is characterized by an extremely-fine and highly-developed dendrite network, from the original well-branched dendritic structure to a fine cellular-dendrite or regular cell structure, accompanying which the primary arm spacing, the severity of segregation and the amount of microporosity decreased remarkably. The newly formed cellular dendrite or cell structure transforms always gradually to the initial coarse dendrite structure as the lateral constraint is finally released whether gradually or sharply. Moreover, an abnormal porosity zone was readily observed in the initial section beneath and away from the eutectic-free zone. The solidification microstructural changes were attributed to the drastic dynamical changes in local solidification cooling conditions and in momentum transport during solidification due to the presence of lateral constraint

  19. Rapidly solidified long-range-ordered alloys

    International Nuclear Information System (INIS)

    Lee, E.H.; Koch, C.C.; Liu, C.T.

    1981-01-01

    The influence of rapid solidification processing on the microstructure of long-range-ordered alloys in the (Fe, Co, Ni) 3 V system has been studied by transmission electron microscopy. The main microstructural feature of the as-quenched alloys was a fine cell structure (approx. 300 nm diameter) decorated with carbide particles. This structure was maintained aftr annealing treatments which develop the ordered crystal structure. Other features of the microstructures both before and after annealing are presented and discussed. 6 figures

  20. Predictive modeling of solidification during laser additive manufacturing of nickel superalloys: recent developments, future directions

    Science.gov (United States)

    Ghosh, Supriyo

    2018-01-01

    Additive manufacturing (AM) processes produce parts with improved physical, chemical, and mechanical properties compared to conventional manufacturing processes. In AM processes, intricate part geometries are produced from multicomponent alloy powder, in a layer-by-layer fashion with multipass laser melting, solidification, and solid-state phase transformations, in a shorter manufacturing time, with minimal surface finishing, and at a reasonable cost. However, there is an increasing need for post-processing of the manufactured parts via, for example, stress relieving heat treatment and hot isostatic pressing to achieve homogeneous microstructure and properties at all times. Solidification in an AM process controls the size, shape, and distribution of the grains, the growth morphology, the elemental segregation and precipitation, the subsequent solid-state phase changes, and ultimately the material properties. The critical issues in this process are linked with multiphysics (such as fluid flow and diffusion of heat and mass) and multiscale (lengths, times and temperature ranges) challenges that arise due to localized rapid heating and cooling during AM processing. The alloy chemistry-process-microstructure-property-performance correlation in this process will be increasingly better understood through multiscale modeling and simulation.

  1. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.

    2000-01-01

    Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial and tempo......Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  2. The development of additive manufacturing technique for nickel-base alloys: A review

    Science.gov (United States)

    Zadi-Maad, Ahmad; Basuki, Arif

    2018-04-01

    Nickel-base alloys are an attractive alloy due to its excellent mechanical properties, a high resistance to creep deformation, corrosion, and oxidation. However, it is a hard task to control performance when casting or forging for this material. In recent years, additive manufacturing (AM) process has been implemented to replace the conventional directional solidification process for the production of nickel-base alloys. Due to its potentially lower cost and flexibility manufacturing process, AM is considered as a substitute technique for the existing. This paper provides a comprehensive review of the previous work related to the AM techniques for Ni-base alloys while highlighting current challenges and methods to solving them. The properties of conventionally manufactured Ni-base alloys are also compared with the AM fabricated alloys. The mechanical properties obtained from tension, hardness and fatigue test are included, along with discussions of the effect of post-treatment process. Recommendations for further work are also provided.

  3. Bridging the gap between molecular dynamics simulations and phase-field modelling: dynamics of a [NixZr1-x]liquid-Zrcrystal solidification front

    International Nuclear Information System (INIS)

    Danilov, Denis; Nestler, Britta; Guerdane, Mohammed; Teichler, Helmar

    2009-01-01

    Results are presented from phase-field modelling and molecular dynamics simulations concerning the relaxation dynamics in a finite-temperature two-phase crystal-liquid sample subjected to an abrupt temperature drop. Relaxation takes place by propagation of the solidification front under formation of a spatially varying concentration profile in the melt. The molecular dynamics simulations are carried out with an interatomic model appropriate for the NiZr alloy system and provide the thermophysical data required for setting up the phase-field simulations. Regarding the concentration profile and velocity of the solidification front, best agreement between the phase-field model and molecular dynamics simulation is obtained when increasing the apparent diffusion coefficients in the phase-field treatment by a factor of four against their molecular dynamics estimates.

  4. Free energy change of off-eutectic binary alloys on solidification

    Science.gov (United States)

    Ohsaka, K.; Trinh, E. H.; Lin, J.-C.; Perepezko, J. H.

    1991-01-01

    A formula for the free energy difference between the undercooled liquid phase and the stable solid phase is derived for off-eutectic binary alloys in which the equilibrium solid/liquid transition takes place over a certain temperature range. The free energy change is then evaluated numerically for a Bi-25 at. pct Cd alloy modeled as a sub-subregular solution.

  5. Comparison of microstructure and mechanical properties of A356 aluminum alloy/Al2O3 composites fabricated by stir and compo-casting processes

    International Nuclear Information System (INIS)

    Sajjadi, S.A.; Ezatpour, H.R.; Torabi Parizi, M.

    2012-01-01

    Highlights: → Nano and micro-composites (A356/Al 2 O 3 ) were fabricated by stir-casting and compo-casting. → Uniform distribution, grain refinement and low porosity in the composites were attained. → Addition of alumina led to the improvement in yield, ultimate tensile and compression strength. → Nano-alumina particles and compo-casting process obtained the best mechanical properties. -- Abstract: Metal-matrix composites (MMCs), as light and strong materials, are very attractive for application in different industries. In the present work, nano and micro-composites (A356/Al 2 O 3 ) with different weight percent of particles were fabricated by two melt techniques such as stir-casting and compo-casting. Microstructural characterization was investigated by optical (OP) and scanning electron microscopy (SEM). Tensile, hardness and compression tests were carried out in order to identify mechanical properties of the composites. The results of microstructural study revealed uniform distribution, grain refinement and low porosity in micro and nano-composite specimens. The mechanical results showed that the addition of alumina (micro and nano) led to the improvement in yield strength, ultimate tensile strength, compression strength and hardness. It was indicated that type of fabrication process and particle size were the effective factors influencing on the mechanical properties. Decreasing alumina particle size and using compo-casting process obtained the best mechanical properties.

  6. The modelling of heat, mass and solute transport in solidification systems

    Science.gov (United States)

    Voller, V. R.; Brent, A. D.; Prakash, C.

    1989-01-01

    The aim of this paper is to explore the range of possible one-phase models of binary alloy solidification. Starting from a general two-phase description, based on the two-fluid model, three limiting cases are identified which result in one-phase models of binary systems. Each of these models can be readily implemented in standard single phase flow numerical codes. Differences between predictions from these models are examined. In particular, the effects of the models on the predicted macro-segregation patterns are evaluated.

  7. Solidification microstructure development

    Indian Academy of Sciences (India)

    Unknown

    A majority of manufacturing processes involve melting and solidification of metals and ... In such a case (for example, chill casting), the solidification thickness (S) is ... (5). Here, LX is the system length scale in one dimension and DS is the solute diffusivity in solid. Thermal and solutal diffusivities are finite and usually very ...

  8. Macrosegregation Caused by Convection Associated with Directional Solidification through Cross-Section Change

    Science.gov (United States)

    Ghods, M.; Lauer, M.; Tewari, S. N.; Poirier, D. R..; Grugel, R. N.

    2015-01-01

    Al-7 wt% Si and Pb-6 wt% Sb alloy samples were directionally solidified (DS), with liquid above and solid below and gravity pointing down, in cylindrical graphite crucibles through an abrupt cross-section change. Fraction eutectic distribution in the microstructure, primary dendrite spacing and primary dendrite trunk diameters have been measured in the DS samples in the vicinity of section change in order to examine the effect of convection associated with the combined influence of thermosolutal factors and solidification shrinkage. It is observed that convection not only produces extensive radial and axial macrosegregation near cross-section change, it also affects the dendritic array morphology. Primary dendrite spacing and primary dendrite trunk diameter, both, are influenced by this convection. In addition to the experimental results, preliminary results from a numerical model which includes solidification shrinkage and thermosolutal convection in the mushy zone in its analysis will also be presented

  9. Microstructures and microhardness evolutions of melt-spun Al–8Ni–5Nd–4Si alloy

    International Nuclear Information System (INIS)

    Karaköse, Ercan; Keskin, Mustafa

    2012-01-01

    Al–Ni–Nd–Si alloy with nominal composition of Al–8 wt.%Ni–5 wt.%Nd–4 wt.%Si was rapidly solidified by using melt-spinning technique to examine the influence of the cooling rate/conditions on microstructure and mechanical properties. The resulting conventional cast (ingot) and melt-spun ribbons were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy together with energy dispersive spectroscopy, differential scanning calorimetry, differential thermal analysis and Vickers microhardness tester. The ingot alloys consists of four phases namely α-Al, intermetallic Al 3 Ni, Al 11 Nd 3 and fcc Si. Melt-spun ribbons are completely composed of α-Al phase. The optical microscopy and scanning electron microscopy results show that the microstructures of rapidly solidified ribbons are clearly different from their ingot alloy. The change in microhardness is discussed based on the microstructural observations. - Highlights: ► Rapid solidification allows a reduction in grain size, extended solid solution ranges. ► We observed the matrix lattice parameter increases with increasing wheel speed. ► Melt-spun ribbons consist of partly amorphous phases embedded in crystalline phases. ► The solidification rate is high enough to retain most of alloying elements in the Al matrix. ► The rapid solidification has effect on the phase constitution.

  10. Comparison of the heat treatment response of SSM-HPDC 6082 and 6004 wrought alloys with A356 and F357 casting alloys

    CSIR Research Space (South Africa)

    Müller, H

    2011-06-01

    Full Text Available advantages, including a faster artificial aging response, higher strength for comparable Mg contents and less sensitivity to prior natural aging on peak strength. However, over-aging occurs earlier in the casting alloys than in the wrought alloys....

  11. Microstructure and electrochemical corrosion behavior of a Pb-1 wt%Sn alloy for lead-acid battery components

    Energy Technology Data Exchange (ETDEWEB)

    Peixoto, Leandro C.; Osorio, Wislei R.; Garcia, Amauri [Department of Materials Engineering, University of Campinas - UNICAMP, PO Box 612, 13083-970, Campinas - SP (Brazil)

    2009-07-15

    The aim of this study was to evaluate the effect of solidification cooling rates on the as-cast microstructural morphologies of a Pb-1 wt%Sn alloy, and to correlate the resulting microstructure with the corresponding electrochemical corrosion resistance in a 0.5 M H{sub 2}SO{sub 4} solution at 25 C. Cylindrical low-carbon steel and insulating molds were employed permitting the two extremes of a significant range of solidification cooling rates to be experimentally examined. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical corrosion response of Pb-1 wt%Sn alloy samples. It was found that lower cooling rates are associated with coarse cellular arrays which result in better corrosion resistance than fine cells which are related to high cooling rates. The experimental results have shown that that the pre-programming of microstructure cell size of Pb-Sn alloys can be used as an alternative way to produce as-cast components of lead-acid batteries with higher corrosion resistance. (author)

  12. Microstructural and mechanical properties analysis of extruded Sn–0.7Cu solder alloy

    Directory of Open Access Journals (Sweden)

    Abdoul-Aziz Bogno

    2015-01-01

    Full Text Available The properties and performance of lead-free solder alloys such as fluidity and wettability are defined by the alloy composition and solidification microstructure. Rapid solidification of metallic alloys is known to result in refined microstructures with reduced microsegregation and improved mechanical properties of the final products as compared to normal castings. The rapidly solidified Sn-based solders by melt spinning were shown to be suitable for soldering with low temperature and short soldering duration. In the present study, rapidly solidified Sn–0.7 wt.%Cu droplets generated by impulse atomization (IA were achieved as well as directional solidification under transient conditions at lower cooling rate. This paper reports on a comparative study of the rapidly solidified and the directionally solidified samples. Different but complementary characterization techniques were used to fully analyze the solidification microstructures of the samples obtained under the two cooling regimes. These include X-ray diffractometry (XRD and scanning electron microscopy (SEM. In order to compare the tensile strength and elongation to fracture of the directionally solidified ingot and strip castings with the atomized droplet, compaction and extrusion of the latter were carried out. It was shown that more balanced and superior tensile mechanical properties are available for the hot extruded samples from compacted as-atomized Sn–0.7 wt.%Cu droplets. Further, elongation-to-fracture was 2–3× higher than that obtained for the directionally solidified samples.

  13. A comparative study of ternary Al-Sn-Cu immiscible alloys prepared by conventional casting and casting under high-intensity ultrasonic irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Kotadia, H.R., E-mail: hiren.kotadia@kcl.ac.uk [Department of Physics, King' s College London, Strand, London WC2R 2LS (United Kingdom); Das, A. [Materials Research Centre, College of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom); Doernberg, E.; Schmid-Fetzer, R. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Systematic investigation on the solidification microstructure of ternary Al-Sn-Cu immiscible system aided by computational thermodynamics calculations. Black-Right-Pointing-Pointer Comparative study of conventional casting and casting under high-intensity ultrasonic irradiation. Black-Right-Pointing-Pointer Demonstrated the high effectiveness of ultrasound exposure during solidification. Black-Right-Pointing-Pointer Effect of cavitation on nucleation and the relative effects of cavitation and acoustic streaming on the dispersion of Sn-rich liquid phases have been explained from the experimental observation. Cavitation was found to promote fragmentation and dispersion of Sn-rich liquid leading to homogeneous dispersion of refined Sn phase. Microstructural modification was found to be contributed by cavitation and associated shockwave generation while bulk fluid flow under acoustic streaming was found to be less effective on the microstructure evolution. Black-Right-Pointing-Pointer Globular and highly refined {alpha}-Al formed near the radiator through enhanced heterogeneous nucleation in contrast to dendritic {alpha}-Al observed in conventional solidification. - Abstract: A comparative study on the microstructure of four ternary Al-Sn-Cu immiscible alloys, guided by the recent thermodynamic assessment of the system, was carried out with specific focus on the soft Sn particulate distribution in hard Al-rich matrix in the presence and absence of ultrasonic irradiation during solidification. The results clearly demonstrate high effectiveness of ultrasonication in promoting significantly refined and homogeneously dispersed microstructure, probably aided by enhanced nucleation and droplet fragmentation under cavitation. While conventional solidification produced highly segregated Sn phase at the centre and bottom of Sn-rich alloy ingots, ultrasonic treatment produced effective dispersion irrespective of the alloy constitution in

  14. The Enhancement of Mg Corrosion Resistance by Alloying Mn and Laser-Melting

    Directory of Open Access Journals (Sweden)

    Youwen Yang

    2016-03-01

    Full Text Available Mg has been considered a promising biomaterial for bone implants. However, the poor corrosion resistance has become its main undesirable property. In this study, both alloying Mn and laser-melting were applied to enhance the Mg corrosion resistance. The corrosion resistance, mechanical properties, and microstructure of rapid laser-melted Mg-xMn (x = 0–3 wt % alloys were investigated. The alloys were composed of dendrite grains, and the grains size decreased with increasing Mn. Moreover, Mn could dissolve and induce the crystal lattice distortion of the Mg matrix during the solidification process. Mn ranging from 0–2 wt % dissolved completely due to rapid laser solidification. As Mn contents further increased up to 3 wt %, a small amount of Mn was left undissolved. The compressive strength of Mg-Mn alloys increased first (up to 2 wt % and then decreased with increasing Mn, while the hardness increased continuously. The refinement of grains and the increase in corrosion potential both made contributions to the enhancement of Mg corrosion resistance.

  15. Industrial heat treatment of R-HPDC A356 automotive brake callipers

    CSIR Research Space (South Africa)

    Chauke, L

    2012-10-01

    Full Text Available Heat treatment of rheo-high pressure die cast (R-HPDC) A356 brake callipers has produced good mechanical properties on the laboratory scale. An industrial heat treatment is required to evaluate the applicability and conformance of the R-HPDC A356...

  16. Characterisation of intermetallic particles formed during solution treatment of an Al–7Si–0.4Mg–0.12Fe alloy

    International Nuclear Information System (INIS)

    Yao, J.Y.; Taylor, J.A.

    2012-01-01

    Highlights: ► It is concluded in this work that the fine needle-like particles formed during the solution treatment of the 356 type alloy are indeed β phase plates similar to those frequently observed in as-cast aluminium alloys but of much finer sizes, most likely formed by precipitation in the vicinity of the dissolving π phase particles. ► The crystal structure of the needle-like particles, as examined by selected area electron diffraction, can be essentially indexed as either the A-Centred Monoclinic lattice or the Orthorhombic lattice . ► The particles appear to co-exist in two distinct forms: single crystal particles and composite micro-constituent particles. - Abstract: When Fe-containing Al–7Si–xMg alloys are solution-treated, usually as the initial stage of a T6 heat treatment, some of the π-Al 9 Mg 3 FeSi 5 phase present in the as-cast alloy transforms into fine needle-like intermetallic particles (as seen on a polished surface). These precipitated needles, speculated to be β-Al 5 FeSi phase, have not been definitively characterised to date. In this work, electron microscopy characterisation by various techniques was conducted to assess the nature (i.e. the composition, morphology and crystallography) of these particles to verify or otherwise the validity of the above hypothesis. It is found that the particles are indeed β phase platelets, of the same Al 5 FeSi or Al 4.5 FeSi stoichiometry as particles formed during solidification. Close observation of their crystallographic structure suggests fine-scale internal complexities in some of the particles.

  17. Multi-functional magnesium alloys containing interstitial oxygen atoms.

    Science.gov (United States)

    Kang, H; Choi, H J; Kang, S W; Shin, S E; Choi, G S; Bae, D H

    2016-03-15

    A new class of magnesium alloys has been developed by dissolving large amounts of oxygen atoms into a magnesium lattice (Mg-O alloys). The oxygen atoms are supplied by decomposing titanium dioxide nanoparticles in a magnesium melt at 720 °C; the titanium is then completely separated out from the magnesium melt after solidification. The dissolved oxygen atoms are located at the octahedral sites of magnesium, which expand the magnesium lattice. These alloys possess ionic and metallic bonding characteristics, providing outstanding mechanical and functional properties. A Mg-O-Al casting alloy made in this fashion shows superior mechanical performance, chemical resistance to corrosion, and thermal conductivity. Furthermore, a similar Mg-O-Zn wrought alloy shows high elongation to failure (>50%) at room temperature, because the alloy plastically deforms with only multiple slips in the sub-micrometer grains (alloys are expected to open a new paradigm in commercial alloy design.

  18. Section thickness-dependent tensile properties of squeeze cast magnesium alloy AM60

    Directory of Open Access Journals (Sweden)

    Xuezhi Zhang

    2012-05-01

    Full Text Available The development of alternative casting processes is essential for the high demand of light weight magnesium components to be used in the automotive industry, which often contain different section thicknesses. Squeeze casting with its inherent advantages has been approved for the capability of minimizing the gas porosity in magnesium alloys. For advanced engineering design of light magnesium automotive applications, it is critical to understand the effect of section thickness on mechanical properties of squeeze cast magnesium alloys. In this study, magnesium alloy AM60 with different section thicknesses of 6, 10 and 20 mm squeeze cast under an applied pressure of 30 MPa was investigated. The prepared squeeze cast AM60 specimens were tensile tested at room termperature. The results indicate that the mechanical properties including yield strength (YS, ultimate tensile strength (UTS and elongation (A decrease with an increase in section thickness of squeeze cast AM60. The microstructure analysis shows that the improvement in the tensile behavior of squeeze cast AM60 is primarily attributed to the low-gas porosity level and fine grain strucuture which result from the variation of cooling rate of different section thickness. The numerical simulation (Magmasoft? was employed to determine the solidification rates of each step, and the simulated results show that the solidification rate of the alloy decreases with an increase in the section thickness. The computed solidification rates support the experimental observation on grain structural development.

  19. FY 1997 report on the study on solidification process of high-temperature melt of heat resistant metals; 1997 nendo chosa hokokusho (tainetsu kinzoku koon yueki no gyoko katei no kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Study was made on a solidification process of metal melt under micro-gravity condition in an underground non-gravity experiment center, considering that improvement of the heat resistance of turbine blades for jet engines and power generation gas turbines contributes to prevention of global warming through improvement of thermal engine efficiencies and consumption reduction of precious fossil fuel. Study was made on a simulation program and precise measurement of thermal properties for precision casting of heat-resistant alloy members. Study was also made on Al and Zn alloys and their welding for production and evaluation technologies of new metal textures by supercooling solidification. Some issues for strongly desired improvement of a simulation program for precision casting were clarified. In addition, since thermal property data of practical heat-resistant polyalloy members are poor, data and measurement method for precision casting were clarified. It was also suggested that basic elucidation of the solidification process under micro- gravity condition is possible. 34 refs., 41 figs., 5 tabs.

  20. Advances in Solidification Processing

    Directory of Open Access Journals (Sweden)

    Hugo F. Lopez

    2015-08-01

    Full Text Available Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern technological societies. As a result, there have been innumerable efforts and full conferences dedicated to this important subject [1–6]. In addition, there are various scientific journals fully devoted to investigating the various aspects which give rise to various solidification microstructures [7–9]. [...

  1. Crystallographic investigation of grain selection during initial solidification

    International Nuclear Information System (INIS)

    Esaka, H; Shinozuka, K; Kataoka, Y

    2016-01-01

    Normally, macroscopic solidified structure consists of chill, columnar and equiaxed zones. In a chill zone, many fine grains nucleate on the mold surface and grow their own preferred growth direction. Only a few of them continue to grow because of grain selection. In order to understand the grain selection process, crystallographic investigation has been carried out in the zone of initial solidification in this study. 10 g of Al-6 wt%Si alloy was melted at 850 °C and poured on the thick copper plate. Longitudinal cross section of the solidified shell was observed by a SEM and analyzed by EBSD. The result of EBSD mapping reveals that crystallographic orientation was random in the range of initial solidification. Further, some grains are elongated along their <100> direction. Columnar grains, whose growth directions are almost parallel to the heat flow direction, develop via grain selection. Here, a dendrite whose growth direction is close to the heat flow direction overgrows the other dendrite whose growth direction is far from the heat flow direction. However, sometimes we observed that dendrite, whose zenith angle is large, overgrew the other dendrite. It can be deduced that the time of nucleation on the mold surface is not constant. (paper)

  2. Manufacturing of High Entropy Alloys

    Science.gov (United States)

    Jablonski, Paul D.; Licavoli, Joseph J.; Gao, Michael C.; Hawk, Jeffrey A.

    2015-07-01

    High entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion they have high configurational entropy, and thus they hold the promise of interesting and useful properties such as enhanced strength and phase stability. The present study investigates the microstructure of two single-phase face-centered cubic (FCC) HEAs, CoCrFeNi and CoCrFeNiMn, with special attention given to melting, homogenization and thermo-mechanical processing. Large-scale ingots were made by vacuum induction melting to avoid the extrinsic factors inherent in small-scale laboratory button samples. A computationally based homogenization heat treatment was applied to both alloys in order to eliminate segregation due to normal ingot solidification. The alloys fabricated well, with typical thermo-mechanical processing parameters being employed.

  3. Effect of current and atomized grain size distribution on the solidification of Plasma Transferred Arc coatings

    Directory of Open Access Journals (Sweden)

    Danielle Bond

    2012-10-01

    Full Text Available Plasma Transferred Arc (PTA is the only thermal spray process that results in a metallurgical bond, being frequently described as a hardfacing process. The superior properties of coatings have been related to the fine microstructures obtained, which are finer than those processed under similar heat input with welding techniques using wire feedstock. This observation suggests that the atomized feedstock plays a role on the solidification of coatings. In this study a model for the role of the powders grains in the solidification of PTA coatings is put forward and discussed. An experiment was setup to discuss the model which involved the deposition of an atomized Co-based alloy with different grain size distributions and deposition currents. X ray diffraction showed that there were no phase changes due to the processing parameters. Microstructure analysis by Laser Confocal Microscopy, dilution with the substrate steel and Vickers microhardness were used the characterized coatings and enriched the discussion confirming the role of the powdered feedstock on the solidification of coatings.

  4. Comparative Study on the Grain Refinement of Al-Si Alloy Solidified under the Impact of Pulsed Electric Current and Travelling Magnetic Field

    Directory of Open Access Journals (Sweden)

    Yunhu Zhang

    2016-07-01

    Full Text Available It is high of commercial importance to generate the grain refinement in alloys during solidification by means of electromagnetic fields. Two typical patterns of electromagnetic fields, pulsed electric currents (ECP and traveling magnetic field (TMF, are frequently employed to produce the finer equiaxed grains in solidifying alloys. Various mechanisms were proposed to understand the grain refinement in alloys caused by ECP and TMF. In this paper, a comparative study is carried out in the same solidification regime to investigate the grain refinement of Al-7 wt. %Si alloy driven by ECP and TMF. Experimental results show that the application of ECP or TMF can cause the same grain refinement occurrence period, during which the refinement of primary Al continuously occurs. In addition, the related grain refinement mechanisms are reviewed and discussed, which shows the most likely one caused by ECP and TMF is the promoted dendrite fragmentation as the result of the ECP-induced or TMF-induced forced flow. It suggests that the same grain refinement process in alloys is provoked when ECP and TMF are applied in the same solidification regime, respectively.

  5. Modeling of TiAl Alloy Grating by Investment Casting

    OpenAIRE

    Yi Jia; Shulong Xiao; Jing Tian; Lijuan Xu; Yuyong Chen

    2015-01-01

    The investment casting of TiAl alloys has become the most promising cost-effective technique for manufacturing TiAl components. This study aimed to investigate a series of problems associated with the investment casting of TiAl alloys. The mold filling and solidification of this casting model were numerically simulated using ProCAST. Shrinkage porosity was quantitatively predicted by a built-in feeding criterion. The results obtained from the numerical simulations were compared with experimen...

  6. 7 CFR 356.8 - Return procedure.

    Science.gov (United States)

    2010-01-01

    ... receipt provided by Plant Protection and Quarantine, the seized property is authorized to be released. ... 7 Agriculture 5 2010-01-01 2010-01-01 false Return procedure. 356.8 Section 356.8 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE...

  7. High strength cast aluminum alloy development

    Science.gov (United States)

    Druschitz, Edward A.

    The goal of this research was to understand how chemistry and processing affect the resulting microstructure and mechanical properties of high strength cast aluminum alloys. Two alloy systems were investigated including the Al-Cu-Ag and the Al-Zn-Mg-Cu systems. Processing variables included solidification under pressure (SUP) and heat treatment. This research determined the range in properties that can be achieved in BAC 100(TM) (Al-Cu micro-alloyed with Ag, Mn, Zr, and V) and generated sufficient property data for design purposes. Tensile, stress corrosion cracking, and fatigue testing were performed. CuAl2 and Al-Cu-Fe-Mn intermetallics were identified as the ductility limiting flaws. A solution treatment of 75 hours or longer was needed to dissolve most of the intermetallic CuAl 2. The Al-Cu-Fe-Mn intermetallic was unaffected by heat treatment. These results indicate that faster cooling rates, a reduction in copper concentration and a reduction in iron concentration might increase the ductility of the alloy by decreasing the size and amount of the intermetallics that form during solidification. Six experimental Al-Zn-Mg-Cu series alloys were produced. Zinc concentrations of 8 and 12wt% and Zn/Mg ratios of 1.5 to 5.5 were tested. Copper was held constant at 0.9%. Heat treating of the alloys was optimized for maximum hardness. Al-Zn-Mg-Cu samples were solution treated at 441°C (826°F) for 4 hours before ramping to 460°C (860°F) for 75 hours and then aged at 120°C (248°F) for 75 hours. X-ray diffraction showed that the age hardening precipitates in most of these alloys was the T phase (Mg32Zn 31.9Al17.1). Tensile testing of the alloys showed that the best mechanical properties were obtained in the lowest alloy condition. Chilled Al-8.2Zn-1.4Mg-0.9Cu solidified under pressure resulted in an alloy with a yield strength of 468MPa (68ksi), tensile strength of 525MPa (76ksi) and an elongation of 9%.

  8. Atomic bonding and mechanical properties of Al-Mg-Zr-Sc alloy

    Institute of Scientific and Technical Information of China (English)

    高英俊; 班冬梅; 韩永剑; 钟夏平; 刘慧

    2004-01-01

    The valence electron structures of Al-Mg alloy with minor Sc and Zr were calculated according to the empirical electron theory(EET) in solid. The results show that because of the strong interaction of Al atom with Zr and Sc atom in melting during solidification, the Al3 Sc and Al3 (Sc1-xZrx) particles which act as heterogeneous nuclear are firstly crystallized in alloy to make grains refine. In progress of solidification, the Al-Sc, Al-Zr-Sc segregation regions are formed in solid solution matrix of Al-Mg alloy owing to the strong interaction of Al atom with Zr, Scatoms in bulk of alloy, so in the following homogenization treatment, the finer dispersed Al3 Sc and Al3 (Sc1-x Zrx) second-particles which are coherence with the matrix are precipitated in the segregation region. These finer second particles with the strong Al-Zr, Al-Sc covalent bonds can strengthen the covalent bonds in matrix of the alloy, and also enhance the hardness and strength of Al-Mg alloy. Those finer second-particles precipitated in interface of sub-grains can also strengthen the covalence bonds there, and effectively hinder the interface of sub-grains from migrating and restrain the sub-grains from growing, and cause better thermal stability of Al-Mg alloy.

  9. 46 CFR 356.41 - Management agreements.

    Science.gov (United States)

    2010-10-01

    ... which the management company provides marketing services, consulting services or other services that are... otherwise effectively gain control over the management and operation of the vessel or vessel-owning entity... 46 Shipping 8 2010-10-01 2010-10-01 false Management agreements. 356.41 Section 356.41 Shipping...

  10. Calorimetric measurements of the Ca-Li liquid alloys

    Directory of Open Access Journals (Sweden)

    Dębski A.

    2017-01-01

    Full Text Available The ternary Cu-Al-Sn phase diagram is the base for several important types of alloys, with relevant industrial interest and applications. The knowledge of the melting/solidification alloys characteristics are determinant for their preparation and properties control. However, there is a lack of experimental information on the ternary phase diagram, at high temperature. In this work, several alloys, with high copper content and additions of Al, up to 10%, and Sn, up to 14% (in wt%, were studied by thermal analysis and by isothermal phase equilibria determination. The alloys liquidus and solidus lines and the binary α + β phase field, at 800 °C, are presented for the studied range of compositions.

  11. Development Program for Natural Aging Aluminum Casting Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Geoffrey K. Sigworth

    2004-05-14

    A number of 7xx aluminum casting alloys are based on the ternary Al-Zn-Mg system. These alloys age naturally to high strength at room temperature. A high temperature solution and aging treatment is not required. Consequently, these alloys have the potential to deliver properties nearly equivalent to conventional A356-T6 (Al-Si-Mg) castings, with a significant cost saving. An energy savings is also possible. In spite of these advantages, the 7xx casting alloys are seldom used, primarily because of their reputation for poor castibility. This paper describes the results obtained in a DOE-funded research study of these alloys, which is part of the DOE-OIT ''Cast Metals Industries of the Future'' Program. Suggestions for possible commercial use are also given.

  12. Microstructures and microhardness evolutions of melt-spun Al-8Ni-5Nd-4Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Karakoese, Ercan, E-mail: ekarakose@karatekin.edu.tr [Karatekin University, Faculty of Sciences, Department of Physics, 18100 Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I (Turkey); Keskin, Mustafa [Erciyes University, Faculty of Sciences, Department of Physics, 38039 Kayseri (Turkey)

    2012-03-15

    Al-Ni-Nd-Si alloy with nominal composition of Al-8 wt.%Ni-5 wt.%Nd-4 wt.%Si was rapidly solidified by using melt-spinning technique to examine the influence of the cooling rate/conditions on microstructure and mechanical properties. The resulting conventional cast (ingot) and melt-spun ribbons were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy together with energy dispersive spectroscopy, differential scanning calorimetry, differential thermal analysis and Vickers microhardness tester. The ingot alloys consists of four phases namely {alpha}-Al, intermetallic Al{sub 3}Ni, Al{sub 11}Nd{sub 3} and fcc Si. Melt-spun ribbons are completely composed of {alpha}-Al phase. The optical microscopy and scanning electron microscopy results show that the microstructures of rapidly solidified ribbons are clearly different from their ingot alloy. The change in microhardness is discussed based on the microstructural observations. - Highlights: Black-Right-Pointing-Pointer Rapid solidification allows a reduction in grain size, extended solid solution ranges. Black-Right-Pointing-Pointer We observed the matrix lattice parameter increases with increasing wheel speed. Black-Right-Pointing-Pointer Melt-spun ribbons consist of partly amorphous phases embedded in crystalline phases. Black-Right-Pointing-Pointer The solidification rate is high enough to retain most of alloying elements in the Al matrix. Black-Right-Pointing-Pointer The rapid solidification has effect on the phase constitution.

  13. Quantitative determination of the solidus line in the dilute limit of succinonitrile-camphor alloys

    Science.gov (United States)

    Mota, F. L.; Fabietti, L. M.; Bergeon, N.; Strutzenberg, L. L.; Karma, A.; Billia, B.; Trivedi, R.

    2016-08-01

    Different phase diagram measurements for succinonitrile-camphor alloys to date have yielded different values of the solute partition coefficient and the freezing range of the alloy. These parameters are critical to model solidification microstructure evolution. New measurements are made to precisely characterize the dilute limit of the succinonitrile-camphor phase diagram using thin-sample directional solidification experiments where convection is negligible, so that solute transport in the melt is purely diffusive, and the temperature gradient is constant in time. These results are confirmed through complementary measurements by differential scanning calorimetry and isothermal annealing. Possible measurement uncertainties in previously measured solidus lines are discussed. Experimental results were further confirmed using a boundary layer model of transient planar interface dynamics.

  14. Thermal and microstructural analysis of alloys of Al-Mg-Li system

    International Nuclear Information System (INIS)

    Ovsyannikov, B.V.; Zamaytin, V.M.; Smirnov, V.L.; Mushnikov, V.S.

    2008-01-01

    By means of the thermal analysis one investigated into melting and solidification of Al-Mg-Li system 1420, 1421 and 1424 aluminum-lithium alloys. One determined the temperature values of the nonequilibrium and the equilibrium solidus, the initiation of the liquidus linear shrinkage of the listed alloys. Making use of a scanning electron microscope with a microanalyser unit one studied the microstructure of the alloys and determined the local chemical composition of the phases unsoluble under homogenization of ingots along the aluminum matrix grain boundaries [ru

  15. Experimental Observation and Analytical Modeling of Melting and Solidification during Aluminum Alloy Repair by Turbulence Flow Casting

    Directory of Open Access Journals (Sweden)

    Muki Satya Permana

    2017-03-01

    Full Text Available This paper presents an overview on the state of the art of applicable casting technology for applications in the field of repairing Aluminium Alloy components. Repair process on the Aluminium sample using similar metal has been carried out to investigate the micro-structural effect. Joining occurs as a result of convection heat transfer of molten flow into the sand mold which melts the existing base metal inside the mold and subsequent solidification. The analytical model has been developed to describe aluminium component repair by Turbulence Flow Casting. The model built is based on heat transfer principle that can handle the phenomena of heat flow. The experimental result and analytical model analyses pointed out that joint quality are greatly affected by parameters of preheating temperature and duration of molten metal flow in the mold. To obtain a desired metallurgical sound at the joint, the optimum temperature and time were adjusted in order to obtain a similarity of microstructure between filler and base metal. This model is aimed to predict the use of the process parameter ranges in order to have the optimum parameters when it is applied to the experiment. The fixed parameters are flow rate, sand ratio, and pouring temperature. The process parameters are preheating temperature and pouring time. It is concluded that anaytical modeling has good agreement with the experimental result

  16. Hot corrosion resistance of a Pb-Sb alloy for lead acid battery grids

    Energy Technology Data Exchange (ETDEWEB)

    Osorio, Wislei R.; Garcia, Amauri [Department of Materials Engineering, University of Campinas - UNICAMP, PO Box 6122, 13083-970 Campinas, SP (Brazil); Aoki, Claudia S.C. [Research and Development Centre - CPqD Foundation, Rod. Campinas/Mogi, km 118.5, 13086-912 Campinas, SP (Brazil)

    2008-12-01

    The aim of this study was to evaluate the effects of the microstructural morphologies of a Pb-6.6 wt%Sb alloy on the resulting corrosion resistance in a 0.5 M H{sub 2}SO{sub 4} solution at different temperatures: environment temperature, 50 C and 70 C. A water-cooled unidirectional solidification system was employed permitting a wide range of microstructures to be analyzed. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the corrosion behavior of the Pb-Sb alloy samples. It was found that with increasing temperatures the general corrosion resistance of Pb-Sb dendritic alloys decreases, and that independently of the working temperature finer dendritic spacings exhibit better corrosion resistance than coarser ones. (author)

  17. Melting and solidification behavior of Cu/Al and Ti/Al bimetallic core/shell nanoparticles during additive manufacturing by molecular dynamics simulation

    Science.gov (United States)

    Rahmani, Farzin; Jeon, Jungmin; Jiang, Shan; Nouranian, Sasan

    2018-05-01

    Molecular dynamics (MD) simulations were performed to investigate the role of core volume fraction and number of fusing nanoparticles (NPs) on the melting and solidification of Cu/Al and Ti/Al bimetallic core/shell NPs during a superfast heating and slow cooling process, roughly mimicking the conditions of selective laser melting (SLM). One recent trend in the SLM process is the rapid prototyping of nanoscopically heterogeneous alloys, wherein the precious core metal maintains its particulate nature in the final manufactured part. With this potential application in focus, the current work reveals the fundamental role of the interface in the two-stage melting of the core/shell alloy NPs. For a two-NP system, the melting zone gets broader as the core volume fraction increases. This effect is more pronounced for the Ti/Al system than the Cu/Al system because of a larger difference between the melting temperatures of the shell and core metals in the former than the latter. In a larger six-NP system (more nanoscopically heterogeneous), the melting and solidification temperatures of the shell Al roughly coincide, irrespective of the heating or cooling rate, implying that in the SLM process, the part manufacturing time can be reduced due to solidification taking place at higher temperatures. The nanostructure evolution during the cooling of six-NP systems is further investigated. [Figure not available: see fulltext.

  18. Microstructure Of MnBi/Bi Eutectic Alloy

    Science.gov (United States)

    Wilcox, William R.; Eisa, G. F.; Baskaran, B.; Richardson, Donald C.

    1988-01-01

    Collection of three reports describes studies of directional solidification of MnBi/Bi eutectic alloy. Two of the reports, "Influence of Convection on Lamellar Spacing of Eutectics" and "Influence of Convection on Eutectic Microstructure," establish theoretical foundation for remaining document. Reports seek to quantify effect of convection on concentration field of growing lamellar eutectic. Remaining report, "Study of Eutectic Formation," begins by continuing theoretical developments. New technique under development by one of the authors helps to reveal three-dimensional microstructures of alloys.

  19. Plastic solidification of radioactive wastes

    International Nuclear Information System (INIS)

    Moriyama, Noboru

    1981-01-01

    Over 20 years have elapsed after the start of nuclear power development, and the nuclear power generation in Japan now exceeds the level of 10,000 MW. In order to meet the energy demands, the problem of the treatment and disposal of radioactive wastes produced in nuclear power stations must be solved. The purpose of the plastic solidification of such wastes is to immobilize the contained radionuclides, same as other solidification methods, to provide the first barrier against their move into the environment. The following matters are described: the nuclear power generation in Japan, the radioactive wastes from LWR plants, the position of plastic solidification, the status of plastic solidification in overseas countries and in Japan, the solidification process for radioactive wastes with polyethylene, and the properties of solidified products, and the leachability of radionuclides in asphalt solids. (J.P.N.)

  20. Liquid Phase Separation and the Aging Effect on Mechanical and Electrical Properties of Laser Rapidly Solidified Cu100−xCrx Alloys

    Directory of Open Access Journals (Sweden)

    Song-Hua Si

    2015-11-01

    Full Text Available Duplex structure Cu-Cr alloys are widely used as contact materials. They are generally designed by increasing the Cr content for the hardness improvement, which, however, leads to the unfavorable rapid increase of the electrical resistivity. The solidification behavior of Cu100−xCrx (x = 4.2, 25 and 50 in wt.% alloys prepared by laser rapid solidification is studied here, and their hardness and electrical conductivity after aging are measured. The results show that the Cu-4.2%Cr alloy has the most desirable combination of hardness and conductive properties after aging in comparison with Cu-25%Cr and Cu-50%Cr alloys. Very importantly, a 50% improvement in hardness is achieved with a simultaneous 70% reduction in electrical resistivity. The reason is mainly attributed to the liquid phase separation occurring in the Cu-4.2%Cr alloy, which introduces a large a

  1. Isothermal solidification based packaging of biosensors at low temperatures

    International Nuclear Information System (INIS)

    Sharma, R.P.; Khanna, P.K.; Kumar, D.

    2010-01-01

    Thick film Au printed square contact pads are interconnected to Cu substrates at constant pressure and temperature using the isothermal solidification of Bi-In alloy on the joining surfaces. The effect of reaction time on the mechanical strength of the package has been analyzed. Thermal stability of the fabricated specimens have been measured and discussed. The delaminated surfaces examined optically reveal the morphology of the metallization zones on the joining substrates. The scanning electron microscopy of these surfaces is reported in this paper. Tests for thermal shock, pH resistivity and shelf life have been carried out to predict the reliability of the packaging for long term applications.

  2. Microstructural study of tungsten influence on Co-Cr alloys

    International Nuclear Information System (INIS)

    Karaali, A.; Mirouh, K.; Hamamda, S.; Guiraldenq, P.

    2005-01-01

    Alloying elements, such as W, Mo, Mn,..., are of a great importance in the preoxidation of dental alloys and, consequently, on the ceramic/metal bond quality. This study deals with the effect of tungsten addition on the microstructural state of Co-Cr dental alloys, before the ceramisation process. These materials were prepared by unidirectional solidification. Their characterization has been carried out, using transmission electron microscopy (TEM) and X-ray diffraction. It shows that the addition of tungsten up to 8 wt.% induces structural transformations, which are believed to be linked to the added amount of tungsten

  3. Rapidly solidified Ti-25Al-Nb alloys

    International Nuclear Information System (INIS)

    Ward, C.H.; Broderick, T.F.; Jackson, A.G.; Rowe, R.G.; Froes, F.H.

    1987-01-01

    Alloys based on the Ti-25Al-Nb intermetallic system were studied to determine the effects of rapid solidification on structure. Compositions ranging from 12 to 30 at% niobium which are beyond the α/sub 2/ single phase field were evaluated. Alloys were prepared using a melt spinning process. The resulting ribbons were characterized using transmission electron microscopy and x-ray diffraction. The alloys were all found to have a retained ordered B2 structure in the melt spun condition with an antiphase domain size that significantly decreased with increasing niobium content. ''Tweed-like'' striations, indicating planar shear strain, were observed in all compositions. The characteristic diffraction pattern of an ordered ''omega-type'' phase was found to occur in the patterns taken from the 12 at% niobium alloy

  4. High chromium nickel base alloys hot cracking susceptibility

    International Nuclear Information System (INIS)

    Tirand, G.; Primault, C.; Robin, V.

    2014-01-01

    High Chromium nickel based alloys (FM52) have a higher ductility dip cracking sensitivity. New filler material with higher niobium and molybdenum content are developed to decrease the hot crack formation. The behavior of these materials is studied by coupling microstructural analyses and hot cracking test, PVR test. The metallurgical analyses illustrate an Nb and Mo enrichment of the inter-dendritic spaces of the new materials. A niobium high content (FM52MSS) induces the formation of primary carbide at the end of solidification. The PVR test reveal a solidification crack sensitivity of the new materials, and a lowest ductility dip cracking sensitivity for the filler material 52MSS. (authors)

  5. Basic design of a rotating disk centrifugal atomizer for uranium-molybdenum alloys

    International Nuclear Information System (INIS)

    Alzari, Silvio

    2001-01-01

    One of the most used techniques to produce metallic powders is the centrifugal atomization with a rotating disk. This process is employ to fabricate ductile metallic particles of uranium-molybdenum alloys (typically U- 7 % Mo, by weight) for nuclear fuel elements for research and testing reactors. These alloys exhibit a face-centered cubic structure (γ phase) which is stable above 700 C degrees and can be retained at room temperature. The rotating disk centrifugal atomization allows a rapid solidification of spherical metallic droplets of about 40 to 100 μm, considered adequate to manufacture nuclear fuel elements. Besides the thermo-physical properties of both the alloy and the cooling gas, the main parameters of the process are the radius of the disk (R), the diameter of the atomization chamber (D), the disk rotation speed (ω), the liquid volume flow rate (Q) and the superheating of the liquid (ΔT). In this work, they were applied approximate analytical models to estimate the optimal geometrical and operative parameters to obtain spherical metallic powder of U- 7 % Mo alloy. Three physical phenomena were considerate: the liquid metal flow along the surface of the disk, the fragmentation and spheroidization of the droplets and the cooling and solidification of the droplets. The principal results are the more suitable gas is helium; R ≅ 20 mm; D ≥ 1 m; ≅ 20,000 - 50,000 rpm; Q ≅ 4 - 10 cm 3 /s; ΔT ≅ 100 - 200 C degrees. By applying the relevant non-dimensional parameters governing the main physical phenomena, the conclusion is that the more appropriate non-radioactive metal to simulate the atomization of U- 7 % Mo is gold [es

  6. Improving the casting properties of high-strength aluminium alloys:

    OpenAIRE

    Ekrt, Ondřej; Šerák, Jan; Vojtěch, Dalibor

    2004-01-01

    Al-Zn-Mg-Cu alloys are examples of high-strength alloys. After age-hardening they often possess tensile strengths of more than 500 MPa. However, their casting properties are relatively poor as a result of solidification intervals that are too wide. Therefore, they often require an extrusion, rolling, or forging treatment, and the production of small series of special parts can, as a consequence, be very expensive. In this study, an improvement in the castability and a reduction of the hot-tea...

  7. 24 CFR 92.356 - Conflict of interest.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Conflict of interest. 92.356... Development HOME INVESTMENT PARTNERSHIPS PROGRAM Other Federal Requirements § 92.356 Conflict of interest. (a... subrecipients, the conflict of interest provisions in 24 CFR 85.36 and 24 CFR 84.42, respectively, apply. In all...

  8. Containerless solidification of undercooled oxide and metallic eutectic melts

    International Nuclear Information System (INIS)

    Li Mingjun; Nagashio, Kosuke; Kuribayashi, Kazuhiko

    2004-01-01

    A high-speed video was employed to monitor the in situ recalescence of undercooled oxide Al 2 O 3 -36.8 at.% ZrO 2 and metallic Ni-18.7 at.% Sn eutectics that were processed on an aero-acoustic levitator and an electromagnetic levitator, respectively. For the oxide eutectic, the entire sample becomes brighter and brighter without any clear recalescence front during spontaneous crystallization. When the sample was seeded at desired undercoolings, crystallization started from the seeding point and then spread through the entire sample. Microstructures of the oxide solidified via both the spontaneous crystallization and external seeding consist of many independent eutectic colonies at the sample surface, indicating that copious nucleation takes place regardless of melt undercooling and solidification mode. For the metallic eutectics, two kinds of recalescence are visualized. The surface and cross sectional microstructures reveal that copious nucleation is also responsible for the formation of independent eutectic colonies distributing within the entire sample. It is not possible to measure the growth velocity of a single eutectic colony using optical techniques under the usual magnification. The conventional nucleation concept derived from single-phase alloys may not be applicable to the free solidification of the undercooled double-phase oxide and metallic eutectic systems

  9. Hydrogen as a New Alloying Element in Metals

    International Nuclear Information System (INIS)

    Shapovalov, Vladimir

    1999-01-01

    Hydrogen was regarded as a harmful impurity in many alloys and particularly in steels where it gives rise to a specific type of embrittlement and forms various discontinuities like flakes and blowholes. For this reason, the researcher efforts were mainly focused on eliminating hydrogen's negative impacts and explaining its uncommonly high diffusivity in condensed phases. Meanwhile, positive characteristics of hydrogen as an alloying element remained unknown for quite a long time. Initial reports in this field did not appear before the early 1970s. Data on new phase diagrams are given for metal-hydrogen systems where the metal may or may not form hydrides. Various kinds of hydrogen impact on structure formation in solidification, melting and solid-solid transformations are covered. Special attention is given to the most popular alloys based on iron, aluminum, copper, nickel, magnesium and titanium. Detailed is what is called gas-eutectic reaction resulting in a special type of gas-solid structure named gasarite. Properties and applications of gasars - gasaritic porous materials - are dealt with. Various versions of solid-state alloying with hydrogen are discussed that change physical properties and fabrication characteristics of metals. Details are given on a unique phenomenon of anomalous spontaneous deformation due to combination of hydrogen environment and polymorphic transformation. All currently known versions of alloying with hydrogen are categorized for both hydride-forming and non-hydrid forming metals

  10. Diffusivities of an Al-Fe-Ni melt and their effects on the microstructure during solidification

    International Nuclear Information System (INIS)

    Zhang Lijun; Du Yong; Steinbach, Ingo; Chen Qing; Huang Baiyun

    2010-01-01

    A systematical investigation of the diffusivities in an Al-Fe-Ni melt was presented. Based on the experimental and theoretical data about diffusivities, the temperature- and composition-dependent atomic mobilities were evaluated for the elements in Al-Ni, Al-Fe, Fe-Ni and Al-Fe-Ni melts via an effective approach. Most of the reported diffusivities can be reproduced well by the obtained atomic mobilities. In particular, for the first time the ternary diffusivity of the liquid in a ternary system is described in conjunction with the established atomic mobilities. The effect of the atomic mobilities in a liquid on microstructure and microsegregation during solidification was demonstrated with one Al-Ni binary alloy. The simulation results indicate that accurate databases of mobilities in the liquid phase are much needed for the quantitative simulation of microstructural evolution during solidification by using various approaches, including DICTRA and the phase-field method.

  11. Method of plastic solidification of radioactive wastes

    International Nuclear Information System (INIS)

    Oikawa, Yasuo; Tokimitsu, Fujio.

    1986-01-01

    Purpose: To prevent occurrence of deleterious cracks to the inside and the surface of solidification products, as well as eliminate gaps between the products and the vessel inner wall upon plastic solidification processing for powdery or granular radioactive wastes. Method: An appropriate amount of thermoplastic resins such as styrenic polymer or vinyl acetate type polymer as a low shrinking agent is added and mixed with unsaturated polyester resins to be mixed with radioactive wastes so as to reduce the shrinkage-ratio to 0 % upon curing reaction. Thus, a great shrinkage upon hardening the mixture is suppressed to prevent the occurrence of cracks to the surface and the inside of the solidification products, as well as prevent the gaps between the inner walls of a drum can vessel and the products upon forming solidification products to the inside of the drum can. The resultant solidification products have a large compression strength and can sufficiently satisfy the evaluation standards as the plastic solidification products of radioactive wastes. (Horiuchi, T.)

  12. Fundamental Metallurgy of Solidification

    DEFF Research Database (Denmark)

    Tiedje, Niels

    2004-01-01

    The text takes the reader through some fundamental aspects of solidification, with focus on understanding the basic physics that govern solidification in casting and welding. It is described how the first solid is formed and which factors affect nucleation. It is described how crystals grow from...

  13. Radioactive waste solidification material

    International Nuclear Information System (INIS)

    Nishihara, Yukio; Wakuta, Kuniharu; Ishizaki, Kanjiro; Koyanagi, Naoaki; Sakamoto, Hiroyuki; Uchida, Ikuo.

    1992-01-01

    The present invention concerns a radioactive waste solidification material containing vermiculite cement used for a vacuum packing type waste processing device, which contains no residue of calcium hydroxide in cement solidification products. No residue of calcium hydroxide means, for example, that peak of Ca(OH) 2 is not recognized in an X ray diffraction device. With such procedures, since calcium sulfoaluminate clinker and Portland cement themselves exhibit water hardening property, and slugs exhibit hydration activity from the early stage, the cement exhibits quick-hardening property, has great extension of long term strength, further, has no shrinking property, less dry- shrinkage, excellent durability, less causing damages such as cracks and peeling as processing products of radioactive wastes, enabling to attain highly safe solidification product. (T.M.)

  14. The dynamics of nucleation and growth of a particle in the ternary alloy melt with anisotropic surface tension.

    Science.gov (United States)

    Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min

    2017-08-28

    The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.

  15. Semi-solid rheocasting of grain refined aluminum alloy 7075

    CSIR Research Space (South Africa)

    Curle, UA

    2010-09-01

    Full Text Available mm×6 mm. Fig.1 shows the whole casting including the runner and the biscuit. A batch of the 7075 alloy was melted in a 20 kg tilting furnace and degassed with argon. A sample was poured and cooled to analyze the starting chemical composition... of the liquid metal by optical emission spectroscopy (Thermo Quantris OES). Thermodynamic properties of the starting alloy were then calculated (Scheil solidification model) with an aluminum thermodynamic database (ProCast 2009.1) using the OES composition...

  16. Natural and artificial aging response of semisolid metal processed Al–Si–Mg alloy A356

    CSIR Research Space (South Africa)

    Moller, H

    2007-12-01

    Full Text Available aging at 180uC (Table 2). It can be seen from Table 2 that it takes approximately six times longer to reach peak hardness at 160uC compared to at 180uC. The diffusivity of silicon in aluminium is about double that of magnesium in aluminium... in the content of alloying elements. In Al–Mg–Si alloys containing an excess of silicon, the decomposition of the super- saturated solid solution (SSS) is believed to occur as follows7 SSS?(MgzSi)clusters=GP(I)spherical ?b=GP(II)needles?b0rodsz...

  17. Characteristics of Cement Solidification of Metal Hydroxide Waste

    Directory of Open Access Journals (Sweden)

    Dae-Seo Koo

    2017-02-01

    Full Text Available To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

  18. Characteristics of cement solidification of metal hydroxide waste

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Dae Seo; Sung, Hyun Hee; Kim, Seung Soo; Kim, Gye Nam; Choi, Jong Won [Dept. of Decontemination Decommission Technology Development, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-02-15

    To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

  19. Mechanical Properties of Al-Si-Mg Alloy Castings as a Function of Structure Refinement and Porosity Fraction

    Directory of Open Access Journals (Sweden)

    Hajkowski M.

    2012-12-01

    Full Text Available During design of the casting products technology, an important issue is a possibility of prediction of mechanical properties resulting from the course of the casting solidification process. Frequently there is a need for relations describing mechanical properties of silumin alloys as a function of phase refinement in a structure and a porosity fraction, and relations describing phase refinement in the structure and the porosity fraction as a function of solidification conditions. The study was conducted on castings of a 22 mm thick plate, made of EN AC-AlSi7Mg0,3 alloy in moulds: of quartz sand, of quartz sand with chill and in permanent moulds. On the basis of cooling curves, values of cooling rate in various casting parts were calculated. The paper also presents results of examination of distance between arms in dendrites of a solid solution α (DASL, precipitations length of silicon in an eutectic (DlSi and gas-shrinkage porosity (Por as a function of cooling rate. Statistical relations of DASL, DlSi, Por as a function of cooling rate and statistical multiparameter dependencies describing mechanical properties (tensile strength, yield strength, elongation of alloy as a function of DASL, DlSi and Por are also presented in the paper.

  20. Ageless Aluminum-Cerium-Based Alloys in High-Volume Die Casting for Improved Energy Efficiency

    Science.gov (United States)

    Stromme, Eric T.; Henderson, Hunter B.; Sims, Zachary C.; Kesler, Michael S.; Weiss, David; Ott, Ryan T.; Meng, Fanqiang; Kassoumeh, Sam; Evangelista, James; Begley, Gerald; Rios, Orlando

    2018-04-01

    Strong chemical reactions between Al and Ce lead to the formation of intermetallics with exceptional thermal stability. The rapid formation of intermetallics directly from the liquid phase during solidification of Al-Ce alloys leads to an ultrafine microconstituent structure that effectively strengthens as-cast alloys without further microstructural optimization via thermal processing. Die casting is a high-volume manufacturing technology that accounts for greater than 40% of all cast Al products, whereas Ce is highly overproduced as a waste product of other rare earth element (REE) mining. Reducing heat treatments would stimulate significant improvements in manufacturing energy efficiency, exceeding (megatonnes/year) per large-scale heat-treatment line. In this study, multiple compositions were evaluated with wedge mold castings to test the sensitivity of alloys to the variable solidification rate inherent in high-pressure die casting. Once a suitable composition was determined, it was successfully demonstrated at 800 lbs/h in a 600-ton die caster, after which the as-die cast parts performed similarly to ubiquitous A380 in the same geometry without requiring heat treatment. This work demonstrates the compatibility of Al REE alloys with high-volume die-casting applications with minimal heat treatments.

  1. Ageless Aluminum-Cerium-Based Alloys in High-Volume Die Casting for Improved Energy Efficiency

    Science.gov (United States)

    Stromme, Eric T.; Henderson, Hunter B.; Sims, Zachary C.; Kesler, Michael S.; Weiss, David; Ott, Ryan T.; Meng, Fanqiang; Kassoumeh, Sam; Evangelista, James; Begley, Gerald; Rios, Orlando

    2018-06-01

    Strong chemical reactions between Al and Ce lead to the formation of intermetallics with exceptional thermal stability. The rapid formation of intermetallics directly from the liquid phase during solidification of Al-Ce alloys leads to an ultrafine microconstituent structure that effectively strengthens as-cast alloys without further microstructural optimization via thermal processing. Die casting is a high-volume manufacturing technology that accounts for greater than 40% of all cast Al products, whereas Ce is highly overproduced as a waste product of other rare earth element (REE) mining. Reducing heat treatments would stimulate significant improvements in manufacturing energy efficiency, exceeding (megatonnes/year) per large-scale heat-treatment line. In this study, multiple compositions were evaluated with wedge mold castings to test the sensitivity of alloys to the variable solidification rate inherent in high-pressure die casting. Once a suitable composition was determined, it was successfully demonstrated at 800 lbs/h in a 600-ton die caster, after which the as-die cast parts performed similarly to ubiquitous A380 in the same geometry without requiring heat treatment. This work demonstrates the compatibility of Al REE alloys with high-volume die-casting applications with minimal heat treatments.

  2. A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni2MnGa by directional solidification

    International Nuclear Information System (INIS)

    Zhu, Yuping; Gu, Yunling; Liu, Hongguang

    2015-01-01

    Directional solidification technology has been widely used to improve the properties of polycrystalline Ni 2 MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni 2 MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering

  3. Method of storing solidification products

    International Nuclear Information System (INIS)

    Tani, Yutaro.

    1985-01-01

    Purpose: To enable to efficiently and satisfactorily cool and store solidification products of liquid wastes generated from the reactor spent fuel reprocessing process by a simple facility. Method: Liquid wastes generated from the reactor spent fuel reprocessing process are caused to flow from the upper opening to the inside of a spherical canistor. The opening of the spherical canistor is welded with a lid by a remote control and the liquid wastes are tightly sealed within the spherical canistor as glass solidification products. Spherical canistors having the solidification products tightly sealed therein are sent into and stored in a hopper by the remote control. Further, a blower is driven upon storing to suck cooling air from the cooling air intake port to the inside of the hopper to absorb the decay heat of radioactive materials in the solidification products and the air is discharged from the duct and through the stack to the atmosphere. (Kawakami, Y.)

  4. Metallurgical Parameters Controlling the Eutectic Silicon Charateristics in Be-Treated Al-Si-Mg Alloys.

    Science.gov (United States)

    Ibrahim, Mohamed F; Elgallad, Emad M; Valtierra, Salvador; Doty, Herbert W; Samuel, Fawzy H

    2016-01-27

    The present work was carried out on Al-7%Si-0.4%Mg-X alloy (where X = Mg, Fe, Sr or Be), where the effect of solidification rate on the eutectic silicon characteristics was investigated. Two solidification rates corresponding to dendrite arm spacings (DAS) of 24 and 65 μm were employed. Samples with 24 μm DAS were solution heat-treated at 540 °C for 5 and 12 h prior to quenching in warm water at 65 °C. Eutectic Si particle charateristics were measured using an image analyzer. The results show that the addition of 0.05% Be leads to partial modification of the Si particles. Full modification was only obtained when Sr was added in an amount of 150-200 ppm, depending on the applied solidification rate. Increasing the amount of Mg to 0.8% in Sr-modified alloys leads to a reduction in the effectiveness of Sr as the main modifier. Similar observations were made when the Fe content was increased in Be-treated alloys due to the Be-Fe interaction. Over-modification results in the precipitation of hard Sr-rich particles, mainly Al₄SrSi₂, whereas overheating causes incipient melting of the Al-Cu eutectic and hence the surrounding matrix. Both factors lead to a deterioration in the alloy mechanical properties. Furthermore, the presence of long, acicular Si particles accelerates the occurrence of fracture and, as a result, yields poor ductility. In low iron (less than 0.1 wt%) Al-Si-Mg alloys, the mechanical properties in the as cast, as well as heat treated conditions, are mainly controlled by the eutectic Si charatersitics. Increasing the iron content and, hence, the volume fraction of Fe-based intermetallics leads to a complex fracture mode.

  5. Metallurgical Parameters Controlling the Eutectic Silicon Charateristics in Be-Treated Al-Si-Mg Alloys

    Directory of Open Access Journals (Sweden)

    Mohamed F. Ibrahim

    2016-01-01

    Full Text Available The present work was carried out on Al-7%Si-0.4%Mg-X alloy (where X = Mg, Fe, Sr or Be, where the effect of solidification rate on the eutectic silicon characteristics was investigated. Two solidification rates corresponding to dendrite arm spacings (DAS of 24 and 65 μm were employed. Samples with 24 μm DAS were solution heat-treated at 540 °C for 5 and 12 h prior to quenching in warm water at 65 °C. Eutectic Si particle charateristics were measured using an image analyzer. The results show that the addition of 0.05% Be leads to partial modification of the Si particles. Full modification was only obtained when Sr was added in an amount of 150–200 ppm, depending on the applied solidification rate. Increasing the amount of Mg to 0.8% in Sr-modified alloys leads to a reduction in the effectiveness of Sr as the main modifier. Similar observations were made when the Fe content was increased in Be-treated alloys due to the Be-Fe interaction. Over-modification results in the precipitation of hard Sr-rich particles, mainly Al4SrSi2, whereas overheating causes incipient melting of the Al-Cu eutectic and hence the surrounding matrix. Both factors lead to a deterioration in the alloy mechanical properties. Furthermore, the presence of long, acicular Si particles accelerates the occurrence of fracture and, as a result, yields poor ductility. In low iron (less than 0.1 wt% Al-Si-Mg alloys, the mechanical properties in the as cast, as well as heat treated conditions, are mainly controlled by the eutectic Si charatersitics. Increasing the iron content and, hence, the volume fraction of Fe-based intermetallics leads to a complex fracture mode.

  6. The buoyancy convection during directional solidification of AlZn eutectic

    International Nuclear Information System (INIS)

    Prazak, M.; Procio, M.; Holecek, S.

    1993-01-01

    A study has been made of the effect of buoyancy convection during the directional solidification of AlZn eutectic alloy. Experiments have been conducted using a Bridgman-Stockbarger arrangement with the furnace moving along the specimen. The apparatus rotated around the horizontal axis, which made it possible to carry out measurements at different angles β contained by the gravity and temperature gradient vectors in the specimen. The anisotropy of both the linear thermal expansion coefficient a and the hardness HK measured by the Knoop method has been studied. The dilatation measurements confirmed the expected anisotropy of the linear thermal expansion of directionally solidified specimens. The values of HK correspond with the lamellar spacing measured in the metallographic study. (orig.)

  7. 31 CFR 356.31 - How does the STRIPS program work?

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false How does the STRIPS program work? 356.31 Section 356.31 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued...) Miscellaneous Provisions § 356.31 How does the STRIPS program work? (a) General. Notes or bonds may be “stripped...

  8. Effect of vanadium on the microstructures and mechanical properties of an Al–Mg–Si–Cu–Cr–Ti alloy of 6XXX series

    International Nuclear Information System (INIS)

    Meng, Yi; Cui, Jianzhong; Zhao, Zhihao; Zuo, Yubo

    2013-01-01

    Highlights: •The shapes of Al 3 V and Al 10 V are like petal and coarse plate respectively. •Fine elliptical-shaped Al(VCrTi)Si phases are present when Al 3 V phases are added. •Coarse AlVMg phases are present when Al 10 V phases are added. •Larger as-cast grain refinement is carried out by Al 3 V phases rather than Al 10 V. •V improves the UTS and plasticity of the alloy only when Al 3 V phases are added. -- Abstract: Vanadium can be considered as a minor element to improve mechanical properties of wrought aluminium alloys by modifying their microstructures. However, so far, it is not widely used in wrought aluminium alloys due to its indissolubility during smelting and solidification. In the present work, Al–4 wt.% V master alloys were prepared with different solidification rates and these master alloys were introduced to a commercial Al–1.6Mg–1.2Si–1.1Cu–0.16Cr–0.03Ti (all in wt.%) wrought alloy to study the effect of vanadium on the microstructures and mechanical properties of this alloy. The results showed that the fast solidification rate resulted in the formation of petal-like shaped Al 3 V phase in Al–4 wt.% V master alloy, while the slow solidification rate resulted in the formation of Al 10 V phase with coarse plate shape. The addition of Al 3 V phases into the experimental alloy not only promotes the formation of a fine, equiaxed as-cast grain structure, but also inhibits the recrystallisation nucleation and grain growth during hot extrusion and subsequent T6 heat treatment. In this case, the main vanadium phase in this alloy is the metastable and fine Al(VCrTi)Si phase with elliptical morphology and relatively high vanadium content. And the Al(VCrTi)Si phases developed from Al 3 V phases could pin the movement of dislocations and impede recrystallisation nucleation and growth, resulting in the improvement of mechanical properties. In the experimental alloy with the addition of Al 10 V phases, the stable AlVMg phase and Al 10 V

  9. Influence of Processing on the Microstructure and Mechanical Properties of a NbAl3-Base Alloy

    Science.gov (United States)

    Hebsur, Mohan G.; Locci, Ivan E.; Raj, S. V.; Nathal, Michael V.

    1992-01-01

    Induction melting and rapid solidification processing, followed by grinding to 75-micron powder and P/M consolidation, have been used to produce a multiphase, NbAl3-based, oxidation-resistant alloy of Nb-67Al-7Cr-0.5Y-0.25W composition whose strength and ductility are significantly higher than those of the induction-melted alloy at test temperatures of up to 1200 K. Attention is given to the beneficial role of microstructural refinement; the major second phase, AlNbCr, improves both oxidation resistance and mechanical properties.

  10. Effect of processing on the microstructural development in a rapidly solidified Al-Fe-V-Si alloy

    International Nuclear Information System (INIS)

    Srivastava, A.K.; Ranganathan, S.; Ojha, S.N.

    1993-01-01

    An Al 80 Fe 10 Si 6 alloy has been rapidly solidified using melt spinning, gas atomization and spray forming processes. The effect of processing techniques on the microstructural characteristics of the alloy has ben evaluated. The melt spun alloy has shown an icosahedral quasicrystalline phase surrounded by a rational approximant structure of the icosahedral phase. The rational approximant structure has been identified as a crystalline cubic silicide phase. The atomized powders have exhibited cellular and dendritic morphology depending on the size of particles. In addition, the second phase particles of the silicide phase are observed to decorate the cell boundaries and interdendritic regions. In contrast, the alloy processed by spray deposition has revealed an equiaxed solidification morphology with a uniform dispersion of find silicon phase inside the grain. The origin of the microstructure in the alloy processed by these techniques is discussed. The results are compared wherever possible with the commercially available Al-Fe-V-Si alloys

  11. Solidification process for toxic and hazardous wastes. Second part: Cement solidification matrices

    International Nuclear Information System (INIS)

    Donato, A.; Arcuri, L.; Dotti, M.; Pace, A.; Pietrelli, L.; Ricci, G.; Basta, M.; Cali, V.; Pagliai, V.

    1989-05-01

    This paper reports the second part of a general study carried out at the Nuclear Fuel Division aiming at verifying the possible application of the radioactive waste solidification processes to industrial hazardous wastes (RTN). The cement solidification of several RTN types has been taken into consideration, both from the technical and from the economic point of view. After a short examination of the Italian juridical and economical situation in the field, which demonstrates the need of the RTN solidification, the origin and characteristics of the RTN considered in the study and directly provided by the producing industries are reviewed. The laboratory experimental results of the cementation of RTN produced by gold manufacturing industries and by galvanic industries are reported. The cementation process can be considered a very effective mean for reducing both the RTN management costs and the environmental impact of RTN disposal. (author)

  12. Micro-scale thermocapillary convection with solidification

    International Nuclear Information System (INIS)

    Yang, W.J.; Liu, J.C.; Chai, A.T.

    1991-01-01

    This paper reports on an experimental study performed on heat transfer in sessile drops of lysozyme solutions with solidification. Solidification inside the sessile drop is initiated by means of the center cooling method. The internal flow behavior and solidification front movement are observed using a microscope-video monitor system. Results are obtained for lysozyme, and buffer solutions, and water, representing media possessing surface tension coefficients. It is disclosed that the time history of the solidification front movement can be divided into two stages; initial and stable. In the stable stage, the front movement x follows the power-law behavior x = Ct n . C is an empirical constant, and t denotes time. The exponent n takes on a value close to unity in the stable stage

  13. Investigation of the effects of cooling rate on the microstructure of investment cast biomedical grade Co alloys

    International Nuclear Information System (INIS)

    Kaiser, R; Browne, D J; Williamson, K

    2012-01-01

    The objective of this work is to determine the microstructural characteristics of investment cast cobalt alloy as the cross-sectional area is varied, thus changing the local effective cooling rates and solidification times. The extent of published work on the as-cast properties of cobalt alloys is minimal. The primary aim of this work is therefore to extend knowledge of the behaviour of such alloys as they solidify, which will influence the design of new products as well as the industrial optimisation of the casting process. Wedge-shaped parts were cast from a biomedical grade cobalt alloy employing the method of lost wax investment casting. Analytical techniques such as optical microscopy, image analysis and microhardness testing were used to characterise the as-cast parts. Parameters studied include variations in grain structure, nature of the columnar and equiaxed zones and the spread of porosity (both shrinkage and gas). Changes in microstructure were compared to microhardness values obtained. The solidification profile of the alloy through the prototype cast component was investigated based on measurement of the dendrite arm spacings. A discussion on the physical phenomena controlling the microstructural variations is presented.

  14. Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

    DEFF Research Database (Denmark)

    Tiedje, Niels Skat; Taylor, John A.; Easton, Mark A.

    2012-01-01

    Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings...... of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer...... as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline...

  15. 31 CFR 356.32 - What tax rules apply?

    Science.gov (United States)

    2010-07-01

    ... political subdivision of a State, except for State estate or inheritance taxes and other exceptions as... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false What tax rules apply? 356.32 Section...) Miscellaneous Provisions § 356.32 What tax rules apply? (a) General. Securities issued under this part are...

  16. Fusion boundary microstructure evolution in aluminum alloys

    Science.gov (United States)

    Kostrivas, Anastasios Dimitrios

    2000-10-01

    A melting technique was developed to simulate the fusion boundary of aluminum alloys using the GleebleRTM thermal simulator. Using a steel sleeve to contain the aluminum, samples were heated to incremental temperatures above the solidus temperature of a number of alloys. In alloy 2195, a 4wt%Cu-1wt%Li alloy, an equiaxed non-dendritic zone (EQZ) could be formed by heating in the temperature range from approximately 630 to 640°C. At temperatures above 640°C, solidification occurred by the normal epitaxial nucleation and growth mechanism. Fusion boundary behavior was also studied in alloys 5454-H34, 6061-T6, and 2219-T8. Additionally, experimental alloy compositions were produced by making bead on plate welds using an alloy 5454-H32 base metal and 5025 or 5087 filler metals. These filler metals contain zirconium and scandium additions, respectively, and were expected to influence nucleation and growth behavior. Both as-welded and welded/heat treated (540°C and 300°C) substrates were tested by melting simulation, resulting in dendritic and EQZ structures depending on composition and substrate condition. Orientation imaging microscopy (OIM(TM)) was employed to study the crystallographic character of the microstructures produced and to verify the mechanism responsible for EQZ formation. OIM(TM) proved that grains within the EQZ have random orientation. In all other cases, where the simulated microstructures were dendritic in nature, it was shown that epitaxy was the dominant mode of nucleation. The lack of any preferred crystallographic orientation relationship in the EQZ supports a theory proposed by Lippold et al that the EQZ is the result of heterogeneous nucleation within the weld unmixed zone. EDS analysis of the 2195 on STEM revealed particles with ternary composition consisted of Zr, Cu and Al and a tetragonal type crystallographic lattice. Microdiffraction line scans on EQZ grains in the alloy 2195 showed very good agreement between the measured Cu

  17. Microstructure and mechanical properties of AC AlSi9CuX alloys

    OpenAIRE

    L.A. Dobrzański; R. Maniara; M. Krupiński; J.H. Sokołowski

    2007-01-01

    Purpose: In order to gain a better understanding of how to control the as-cast microstructure, it is important to understand the evaluation of microstructure during solidification and understanding how influence the changes of chemical concentration on this microstructure and mechanical properties. In this research, the effect of Cu content on the microstructure and mechanical properties of AC AlSi9CuX series alloys has been investigated.Design/methodology/approach: The experimental alloy ...

  18. Chemical leaching of rapidly solidified Al-Si binary alloys

    International Nuclear Information System (INIS)

    Yamauchi, I.; Takahara, K.; Tanaka, T.; Matsubara, K.

    2005-01-01

    Various particulate precursors of Al 100-x Si x (x = 5-12) alloys were prepared by a rapid solidification process. The rapidly solidified structures of the precursors were examined by XRD, DSC and SEM. Most of Si atoms were dissolved into the α-Al(fcc) phase by rapid solidification though the solubility of Si in the α-Al phase is negligibly small in conventional solidification. In the case of 5 at.% Si alloy, a single α-Al phase was only formed. The amount of the primary Si phase increased with increase of Si content for the alloys beyond 8 at.% Si. Rapid solidification was effective to form super-saturated α-Al precursors. These precursors were chemically leached by using a basic solution (NaOH) or a hydrochloric acid (HCl) solution. All Al atoms were removed by a HCl solution as well as a NaOH solution. Granules of the Si phase were newly formed during leaching. The specific surface area was about 50-70 m 2 /g independent of Si content. The leaching behavior in both solutions was slightly different. In the case of a NaOH solution, the shape of the precursor often degenerated after leaching. On the other hand, it was retained after leaching by a HCl solution. Fine Si particles precipitated in the α-Al phase by annealing of as-rapidly solidified precursors at 773 K for 7.2 x 10 3 s. In this case, it was difficult to obtain any products by NaOH leaching, but a few of Si particles were obtained by HCl leaching. Precipitated Si particles were dissolved by the NaOH solution. The X-ray diffraction patterns of leached specimens showed broad lines of the Si phase and its lattice constant was slightly larger than that of the pure Si phase. The microstructures of the leached specimens were examined by transmission electron microscopy. It showed that the leached specimens had a skeletal structure composed of slightly elongated particles of the Si phase and quite fine pores. The particle size was about 30-50 nm. It was of comparable order with that evaluated by Scherer

  19. Separation of primary solid phases from Al-Si alloy melts

    Directory of Open Access Journals (Sweden)

    Ki Young Kim

    2014-07-01

    Full Text Available The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical, physical and chemical properties of the alloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts. This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation, draining, filtration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.

  20. A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni{sub 2}MnGa by directional solidification

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuping, E-mail: zhuyuping@126.com; Gu, Yunling; Liu, Hongguang

    2015-02-25

    Directional solidification technology has been widely used to improve the properties of polycrystalline Ni{sub 2}MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni{sub 2}MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering.

  1. Influence of solidification parameters on the cellular sub-structure of tin and some tin alloys

    International Nuclear Information System (INIS)

    Milosavljevic, Dj.

    1965-01-01

    This paper describes an attempt to obtain qualitative data on sub-structure of samples solidified in contact with the cooler. The objective of experiments was to study micro segregation phenomena by investigating the substructure in the solidified sample obtained under experimental conditions which are similar to real solidification conditions

  2. Solidification and vitrification life-cycle economics study

    International Nuclear Information System (INIS)

    Gimpel, R.F.

    1992-01-01

    Solidification (making concrete) and vitrification (making glass) are frequently the treatment methods recommended for treating inorganic or radioactive wastes. Ex-situ solidification and vitrification are the competing methods for treating in excess of 450 000 cm 3 of low-level radioactive and mixed wastes at the Fernald Environmental Management Project (FEMP) located near Cincinnati, Ohio. This paper summarizes a detailed study done to: (1) compare the economics of the solidification and vitrification processes, (2) determine if the stigma assigned to vitrification is warranted and, (3) determine if investing millions of dollars into vitrification development, along with solidification development, at Fernald is warranted

  3. Phase formation in Mg-Sn-Si and Mg-Sn-Si-Ca alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, A.; Groebner, J. [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, R., E-mail: schmid-fetzer@tu-clausthal.de [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)

    2011-02-17

    Research highlights: > The solidification paths of ternary and quaternary alloys are analyzed in detail, using the tool of thermodynamic calculations. > The precipitation sequence of phases and their