Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg₂Ni-type Alloy by Melt Spinning.

Science.gov (United States)

Zhang, Yang-Huan; Li, Bao-Wei; Ren, Hui-Ping; Li, Xia; Qi, Yan; Zhao, Dong-Liang

2011-01-18

Mg₂Ni-type Mg₂Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg₂Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio () of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio () from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10 - 11 to 3.88 × 10 - 11 cm²/s and the limiting current density I L from 150.9 to 887.4 mA/g.

Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

International Nuclear Information System (INIS)

Firstov, G.S.; Koval, Yu.N.; Van Humbeeck, J.; Portier, R.; Vermaut, P.; Ochin, P.

2006-01-01

The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed

Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Firstov, G.S. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine)]. E-mail: gfirst@imp.kiev.ua; Koval, Yu.N. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine); Van Humbeeck, J. [Department MTM, Catholic University of Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven) (Belgium); Portier, R. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Vermaut, P. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Ochin, P. [Centre d' Etudes de Chimie Metallurgique-CNRS UPR2801, 15 rue Georges Urbain, 94407 Vitry-sur-Seine (France)

2006-11-25

The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed.

Characterisation of melt spun Ni-Ti shape memory Ribbons' microstructure

Science.gov (United States)

Mehrabi, Kambiz; Brunčko, Mihael; Kneissl, Albert C.; Čolič, Miodrag; Stamenković, Dragoslav; Ferčec, Janko; Anžel, Ivan; Rudolf, Rebeka

2012-06-01

NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

Microstructure and grain refining performance of melt-spun Al-5Ti-1B master alloy

International Nuclear Information System (INIS)

Zhang Zhonghua; Bian Xiufang; Wang Yan; Liu Xiangfa

2003-01-01

In the present work, the microstructure and grain refining performance of the melt-spun Al-5Ti-1B (wt%) master alloy have been investigated, using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and grain refining tests. It has been found that the microstructure of the melt-spun Al-5Ti-1B master alloy is mainly composed of two phases: metastable, supersaturated α-Al solid solution and uniformly dispersed TiB 2 particles, quite different from that of the rod-like alloy consisting of three phases: α-Al, blocky TiAl 3 , and clusters of TiB 2 particles. Quenching temperatures and wheel speeds (cooling rates), however, have no obvious effect on the microstructure of the melt-spun Al-5Ti-1B alloy. Grain refining tests show that rapid solidification has a significant effect on the grain refining performance of Al-5Ti-1B alloy and leads to the great increase of nucleation rate of the alloy. Nevertheless, the melt-spun Al-5Ti-1B master alloy prepared at different wheel speeds and quenching temperatures possesses the similar grain refining performance. The reasons for the microstructure formation and the improvement of the grain refining performance of the melt-spun Al-5Ti-1B master alloy have been also discussed

Hard magnetic properties and coercivity mechanism of melt-spun Misch Metal-Fe-B alloy

Energy Technology Data Exchange (ETDEWEB)

Quan, Ningtao; Luo, Yang, E-mail: eluoyang@foxmail.com; Yan, Wenlong; Yuan, Chao; Yu, Dunbo; Sun, Liang; Lu, Shuo; Li, Hongwei; Zhang, Hongbin

2017-09-01

Highlights: • Melt-spun MM{sub 13}Fe{sub 81}B{sub 6} alloy shows that the distributions of the La, Ce, Pr, Nd, Fe and B elements is uniformly distributed, and the grain size is in the range of 30–40 nm, it can be seen that Pr-rich and La-rich phases concentrated on grain boundaries, which resulted in the coercivity augment with the increase of MMFe{sub 2} content, and the grain size is around 40–50 nm in MM{sub 16}Fe{sub 78}B{sub 6}. • There is a significant formation of MMFe{sub 2} with abundant Pr and La, and a small amount of Ce and Nd enriched at the interfacial region in MM{sub 16}Fe{sub 78}B{sub 6}, thus an inhomogeneous region was formed. It is considered that the inhomogeneous region is effective in increasing the coercivity. • The optimum-quenched MM{sub 13}Fe{sub 81}B{sub 6} alloy have been shown to exhibit a coercive force of 6.9 kOe and an energy product of 8.5 MGOe, which is superior to anisotropic ferrite magnets of 4.5 MGOe. - Abstract: Magnetic and structural properties of Misch Metal (MM)-Fe-B alloys, were examined in the melt-spun ribbons. Melt-spun MM-Fe-B samples were prepared at the surface velocities of 18–30 m/s. Crystalline structure and their room-temperature magnetization characteristics were analyzed, and the optimum surface velocity of 20 m/s and nominal composition of MM{sub 13}Fe{sub 81}B{sub 6} were obtained. Microstructural analyses indicate that the grain size is approximately 30–50 nm in the alloys with the optimum characteristics. In the MM{sub 16}Fe{sub 78}B{sub 6} alloys, Pr-rich and La-rich phases concentrated on grain boundaries, which resulted in the coercivity augment with the increase of MMFe{sub 2} content. Dependence of coercivity on applied magnetic field suggested that the mechanism of coercivity in moderate MM-content samples was inhomogeneous domain wall pinning type. The melt-spun ribbons in the optimum condition exhibit a coercive force of 6.9 kOe and an energy product of 8.5 MGOe, which can be used as

Evolution of the microstructure and magnetic properties of as-cast and melt spun Fe2NiAl alloy during aging

International Nuclear Information System (INIS)

Menushenkov, V.P.; Gorshenkov, M.V.; Shchetinin, I.V.; Savchenko, A.G.; Savchenko, E.S.; Zhukov, D.G.

2015-01-01

Fe 2 NiAl-based alloy with the nominal composition Fe 51.1 Ni 23.5 Al 23.7 Si 1.7 was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500–900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β 2 phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force H c ~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β 2 phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at T ag >700 °C that decreases H c ≤350 Oe. The dependence δ M (H) was measured and negative values of δ M (H) in the H=0–2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β′- and β 2 ′ type phases were formed after aging the ribbons at T ag >500 °C. At T ag >700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β 2 phases develops by the coalescence of the primary DP products that decrease H c ≤250 Oe. MFM image of the magnetic structure

Magnetic properties of ND Rich Melt-Spun ND-FE-B alloy

Directory of Open Access Journals (Sweden)

Grujić Aleksandar

2005-01-01

Full Text Available As a part of these experimental investigations of melt-spun Nd-Fe-B alloy with Nd rich content in relation to Nd2Fe14B prepared by rapid quenching process for optimally selected cooling rate and heat treatment, the influence of the chosen chemical composition on magnetic properties was observed. The results of X-ray diffraction, Mössbauer spectroscopy phase analysis and magnetic measurement of investigated melt-spun Nd14.5Fe78.5B7 alloy are presented to bring some new information concerning the relation between their structure and magnetic properties.

Investigations on sysnthesis, characterization and hydrogenation behaviour of the spin- and thermal-melted versions of LaNi{sub 5-x}Si{sub x}(x=0.1, 0.3, 0.5) hydrogen storage materials

Energy Technology Data Exchange (ETDEWEB)

Srivastava, S.; Srivastava, O.N. [Banaras Hindu Univ., Varanasi (India). Dept. of Physics

1998-03-06

The present study deals with investigations on the synthesis and characterisation of negative electrode material for high energy density Ni-MH battery. The hydrogen storage material (MH) has been synthesised trough normal casting and melt-spinning techniques. In LaNi{sub 5}/MmNi{sub 5} family various substitutions like Al, Mn, Co have been studied. The substitution of metalloid like Si is known to be very helpful in improving several hydrogenation properties. In the present study, the Si substituted versions of AB{sub 5}-type storage materials typified by LaNi{sub 5-x}Si{sub x} (x=0.1, 0.3, 0.5) habe been investigated. A comparison between the present material and the conventional AB{sub 5}-type material MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4} has been made which has been previously studied. The main features revealed by XRD characterisations are the existence of the free Ni and Si together with AB{sub 5} material for all the three compositions. These free Ni and Si were found to disappear and yield, giving rise to a singular material after hydrogenation. The melt-spun version of the material was found to grow invariably in a direction perpendicular to the c-axis. The kinetics and activation process was better for the melt-spun version of the LaNi{sub 4.7}Si{sub 0.3} alloy than its thermally-melted counterpart (bulk) as well as to the alloy MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4}. For example, the kinetics of the melt-spun version of LaNi{sub 4.7}Si{sub 0.3} is 60% faster than its bulk version and 70% faster than the melt-spun version of MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4}. Similarly, the melt-spund version of the alloy LaNi{sub 4.7}Si{sub 0.3} gets activated in the 2nd cycle itself where as the alloy MmNi{sub 4.3}Al{sub 0.3}Mn{sub 0.4} attains this stage only in the 6th cycle. (orig.) 13 refs.

Electrochemical properties of the ball-milled LaMg10NiMn alloy with Ni powders

International Nuclear Information System (INIS)

Wang Yi; Wang Xin; Gao Xueping; Shen Panwen

2008-01-01

The electrochemical characteristics of the ball-milled LaMg 10 NiMn alloys with Ni powders were investigated. It was found that the ball-milled LaMg 10 NiMn + 150 wt.% Ni composite exhibited higher first discharge capacity and better cycle performance. By means of the analysis of electrochemical impedance spectra (EIS), it was shown that the existence of manganese in LaMg 10 NiMn alloy increased the electrocatalytic activity due to its catalytic effect, and destabilized metal hydrides, and so reduced the hydrogen diffusion resistance. These contributed to the higher discharge capacity of the ball-milled LaMg 10 NiMn-Ni composite. According to the analytical results of X-ray diffraction (XRD), EIS and steady-state polarization (SSP) experiments, the inhibition of metal corrosion is not the main reason for the better cycle performance. The main reason is that the electrochemical reaction resistance of the ball-milled LaMg 10 NiMn-Ni composite is always lower than that of the ball-milled LaMg 10 Ni 2 -Ni composite because the former one contains manganese, which is a catalyst for the electrode reaction

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.

Hydrogen storage performances of LaMg{sub 11}Ni + x wt% Ni (x = 100, 200) alloys prepared by mechanical milling

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yanghuan, E-mail: zhangyh59@sina.com [Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China); Wang, Haitao [Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China); Zhai, Tingting; Yang, Tai; Yuan, Zeming; Zhao, Dongliang [Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China)

2015-10-05

Highlights: • Amorphous and nanostructured alloys were prepared by mechanical milling. • The maximum discharge capacity of ball milled alloys reaches to 1053.5 mA h/g. • The addition of Ni significantly increases the discharge capacity. • Increasing milling time reduces the kinetic performances of ball milled alloys. - Abstract: In order to improve the hydrogen storage performances of Mg-based materials, LaMg{sub 11}Ni alloy was prepared by vacuum induction melting. Then the nanocrystalline/amorphous LaMg{sub 11}Ni + x wt% Ni (x = 100, 200) hydrogen storage alloys were synthesized by ball milling technology. The structure characterizations of the alloys were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage characteristics were tested by using programmed control battery testing system. The electrochemical impedance spectra (EIS), potentiodynamic polarization curves and potential-step curves were also plotted by an electrochemical workstation (PARSTAT 2273). The results indicate that the as-milled alloys exhibit a nanocrystalline and amorphous structure, and the amorphization degree of the alloys visibly increases with extending milling time. Prolonging the milling duration markedly enhances the electrochemical discharge capacity and cyclic stability of the alloys. The electrochemical kinetics, including high rate discharge ability (HRD), charge transfer rate, limiting current density (I{sub L}), hydrogen diffusion coefficient (D), monotonously decrease with milling time prolonging.

Methods of characterization of multiphase Nd-Fe-B melt-spun alloys

Directory of Open Access Journals (Sweden)

Grujić A.

2007-01-01

Full Text Available Nanocomposite permanent magnetic materials based on Nd-Fe-B alloys with a low Nd content are a new type of permanent magnetic material. The microstructure of these nanocomposite permanent magnets is composed of a mixture of magnetically soft and hard phases providing the so called exchange coupling effect. Beside the optimization process parameters, methods of characterization have a very important role in the design of an optimal magnetic matrix of multiphase melt-spun Nd-Fe-B alloys. Different methods and techniques of characterization were used for observation and study of the microstructure evolution during crystallization. A summary results of measurements using different methods of characterization are presented to enable a better insight into relations between the microstructure and magnetic properties of the investigated melt-spun Nd-Fe-B alloys. .

Composition-dependent magnetic properties of melt-spun La or/and Ce substituted nanocomposite NdFeB alloys

Energy Technology Data Exchange (ETDEWEB)

Hussain, M.; Zhao, L.Z.; Zhang, C.; Jiao, D.L.; Zhong, X.C.; Liu, Z.W.

2016-02-15

Aiming at high-performance low-cost NdFeB magnets, the magnetic properties and microstructure for melt spun nanocrystalline (Nd{sub 1−x}M{sub x}){sub 10}Fe{sub 84}B{sub 6} (M=La, Ce, or La{sub 0.5}Ce{sub 0.5}; x=0–0.7) alloys were investigated. Relatively, LaCe-substituted alloys show high values of the remanent magnetization M{sub r}, the maximum energy product (BH){sub max} and the coercivity H{sub c}, up to 114 emu/g (1.07 T), 147 kJ/m{sup 3} and 471 kA/m, respectively, at x=0.1. The unusual increase in coercivity for the alloys with 10% La or 10% La{sub 0.5}Ce{sub 0.5} substitution is possibly attributed to the phase segregation in alloys with certain La or LaCe contents. The reduced Curie temperature and spin-reorientation temperature were obtained for La, Ce or LaCe substituted alloys. Transmission electron microscope analysis has revealed that a fine and uniform distributed grain structure leads to remanence enhancement for La{sub 0.5}Ce{sub 0.5} substituted alloys. The present results indicate that partially substituting Nd by La or/and Ce cannot only effectively reduce the cost of nanocrystalline NdFeB based magnetic powders but also can maintain a relatively good combination of magnetic properties.

Evolution of the microstructure and magnetic properties of as-cast and melt spun Fe{sub 2}NiAl alloy during aging

Energy Technology Data Exchange (ETDEWEB)

Menushenkov, V.P., E-mail: menushenkov@gmail.com; Gorshenkov, M.V.; Shchetinin, I.V.; Savchenko, A.G.; Savchenko, E.S.; Zhukov, D.G.

2015-09-15

Fe{sub 2}NiAl-based alloy with the nominal composition Fe{sub 51.1}Ni{sub 23.5}Al{sub 23.7}Si{sub 1.7} was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500–900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β{sub 2} phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force H{sub c}~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β{sub 2} phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at T{sub ag}>700 °C that decreases H{sub c}≤350 Oe. The dependence δ{sub M}(H) was measured and negative values of δ{sub M}(H) in the H=0–2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β′- and β{sub 2}′ type phases were formed after aging the ribbons at T{sub ag}>500 °C. At T{sub ag}>700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β{sub 2} phases develops by the coalescence of the primary DP products that

Phase Transformation and Hydrogen Storage Properties of an La7.0Mg75.5Ni17.5 Hydrogen Storage Alloy

Directory of Open Access Journals (Sweden)

Lin Hu

2017-10-01

Full Text Available X-ray diffraction showed that an La7.0Mg75.5Ni17.5 alloy prepared via inductive melting was composed of an La2Mg17 phase, an LaMg2Ni phase, and an Mg2Ni phase. After the first hydrogen absorption/desorption process, the phases of the alloy turned into an La–H phase, an Mg phase, and an Mg2Ni phase. The enthalpy and entropy derived from the van’t Hoff equation for hydriding were −42.30 kJ·mol−1 and −69.76 J·K−1·mol−1, respectively. The hydride formed in the absorption step was less stable than MgH2 (−74.50 kJ·mol−1 and −132.3 J·K−1·mol−1 and Mg2NiH4 (−64.50 kJ·mol−1 and −123.1 J·K−1·mol−1. Differential thermal analysis showed that the initial hydrogen desorption temperature of its hydride was 531 K. Compared to Mg and Mg2Ni, La7.0Mg75.5Ni17.5 is a promising hydrogen storage material that demonstrates fast adsorption/desorption kinetics as a result of the formation of an La–H compound and the synergetic effect of multiphase.

Exchange correlation length and magnetoresistance in Fe-Cu and Fe-Cu-Ni melt-spun ribbons

International Nuclear Information System (INIS)

El Ghannami, M.; Gomez-Polo, C.; Rivero, G.; Hernando, A.

1994-01-01

The magnetic properties of Fe 30 Cu 70 melt-spun ribbons are reported for the first time. In the as-cast state, the microstructure consists of b.c.c.-Fe grains immersed in a Cu-rich matrix. However, the addition of a small percentage of Ni gives rise to the appearance of new Cu-Fe-Ni phases. Under suitable thermal treatments, the microstructure of both alloys evolves towards a complete phase segregation in b.c.c-Fe and f.c.c.-Cu immiscibles phases. The temperature dependence of the magnetic properties is analysed and related to the microstructural changes produced during the thermal treatments. Remarkable magneto-resistance effects have been observed in both as-cast alloys, with maximum values of the order of 6% at low measuring temperatures. (orig.)

Preparation and electrochemical properties of La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 (x = 0, 0.30, 0.33, 0.36, 0.39) hydrogen storage alloys

International Nuclear Information System (INIS)

Tian, Xiao; Wei, Wei; Duan, Ruxia; Zheng, Xinyao; Zhang, Huaiwei; Tegus, O.; Li, Xingguo

2016-01-01

The as-cast alloy with the composition of La_0_._7_0Ni_2_._4_5Co_0_._7_5Al_0_._3_0 was prepared by vacuum arc melting. La–Mg–Ni-based La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 hydrogen storage alloy has been synthesized by high-energy vibratory milling blending of the La_0_._7_0Ni_2_._4_5Co_0_._7_5Al_0_._3_0 as-cast alloy and elemental Mg, followed by an isothermal annealing. The microstructures and electrochemical properties of the La_0_._7_0Ni_2_._4_5Co_0_._7_5Al_0_._3_0 and La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloys were investigated by XRD, SEM and electrochemical measurements. The XRD analysis and Rietveld refinement showed that the as-cast La_0_._7_0Ni_2_._4_5Co_0_._7_5Al_0_._3_0 alloy consists of single LaNi_5 phase, whereas the La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloys contain the LaNi_5 and (La, Mg)_2Ni_7. The electrochemical measurements indicated that the maximum discharge capacity and discharge potential characteristic of the La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloys increases first and then decreases with increasing x. The maximum discharge capacity and discharge potential characteristic of alloy reaches the optimum when x is 0.36. The cyclic stability of the La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloy with a smaller quantity of Mg is better than that of the alloy with a larger quantity of Mg. - Highlights: • La–Mg–Ni-based alloy was synthesized by melting, milling and subsequent annealing. • Mg atoms exist in the La_2Ni_7 phase prior to LaNi_5 phase. • The La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloys consist of the LaNi_5 and (La, Mg)_2Ni_7. • The more Mg element the alloys contain, the easier aggregation Mg atom is. • The C_m_a_x of La_0_._7_0Mg_xNi_2_._4_5Co_0_._7_5Al_0_._3_0 alloy first increases and then decreases with rising x.

Metallurgical characterization of melt-spun ribbons of U-5.4 wt%Nb alloy

Science.gov (United States)

Ma, Rong; Ren, Zhiyong; Tang, Qingfu; Chen, Dong; Liu, Tingyi; Su, Bin; Wang, Zhenhong; Luo, Chao

2018-06-01

The microstructures and micro-mechanical properties of the melt-spun ribbons of U-5.4 wt%Nb alloy were characterized using optical microscopy, scanning electron microscopy, X-ray diffraction and nanoindentation. Observed variations in microstructures and properties are related to the changes in ribbon thicknesses and cooling rates. The microstructures of the melt-spun ribbon consist of fine-scale columnar grains (∼1 μm) adjacent to the chill surface and coarse cellular grains in the remainder of the ribbon. In addition, the formation of inclusions in the ribbon is suppressed kinetically due to the high cooling rate during melt spinning. Compared with the water-quenched specimen prepared by traditional gravity casting and solution heat treatment, the elastic modulus values of the U-5.4 wt%Nb alloy were examined to vary with grain size and exhibited diverse energy dissipation capacities.

Phase structure and electrochemical properties of La0.67Mg0.33Ni3.0-xCox (x=0.0, 0.25, 0.5, 0.75) hydrogen storage alloys

International Nuclear Information System (INIS)

Wang Dahui; Luo Yongchun; Yan Ruxu; Zhang Faliang; Kang Long

2006-01-01

La 0.67 Mg 0.33 Ni 3.0-x Co x (x=0.0, 0.25, 0.50, 0.75) hydrogen storage alloys were prepared by induction melting. Influences of partial substitution of Co for Ni on phase structure and electrochemical properties of La 0.67 Mg 0.33 Ni 3.0 were investigated by means of X-ray diffraction (XRD), electron probe X-ray microanalysis (EPMA) and electrochemical measurements. XRD patterns and back scattered electron images show that the alloys were composed of the (La,Mg)Ni 3 phase with the PuNi 3 -type structure and the (La,Mg) 2 Ni 7 phase with the Ce 2 Ni 7 -type structure. The lattice parameters a, c and the unit-cell volumes v vary with the increase of Co content x. The electrochemical measurements show that partial Co substitution for Ni had no influence on the initial activation rate of the alloys. The maximum electrochemical discharge capacity increases firstly then decreases, the high-rate dischargeabilities (HRDs) of La 0.67 Mg 0.33 Ni 3.0-x Co x alloy electrodes increase with the increase of Co content. Moreover, the cycle stabilities of La 0.67 Mg 0.33 Ni 3.0-x Co x is not improved by small quantity replacement Ni by Co except for x=0.75

Investigation on the Structure and Electrochemical Properties of La-Ce-Mg-Al-Ni Hydrogen Storage Alloy

Directory of Open Access Journals (Sweden)

Yuqing Qiao

2013-01-01

Full Text Available Structure and electrochemical characteristics of La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy have been investigated. X-ray diffraction analyses reveal that the La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy consisted of a (La, MgNi3 phase with the rhombohedral PuNi3-type structure and a LaNi5 phase with the hexagonal CaCu5-type structure. TEM shows that the alloy is multicrystal with a lattice space 0.187 nm. EDS analyse shows that the content of Mg is 3.48% (atom which coincide well with the designed composition of the electrode alloy. Electrochemical investigations show that the maximum discharge capacity of the alloy electrode is 325 mAh g−1. The alloy electrode has higher discharge capacity within the discharge current density span from 60 mA g−1 to 300 mA g−1. Electrochemical impedance spectroscopy measurements indicate that the charge transfer resistance RT on the alloy electrode surface and the calculated exchange current density I0 are 0.135 Ω and 1298 mA g−1, respectively; the better eletrochemical reaction kinetic of the alloy electrode may be responsible for the better high-rate dischargeability.

Influence of minor alloying additions on the glass-forming ability of Mg-Ni-La bulk metallic glasses

International Nuclear Information System (INIS)

Gonzalez, S.; Figueroa, I.A.; Todd, I.

2009-01-01

Bulk metallic glasses of Mg 60 Ni 23.6 Y x La (16.4-x) and Mg 65 Ni 20 Y x LaMM (15-x) with 0 ≤ x ≤ 1 at.% have been produced by injection casting. For the La-containing alloy a maximum amorphous diameter of 4 mm for x = 0.5 and 0.75 was obtained. The LaMM-containing alloy showed a maximum amorphous diameter of 2 mm for x = 0 and 0.25 but decreased to 1 mm with further Y additions. The glass-forming ability of the Mg 60 Ni 23.6 La 16.4 alloy decreased when La is partially substituted by small amounts of small atoms (Si or B) or by large atoms (Y and Si).

An investigation on the hydrogen storage characteristics of the melt-spun nanocrystalline and amorphous Mg20-xLaxNi10 (x = 0, 2) hydrogen storage alloys

International Nuclear Information System (INIS)

Zhang Yanghuan; Li Baowei; Ren Huiping; Guo Shihai; Wu Zhongwang; Wang Xinlin

2009-01-01

Mg 2 Ni-type hydrogen storage alloys Mg 20-x La x Ni 10 (x = 0, 2) were prepared by casting and rapid quenching. The structures and morphologies of the as-cast and quenched alloys were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). Thermal stability of the as-quenched alloys was researched by differential scanning calorimetry (DSC). The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus, and their electrochemical properties were measured by a tri-electrode open cell. The results showed that the no amorphous phase formed in the as-quenched La-free alloy, but the as-quenched alloys containing La held a major amorphous phase. The quenching rate induced a light influence on the crystallization temperature of the amorphous phase, and it significantly improved the initial hydrogenation rate and the hydrogen absorption capacity of the alloys. The discharge capacity and the cycle stability of the alloys grew with the increase of the quenching rate. When the quenching rate increased from 0 (as-cast was defined at a quenching rate of 0 m s -1 ) to 30 m s -1 , the hydrogen absorption capacity of the alloys for x = 0 and 2 at 200 deg. C and 1.5 MPa in 10 min changed from 1.21 to 3.10 wt.% and from 1.26 to 2.60 wt.%, the maximum discharge capacity from 30.26 to 135.51 mAh g -1 and from 197.23 to 406.51 mAh g -1 at a current density of 20 mA g -1 , and the capacity retaining rate at 20th cycle from 36.71 to 27.06% and from 37.26 to 78.33%, respectively

Microstructure of the Ni–Fe–Cu–P melt-spun ribbons produced from the single-chamber and from the double-chamber crucibles

Energy Technology Data Exchange (ETDEWEB)

Ziewiec, Krzysztof, E-mail: kziewiec@up.krakow.pl [Institute of Technology, Faculty of Mathematics, Physics and Technical Science, Pedagogical University of Cracow, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Błachowski, Artur; Ruebenbauer, Krzysztof [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ziewiec, Aneta [AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science, Al. A. Mickiewicza 30, 30-059 Kraków (Poland); Prusik, Krystian [Faculty of Computer Science and Materials Science, University of Silesia, ul. Bankowa 12, PL-40-007 Katowice (Poland); Latuch, Jerzy [Warsaw University of Technology, Faculty of Materials Science and Engineering, ul. Wołoska 141, PL-02-507 Warszawa (Poland); Zięba, Marcin; Bryła, Krzysztof [Institute of Technology, Faculty of Mathematics, Physics and Technical Science, Pedagogical University of Cracow, ul. Podchorążych 2, PL-30-084 Kraków (Poland)

2014-12-05

Highlights: • A new method for production of metallic amorphous/amorphous composite is proposed. • The unique microstructure was obtained by rapid cooling of the two unmixed liquids. • The composite TCMS Ni–Fe–Cu–P amorphous alloy forms ductile fracture. - Abstract: The aim of the work was to investigate the influence of the processing on the final microstructure and properties of the melt-spun Ni–Fe–Cu–P, Ni–Fe–P and Ni–Cu–P alloys ejected in two ways. In the first case, the alloy was molten in a simple single-chamber crucible, then ejected as uniform liquid. In the second case the double-chamber crucible was used, and the flux composed of the two Ni–Fe–P and Ni–Cu–P liquids was cooled on a copper roller before forming a uniform mixture. The two component melt spinning (TCMS) was performed starting from the Ni{sub 40}Fe{sub 40}P{sub 20} and Ni{sub 70}Cu{sub 10}P{sub 20} alloys. Three of the alloys i.e. Ni{sub 55}Fe{sub 20}Cu{sub 4}P{sub 20}, Ni{sub 40}Fe{sub 40}P{sub 20} and Ni{sub 70}Cu{sub 10}P{sub 20} were melt-spun from the traditional single-chamber crucible. The methods applied in this study for microstructural investigations include scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Mössbauer spectroscopy. Thermal stability of the melt-spun alloys was tested using differential scanning calorimetry (DSC). The results of the investigations are described and discussed in terms of the unique features of the TCMS amorphous microstructure. It is shown that this complex phase composition of the amorphous alloy favors formation of the ductile fracture and the multiple shear band formation.

Magnetic properties of centrifugally prepared melt-spun Nd-Fe-B alloys and their powders

International Nuclear Information System (INIS)

Andreev, S.V.; Kudrevatykh, N.V.; Kozlov, A.I.; Markin, P.E.; Pushkarskiy, V.I.

1998-01-01

Magnetic hysteresis properties and microstructure peculiarities of melt spun Nd-Fe-B alloys (ribbons) prepared by melt quenching on to the internal surface of an iron spinning wheel at the tangential speeds in the range 5-20 m/sec are reported. The alloy composition was Nd-36% wt. B-1.2% wt. and Fe-reminder. It was found that the coercivity of ribbons does not practically depend on the wheel speed in the applied range (1430 kA/m at 5 m/sec and 1750 kA/m at 20 m/sec), whereas the grain size of the basic phase (2-14-1) steadily decreases when the speed rises, starting from 2-3 μm for 5 m sec alloy down to the 200-300 nm for 20 m/sec alloy. All ribbons have normal convex demagnetization curves, even those prepared at low wheel speeds (without peculiar step near H∝0, which usually exists on such curves for traditionally prepared underquenched melt-spun Nd-Fe-B alloys). Grinding the ribbons subjected to hydrogen and annealing treatments causes the coercivity drop. However, this operations increase the powder alignment ability and, as a result, the energy product for fully dense magnet from such powder rises to 160-180 kJ/m 3 . (orig.)

Magnetic properties of melt-spun FeMnAlB alloys

International Nuclear Information System (INIS)

Betancourt, I.; Nava, F.

2007-01-01

Magnetic properties of melt spun Fe 89-x Mn 11 Al x (x=2,4,8,15) and Fe 87-y Mn 11 Al 2 By(y=6,8,10) alloy series were studied by vibrating sample magnetometry and complex permeability measurements. The saturation magnetization exhibited an initial high value of 210emu/g followed by a decreasing tendency with increasing Al and B additions (up to 139emu/g). On the other hand, the initial permeability showed variations within the range 1000-2000, whereas the relaxation frequency displayed a maximum of 2MHz for the 4at% Al alloy

Evolution of the microstructure and hardness of a rapidly solidified/melt-spun AZ91 alloy upon aging at different temperatures

International Nuclear Information System (INIS)

Wang Baishu; Liu Yongbing; An Jian; Li Rongguang; Su Zhenguo; Su Guihua; Lu You; Cao Zhanyi

2009-01-01

The effect of aging at different temperatures on a rapidly solidified/melt-spun AZ91 alloy has been investigated in depth. The microstructures of as-spun and aged ribbons with a thickness of approximately 60 μm were characterized using X-ray diffraction, transmission electron microscopy and laser optical microscopy; microhardness measurements were also conducted. It was found that the commercial AZ91 alloy undergoes a cellular/dendritic transition during melt-spinning at a speed of 34 m/s. A strengthening effect due to aging was observed: a maximum hardness of 110 HV/0.05 and an age-hardenability of 50% were obtained when the ribbon was aged at 200 deg. C for 20 min. The β-Mg 17 Al 12 phase exhibits net and dispersion types of distribution during precipitation. The dispersion of precipitates in dendritic grains or cells is the main source of strengthening

Geometric Effects of La1+xMg2-xNi9 (x=0.0～1.0) Ternary Alloys on Their Hydrogen Storage Capacities

Institute of Scientific and Technical Information of China (English)

Zhiqing YUAN; Guanglie LU; Bin LIAO; Yongquan LEI

2005-01-01

Structural analysis was made using X-ray diffraction (XRD) Rietveld refinement on a series of La1+xMg2-xNi9(x=0.0～1.0) ternary alloys. Results showed that each of La1+xMg2-xNi9 alloys was a PuNi3-type structure stacked by LaNi5 and (La, Mg) Ni2 blocks. Electrochemical tests revealed that discharge abilities of these La-Mg-Ni ternary alloys mainly depended on their atomic distances between (La, Mg) and Ni, which could be modified by varying the atomic ratios of La/Mg.

Microstructural evolution in Mg-rich Mg-Zn-Y alloys

International Nuclear Information System (INIS)

Biswas, T.; Ranganathan, S.; Nair, S.; Bajargan, G.

2005-01-01

Mg-rich Mg-Zn-Y alloys with nominal compositions Mg 97 Zn 1 Y 2 , Mg 97 Zn 2 Y 1 , Mg 92 Zn 6.5 Y 1.5 and Mg 97-x Zn 1 Y 2 Zr x have been chosen for the present study. These alloys are prepared by using sand casting mold. The sand cast alloys are remelted and subjected to copper mold casting and melt spinning techniques. The effect of cooling rate on microstructures was studied. It is observed that the size of the precipitates decreases with an increase of cooling rate. The formation of nano precipitates results in higher strength of the alloy as compared to the conventional alloys. The microstructures of melt spun ribbons are compared with RS/PM (rapidly solidified power metallurgy) Mg 97 Zn 1 Y 2 alloy, obtained from a different source. (author)

HRTEM characterization of melt-spun Al-Si-Cu-Mg alloys solidified at different rates

International Nuclear Information System (INIS)

Alfonso, Ismeli; Maldonado, Cuauhtemoc; Medina, Ariosto; Gonzalez, Gonzalo; Bejar, Luis

2006-01-01

Six quaternary alloys Al-6Si-3Cu-xMg (x = 0.59, 3.80 and 6.78 wt.%) were produced by melt spinning using two different tangential speeds of the copper wheel (30 and 45 ms -1 ), and characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and microhardness. At 30 ms -1 , XRD and TEM investigations revealed the presence of Al 2 Cu (θ) for the alloy with 0.59%Mg and Al 5 Cu 2 Mg 8 Si 6 (Q) for the alloys with 3.80 and 6.78%Mg. The increase in microhardness of the alloys with higher Mg content is attributed to the presence of nanosized a-Al particles and a higher content of Q nanoparticles. At 45 ms -1 the alloying element content in solid solution is increased due to the fact that the quantity of free second phases (θ and Q nanoparticles) has decreased. For this rotation speed, amorphous regions of α -Al were observed, increasing microhardness compared to the 30 ms -1 ribbons

Magnetic hysteresis properties of melt-spun Nd-Fe-B alloys prepared by centrifugal method

International Nuclear Information System (INIS)

Andreev, S.V.; Kudrevatykh, N.V.; Pushkarsky, V.I.; Markin, P.E.; Zaikov, N.K.; Tarasov, E.N.

1998-01-01

Magnetic hysteresis properties and microstructure peculiarities of melt spun Nd-Fe-B alloys (ribbons) prepared by melt quenching onto the internal surface of an iron spinning wheel at tangential speeds in the range 5-20 m/s are reported. The alloy composition was Nd-36% wt, B-1.2% wt. and Fe-remainder. It was found that the coercivity of ribbons does not practically depend on the wheel speed in applied range (18 kOe at 5 m/s and 22 kOe at 20 m/s), whereas the grain size of the basic phase (2-14-1) ste[ily decreases when the speed rises, starting from 2-3 μm for 5 m/s alloy down to the 200-300 nm for 20 m/s alloy. All ribbons have normal convex demagnetization curves, even those prepared at low wheel speeds (without peculiar step near H∝0, which usually exists on such curves for tr[itionally prepared underquenched melt-spun Nd-Fe-B alloys). Grinding the ribbon in a vibration mill causes the coercivity drop to 7 kOe after 120 min of treatment. However, this operation increases the powder alignment ability and, as a result, the energy product for a fully dense magnet from anisotropic powder prepared from some ribbons rises to 20-23 MGOe. (orig.)

A new dental powder from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons

International Nuclear Information System (INIS)

Do-Minh, N.; Le-Thi, C.; Nguyen-Anh, S.

2003-01-01

A new non-gamma-two dental powder has been developed from nanocrystalline melt-spun Ag-Sn-Cu alloy ribbons. The amalgam made from this powder exhibits excellent properties for dental filling. The nanocrystalline microstructure was found for the first time in as-spun and heat treated Ag(27-28)Sn(9-32) Cu alloy ribbons, using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. As-spun ribbons exhibited a multi-phase microstructure with preferred existence of β (Ag 4 Sn) phase formed during rapid solidification (RS) due to supersaturating of copper (Cu) atoms and homogenous nanostructure with subgrain size of about (40-50) nm, which seems to be developed during RS process and can be caused by eutectic reaction of the Ag 3 Sn/Ag 4 Sn-Cu 3 Sn system. In heat treated ribbons the clustering of Cu atoms was always favored and stable in an ageing temperature and time interval determined by Cu content. The heat treatment led to essential changes of subgrain morphology, resulted in the appearance of large-angle boundaries with fine Cu 3 Sn precipitates and forming typical recrystallization twins. Such a microstructure variation in melt-spun ribbons could eventually yield enhanced technological, clinical and physical properties of the dental products, controlled by the ADA Specification N deg 1 and reported before. Thus, using the rapid solidification technique a new non-gamma-two dental material of high quality, nanocrystalline ribbon powder, can be produced. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd

Study on glass-forming ability and hydrogen storage properties of amorphous Mg60Ni30La10−xCox (x = 0, 4) alloys

International Nuclear Information System (INIS)

Lv, Peng; Wang, Zhong-min; Zhang, Huai-gang; Balogun, Muhammad-Sadeeq; Ji, Zi-jun; Deng, Jian-qiu; Zhou, Huai-ying

2013-01-01

Mg 60 Ni 30 La 10−x Co x (x = 0, 4) amorphous alloys were prepared by rapid solidification, using a melt-spinning technique. X-ray diffraction and differential scanning calorimetry analysis were employed to measure their microstructure, thermal stability and glass-forming ability, and hydrogen storage properties were studied by means of PCTPro2000. Based on differential scanning calorimetry results, their glass-forming ability and thermal stability were investigated by Kissinger method, Lasocka curves and atomic cluster model, respectively. The results indicate that glass-forming ability, thermal properties and hydrogen storage properties in the Mg-rich corner of Mg–Ni–La–Co system alloys were enhanced by Co substitution for La. It can be found that the smaller activation energy (ΔΕ) and frequency factor (υ 0 ), the bigger value of B (glass transition point in Lasocka curves), and higher glass-forming ability of Mg–Ni–La–Co alloys would be followed. In addition, atomic structure parameter (λ), deduced from atomic cluster model is valuable in the design of Mg–Ni–La–Co system alloys with good glass-forming ability. With an increase of Co content from 0 to 4, the hydrogen desorption capacity within 4000 s rises from 2.25 to 2.85 wt.% at 573 K. - Highlights: • Amorphous Mg 60 Ni 30 La 10−x Co x (x = 0 and 4) alloys were produced by melt spinning. • The GFA and hydrogen storage properties were enhanced by Co substitution for La. • With an increase of Co content, the hydrogen desorption capacity rises at 573 K

Hydrogen storage in Mg-Ni-Fe compounds prepared by melt spinning and ball milling

Energy Technology Data Exchange (ETDEWEB)

Palade, P. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Sartori, S. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); Maddalena, A. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); Principi, G. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy)]. E-mail: giovanni.principi@unipd.it; Lo Russo, S. [Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, 35131 Padova (Italy); Lazarescu, M. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Schinteie, G. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Kuncser, V. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Filoti, G. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania)

2006-05-18

Magnesium-rich Mg-Ni-Fe intermetallic compounds have been prepared by two different routes: (a) short time ball milling of ribbons obtained by melt spinning; (b) long time ball milling of a mixture of MgH{sub 2}, Ni and Fe powders. The first type of samples displays an hydrogen desorption kinetics better than the second one. Pressure composition isotherm measurements exhibit for both type of samples two plateaux, the lower and wider corresponding to the MgH{sub 2} phase and the upper and shorter corresponding to the Mg{sub 2}NiH{sub 4} phase. The presence of the two types of hydrides is confirmed by X-ray diffraction analysis. Moessbauer spectroscopy shows that in melt spun and subsequently milled samples iron is mainly in a disordered structure and segregates after hydrogenation, while in directly milled powders remains mainly unalloyed. After multiple hydrogen absorption/desorption cycles the main part of iron is in metallic state in samples of both types, those of first type preserving better hydrogen desorption kinetics.

The microstructures and electrochemical performances of La0.6Gd0.2Mg0.2Ni3.0Co0.5-xAlx (x=0-0.5) hydrogen storage alloys as negative electrodes for nickel/metal hydride secondary batteries

Science.gov (United States)

Li, Rongfeng; Xu, Peizhen; Zhao, Yamin; Wan, Jing; Liu, Xiaofang; Yu, Ronghai

2014-12-01

La0.6Gd0.2Mg0.2Ni3.0Co0.5-xAlx (x = 0-0.5) hydrogen storage alloys were prepared by induction melting followed by annealing treatment at 1173 K for 8 h. The effects of substitution Al for Co on the microstructures and electrochemical performances were studied systematically. The structure analyses show that all alloys consist of multiphase structures such as (La, Mg)2Ni7 phase, (La, Mg) Ni3 phase and LaNi5 phase. The abundance of (La, Mg)2Ni7 phase decreases while the abundance of LaNi5 phase and (La, Mg)Ni3 phase increases directly as the Al content increasing. The electrochemical tests show that the maximum discharge capacity of alloy electrodes are almost unchanged when x ≤ 0.2 while the cyclic stability of the alloy electrode are improved significantly after proper amount of Al substitution for Co. The alloy electrode with x = 0.1 exhibits the better balance between discharge capacity and cycling life than any others. Moreover, at the discharge current density of 900 mA g-1, the high rate dischargeability (HRD) of the alloy electrodes decreases with increasing Al substitution and the relative analyses reveal that the charge transfer on alloy surface is more important than the hydrogen diffusion in alloy bulk for the kinetic properties of the alloy electrodes.

Effect of the La/Mg ratio on the structure and electrochemical properties of La xMg 3- xNi 9 ( x=1.6-2.2) hydrogen storage electrode alloys for nickel-metal hydride batteries

Science.gov (United States)

Liao, B.; Lei, Y. Q.; Chen, L. X.; Lu, G. L.; Pan, H. G.; Wang, Q. D.

Effect of La/Mg ratio on the structure and electrochemical properties of La xMg 3- xNi 9 ( x=1.6-2.2) ternary alloys was investigated. All alloys are consisted of a main phase with hexagonal PuNi 3-type structure and a few impurity phases (mainly LaNi 5 and MgNi 2). The increase of La/Mg ratio in the alloys leads to an increase in both the cell volume and the hydride stability. The discharge capacity of the alloys at 100 mA/g increases with the increase of La/Mg ratio and passes though a maximum of 397.5 mAh/g at x=2.0. As the La/Mg ratio increases, the high-rate dischargeability of the alloy electrodes at 1200 mA/g HRD 1200 decreases from 66.7% ( x=1.6) to 26.5% ( x=2.2). The slower decrease of HRD 1200 (from 66.7 to 52.7%) of the alloys with x=1.6-2.0 is mainly attributed to the decrease of electrocatalytic activity of the alloys for charge-transfer reaction, the more rapid decrease of HRD 1200 of the alloys with x>2.0 is mainly attributed to the lowering of the hydrogen diffusion rate in the bulk of alloy. The cycling capacity degradation of the alloys is rather fast for practical application due to the corrosion of La and Mg and the large VH in the hydride phase.

Effect of boron addition on the microstructure and electrochemical performance of La2Mg(Ni0.85Co0.15)9 hydrogen storage alloy

International Nuclear Information System (INIS)

Zhang Yanghuan; Dong Xiaoping; Wang Guoqing; Guo Shihai; Ren Jiangyuan; Wang Xinlin

2006-01-01

In order to improve the electrochemical performances of La-Mg-Ni system (PuNi 3 -type) hydrogen storage alloy, a trace of boron was added in La 2 Mg(Ni 0.85 Co 0.15 ) 9 and rapid quenching techniques were used. La 2 Mg(Ni 0.85 Co 0.15 ) 9 B x (x = 0, 0.05, 0.1, 0.15, 0.2) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured. The effects of the boron content and the quenching rate on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni 3 phase (PuNi 3 structure), the LaNi 5 phase and the LaNi 2 phase. A trace of the Ni 2 B phase exists in the as-cast alloys containing boron. The Ni 2 B phase in the alloys containing boron nearly disappears after rapid quenching and the relative amount of each phase in the alloys changes with the variety of the quenching rate. The addition of boron obviously enhances the cycle stability of the as-cast and quenched alloys. The effects of boron content on the capacities of the as-cast and quenched alloys are different. The capacities of the as-cast alloys monotonously decrease with the increase of boron content, whereas the capacities of the as-quenched alloys have a maximum value with the change of boron content. The as-cast and quenched alloys have an excellent activation performance

Two directional microstructure and effects of nanoscale dispersed Si particles on microhardness and tensile properties of AlSi7Mg melt-spun alloy

Energy Technology Data Exchange (ETDEWEB)

Dong, Xixi, E-mail: dongxx09@mails.tsinghua.edu.cn [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); He, Liangju [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); School of Aerospace, Tsinghua University, Beijing 100084 (China); Mi, Guangbao [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Li, Peijie [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)

2015-01-05

Highlights: • Both surface and cross-sectional microstructure of AlSi7Mg ribbon were characterized. • 13–50 nm and 50-hundreds of nm Si particles were dispersed both in α-Al and its boundary. • Tensile property of AlSi7Mg ribbon was studied with UTS 1.5 times higher than ingot. • Effects of nanoscale Si particles on hardness and tensile properties were provided. - Abstract: The two directional microstructure and multiple mechanical properties of the AlSi7Mg ribbon produced by melt-spun were investigated by optical microscopy (OM), field emission gun scanning electron microscope (FEGSEM), X-ray diffraction (XRD), microhardness and tensile tests. Both the surface and cross-sectional microstructure of the melt-spun ribbon were characterized in detail to give a clear and integrated description of the microstructure. Two kinds of nanoscale Si particles were observed, i.e., small Si particles ranging from 13 to 50 nm and large Si particles ranging from 50 nm to several hundreds of nanometers with clear size boundary were dispersed both in the interior and boundary of fine α-Al. XRD results revealed supersaturated solution of Si in Al matrix to be 0.62 at.%. The ultimate tensile strength, yield strength, and hardness of the ribbon were 1.53, 1.75 and 1.56 times higher than that of the conventional cast ingot separately. The breaking elongation of the ribbon was 1.73% with intergranular fracture feature. The effects of nanoscale dispersed Si particles on the significant improvement of both hardness and tensile properties of the AlSi7Mg melt-spun ribbon were discussed in detail.

The electrochemical properties of melt-spun Al-Si-Cu alloys

International Nuclear Information System (INIS)

Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing; Sun Zhanbo; Song Xiaoping; Yang Sen; Wang Liqun

2011-01-01

Highlights: → Non-equilibrium Al 75-X Si 25 Cu X alloys exhibit high lithiation storages. → The lithiation mechanism is different from melt-spun Al-Si-Mn system. → The structural evolution is mitigated in the non-equilibrium alloys. → Volume variation is alleviated due to the co-existence of Al 2 Cu, α-Si and α-Al. - Abstract: Melt spinning was used to prepare Al 75-X Si 25 Cu X (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, α-Si and Al 2 Cu co-existed in the alloys. Nano-scaled α-Al grains, as the matrix, formed in the as-quenched ribbons. The Al 74 Si 25 Cu 1 and Al 71 Si 25 Cu 4 anodes exhibited initial discharge specific capacities of 1539 mAh g -1 , 1324 mAh g -1 and reversible capacities above 472 mAh g -1 , 508 mAh g -1 at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled α-Al, α-Si, and Al 2 Cu for the present alloys.

Comparative study of crystallized melt-spun iron-boron alloys by Moessbauer effect and resistivity measurements

International Nuclear Information System (INIS)

Arshad, M.; Siddique, M.; Anwar-ul-Islam, M.; Butt, N.M.; Ashfaq, A.; Shamim, A.

1993-01-01

Moessbauer study of two as-quenched, melt-spun iron-boron completely crystallized alloys, Fe/sub 72/01/B/sub 28/ and Fe/sub 88/01/B/sub 12/, indicates the presence of alpha-Fe, Fe/sub 2/B and Fe/sub 3/B. The percentage of these phases is different in the two alloys. Resistivity measurements show to phase transformation of Fe/sub 3/B and Fe/sub 2/B, respectively. (author)

Discharge capacity and microstructures of La Mg Pr Al Mn Co Ni alloys for nickel-metal hydride batteries

International Nuclear Information System (INIS)

Casini, J.C.S.; Galdino, G.S.; Ferreira, E.A.; Takiishi, H.; Faria, R.N.

2010-01-01

La 0.7-x Mg x Pr 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 (x = 0.0, 0.3 and 0.7) alloys have been investigated aiming the production of negative electrodes for nickel-metal hydride batteries. The alloys employed in this work were used in the as cast state. The results showed that the substitution of magnesium by lanthanum increased the discharge capacity of the Ni-MH batteries. A battery produced with the La 0.4 Mg 0.3 Pr 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 alloy shown a high discharge capacity (380mAh/g) also good stability compared to other alloys. The electrode materials were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). (author)

The electrochemical properties of melt-spun Al-Si-Cu alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Sun Zhanbo, E-mail: szb@mail.xjtu.edu.cn [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Song Xiaoping; Yang Sen; Wang Liqun [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

2011-10-03

Highlights: {yields} Non-equilibrium Al{sub 75-X}Si{sub 25}Cu{sub X} alloys exhibit high lithiation storages. {yields} The lithiation mechanism is different from melt-spun Al-Si-Mn system. {yields} The structural evolution is mitigated in the non-equilibrium alloys. {yields} Volume variation is alleviated due to the co-existence of Al{sub 2}Cu, {alpha}-Si and {alpha}-Al. - Abstract: Melt spinning was used to prepare Al{sub 75-X}Si{sub 25}Cu{sub X} (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, {alpha}-Si and Al{sub 2}Cu co-existed in the alloys. Nano-scaled {alpha}-Al grains, as the matrix, formed in the as-quenched ribbons. The Al{sub 74}Si{sub 25}Cu{sub 1} and Al{sub 71}Si{sub 25}Cu{sub 4} anodes exhibited initial discharge specific capacities of 1539 mAh g{sup -1}, 1324 mAh g{sup -1} and reversible capacities above 472 mAh g{sup -1}, 508 mAh g{sup -1} at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled {alpha}-Al, {alpha}-Si, and Al{sub 2}Cu for the present alloys.

Influence of Pr in the microstructure and electrical properties in LaPrMgAlMnCoNi based alloys for using for Ni-MH batteries

International Nuclear Information System (INIS)

Galdino, Gabriel Souza

2011-01-01

The La 0.7-x Pr x Mg 0.3 Al 0.3 Mn- 0.4 Co 0.5 Ni 3.8 (x= 0 a 0.7) as-cast alloys to apply in negative electrodes for nickel-metal hydride batteries (Ni-MH). The characterizations of the alloys were realized by: scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction techniques. A study of hydrogen absorption capacity of the alloys realized. The hydrogenation of the material was performed in two processes: the low pressure (0.2 MPa of hydrogen and temperature of the 773 K) and high pressure (1 MPa of hydrogen and temperature of the 298 K). It was observed that with increasing Pr content occurred a decrease the hydrogen absorption capacity. The capacity of discharge of the batteries was determined utilizing an analyzer digital computerized composed of four channels. It was observed decreases of the discharge capacity of the batteries when increase praseodymium content in La 0.7- x Pr x Mg 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni-3 .8 (x= 0 a 0.3) alloys. The highest discharge capacity (386 mAhg -1 ) and stability cyclic were obtained to La 0.2 Pr 0.5 Mg 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 alloy. This capacity can be related to the higher proportion of phase LaMg 2 Ni 9 in the alloy with the addition of 0.5 at.% Pr. (author)

Giant magnetoresistance in melt spun Cu85Co10Ni5

DEFF Research Database (Denmark)

Curiotto, Stefano; Johnson, Erik; Celegato, Federica

2009-01-01

CuCoNi rapidly solidified alloys are interesting because they display giant magnetoresistance (GMR). In the present work a Cu85Co10Ni5 alloy has been synthesized by melt spinning and analysed for GMR. The ribbons obtained have been annealed at different temperatures and the evolution of the crystal...... structure with annealing has been studied by X-ray diffraction. The. ne microstructure has been observed by TEM and related to the magnetic properties, investigated in a vibrating sample magnetometer. In the studied composition the magnetoresistance was found to be lower than in binary CuCo alloys without...

Discharge capacity and microstructures of La Mg Pr Al Mn Co Ni alloys for nickel-metal hydride batteries

Energy Technology Data Exchange (ETDEWEB)

Casini, J.C.S.; Galdino, G.S.; Ferreira, E.A.; Takiishi, H.; Faria, R.N., E-mail: jcasini@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (DM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Dept. de Metalurgia

2010-07-01

La{sub 0.7-x}Mg{sub x}Pr{sub 0.3}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} (x = 0.0, 0.3 and 0.7) alloys have been investigated aiming the production of negative electrodes for nickel-metal hydride batteries. The alloys employed in this work were used in the as cast state. The results showed that the substitution of magnesium by lanthanum increased the discharge capacity of the Ni-MH batteries. A battery produced with the La{sub 0.4}Mg{sub 0.3}Pr{sub 0.3}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} alloy shown a high discharge capacity (380mAh/g) also good stability compared to other alloys. The electrode materials were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). (author)

Magnetic properties of (misch metal, Nd-Fe-B melt-spun magnets

Directory of Open Access Journals (Sweden)

R. Li

2017-05-01

Full Text Available The effect of replacing Nd with misch metal (MM on magnetic properties and thermal stability has been investigated on melt-spun (Nd1-xMMx13.5Fe79.5B7 ribbons by varying x from 0 to 1. All of the alloys studied crystallize in the tetragonal 2:14:1 structure with single hard magnetic phase. Curie temperature (Tc, coercivity (Hcj, remanence magnetization (Br and maximum energy product ((BHmax all decrease with MM content. The melt-spun MM13.5Fe79.5B ribbons with high ratio of La and Ce exhibit high magnetic properties of Hcj = 8.2 kOe and (BHmax= 10.3 MGOe at room temperature. MM substitution also significantly strengthens the temperature stability of coercivity. The coercivities of the samples with x = 0.2 and even 0.4 exhibit large values close to that of Nd13.5Fe79.5B7 ribbons above 400 K.

Large magnetic entropy change in melt-spun LaFe11.5Si1.5 ribbons

International Nuclear Information System (INIS)

Xie Kun; Song Xiaoping; Zhu Yaoming; Lv Weipeng; Sun Zhanbo

2004-01-01

The microstructure transformation and the magnetic entropy change of LaFe 11.5 Si 1.5 melt-spun ribbons were investigated. The melt-spun ribbons show a homogeneous distribution of elements, and the homogeneity develops further after 5 h annealing. XRD results show that the ribbons are composed of NaZn 13 -type LaFe 11.5 Si 1.5 compounds and an α-Fe phase. After annealing, the ribbons crystallize well in the NaZn 13 -type structure and exhibit a very large magnetic entropy change. A first-order magnetic transition is observed in the annealed ribbons, and this is believed to be the origin of the large magnetic entropy. These results suggest that NaZn 13 -type LaFe 11.5 Si 1.5 compounds with a large magnetic entropy change can be produced by melt-spinning, the annealing time can be shortened significantly and the production cost of the magnetic refrigerant will be cut down accordingly

Hydrogen absorption study of Ti-based alloys performed by melt-spinning

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, R.M.; Lemus, L.F.; Santos, D.S. dos, E-mail: rafaella@metalmat.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEMM/COPPEP/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Metalurgica e de Materiais

2013-11-01

The hydrogen absorption and desorption of Ti{sub 53}Zr{sub 27}Ni{sub 20} icosahedral quasicrystal (ICQ) and Ti{sub 50}Ni{sub 50} shape memory alloy (SMA) melt-spun ribbons was studied. Samples were exposed to hydrogen gas at 623 K and 4 MPa for 1000 minutes. The total capacity of hydrogen obtained for Ti{sub 53}Zr{sub 27}Ni{sub 20} and Ti{sub 50}Ni{sub 50} was 3.2 and 2.4 wt. % respectively. The Thermal Desorption Spectrometry (TDS) of the hydrogenated alloys shows that both alloys start to desorb hydrogen around 750 K. X-ray diffraction (XRD) patterns, performed after hydrogenation, indicate a complete amorphization of the Ti{sub 53}Zr{sub 27}Ni{sub 20} i-phase alloy, while the Ti{sub 50}Ni{sub 50} alloy remained crystalline after hydride formation. (author)

Properties of mechanically alloyed Mg-Ni-Ti ternary hydrogen storage alloys for Ni-MH batteries

Science.gov (United States)

Ruggeri, Stéphane; Roué, Lionel; Huot, Jacques; Schulz, Robert; Aymard, Luc; Tarascon, Jean-Marie

MgNiTi x, Mg 1- xTi xNi and MgNi 1- xTi x (with x varying from 0 to 0.5) alloys have been prepared by high energy ball milling and tested as hydrogen storage electrodes. The initial discharge capacities of the Mg-Ni-Ti ternary alloys are inferior to the MgNi electrode capacity. However, an exception is observed with MgNi 0.95Ti 0.05, which has an initial discharge capacity of 575 mAh/g compared to 522 mAh/g for the MgNi electrode. The Mg-Ni-Ti ternary alloys show improved cycle life compared to Mg-Ni binary alloys with the same Mg/Ni atomic ratio. The best cycle life is observed with Mg 0.5Ti 0.5Ni electrode which retains 75% of initial capacity after 10 cycles in comparison to 39% for MgNi electrodes, in addition to improved high-rate dischargeability (HRD). According to the XPS analysis, the cycle life improvement of the Mg 0.5Ti 0.5Ni electrode can be related to the formation of TiO 2 which limits Mg(OH) 2 formation. The anodic polarization curve of Mg 0.5Ti 0.5Ni electrode shows that the current related to the active/passive transition is much less important and that the passive region is more extended than for the MgNi electrode but the corrosion of the electrode is still significant. This suggests that the cycle life improvement would be also associated with a decrease of the particle pulverization upon cycling.

Effect of precipitation on the shape memory effect of Ti50Ni25Cu25 melt-spun ribbon

International Nuclear Information System (INIS)

Tong Yunxiang; Liu Yong; Xie Zeliang; Zarinejad, Mehrdad

2008-01-01

The present research aims to provide accurate understanding of the relation between precipitation (volume fraction, morphology, type) and shape memory effect of Ti 50 Ni 25 Cu 25 melt-spun ribbon. Rapid thermal annealing was used to control the microstructural development while the shape memory effect of the ribbon was determined under constraint thermal cycling. The results show that the precipitation process takes the following sequence: B11 TiCu → B11 TiCu + Ti 2 (Ni, Cu) → Ti 2 (Ni, Cu) with increasing annealing temperature or duration. The shape memory effect is found to depend on both the volume fraction and the distribution of the precipitates. The former affects the shape recovery strain through reduction of the transformation volume participating the shape recovery. The latter affects the shape recovery strain through strengthening the matrix thus reducing the martensite strain which is more predominant under low constraint stresses. Precipitation strengthening, on the other hand, reduces the tendency of dislocation generation/movement, thus reducing the irreversible strain and improving shape recovery strain. This understanding provides guidelines on the optimization of the shape memory properties of the Ti 50 Ni 25 Cu 25 melt-spun ribbon via post-processing annealing

Microstructure and mechanical properties of multiphase NiAl-based alloys

Science.gov (United States)

Pank, D. R.; Koss, D. A.; Nathal, M. V.

1990-01-01

The effect of the gamma-prime phase on the deformation behavior and fracture resistance of melt-spun ribbons and consolidated bulk specimens of a series of Nial-based alloys with Co and Hf additions has been examined. The morphology, location, and volume fraction of the gamma-prime phase are significant factors in enhancing the fracture resistance of the normally brittle NiAl-based alloys. In particular, the results indicate that a continuous-grain-boundary film of gamma-prime can impart limited room-temperature ductility regardless of whether B2 or L10 NiAl is present. Guidelines for microstructure control in multiphase NiAl-based alloys are also presented.

Magnetoresistance in ferromagnetic shape memory alloy NiMnFeGa

International Nuclear Information System (INIS)

Liu, Z.H.; Ma, X.Q.; Zhu, Z.Y.; Luo, H.Z.; Liu, G.D.; Chen, J.L.; Wu, G.H.; Zhang Xiaokai; Xiao, John Q.

2011-01-01

The magnetoresistance (MR){=[R(H)-R(0)]/R(0)} properties in ferromagnetic shape memory alloy of NiMnFeGa ribbons and single crystals, and NiFeGa ribbons have been investigated. It is found that the NiMnFeGa melt-spun ribbon exhibited GMR effect, arising from the spin-dependent scattering from magnetic inhomogeneities consisting of antiferromagnetically coupled Mn atoms in B2 structure. In the absence of these magnetic inhomogeneities, Heusler alloys seem to show a common linear MR behavior at around 0.8T C , regardless of sample structures. This may be explained by the s-d model. At low temperatures, conventional AMR behaviors due to the spin-orbital coupling are observed. This is most likely due to the diminished MR from s-d model because of much less spin fluctuation, and is not associated with martensite phase. MR anomaly at intermediate field (ρ perpendicular >ρ || ) is also observed in single crystal samples, which may be related to unique features of Heusler alloys. - Highlights: → NiMnFeGa melt-spun ribbon exhibited GMR effect with a large negative MR up to -13%. → GMR behavior is arising from the spin-dependent scattering from magnetic inhomogeneities. → In the absence of these magnetic inhomogeneities, Heusler alloys seem to show a common linear MR behavior at around 0.8T C . → Conventional AMR behaviors due to the spin-orbital coupling are observed in NiMnFeGa single crystal and Ni 2 FeGa ribbon samples at low temperatures.

Stability of rapidly quenched and hydrogenated Mg-Ni-Y and Mg-Cu-Y alloys in extreme alkaline medium

International Nuclear Information System (INIS)

Gebert, A.; Khorkounov, B.; Wolff, U.; Mickel, Ch.; Uhlemann, M.; Schultz, L.

2006-01-01

Amorphous-nanocrystalline Mg 50 Ni 30 Y 20 and Mg 63 Ni 30 Y 7 and amorphous Mg 65 Cu 25 Y 10 alloys were produced by melt-spinning and characterized regarding their microstructure and thermal behaviour using XRD, TEM and DSC. Their electrochemical behaviour in the as-quenched state and after hydrogen charging at -25 mA/cm 2 for up to 20 h was studied in electrolytes with pH 5-7 and 13, but mainly in a battery electrolyte: 6 M KOH with pH 14.8 by means of anodic and cathodic polarization measurements. In the as-quenched state, the highest alloys stability was observed at pH 13. At pH 14.8, gradual oxidation and dissolution of copper or nickel governs the anodic behaviour before a passive state is attained. The dissolution of nickel is much more inhibited than that of copper due to its lower tendency to form soluble oxidized ions and to a stabilizing effect of higher fractions of yttrium in the alloy on the passivation. By galvanostatic charging, the Mg 65 Cu 25 Y 10 alloy shows the highest hydrogen absorption capacity followed by Mg 50 Ni 30 Y 20 and Mg 63 Ni 30 Y 7 . During the charging process, the alloys exhibit a change in the surface state chemistry, i.e. an enrichment of nickel- or copper-rich species, causing preferential oxidation and dissolution during subsequent exposure under free corrosion and anodic conditions. Mg-Ni-Y alloys demonstrate a higher stability during this treatment in extreme alkaline medium. The reasons for this and consequences regarding the use as electrode materials are discussed in detail

Hydrogen storage thermodynamics and kinetics of LaMg11Ni + x wt.% Ni (x = 100, 200) alloys synthesized by mechanical milling

International Nuclear Information System (INIS)

Zhang, Yanghuan; Jia, Zhichao; Central Iron and Steel Research Institute, Beijing; Yuan, Zeming; Qi, Yan; Zhao, Dongliang; Hou, Zhonghui

2016-01-01

LaMg 11 Ni + x wt.% Ni (x = 100, 200) composite hydrogen storage alloys with a nanocrystalline/amorphous structure were synthesized using ball milling technology. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were investigated systematically. The hydrogen desorption properties were assessed using a Sieverts apparatus and differential scanning calorimetry. The thermodynamic parameters for the hydrogen absorption and desorption were calculated using the Van't Hoff equation. The hydrogen desorption activation energies of the hydrogenated alloys were also estimated by Arrhenius and Kissinger methods. Results indicate that the amount of Ni added has no effect on the thermodynamics of the alloys, but it significantly improves their absorption and desorption kinetics. Furthermore, the milling time has a great influence on the hydrogen storage properties. To be specific, the hydrogen absorption capacities reach the maximum values with the variation of milling time, and the hydrogen desorption activation energy obviously decreases with increasing milling time.

Combinatorial search for hydrogen storage alloys: Mg-Ni and Mg-Ni-Ti

Energy Technology Data Exchange (ETDEWEB)

Oelmez, Rabia; Cakmak, Guelhan; Oeztuerk, Tayfur [Dept. of Metallurgical and Materials Engineering, Middle East Technical University, 06531 Ankara (Turkey)

2010-11-15

A combinatorial study was carried out for hydrogen storage alloys involving processes similar to those normally used in their fabrication. The study utilized a single sample of combined elemental (or compound) powders which were milled and consolidated into a bulk form and subsequently deformed to heavy strains. The mixture was then subjected to a post annealing treatment, which brings about solid state reactions between the powders, yielding equilibrium phases in the respective alloy system. A sample, comprising the equilibrium phases, was then pulverized and screened for hydrogen storage compositions. X-ray diffraction was used as a screening tool, the sample having been examined both in the as processed and the hydrogenated state. The method was successfully applied to Mg-Ni and Mg-Ni-Ti yielding the well known Mg{sub 2}Ni as the storage composition. It is concluded that a partitioning of the alloy system into regions of similar solidus temperature would be required to encompass the full spectrum of equilibrium phases. (author)

Electrochemical deposition of La-Mg alloys in LaCl3-MgCl2-KCl system with molten salt electrolysis process

Directory of Open Access Journals (Sweden)

Sahoo Kumar D.

2014-01-01

Full Text Available La-Mg alloys of different compositions were prepared by electrolysis of LaCl3-MgCl2-KCl melts. Different phases of La-Mg alloys were characterized by X-ray diffraction (XRD and Scanning Electron Microscopy (SEM. Energy dispersive spectrometry (EDS and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES analyses showed that chemical compositions of La-Mg alloys were consistent with phase structures of XRD pattern, and magnesium content in the alloy could be controlled by electrolysis parameters. The effects of various process parameters such as concentration of magnesium chloride in the bath, temperature of electrolysis and cathode current density on the current efficiency have been investigated. A maximum current efficiency of 85% and yield of 80% was obtained from the bath at 12.5A/cm2 current density at an operating temp 850°C.

Synthesis and characterization of Mg-based amorphous alloys and their use for decolorization of Azo dyes

International Nuclear Information System (INIS)

Iqbal, M; Wang, W H

2014-01-01

Mg-based alloys are light weight and have wide range of applications in the automotive industry. These alloys are widely used because of their very attractive physical and mechanical properties and corrosion resistance. The properties and applications can be further improved by changing the nature of materials from crystalline to amorphous. In this study, melt spun ribbons (MSRs) of Mg 70 Zn 25 Ca 5 Mg 68 Zn 27 Ca 5 alloys were prepared by melt spinning technique by using 3-4N pure metals. Characterization of the samples was done by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and energy dispersive x-ray analyzer (EDAX). Microstructural investigations were conducted by using scanning electron microscopy (SEM), atomic force microscopy (AFM) as well as optical and stereo scan microscopy techniques. DSC results showed multistage crystallization. Activation energy was found to be 225 kJ/mol by Kissinger method indicating good thermal stability against crystallization. XRD, DSC, SEM and EDS (energy dispersive spectroscopy) results are agreed very well. In order to study decolorization, the MSRs of Mg 70 Zn 25 Ca 5 Mg 68 Zn 27 Ca 5 alloys were treated repeatedly with various azo dyes at room temperature. In order to compare the results, MSRs of amorphous Zr- and Ni-based metallic glasses were also treated. Reaction of MSRs with azo dyes results in their decolorization in a few hours. Decolorization of azo dyes takes place by introducing amorphous MSRs which results in breaking the -N=N- bonds that exist in dye contents. It is concluded that Mg-based alloys are useful for paint and dye industries and will be beneficial to control water pollution. Comparison of results showed that Mg-based alloys are more efficient than Zr- and Ni-based amorphous alloys for decolorization of azo dyes

Stability of an amorphous alloy of the Mm-Al-Ni-Cu system

Directory of Open Access Journals (Sweden)

Carlos Triveño Rios

2012-10-01

Full Text Available An investigation was made of the stability of melt-spun ribbons of Mm55Al25Ni10Cu10 (Mm = Mischmetal amorphous alloy. The structural transformations that occurred during heating were studied using a combination of X-ray diffraction (XRD and differential scanning calorimetry (DSC. Crystallization took place through a multi-stage process. The first stage of transformation corresponded to the formation of a metastable phase followed by cfc-Al precipitation, while in the second stage, exothermic transformations led to the formation of complex and unidentified Mm(Cu, Ni and MmAl(Cu, Ni phases. The transformation curves recorded from isothermal treatments at 226 °C and 232 °C indicated that crystallization occurred through nucleation and growth, with diffusion-controlled growth occurring in the first crystallization stage. The supercooled liquid region, ∆Tx, at 40 K/min was ~80 K. This value was obtained by the substitution of Mm (=Ce + La + Nd + Pr for La or Ce, saving chemical element-related costs.

Material for the storage of Mg-Ni-Based hydrogen produced by mechanical alloying; Materiales para almacenamiento de hidrogeno base Mg-Ni producidas por aleado mecanico

Energy Technology Data Exchange (ETDEWEB)

Zaldivar-Cadena, A. A. [Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Leon Santiago, M.; Suarez Alcantara, K.; Morales-Hernandez, J.; Cabanas Moreno, J. G. [Instituto Politecnico Nacional, UPALM, Mexico, D.F. (Mexico)]. E-mail: gcabanas@esfm.ipn.mx

2009-09-15

Combinations of Mg-5%Ni and Mg-20%Ni were prepared with mechanical alloying and evaluated for application as materials to store hydrogen. The effect of the dispersion of nickel in magnesium was studied using grinding times of 15 and 30 hours. Hydration experiments, including batch hydration tests, were performed at 200, 250 and 300 degrees Celsius at 2 Mpa during 30 minutes. Characterization techniques such as SEM-EDX and XRD were used to characterize the microstructure and composition of the powders. The hydrogen absorption-desorption characteristics of the alloys were evaluated using thermal analysis techniques such as DTA-TGA. Batch type preliminary experiments resulted in a variation in the quantities of MgH{sub 2} in the hydrate powders, depending on the hydrate composition and conditions. Gravimetry experiments with Mg-5%Ni powder combinations indicated hydrogen contents of approximately 5.59% - 6.12% in weight, showing rapid hydration kinetics at temperatures under 250 degrees Celsius; although the dehydration process occurred reasonably quickly only at temperatures between 250 and 300 degrees Celsius. The hydration/dehydration behavior is influenced by the tendency of forming Mg{sub 2}Ni in mechanically alloyed powders. This tendency is promoted by high Ni contents, long grinding times and high hydration temperatures. The best results are apparently obtained with an optimal balance of the dispersion of Ni, which depends on the Ni contents and grinding time. [Spanish] Mezclas de Mg-5%Ni y Mg-20%Ni fueron preparadas por aleado mecanico y evaluadas para su aplicacion como materiales para almacenamiento de hidrogeno. El efecto de la dispersion del niquel en el magnesio fue estudiado utilizando tiempos de molienda de 15 y 30 hrs. Experimentos de hidruracion incluyendo pruebas de hidruracion del tipo Batch fueron realizadas a 200, 250 y 300 grados centigrados a 2 Mpa durante 30 minutos. Tecnicas de caracterizacion como MEB-EDX y DRX fueron empleados en la

Preparation and characterization of mechanically alloyed AB3-type based material LaMg2Ni5Al4 and its solid-gaz hydrogen storage reaction

Science.gov (United States)

Jaafar, Hassen; Aymard, Luc; Dachraoui, Walid; Demortière, Arnaud; Abdellaoui, Mohieddine

2018-04-01

We developed in the present paper the synthesis of a new AB3-type compound LaMg2Ni5Al4 by mechanical alloying (MA) process. ​​X-ray diffraction analysis (XRD) was used to determine the structural properties and the phase evolution of the powder mixtures. Two different synthesis pathways have been investigated. The first starting from elemental metals and the second from a mixture of two binary compounds LaNi5 (CaCu5-type structure, P6/mmm space group) and Al(Mg) solid solution (cubic Fm-3 m space group). The results show multiphase alloys which contain LaMg2Ni5Al4 main phase with hexagonal PuNi3-type structure (R-3 m space group). Rietveld analysis shows that using a planetary ball mill, we obtain a good yield of LaMg2Ni5Al4 compound after 5 h of mechanical alloying for both synthesis pathways. TEM analysis confirmed XRD results. SEM-EDX analysis of the final product was in agreement with the nominal chemical formula. A setup of possible solid-gaz hydrogenation reaction will be described so far at the end of this work. Electrochemical results demonstrate evidence on hydrogen absorption in the AB3 material and the discharge capacity was equal to 5.9 H/f.u.

Dysprosium-free melt-spun permanent magnets

International Nuclear Information System (INIS)

Brown, D N; Wu, Z; He, F; Miller, D J; Herchenroeder, J W

2014-01-01

Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd 2 Fe 14 B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175–200 °C. (paper)

Dysprosium-free melt-spun permanent magnets.

Science.gov (United States)

Brown, D N; Wu, Z; He, F; Miller, D J; Herchenroeder, J W

2014-02-12

Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd2Fe14B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175-200 °C.

Structure and magnetic properties of Heusler alloy Co{sub 2}RuSi melt-spun ribbons

Energy Technology Data Exchange (ETDEWEB)

Xin, Yuepeng; Ma, Yuexing; Hao, Hongyue [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Luo, Hongzhi, E-mail: luo_hongzhi@163.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Meng, Fanbin; Liu, Heyan [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, Enke; Wu, Guangheng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2017-08-01

Highlights: • New Heusler alloy Co{sub 2}RuSi has been prepared by melt-spinning successfully. • Magnetic and electronic properties of Co{sub 2}RuSi were investigated. • Ru has a strong site preference for A, C sites in the lattice of Co{sub 2}RuSi. • Site preference of Ru cannot be determined by “number of valence electrons”. - Abstract: Heusler alloy Co{sub 2}RuSi has been synthesized by melt-spinning technology successfully. Co{sub 2}RuSi bulk sample after annealing is composed of an HCP Co-rich phase and a BCC Ru-Si phase, but melt-spinning can suppress the precipitation of the HCP phase and produce a single Co{sub 2}RuSi Heusler phase. In the XRD pattern, it is found that Ru has a strong preference for the (A, C) sites, though it has fewer valence electrons compared with Co. This site preference is different from the case in Heusler alloys containing only 3d elements and is supported further by first-principles calculations. Melt-spun Co{sub 2}RuSi has a M{sub s} of 2.67 μ{sub B}/f.u. at 5 K and a Tc of 491 K. An exothermic peak is observed at 871 K in the DTA curve, corresponding to the decomposition of the Heusler phase. Finally, the site preference and magnetic properties of Co{sub 2}RuSi were discussed based on electronic structure calculation and charge density difference.

Hydrogen diffusion in La1.5Nd0.5MgNi9 alloy electrodes of the Ni/MH battery

International Nuclear Information System (INIS)

Volodin, A.A.; Denys, R.V.; Tsirlina, G.A.; Tarasov, B.P.; Fichtner, M.; Yartys, V.A.

2015-01-01

Highlights: • Hydrogen diffusion in the La 1.5 Nd 0.5 MgNi 9 alloy electrode was studied. • Various techniques of low amplitude potentiostatic data treatment were used. • D H demonstrates a maximum (2 × 10 −11 cm 2 /s) at 85% of discharge of the electrode. • Maximum is associated with a conversion of β-hydride into a solid α-solution. • Optimization of material and electrode will allow high discharge rates. - Abstract: Hydrogen diffusion in the La 1.5 Nd 0.5 MgNi 9 battery electrode material has been studied using low amplitude potentiostatic experiments. Complex diffusion behavior is examined in frames of electroanalytical models proposed for the lithium intercalation materials. Hydrogen diffusion coefficient D H changes with hydrogen content in the metal hydride anode electrode and has a maximum of ca. 2 × 10 −11 cm 2 /s at ca. 85% of discharge. Such a behavior differs from the trends known for the transport in lithium battery materials, but qualitatively agrees with the data for the highly concentrated β-PdH x

The effect of high charging rates activation on the specific discharge capacity and efficiency of a negative electrode based on a LaMgAlMnCoNi alloy

International Nuclear Information System (INIS)

Ferreira, E.A.; Zarpelon, L.M.C.; Casini, J.C.S.; Takiishi, H.; Faria, R.N.

2009-01-01

A nickel-metal hydride (Ni-MH) rechargeable battery has been prepared using a La 0.7 Mg 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 alloy as the negative electrode. The maximum discharge capacity of the La 0.7 Mg 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 alloy has been determined (350 mAh/g). Using a high starting charging rate (2857 mAg -1 ) an efficiency of 49% has been achieved in the 4 th cycle. The alloy and powders have been characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). (author)

Nanocrystallinity and magnetic property enhancement in melt-spun iron-rare earth-base hard magnetic alloys

International Nuclear Information System (INIS)

Davies, H.A.; Manaf, A.; Zhang, P.Z.

1993-01-01

Refinement of the grain size below ∼35 nm mean diameter in melt-spun FeNdB-base alloys leads to enhancement of remanent polarization, J r , above the level predicted by the Stoner-Wohlfarth theory for an aggregate of independent, randomly oriented, and uniaxial magnetic particles. This article summarizes the results of the recent systematic research on this phenomenon, including the influence of alloy composition and processing conditions on the crystallite size, degree of enhancement of J r , and maximum energy product (BH) max . It has been shown that the effect can also occur in ternary FeNdB alloys, without the addition of silicon or aluminum, which was originally thought necessary, providing the nanocrystallites are not magnetically decoupled by a paramagnetic second phase. Values of (BH) max above 160 kJ. m -3 have been achieved. The relationship between grain size, J r , intrinsic coercivity, J H c , and (BH) max are discussed in terms of magnetic exchange coupling, anisotropy, and other parameters. Recent extension of this work to the enhancement of properties in Fe-Mischmental-Boron-base alloys and to bonded magnets with a nanocrystalline structure is also described

The electrochemical characteristics of Mg2Ni nanocrystalline hydrogen storage alloy

International Nuclear Information System (INIS)

Zhang Ling; Zhou Xiaosong; Peng Shuming

2008-06-01

The nanocrystalline Mg 2 Ni materials were prepared by mechanical alloying. The cyclic voltametry results indicated that the potential of oxidation peak was shift as the scan rate increased and the absorption property of Mg 2 Ni prepared by mechanical alloying was increased even at ambient temperature. The absorption and desorption of hydrogen in Mg 2 Ni alloy were remarkably accelerated with the rising temperature. Small angel X-ray scattering results indicated that the Mg 2 Ni powder have 1-5 nm and 5-10 nm particle size distribution, which increased the acting sites of hydrogen absorption/desorption reaction and decreased the diffusion path of hydrogen desorption. It was induced to the enhanced performance of Mg 2 Ni nanocrystalline powder. The cycle life investigated results indicated that the activation property of Mg 2 Ni nanocrystal-line hydrogen storage alloy electrode was excellent, the capacitance maintenance ration was 66% after 200 cycles. The coating of epoxy resin on one side of the electrode had no effect on the activation property and the capacitance maintenance ration was better than the uncoating one. But the anode peak current value and the cathodic peak current value were decreased remarkably which indicated that the hydrogen absorption/desorption rate and the charge/discharge degree had decreased. (authors)

Solidification Rate Dependence of Microstructures and Transformation Behavior of Ti-Ni-Hf Alloys.

Science.gov (United States)

Kim, Dong-Jo; Kim, Yeon-Wook; Nam, Tae-Hyun

2018-09-01

The microstructures and transformation behavior of Ti-49Ni-20Hf, Ti-49.5Ni-20Hf and Ti-50.3Ni- 20Hf alloys, when prepared by conventional casting, were investigated and compared with the properties of the alloys prepared by melt spinning. The area fraction of (Ti,Hf)2Ni in Ti-Ni-Hf alloys decreased to 3.9% from 9.4% as Ni content rose to 50.3 at% from 49 at%. Several cracks were observed in the hot-rolled Ti-49Ni-20Hf alloy sheet but none were found in the Ti-50.3Ni-20Hf alloy sheet. The B2-B19' transformation start temperature (Ms) decreased to 476 K from 580 K as Ni content increased to 50.3 at% from 49 at%. All the as-spun ribbons were amorphous, and the activation energy for crystallization ranged from 167.8 kJ/mol to 182.7 kJ/mol based on Ni content. When annealing temperature ranged from 810 K to 873 K, crystalline Ti-Ni-Hf alloys without (Ti,Hf)2Ni particles were obtained. At annealing temperatures higher than 873 K, very fine (Ti,Hf)2Ni particles, less than 20 nm in size, were found embedded in a crystalline matrix.

Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

International Nuclear Information System (INIS)

Aoki, Masakazu; Saito, Katsushi; Towata, Shin-ichi

2005-01-01

Mg 85 Ni 10 Ca 5 and Mg 90 Ni 10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg 85 Ni 10 Ca 5 , which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg 90 Ni 10 . In addition, the nanometer-scale structure composed of Mg, Mg 2 Ni, Mg 2 Ca was observed in Mg 85 Ni 10 Ca 5 . Mg 85 Ni 10 Ca 5 shows better hydrogen absorption kinetics than Mg 90 Ni 10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg 85 Ni 10 Ca 5 is mainly attributed to the nanometer-scale structure

High quality vacuum induction melting of small quantities of NiTi shape memory alloys in graphite crucibles

International Nuclear Information System (INIS)

Frenzel, J.; Zhang, Z.; Neuking, K.; Eggeler, G.

2004-01-01

Binary NiTi based shape memory alloys can be produced starting from the pure elements (Ni-pellets, Ti-rods) by using vacuum induction melting (VIM). VIM ingot metallurgy is known to produce materials with a good chemical homogeneity; it, moreover, is cheaper than vacuum arc melting (VAM) when small quantities of laboratory materials are needed. In a VIM procedure, graphite crucibles are attractive because they have appropriate electrical properties. For NiTi melting, graphite crucibles are interesting because they are reasonably priced and they show a good resistance against thermal cracking. On the other hand, it is well known that melting of Ti alloys in graphite crucibles is associated with a vigorous interface reaction. And the carbon concentration of NiTi alloys needs to be kept below a certain minimum in order to assure that the functional properties of the alloys meet the required targets. Therefore, it is important to minimize the carbon pick up of the melt. The present work presents experimental results and discusses thermodynamic and kinetic aspects of the reaction of NiTi melts with graphite crucibles; a method is suggested to keep the carbon dissolution into the melt at a minimum

Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

Directory of Open Access Journals (Sweden)

W. Y. Zhang

2016-05-01

Full Text Available Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti3(Fe,Co5B2, FeCo-rich bcc, and NiAl-rich L21 phases; Ti3(Fe,Co5B2, is a new substitutional alloy series whose end members Ti3Co5B2 and Ti3Fe5B2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti11+xFe37.5-0.5xCo37.5−0.5xB14 (x = 0, 4 and alnico-like Ti11Fe26Co26Ni10Al11Cu2B14, the latter also containing an L21-type alloy. The volume fraction of the Ti3(Fe,Co5B2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystalline anisotropy of the tetragonal Ti3(Fe,Co5B2 phase. The alloy containing Ni, Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Our results indicate that magnetocrystalline anisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.

Effect of cooling rate and Mg addition on the structural evaluation of rapidly solidified Al-20wt%Cu-12wt%Fe alloy

Energy Technology Data Exchange (ETDEWEB)

Karaköse, Ercan, E-mail: ekarakose@karatekin.edu.tr [Çankırı Karatekin University, Faculty of Sciences, Department of Physics, 18100 Çankırı (Turkey); Çolak, Hakan [Çankırı Karatekin University, Faculty of Sciences, Department of Chemistry, 18100 Çankırı (Turkey)

2016-11-15

The present work examines the effect of Mg contents and cooling rate on the morphology and mechanical properties of Al{sub 20}Cu{sub 12}Fe quasicrystalline alloy. The microstructure of the alloys was analyzed by scanning electron microscopy and the phase composition was identified by X-ray diffractometry. The melting characteristics were studied by differential thermal analysis under an Ar atmosphere. The mechanical features of the melt-spun and conventionally solidified alloys were tested by tensile-strength test and Vickers micro-hardness test. It was found that the final microstructure of the Al{sub 20}Cu{sub 12}Fe samples mainly depends on the cooling rate and Mg contents, which suggests that different cooling rates and Mg contents produce different microstructures and properties. The average grain sizes of the melt spun samples were about 100–300 nm at 35 m/s. The nanosize, dispersed, different shaped quasicrystal particles possessed a remarkable effect to the mechanical characteristics of the rapidly solidified ribbons. The microhardness values of the melt spun samples were approximately 18% higher than those of the conventionally counterparts. - Highlights: •Quasicrystal-creating materials have high potential for applications. •Different shaped nanosize quasicrystal particles were observed. •The addition of Mg has an important impact on the mechanical properties. •H{sub V} values of the MS0, MS3 and MS5 samples at 35 m/s were 8.56, 8.66 and 8.80 GPa. •The volume fraction of IQC increases with increasing cooling rates.

Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material

International Nuclear Information System (INIS)

Gu, X N; Zhou, W R; Zheng, Y F; Li, X L; Cheng, Y

2010-01-01

Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s -1 , 30 m s -1 and 45 m s -1 ) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 μm) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr -1 for RS15, 0.94 mm yr -1 for RS30 and 0.36 mm yr -1 for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.

Controlling the microstructure and associated magnetic properties of Ni0.2Mn3.2Ga0.6 melt-spun ribbons by annealing

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Mahmud Khan

2017-05-01

Full Text Available Here we report on the structural and magnetic properties of Ni0.2Mn3.2Ga0.6 melt-spun ribbons. The as-spun ribbons were found to exhibit mixed cubic phases that transform to non-cubic structure upon annealing. Additionally, an amorphous phase was found to co-exist in all ribbons. The SEM images show that minor grain formation occurs on the as-spun ribbons. However, the formation of extensive nano-grains was observed on the surfaces of the annealed ribbons. While the as-spun ribbons exhibit predominantly paramagnetic behavior, the ribbons annealed under various thermal conditions were found to be ferromagnetic with a Curie temperature of about 380 K. The ribbons annealed at 450 °C for 30 minutes exhibit a large coercive field of about 2500 Oe. The experimental results show that the microstructure and associated magnetic properties of the ribbons can be controlled by annealing techniques. The coercive fields and the shape of the magnetic hysteresis loops vary significantly with annealing conditions. Exchange bias effects have also been observed in the annealed ribbons.

Molecular field analysis for melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys (18<=60)

CERN Document Server

Yano, K

2000-01-01

The magnetic properties for the melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys were analyzed using the molecular field theory (MFT). A concentration dependence of three exchange interaction constants was derived over a wide concentration range (18=T sub c sub o sub m sub p. Curvature of the Arrott plot in Gd-rich region was qualitatively simulated.

Hydriding properties of amorphous Ni-B alloy studied by DSC and thermogravimetry

International Nuclear Information System (INIS)

Spassov, T.; Rangelova, V.

1999-01-01

The hydrogenation behaviour of melt-spun Ni 81.5 B 18.5 amorphous alloy was studied by means of differential scanning calorimetry (DSC) and thermogravimetry (TG) and compared with the hydriding properties of a Fe-B-Si glass. It was found that the amorphous Ni-B alloy absorbs larger amounts of hydrogen than the Fe-B-Si glass, as the initial kinetics of hydrogen absorption and desorption of both the alloys are comparable. Hydrogen absorption and desorption reactions in Ni-B were observed to proceed with similar rates at ca. 300 K. The hydrogen desorption is revealed in DSC as an endothermic peak in the 350-450 K range, preceding the crystallization peak of the amorphous alloy. The enthalpy of hydrogen desorption (ΔH des =22 kJ/mol H 2 ) for Ni-B was found to be smaller than that for the Fe-B-Si glass, which finding is in contrast to the results on hydrogen diffusion in crystalline αFe and Fe-based alloys and Ni and Ni-based alloys. The hydrogen desorption temperature and enthalpy for Ni 81.5 B 18.5 were found to be independent of the amount of hydrogen absorbed. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Microstructure and electrochemical characterization of laser melt-deposited Ti2Ni3Si/NiTi intermetallic alloys

International Nuclear Information System (INIS)

Dong Lixin; Wang Huaming

2008-01-01

Corrosion and wear resistant Ti 2 Ni 3 Si/NiTi intermetallic alloys with Ti 2 Ni 3 Si as the reinforcing phase and the ductile NiTi as the toughening phase were designed and fabricated by the laser melt-deposition manufacturing process. Electrochemical behavior of the alloys was investigated using potentiodynamic polarization testing and electrochemical impedance spectroscopy in an NaOH solution. The results showed that the alloys have outstanding corrosion resistance due to the formation of a protective passive surface film of Ni(OH) 2 as well as the high chemical stability and strong inter-atomic bonds inherent to Ti 2 Ni 3 Si and NiTi intermetallics. The Ti 2 Ni 3 Si content has a significant influence on the microstructure of the alloys but only a slight effect on electrochemical corrosion properties

Microstructural evolution of direct chill cast Al-15.5Si-4Cu-1Mg-1Ni-0.5Cr alloy during solution treatment

Directory of Open Access Journals (Sweden)

He Kezhun

2011-08-01

Full Text Available Heat treatment has important influence on the microstructure and mechanical properties of Al-Si alloys. The most common used heat treatment method for these alloys is solution treatment followed by age-hardening. This paper investigates the microstructural evolution of a direct chill (DC cast Al-15.5Si-4Cu-1Mg-1Ni-0.5Cr alloy after solution treated at 500, 510, 520 and 530℃, respectively for different times. The major phases observed in the as-cast alloy are α-aluminum dendrite, primary Si particle, eutectic Si, Al7Cu4Ni, Al5Cu2Mg8Si6, Al15(Cr, Fe, Ni, Cu4Si2 and Al2Cu. The Al2Cu phase dissolves completely after being solution treated for 2 h at 500℃, while the eutectic Si, Al5Cu2Mg8Si6 and Al15(Cr, Fe, Ni, Cu4Si2 phases are insoluble. In addition, the Al7Cu4Ni phase is substituted by the Al3CuNi phase. The α-aluminum dendrite network disappears when the solution temperature is increased to 530℃. Incipient melting of the Al2Cu-rich eutectic mixture occurrs at 520℃, and melting of the Al5Cu2Mg8Si6 and Al3CuNi phases is observed at a solution temperature of 530℃. The void formation of the structure and deterioration of the mechanical properties are found in samples solution treated at 530℃.

Hydrogen absorption in Mg1.95Ti0.05Ni0.95Cu0.05 alloy prepared with mechanical alloying and thermal treatment; Absorcion de hidrogeno en la aleacion Mg1.95Ti0.05Ni0.95Cu0.05 preparada por aleado mecanico y tratamiento termico

Energy Technology Data Exchange (ETDEWEB)

Martinez, Juan Bonifacio; Urena Nunez, Fernando [Instituto Nacional de Investigaciones Nucleares, Ocoyoacac, Estado de Mexico (Mexico)]. E-mail: juan.bonifacio@inin.gob.mx

2009-09-15

This work presents hydrogen absorption in quaternary alloy Mg1.95Ti0.05Ni0.95Cu0.05 obtained by the mechanical alloying method, followed by thermal treatment in ultra-high pure argon atmosphere. The composition of the phases, microstructure and morphology of ground powders and with thermal treatment were characterized by DRX, SEM/EDS and TEM. After 20 hours of mechanical grinding and recooked at 300 degrees Celsius/1h in argon atmosphere, the quaternary alloy has a Mg{sub 2}Ni crystalline hexagonal structure with a crystallite size under 10 nm. The absorption measurements were performed under a pressure of 0.2 to 1.2 MPa at a temperature of 200 degrees Celsius in a micro-reactor. The quantification of absorption-desorption of hydrogen in the intermetallic was conducted in a TGA-DSC simultaneous calorimeter. Metallic hydride-dehydride powder was characterized with SEM and XRD. [Spanish] En este trabajo se presenta la absorcion de hidrogeno en la aleacion cuaternaria Mg1.95Ti0.05Ni0.95Cu0.05 obtenida por el metodo de aleado mecanico, seguida de tratamiento termico en atmosfera de argon de ultra alta pureza. La composicion de las fases, microestructura y morfologia de los polvos molidos y con tratamiento termico fue caracterizada por DRX, SEM/EDS y TEM. Despues de 20 h de molienda mecanica con recocido a 300 grados Celsios/1h en atmosfera de argon, la aleacion cuaternaria tiene una estructura cristalina hexagonal Mg{sub 2}Ni con tamano de cristalito menor a 10 nm. Las mediciones de absorcion fueron realizadas bajo una presion de 0.2 a 1.2 MPa a una temperatura de 200 grados Celsios en un micro-reactor. La cuantificacion de absorcion-desorcion de hidrogeno en el intermetalico se realizo en un calorimetro simultaneo TGA-DSC. Se determino que la cantidad maxima absorbida de hidrogeno en la aleacion cuaternaria fue de 3.24% en peso cuando la presion fue de 0.8 MPa a dicha temperatura. Polvos metalicos hidrurados-deshidrurados se caracterizaron por SEM y XRD.

Effect of amorphous Mg50Ni50 on hydriding and dehydriding behavior of Mg2Ni alloy

International Nuclear Information System (INIS)

Guzman, D.; Ordonez, S.; Fernandez, J.F.; Sanchez, C.; Serafini, D.; Rojas, P.A.; Aguilar, C.; Tapia, P.

2011-01-01

Composite Mg 2 Ni (25 wt.%) amorphous Mg 50 Ni 50 was prepared by mechanical milling starting with nanocrystalline Mg 2 Ni and amorphous Mg 50 Ni 50 powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg 50 Ni 50 improved the hydriding and dehydriding kinetics of Mg 2 Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: → First study of the hydriding behavior of composite Mg 2 Ni (25 wt.%) amorphous Mg 50 Ni 50 . → Microstructural characterization of composite material using XRD and SEM was obtained. → An improved effect of Mg 50 Ni 50 on the Mg 2 Ni hydriding behavior was verified. → The apparent activation energy for the hydrogen desorption of composite was obtained.

Hydrogen storage and microstructure investigations of La0.7-xMg0.3PrxAl0.3Mn0.4Co0.5Ni3.8 alloys

International Nuclear Information System (INIS)

Galdino, G.S.; Casini, J.C.S.; Ferreira, E.A.; Faria, R.N.; Takiishi, H.

2010-01-01

The effects of substitution of Pr for La in the hydrogen storage capacity and microstructures of La 0.7-x Pr x Mg 0.3 Al 0.3 Mn 0.4 Co 0.5 Ni 3.8 (x=0, 0.1, 0.3, 0.5, 0.7) alloys electrodes have been studied. X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectrometry (EDS) and electrical tests were carried out in a the alloys and electrodes. Cycles of charge and discharge have also been carried out in the Ni/MH (Metal hydride) batteries based on the alloys negative electrodes. (author)

CO impurities effect on LaNi4∙7Al0∙3 hydrogen storage alloy ...

Indian Academy of Sciences (India)

Administrator

LaNi4∙7Al0∙3 alloy was prepared by vacuum induction melting in high purity helium atmosphere, .... The particle size of the ... tated Ni, and hydrogen molecules are dissociated into .... range of 30–150 °C, the sample weight loss is about 1∙3%.

Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material

Energy Technology Data Exchange (ETDEWEB)

Gu, X N; Zhou, W R; Zheng, Y F [State Key Laboratory for Turbulence and Complex System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871 (China); Li, X L [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Cheng, Y, E-mail: yfzheng@pku.edu.c [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

2010-06-01

Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s{sup -1}, 30 m s{sup -1} and 45 m s{sup -1}) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 {mu}m) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr{sup -1} for RS15, 0.94 mm yr{sup -1} for RS30 and 0.36 mm yr{sup -1} for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.

Magnetic properties and microstructure of as-spun Fe3B/Nd2Fe14B nanocomposite permanent magnets produced by low-speed melt spinning technique

International Nuclear Information System (INIS)

Hirosawa, S.; Kanekiyo, H.; Ping, D.H.; Hono, K.

1998-01-01

Thick permanent magnet flakes of Fe 3 B/Nd 2 Fe 14 B nanocomposites have been produced directly from molten alloys by means of the low surface-velocity melt spinning technique. The thickness of the flakes varies from 70 to 300 μm depending on the surface velocity (V s ) of a quenching copper roll. Melt-spun flakes of Nd 4 Fe 77.5 B 18.5 alloy exhibit the intrinsic coercivity of 276 kA/m at V s of 5 m/s. X-ray diffraction and transmission electron microscopy results have revealed that this material is composed of nanocrystalline Fe 3 B and Nd 2 Fe 14 B grains ranging from 10 to 50 nm in diameter. The melt-spun alloy produced at V s = 3 m/s contains large grains of Nd 2 Fe 14 B, small grains of Fe 3 B, and large dendritic α-Fe of a few μm in length. In contrast, at V s = 7 m/s, a large portion of the quenched alloy is amorphous. These melt-spun alloys do not possess a hard magnetic property. We have also found that small additions of additives affect the optimum range of V s that give rise to hard magnetic properties in the as-melt-spun condition. Cr has a large effect in shifting the optimum V s values down to a 2-3 m/s range. Simultaneous addition of Co and Ga is effective in extending the optimum values of V s . A platelet permanent magnet with a thickness of 240 μm and magnetic properties of (BH) max = 131 kJ/m 3 , H cJ = 400 kA/m, and B r = 1.15 T has been produced from a Nd 3.5 Dy 1 Fe 73 Co 3 Ga 1 B 18.5 alloy. (orig.)

Effect of magnetic field on the microstructure and electrochemical performance of rapidly quenched La{sub 0.1}Nd{sub 0.075}Mg{sub 0.04}Ni{sub 0.65}Co{sub 0.12} alloy

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiangrong [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Wang, Haiyan, E-mail: wanghy419@126.com [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Hunan Dahua New Energy Co., Ltd., Changsha 410600 (China); Zhu, Shuping; Li, Fangfang [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Tang, Yougen, E-mail: ygtang@csu.edu.cn [College of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Liu, Zuming [State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083 (China)

2014-12-25

Highlights: • La{sub 0.1}Nd{sub 0.075}Mg{sub 0.04}Ni{sub 0.65}Co{sub 0.12} alloy is rapidly quenched in a 0.18 T static magnetic field. • The multiphase structures of as-treated alloys remain unchanged. • Grain refinement is achieved with the aid of magnetic field. • Magnetic field favors the formation of La{sub 2}Ni{sub 7} phase. • The as-prepared alloy exhibits improved electrochemical performance. - Abstract: Rare earth–Mg–Ni-based (RE–Mg–Ni-based) La{sub 0.1}Nd{sub 0.075}Mg{sub 0.04}Ni{sub 0.65}Co{sub 0.12} hydrogen storage alloys were rapidly quenched with and without exerting a 0.18 T static magnetic field and investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) studies and various electrochemical measurements. The results show that all samples hold a two-phase structure consisting of La{sub 2}Ni{sub 7} phase and LaNi{sub 5} phase, suggesting that the structure remains unchanged after treatment. Grain refinement, homogeneous composition and increase in La{sub 2}Ni{sub 7} phase abundance are achieved when magnetic field is applied. In comparison to quenched alloys, higher discharge capacities are obtained for the alloys prepared with the aid of magnetic field mainly due to the larger La{sub 2}Ni{sub 7} phase abundance. Cycling stability is improved with increasing quenching rate probably owing to better anti-pulverization ability resulted from refined grain size. Ameliorated electrochemical kinetics of the magnetic field assisted rapidly quenched alloys has been confirmed by potential-step measurements and electrochemical impedance spectroscopy (EIS) tests in accordance with the enhanced electrochemical properties.

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.

Effect of Zr Purity and Oxygen Content on the Structure and Mechanical Properties of Melt-Spun and Suction-Cast Cu46Zr42Al7Y5 Alloy

Directory of Open Access Journals (Sweden)

Kozieł T.

2016-06-01

Full Text Available The effect of oxygen content in zirconium on the structure and mechanical properties of the Cu46Zr42Al7Y5 alloy, in the form of melt-spun ribbons and suction-cast rods, was investigated. Two types of Zr, rod and crystal bar of different nominal purities and oxygen contents, were used to synthesize the alloy by arc melting. Rapidly solidified ribbons were produced by melt spinning and their amorphous structures were confirmed by X-ray diffractometry (XRD and differential scanning calorimetry (DSC. Bulk samples in the form of rods were cast using a special water-cooled suction casting unit attached to the arc melting system. XRD and DSC studies proved the amorphous structure of the bulk alloy synthesized from low-oxygen Zr and partial crystallization of the same alloy for high-oxygen Zr. In both bulk samples, uniformly distributed crystalline particles were identified as yttrium oxides. Higher mean compressive strength of amorphous alloy was observed. The hardness of amorphous phase was close to 500 HV1 in both bulk alloys, while the hardness of crystalline dendritic areas, observed in the alloy synthesized from high oxygen Zr, was lower by about 50 HV1.

Analysis of grain growth process in melt spun Fe-B alloys under the initial saturated grain boundary segregation condition

International Nuclear Information System (INIS)

Chen, Z.; Liu, F.; Yang, X.Q.; Fan, Y.; Shen, C.J.

2012-01-01

Highlights: → We compared pure kinetic, pure thermodynamic and extended thermo-kinetic models. → An initial saturated GB segregation condition of nanoscale Fe-B alloys was determined. → The controlled-mechanism was proposed using two characteristic times (t 1 and t 2 ). - Abstract: A grain growth process in the melt spun low-solid-solubility Fe-B alloys was analyzed under the initial saturated grain boundary (GB) segregation condition. Applying melt spinning technique, single-phase supersaturated nanograins were prepared. Grain growth behavior of the single-phase supersaturated nanograins was investigated by performing isothermal annealing at 700 deg. C. Combined with the effect of GB segregation on the initial GB excess amount, the thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] was extended to describe the initial GB segregation condition of nanoscale Fe-B alloys. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, an initial saturated GB segregation condition was determined. The controlled-mechanism of grain growth under initial saturated GB segregation condition was proposed using two characteristic annealing times (t 1 and t 2 ), which included a mainly kinetic-controlled process (t ≤ t 1 ), a transition from kinetic-mechanism to thermodynamic-mechanism (t 1 2 ) and pure thermodynamic-controlled process (t ≥ t 2 ).

Hydrogen diffusion in La{sub 1.5}Nd{sub 0.5}MgNi{sub 9} alloy electrodes of the Ni/MH battery

Energy Technology Data Exchange (ETDEWEB)

Volodin, A.A. [Institute of Problems of Chemical Physics of RAS, Chernogolovka (Russian Federation); Denys, R.V. [Institute for Energy Technology, P.O. Box 40, Kjeller NO2027 (Norway); Tsirlina, G.A. [Department of Electrochemistry, Moscow State University, Moscow (Russian Federation); Tarasov, B.P. [Institute of Problems of Chemical Physics of RAS, Chernogolovka (Russian Federation); Fichtner, M. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe (Germany); Yartys, V.A., E-mail: volodymyr.yartys@ife.no [Institute for Energy Technology, P.O. Box 40, Kjeller NO2027 (Norway)

2015-10-05

Highlights: • Hydrogen diffusion in the La{sub 1.5}Nd{sub 0.5}MgNi{sub 9} alloy electrode was studied. • Various techniques of low amplitude potentiostatic data treatment were used. • D{sub H} demonstrates a maximum (2 × 10{sup −11} cm{sup 2}/s) at 85% of discharge of the electrode. • Maximum is associated with a conversion of β-hydride into a solid α-solution. • Optimization of material and electrode will allow high discharge rates. - Abstract: Hydrogen diffusion in the La{sub 1.5}Nd{sub 0.5}MgNi{sub 9} battery electrode material has been studied using low amplitude potentiostatic experiments. Complex diffusion behavior is examined in frames of electroanalytical models proposed for the lithium intercalation materials. Hydrogen diffusion coefficient D{sub H} changes with hydrogen content in the metal hydride anode electrode and has a maximum of ca. 2 × 10{sup −11} cm{sup 2}/s at ca. 85% of discharge. Such a behavior differs from the trends known for the transport in lithium battery materials, but qualitatively agrees with the data for the highly concentrated β-PdH{sub x}.

Improvement of the performance of Mg-based alloy electrodes at ambient temperatures

International Nuclear Information System (INIS)

Liu, H.K.; Chen, J.; Sun, L.; Bradhurst, D.H.; Dou, S.X.

1998-01-01

Full text: Rechargeable batteries are finding increased application in modern communications, computers, and electric vehicles. The Nickel-Metal Hydride (Ni-MH) battery has the best comprehensive properties. It is known that the important step to increase the energy density of Ni-MH battery is to improve the negative (metal hydride) electrode properties. Of all the hydrogen storage alloys studied previously, (the best know alloys are LaNi 5 , Mg 2 Ni, Ti 2 Ni , TiNi and Zr 2 Ni), the intermetallic compound Mg 2 Ni has the highest theoretical hydrogen storage capacity. The Mg 2 Ni-based hydrogen storage alloy is a promising material for increasing the negative electrode capacity of Ni-MH batteries because this alloy is superior to the LaNi 5 -system or the Zr-based alloys in materials cost and hydrogen absorption capacity. A serious disadvantage, however, is that the reactions of most magnesium based alloys with hydrogen require relatively high temperature (>300 deg C) and pressure (up to 10 atm) due to the slowness of the hydriding/dehydriding reactions. In this paper it is shown that with a combination of modifications to the alloy composition and methods of electrode preparation, magnesium-based alloys can be made into electrodes which will not only be useful at ambient temperatures but will have a useful cycle life and extremely high capacity

Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

Energy Technology Data Exchange (ETDEWEB)

Zhou Tao, E-mail: tzhou1118@163.com [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chen Zhenhua, E-mail: chenzhenhua45@hotmail.com [College of Material Science and Engineering, Hunan University, Changsha 410082 (China); Yang Mingbo, E-mail: yangmingbo@cqit.edu.cn [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Hu Jianjun, E-mail: hujj@qq.com [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Xia Hua, E-mail: xiahua@cqut.edu.cn [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China)

2012-01-15

Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.

Synthesis of a single phase of high-entropy Laves intermetallics in the Ti-Zr-V-Cr-Ni equiatomic alloy

Science.gov (United States)

Yadav, T. P.; Mukhopadhyay, Semanti; Mishra, S. S.; Mukhopadhyay, N. K.; Srivastava, O. N.

2017-12-01

The high-entropy Ti-Zr-V-Cr-Ni (20 at% each) alloy consisting of all five hydride-forming elements was successfully synthesised by the conventional melting and casting as well as by the melt-spinning technique. The as-cast alloy consists entirely of the micron size hexagonal Laves Phase of C14 type; whereas, the melt-spun ribbon exhibits the evolution of nanocrystalline Laves phase. There was no evidence of any amorphous or any other metastable phases in the present processing condition. This is the first report of synthesising a single phase of high-entropy complex intermetallic compound in the equiatomic quinary alloy system. The detailed characterisation by X-ray diffraction, scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the existence of a single-phase multi-component hexagonal C14-type Laves phase in all the as-cast, melt-spun and annealed alloys. The lattice parameter a = 5.08 Å and c = 8.41 Å was determined from the annealed material (annealing at 1173 K). The thermodynamic calculations following the Miedema's approach support the stability of the high-entropy multi-component Laves phase compared to that of the solid solution or glassy phases. The high hardness value (8.92 GPa at 25 g load) has been observed in nanocrystalline high-entropy alloy ribbon without any cracking. It implies that high-yield strength ( 3.00 GPa) and the reasonable fracture toughness can be achieved in this high-entropy material.

Study the microstructure of three and four component phases in Al-Ni-Fe-La alloys

KAUST Repository

Kolobylina, Natalia

2016-12-21

Aluminium alloys play a key role in modern engineering since they are the most used non-ferrous material. They have been widely used in automotive, aerospace, and construction engineering due to their good corrosion resistance, superior mechanical properties along with good machinability, weldability, and relatively low cost. The progress in practical application has been determined by intensive research and development works on the Al alloys. A new class of Al–REM–TM aluminum alloys (REM indicates rare earth metal and TM is transition metal) was revealed in the end of the last century. These alloys differ from conventional ones by their extraordinary ability to form metal glasses and nanoscale composites in a wide range of compositions. Having low density, these alloys possess unique mechanical characteristics and corrosion resistance. Two as received alloys, namely Al85Ni9Fe2La4 and Al85Ni7Fe4La4 were obtained in the form of ingots from melts of corresponding compositions upon cooling in air were studied by scanning/transmission electron microscopy (STEM), energy dispersive X-ray (EDX) microanalysis and X-ray diffraction (XRD). The microstructural analyses were performed in a aberration corrected TITAN 80-300 TEM/STEM (FEI, USA) attached with EDX spectrometer with ultrathin window (EDAX, USA). The specimens for transmission electron microscopy (TEM) were prepared by an electrochemical or ion etching. It was found that the received alloys exhibits along with fcc Al and Al4La (Al11La3) particles, these alloys contain a ternary phase Al3Ni1 Fe isostructural to the Al3Ni phase and a quaternary phase Al8Fe2 NiLa isostructural to the Al8Fe2Eu phase and monoclinic phase Al9(Fe,Ni)2 isostructural to the Al9Co2. The study by HRSTEM together with a new atomic resolution energy dispersive X-ray microanalysis method demonstrated that Fe and Ni atoms substituted one another in the Al8Fe2–NiLa quaternary compound. Besides, several types of defects were determined: first

Characterization of the kinetic arrest of martensitic transformation in Ni45Co5Mn36.8In13.2 melt-spun ribbons

Science.gov (United States)

Lino-Zapata, F. M.; Yan, H. L.; Ríos-Jara, D.; Sánchez Llamazares, J. L.; Zhang, Y. D.; Zhao, X.; Zuo, L.

2018-01-01

The kinetic arrest (KA) of martensitic transformation (MT) observed in Ni45Co5Mn36.8In13.2 melt-spun ribbons has been studied. These alloy ribbons show an ordered columnar-like grain microstructure with the longer grain axis growing perpendicular to ribbon plane and transform martensitically from a single austenitic (AST) parent phase with the L21-type crystal structure to a monoclinic incommensurate 6 M modulated martensite (MST). Results show that the volume fraction of austenite frozen into the martensitic matrix is proportional to the applied magnetic field. A fully arrest of the structural transition is found for a magnetic field of 7 T. The metastable character of the non-equilibrium field-cooled glassy state was characterized by introducing thermal and magnetic field fluctuations or measuring the relaxation of magnetization. The relaxation of magnetization from a field-cooled kinetically arrested state at 5 and 7 T follows the Kohlrausch-Williams-Watts (KWW) stretched exponential function with a β exponent around 0.95 indicating the weak metastable nature of the system under the strong magnetic fields. The relationship between the occurrence of exchange bias and the frozen fraction of AST into the MST matrix was studied.

The effect of phase constituent on the magnetic properties for melt-spun Nd15Fe77B8 ribbons

International Nuclear Information System (INIS)

Sun Wensheng; Li Shandong; Quan Mingxiu

1997-01-01

Some acicular Nd 2 Fe 14 B grains are precipitated from Nd-rich phase near-coarse grains in melt-spun Nd 15 Fe 77 B 8 alloy, as confirmed by SEM energy spectral analysis. The Nd-rich phase plays an important role in enhancing magnetic properties on annealing. This result suggests that the melted Nd-rich phase may act as a sink for free iron to be captured within Nd-rich phase regions resulting in the decreased iron constituent and enhanced magnetic properties at the annealing temperature at which the Nd-rich phase is melted. After an optimized heat treatment, the higher magnetic properties with ultrahigh coercivity H c , 1400 kAm -1 , and maximum energy product (BH) max , 89 kJm -3 , are obtained. The initial magnetization curves of melt-spun samples are composed of multi-domain and single-domain magnetization processes. (orig.)

Thermal Expansion Properties of Fe-42Ni-Si Alloy Strips Fabricated by Melt Drag Casting Process

International Nuclear Information System (INIS)

Kim, Moo Kyum; Ahn, Yong Sik; Namkung, Jeong; Kim, Moon Chul; Kim, Yong Chan

2007-01-01

Thermal expansion property was investigated on Fe-42% Ni alloy strip added by alloying element of Si of 0∼1.5wt.%. The strip was fabricated by a melt drag casting process. Addition of Si enlarged the solid-liquid region and reduced the melting point which leads to the increase of the formability of a strip. The alloy containing 0.6 wt.% Si showed the lowest thermal expansion ratio in the temperature range between 20 to 350 .deg. C. The grain size was increased with reduction ratio and annealing temperature, which resulted in the decrease of the thermal expansion coefficient of strip. Because of grain refining by precipitation of Ni 3 Fe, the alloy strip containing 1.5 wt.% Si showed higher thermal expansion ratio compared with the alloy containing 0.6 wt.% Si

Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

Energy Technology Data Exchange (ETDEWEB)

Du, Kang, E-mail: du126kang@126.com; Zhu, Qiang, E-mail: zhu.qiang@grinm.com; Li, Daquan, E-mail: lidaquan@grinm.com; Zhang, Fan, E-mail: sk_zf@163.com

2015-08-15

Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al{sub 2}Cu. The fine particles were determined being Al{sub 2}Cu, Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 8}Mg{sub 3}FeSi{sub 2}. Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed.

Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

International Nuclear Information System (INIS)

Du, Kang; Zhu, Qiang; Li, Daquan; Zhang, Fan

2015-01-01

Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al 2 Cu. The fine particles were determined being Al 2 Cu, Al 5 Cu 2 Mg 8 Si 6 and Al 8 Mg 3 FeSi 2 . Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed

Effect of amorphous Mg{sub 50}Ni{sub 50} on hydriding and dehydriding behavior of Mg{sub 2}Ni alloy

Energy Technology Data Exchange (ETDEWEB)

Guzman, D., E-mail: danny.guzman@uda.cl [Departamento de Ingenieria en Metalurgia, Facultad de Ingenieria, Universidad de Atacama y Centro Regional de Investigacion y Desarrollo Sustentable de Atacama (CRIDESAT), Av. Copayapu 485, Copiapo (Chile); Ordonez, S. [Departamento de Ingenieria Metalurgica, Facultad de Ingenieria, Universidad de Santiago de Chile, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Fernandez, J.F.; Sanchez, C. [Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid (Spain); Serafini, D. [Departamento de Fisica, Facultad de Ciencias, Universidad de Santiago de Chile and Center for Interdisciplinary Research in Materials, CIMAT, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Rojas, P.A. [Escuela de Ingenieria Mecanica, Facultad de Ingenieria, Av. Los Carrera 01567, Quilpue, Pontificia Universidad Catolica de Valparaiso, PUCV (Chile); Aguilar, C. [Departamento de Ingenieria Metalurgica y Materiales, Universidad Tecnica Federico Santa Maria, Av. Espana 1680, Valparaiso (Chile); Tapia, P. [Departamento de Ingenieria en Metalurgia, Facultad de Ingenieria, Universidad de Atacama, Av. Copayapu 485, Copiapo (Chile)

2011-04-15

Composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50} was prepared by mechanical milling starting with nanocrystalline Mg{sub 2}Ni and amorphous Mg{sub 50}Ni{sub 50} powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg{sub 50}Ni{sub 50} improved the hydriding and dehydriding kinetics of Mg{sub 2}Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: {yields} First study of the hydriding behavior of composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50}. {yields} Microstructural characterization of composite material using XRD and SEM was obtained. {yields} An improved effect of Mg{sub 50}Ni{sub 50} on the Mg{sub 2}Ni hydriding behavior was verified. {yields} The apparent activation energy for the hydrogen desorption of composite was obtained.

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

OpenAIRE

Wenjin Zhang; Yufeng Peng; Zhongli Liu

2014-01-01

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fit...

Structural Investigation of Fe-Ni-S and Fe-Ni-Si Melts by High-temperature Fluorescence XAFS Measurements

International Nuclear Information System (INIS)

Manghnani, Murli H.; Balogh, John; Hong Xinguo; Newville, Matthew; Amulele, G.

2007-01-01

Iron-nickel (Fe-Ni) alloy is regarded as the most abundant constituent of Earth's core, with an amount of 5.5 wt% Ni in the core based on geochemical and cosmochemical models. The structural role of nickel in liquid Fe-Ni alloys with light elements such as S or Si is poorly understood, largely because of the experimental difficulties of high-temperature melts. Recently, we have succeeded in acquiring Ni K-edge fluorescence x-ray absorption fine structure (XAFS) spectra of Fe-Ni-S and Fe-Ni-Si melts and alloys. Different structural environment of Ni atoms in Fe-Ni-S and Fe-Ni-Si melts is observed, supporting the effect of light elements in Fe-Ni melts

Creep behaviour of a casting titanium carbide reinforced AlSi12CuNiMg piston alloy at elevated temperatures; Hochtemperaturkriechverhalten der schmelzmetallurgisch hergestellten dispersionsverstaerkten Kolbenlegierung AlSi12CuNiMg

Energy Technology Data Exchange (ETDEWEB)

Michel, S.; Scholz, A. [Zentrum fuer Konstruktionswerkstoffe, TU Darmstadt (Germany); Tonn, B. [Institut fuer Metallurgie, TU Clausthal (Germany); Zak, H.

2012-03-15

This paper deals with the creep behaviour of the titanium carbide reinforced AlSi12CuNiMg piston alloy at 350 C and its comparison to the conventional AlSi12Cu4Ni2MgTiZr piston alloy. With only 0,02 vol-% TiC reinforcement the creep strength and creep rupture strength of the AlSi12CuNiMg piston alloy are significantly improved and reach the level of the expensive AlSi12Cu4Ni2MgTiZr alloy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

International Nuclear Information System (INIS)

Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli

2014-01-01

The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801) 0.298 (one-phase approach), 1850(1 + P/12.806) 0.357 (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment

Effect of boron additions on phase formation and magnetic properties of TbCu7-type melt spun SmFe ribbons

International Nuclear Information System (INIS)

Zheng, Chuanjiang; Yu, Dunbo; Li, Kuoshe; Luo, Yang; Jin, Jinling; Lu, Shuo; Li, Hongwei; Mao, Yongjun; Quan, Ningtao

2016-01-01

Melt spun ribbons of a series of SmFe 12 B x (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm–Fe–B melt spun ribbons with single phase TbCu 7 -type structure were prepared from the SmFe 12 B x (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40 m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm–Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm–Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm 2 Fe 23 B 3 that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu 7 -type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe 12 B 1.0 melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36 kOe and a remanence of 4.8 kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe 12 and SmFe 12 B 1.0 ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)melt spun Sm–Fe alloys with TbCu 7 -type structure, and the metastable phase Sm 2 Fe 23 B 3 will appear when the content of boron

Study on phase formation mechanism and electrochemical properties of La{sub 0.75−x}Nd{sub x}Mg{sub 0.25}Ni{sub 3.3} (x = 0, 0.15) alloys prepared by powder sintering

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinding [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Han, Shumin, E-mail: hanshm@ysu.edu.cn [State Key Laboratory of Metastable Materials, Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Li, Yuan; Liu, Jingjing [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Che, Linda [Desert Vista High School, Phoenix, AZ 85048 (United States); Zhang, Lu; Zhang, Junling [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China)

2014-01-05

Highlights: • Gd{sub 2}Co{sub 7} phase abundance increases with Nd substitution dramatically. • Nd substitution results in the depletion of the minor CaCu{sub 5}-type phase. • The equilibrium plateau is elevated and broadened with Nd substitution. -- Abstract: An investigation of the phase formation mechanism and electrochemical properties of the La{sub 0.75−x}Nd{sub x}Mg{sub 0.25}Ni{sub 3.3} (x = 0, 0.15) alloys has been conducted in this paper. As explored by Rietveld analysis of the XRD data, the La{sub 0.75}Mg{sub 0.25}Ni{sub 3.3} alloy is composed of Ce{sub 2}Ni{sub 7}-type and Gd{sub 2}Co{sub 7}-type phases accompanied by minor CaCu{sub 5}-type phase. The partial substitution Nd for La benefits the formation of Gd{sub 2}Co{sub 7}-type phase, indicating that the atoms with smaller radius favor the formation of the Gd{sub 2}Co{sub 7}-type phase. However, CaCu{sub 5}-type phase disappears with Nd substitution. Because part of the replaced La atoms transform into [A{sub 2}B{sub 4}] subunits with the Ni atoms, and the formed [A{sub 2}B{sub 4}] subunits crystallize with [AB{sub 5}] subunits to produce A{sub 2}B{sub 7}-type phase, resulting in the depletion of the minor CaCu{sub 5}-type phase. The electrochemical P–C isotherms present that the La{sub 0.60}Nd{sub 0.15}Mg{sub 0.25}Ni{sub 3.3} alloy only containing A{sub 2}B{sub 7}-type phase has one single plateau while the La{sub 0.75}Mg{sub 0.25}Ni{sub 3.3} alloy which contains minor LaNi{sub 5} phase has two plateaus. It is beneficial for the elevation of equilibrium plateau pressure ascribing to the contraction in cell volumes by Nd substitution. Electrochemical measurements show that the substitution of La by Nd improves the discharge capacity and the high rate dischargeability owing to the increase of A{sub 2}B{sub 7}-type phase abundance.

Nanocontainer-Enhanced Self-Healing for Corrosion-Resistant Ni Coating on Mg Alloy.

Science.gov (United States)

Xie, Zhi-Hui; Li, Dan; Skeete, Zakiya; Sharma, Anju; Zhong, Chuan-Jian

2017-10-18

The ability to manipulate the functionalization of Ni coating is of great importance in improving the corrosion resistance of magnesium (Mg) alloy for many industrial applications. In the present work, MCM-41 type mesoporous silica nanocontainers (MSNs) loaded with corrosion inhibitor (NaF) were synthesized and employed as smart reinforcements to enhance the integrity and corrosion inhibition of the Ni coating. The incorporation of the F-loaded MSNs (F@MSNs) to enhance the corrosion resistant capacity of a metallic coating is reported for the first time. The mesoporous structures of the as-prepared MSNs and F@MSNs were confirmed by transmission electron microscopy (TEM), small angle X-rays scattering (SAXS), and N 2 adsorption-desorption isotherms. The X-ray photoelectron spectroscopy (XPS) data demonstrated the successful immobilization of fluoride ion on the MSNs and formation of a magnesium fluoride (MgF 2 ) protective film at the corrosion sites of the Mg alloy upon soaking in a F@MSNs-containing NaCl solution. The results from potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) for both bare Mg alloy and Ni coatings with and without F@MSNs have revealed a clear decrease in corrosion rate in a corrosive solution for a long-time immersion due to the introduction of F@MSNs. These findings open new opportunities in the exploration of self-healing metallic coatings for highly enhanced anticorrosion protection of Mg alloy.

The effects of vacuum induction melting and electron beam melting techniques on the purity of NiTi shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Otubo, J. [Instituto Tecnologico de Aeronautica (ITA), 12228-900 S.J. Campos, SP (Brazil) and DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil)]. E-mail: jotubo@ita.br; Rigo, O.D. [DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil); Neto, C. Moura [Instituto Tecnologico de Aeronautica (ITA), 12228-900 S.J. Campos, SP (Brazil); Mei, P.R. [DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil)

2006-11-25

The usual process to produce NiTi shape memory alloys is by vacuum induction melting (VIM) using graphite crucible that contaminates the bath with carbon. The contamination by oxygen comes from residual oxygen inside the melting chamber. A new alternative process to produce NiTi alloys is by electron beam melting (EBM) using water-cooled copper crucible that eliminates the carbon contamination and the oxygen contamination would be minimized due to operation in high vacuum. This work compares the two processes and shows that the carbon contamination is four to ten times lower for EBM compared to VIM products and that the final oxygen content is much more dependent on the starting raw materials. The purity of the final product should be very important mainly in terms of biomedical applications and the contaminations by carbon and oxygen affect the direct and reverse martensitic transformation temperatures.

Effect of boron additions on phase formation and magnetic properties of TbCu{sub 7}-type melt spun SmFe ribbons

Energy Technology Data Exchange (ETDEWEB)

Zheng, Chuanjiang; Yu, Dunbo, E-mail: yudb2008@126.com; Li, Kuoshe; Luo, Yang; Jin, Jinling; Lu, Shuo; Li, Hongwei; Mao, Yongjun; Quan, Ningtao

2016-08-15

Melt spun ribbons of a series of SmFe{sub 12}B{sub x} (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm–Fe–B melt spun ribbons with single phase TbCu{sub 7}-type structure were prepared from the SmFe{sub 12}B{sub x} (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40 m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm–Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm–Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm{sub 2}Fe{sub 23}B{sub 3} that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu{sub 7}-type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe{sub 12}B{sub 1.0} melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36 kOe and a remanence of 4.8 kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe{sub 12} and SmFe{sub 12}B{sub 1.0} ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)melt spun Sm–Fe alloys with TbCu{sub 7}-type structure, and the

Study of the high temperature characteristics of hydrogen storage alloys

CERN Document Server

Rong, Li; Shaoxiong, Zhou; Yan, Qi; 10.1016/j.jallcom.2004.07.006

2005-01-01

In this work, the phase structure of as-cast and melt-spun (MmY)/sub 1/(NiCoMnAl)/sub 5/ alloys (the content of yttrium is 0-2.5wt.%) and their electrochemical properties were studied with regard to discharge capacity at different temperatures (30-80 degrees C) and cycling life at 30 degrees C. It is found that the substitution of yttrium increase the electrochemical capacity of the compounds and decrease the difference in capacity between as-cast and as-quenched compounds at 30 degrees C. When increasing the yttrium concentration from 0 to 2.5wt.%, the cycling life of both the as-cast and the melt- spun compounds deteriorated, although the latter have a slightly longer cycle life than the former. The remarkable feature of the alloys obtained by yttrium substitution is the improvement of the high temperature electrochemical properties. It shows that the stability of the hydrides is increased. Compared with the as-cast alloys, the melt-spun ribbons have higher electrochemical charge /discharge capacity in the ...

Magnetic viscosity and coercivity mechanisms in sintered and melt spun NdFeB

International Nuclear Information System (INIS)

Street, R.; Bingham, D.; Day, R.K.; Dunlop, J.B.

1988-01-01

Magnetic viscosity parameters kT/q(=Sv) of sintered and melt spun NdFeB vary with internal field. During initial magnetization of thermally demagnetized specimens signifiant viscosity occurs with melt spun NdFeB but is negligible with sintered NdFeB. Differences in mechanisms of magnetization account for this behaviour

Simultaneous effect of mechanical alloying and arc-melting processes in the microstructure and hardness of an AlCoFeMoNiTi high-entropy alloy

International Nuclear Information System (INIS)

Baldenebro-Lopez, F.J.; Herrera-Ramírez, J.M.; Arredondo-Rea, S.P.; Gómez-Esparza, C.D.; Martínez-Sánchez, R.

2015-01-01

Highlights: • Multi-component systems of AlCoFeMoNiTi were produced by mechanical alloying. • Consolidated samples were fabricated by two different processing routes, sintering and arc melting. • Effect of routes of consolidation on microstructural evolution and microhardness is reported. • High hardness values are found in consolidated samples. • Alloying elements, grain size, and precipitates have a high effect on microhardness. - Abstract: A nanostructured AlCoFeMoNiTi high entropy alloy was synthesized through the mechanical alloying process. Bulk samples were obtained by two different routes to compare the microstructural evolution and hardness behavior: sintering and arc melting. Through electron microscopy analyses the formation of Mo-rich and Ti-rich phases were identified in the melted sample, while Ti-rich nano-precipitates were observed in the sintered sample. A higher microhardness value was achieved on the sintered sample than for the melted sample. The disadvantage of porosity in the sintered sample in comparison to the melted one was overcome by the hardening effect produced by the mechanical alloying

Simultaneous effect of mechanical alloying and arc-melting processes in the microstructure and hardness of an AlCoFeMoNiTi high-entropy alloy

Energy Technology Data Exchange (ETDEWEB)

Baldenebro-Lopez, F.J. [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, 31109 Chihuahua, Chih. (Mexico); Facultad de Ingeniería Mochis, Universidad Autónoma de Sinaloa, Prol. Ángel Flores y Fuente de Poseidón, S.N., 81223 Los Mochis, Sinaloa (Mexico); Herrera-Ramírez, J.M. [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, 31109 Chihuahua, Chih. (Mexico); Arredondo-Rea, S.P. [Facultad de Ingeniería Mochis, Universidad Autónoma de Sinaloa, Prol. Ángel Flores y Fuente de Poseidón, S.N., 81223 Los Mochis, Sinaloa (Mexico); Gómez-Esparza, C.D. [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, 31109 Chihuahua, Chih. (Mexico); Martínez-Sánchez, R., E-mail: roberto.martinez@cimav.edu.mx [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, 31109 Chihuahua, Chih. (Mexico)

2015-09-15

Highlights: • Multi-component systems of AlCoFeMoNiTi were produced by mechanical alloying. • Consolidated samples were fabricated by two different processing routes, sintering and arc melting. • Effect of routes of consolidation on microstructural evolution and microhardness is reported. • High hardness values are found in consolidated samples. • Alloying elements, grain size, and precipitates have a high effect on microhardness. - Abstract: A nanostructured AlCoFeMoNiTi high entropy alloy was synthesized through the mechanical alloying process. Bulk samples were obtained by two different routes to compare the microstructural evolution and hardness behavior: sintering and arc melting. Through electron microscopy analyses the formation of Mo-rich and Ti-rich phases were identified in the melted sample, while Ti-rich nano-precipitates were observed in the sintered sample. A higher microhardness value was achieved on the sintered sample than for the melted sample. The disadvantage of porosity in the sintered sample in comparison to the melted one was overcome by the hardening effect produced by the mechanical alloying.

Effects of Ni-5%RExOy Composite Additives on Electrochemical Hydrogen Storage Performances of Mg2Ni

Directory of Open Access Journals (Sweden)

ZHANG Guo-fang

2017-11-01

Full Text Available The Ni-5%RExOy (CeO2, La2O3, Eu2O3 as composite additives, Mg2Ni-Ni-5%RExOy composites were prepared by the ball milling method. The effects of different additives on the structure, morphology, electrochemistry and kinetic properties of Mg2Ni alloy were studied systematically. The results show that composite additives can improve the proportion of amorphous and nanocrystalline structure of Mg2Ni alloy. The particle size is homogeneous but the agglomeration is observed in the sample with Ni-5%CeO2 additives. The composites with additives show higher maximum discharge capacity and better cycle stabilities. All of these three kinds of composite additives can improve the kinetic properties of the composites effectively, including optimizing the charge-transfer ability, the reversibility of the electrochemical reaction on the alloy surface, and enhancing the diffusion coefficients of H atoms in the bulk of alloy. Among these three kinds of additives, Ni-5%CeO2 additive shows the best catalysis effect on promoting the kinetic properties of the composites.

Crystallization and Martensitic Transformation Behavior of Ti-Ni-Si Alloy Ribbons Prepared via Melt Spinning.

Science.gov (United States)

Park, Ju-Wan; Kim, Yeon-Wook; Nam, Tae-Hyun

2018-09-01

Ti-(50-x)Ni-xSi (at%) (x = 0.5, 1.0, 3.0, 5.0) alloy ribbons were prepared via melt spinning and their crystallization procedure and transformation behavior were investigated using differential scanning calorimtry, X-ray diffraction, and transmission electron microscopy. Ti-Ni-Si alloy ribbons with Si content less than 1.0 at% were crystalline, whereas those with Si content more than 3.0 at% were amorphous. Crystallization occurred in the sequence of amorphous →B2 → B2 → Ti5Si4 + TiNi3 → B2 + Ti5Si4 + TiNi3 + TiSi in the Ti-47.0Ni-3.0Si alloy and amorphous →R → R + Ti5Si4 + TiNi3 → R + Ti5Si4 + TiNi3 + TiSi in the Ti-45.0Ni-5.0Si alloy. The activation energy for crystallization was 189 ±8.6 kJ/mol for the Ti-47Ni-3Si alloy and 212±8.6 kJ/mol for the Ti-45Ni-5Si alloy. One-stage B2-R transformation behavior was observed in Ti-49.5Ni-0.5Si, Ti-49.0Ni-1.0Si, and Ti-47.0Ni- 3.0Si alloy ribbons after heating to various temperatures in the range of 873 K to 1073 K. In the Ti-45.0Ni-5.0Si alloy, one-stage B2-R transformation occurred after heating to 893 K, two-stage B2-R-B19' occurred after heating to 973 K, and two-stage B2-R-B19' occurred on cooling and one-stage B19'-B2 occurred on heating, after heating to 1073 K.

Magnetocaloric effect in textured rare earth intermetallic compound ErNi

Directory of Open Access Journals (Sweden)

Aparna Sankar

2018-05-01

Full Text Available Melt-spun ErNi crystallizes in orthorhombic FeB-type structure (Space group Pnma, no. 62 similar to the arc-melted ErNi compound. Room temperature X-ray diffraction (XRD experiments reveal the presence of texture and preferred crystal orientation in the melt-spun ErNi. The XRD data obtained from the free surface of the melt-spun ErNi show large intensity enhancement for (1 0 2 Bragg reflection. The scanning electron microscopy image of the free surface depicts a granular microstructure with grains of ∼1 μm size. The arc-melted and the melt-spun ErNi compounds order ferromagnetically at 11 K and 10 K (TC respectively. Field dependent magnetization (M-H at 2 K shows saturation behaviour and the saturation magnetization value is 7.2 μB/f.u. for the arc-melted ErNi and 7.4 μB/f.u. for the melt-spun ErNi. The isothermal magnetic entropy change (ΔSm close to TC has been calculated from the M-H data. The maximum isothermal magnetic entropy change, -ΔSmmax, is ∼27 Jkg-1K-1 and ∼24 Jkg-1K-1 for the arc-melted and melt-spun ErNi for 50 kOe field change, near TC. The corresponding relative cooling power values are ∼440 J/kg and ∼432 J/kg respectively. Although a part of ΔSm is lost to crystalline electric field (CEF effects, the magnetocaloric effect is substantially large at 10 K, thus rendering melt-spun ErNi to be useful in low temperature magnetic refrigeration applications such as helium gas liquefaction.

Magnetocaloric effect in textured rare earth intermetallic compound ErNi

Science.gov (United States)

Sankar, Aparna; Chelvane, J. Arout; Morozkin, A. V.; Nigam, A. K.; Quezado, S.; Malik, S. K.; Nirmala, R.

2018-05-01

Melt-spun ErNi crystallizes in orthorhombic FeB-type structure (Space group Pnma, no. 62) similar to the arc-melted ErNi compound. Room temperature X-ray diffraction (XRD) experiments reveal the presence of texture and preferred crystal orientation in the melt-spun ErNi. The XRD data obtained from the free surface of the melt-spun ErNi show large intensity enhancement for (1 0 2) Bragg reflection. The scanning electron microscopy image of the free surface depicts a granular microstructure with grains of ˜1 μm size. The arc-melted and the melt-spun ErNi compounds order ferromagnetically at 11 K and 10 K (TC) respectively. Field dependent magnetization (M-H) at 2 K shows saturation behaviour and the saturation magnetization value is 7.2 μB/f.u. for the arc-melted ErNi and 7.4 μB/f.u. for the melt-spun ErNi. The isothermal magnetic entropy change (ΔSm) close to TC has been calculated from the M-H data. The maximum isothermal magnetic entropy change, -ΔSmmax, is ˜27 Jkg-1K-1 and ˜24 Jkg-1K-1 for the arc-melted and melt-spun ErNi for 50 kOe field change, near TC. The corresponding relative cooling power values are ˜440 J/kg and ˜432 J/kg respectively. Although a part of ΔSm is lost to crystalline electric field (CEF) effects, the magnetocaloric effect is substantially large at 10 K, thus rendering melt-spun ErNi to be useful in low temperature magnetic refrigeration applications such as helium gas liquefaction.

Effect of Ni on eutectic structural evolution in hypereutectic Al-Mg2Si cast alloys

International Nuclear Information System (INIS)

Li Chong; Wu Yaping; Li Hui; Wu Yuying; Liu Xiangfa

2010-01-01

Research highlights: → By the injection of rod-like NiAl 3 phase in Al-Mg 2 Si alloys, Al-Mg 2 Si binary eutectic structure gradually evolves into Al-Mg 2 Si-NiAl 3 ternary eutectic. → The ternary eutectic presents a unique double rod structure that rod-like NiAl 3 and Mg 2 Si uniformly distribute in Al matrix. → The mechanism of structural evolution was analyzed in terms of the detailed microstructural observations. → The high temperature (350 deg. C) tensile strength of the alloy increases by 23% due to the eutectic structural evolution. - Abstract: The aim of this work is to investigate the eutectic structural evolution of hypereutectic Al-20% Mg 2 Si with Ni addition under a gravity casting process. Three-dimensional morphologies of eutectic phases were observed in detail using field emission scanning electron microscopy, after Al matrix was removed by deep etching or extraction. The results show that Al-Mg 2 Si binary eutectic gradually evolves into Al-Mg 2 Si-NiAl 3 ternary eutectic with the increase of Ni content, and flake-like eutectic Mg 2 Si transforms into rods. The ternary eutectic presents a unique double rod structure that rod-like NiAl 3 and Mg 2 Si uniformly distribute in Al matrix. Further, the high temperature (350 deg. C) tensile strength of the alloy increases by 23% due to the eutectic structure evolution, and the mechanism of structural evolution was discussed and analyzed in terms of the detailed microstructural observations.

Preparation of melt-spun antimicrobially modified LDH/polyolefin nanocomposite fibers.

Science.gov (United States)

Kutlu, Burak; Schröttner, Percy; Leuteritz, Andreas; Boldt, Regine; Jacobs, Enno; Heinrich, Gert

2014-08-01

Layered double hydroxide (LDH) was synthesized and organically modified with camphorsulfonic acid (CSA) and ciprofloxacin. The thermal stability of CSA was improved remarkably under LDH shielding. A minimal inhibitory concentration of free CSA against tested bacteria was determined in order to define the essential quantity in LDH modification. The modified LDHs were melt-compounded with high density polyethylene and the prepared nanocomposites were further melt-spun using a piston-type spinning device. The melt-spun fibers were tested for their antimicrobial activity against Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Enterobacter cloacae, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. CSA integrated fibers show susceptibility against Gram-positive bacteria and ciprofloxacin integrated fibers showed activity against both Gram-positive and Gram-negative bacteria. Copyright © 2014 Elsevier B.V. All rights reserved.

Mg-Ca Alloys Produced by Reduction of CaO: Understanding of ECO-Mg Alloy Production

Science.gov (United States)

Jung, In-Ho; Lee, Jin Kyu; Kim, Shae K.

2017-04-01

There have been long debates about the environment conscious (ECO) Mg technology which utilizes CaO to produce Ca-containing Mg alloys. Two key process technologies of the ECO-Mg process are the chemical reduction of CaO by liquid Mg and the maintenance of melt cleanliness during the alloying of Ca. Thermodynamic calculations using FactSage software were performed to explain these two key issues. In addition, an experimental study was performed to compare the melt cleanliness of the Ca-containing Mg alloys produced by the conventional route with metallic Ca and the ECO-Mg route with CaO.

Effect of the milling time on thermal stability of mechanically alloyed Mg{sub 5}0 Ni{sub 5}0 amorphous alloy; Efecto del tiempo de molienda sobre la estabilidad termica del amorfo Mg{sub 5}0 Ni:50 producido mediante aleado mecanico

Energy Technology Data Exchange (ETDEWEB)

Guzman, D.; Ordonez, S.; Serafini, D.; Rojas, P.; Aguilar, C.; Santander, M.; Navea, L.

2009-07-01

In order to study the relationship between the milling time used in the production of Mg{sub 5}0Ni{sub 5}0 amorphous alloy and its thermal stability, seven amorphous alloys were produced by milling for 20, 25, 30, 35, 40, 50 and 60 h each sample. The obtained powders were morphological and structurally characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The thermal stability of amorphous alloys was study by differential scanning calorimetry (DSC). Based on the obtained results, it can be concluded that the increase in the added energy when milling for longer time causes the homogenization of the microstructure with an increase in amorphous phase, which dissolves a large amount of nickel in its structure. Therefore, the simultaneous crystallization of the Mg{sub 2}Ni and MgNi{sub 2} intermetallic compounds at 345 degree centigrade can be explained. (Author) 19 refs.

Thermal stability and primary phase of Al-Ni(Cu)-La amorphous alloys

International Nuclear Information System (INIS)

Huang Zhenghua; Li Jinfu; Rao Qunli; Zhou Youhe

2008-01-01

Thermal stability and primary phase of Al 85+x Ni 9-x La 6 (x = 0-6) and Al 85 Ni 9-x Cu x La 6 (x = 0-9) amorphous alloys were investigated by X-ray diffraction and differential scanning calorimeter. It is revealed that replacing Ni in the Al 85 Ni 9 La 6 alloy by Cu decreases the thermal stability and makes the primary phase change from intermetallic compounds to single fcc-Al as the Cu content reaches and exceeds 4 at.%. When the Ni and La contents are fixed, replacing Al by Cu increases the thermal stability but also promotes the precipitation of single fcc-Al as the primary phase

Thermal desorption of hydrogen from Mg2Ni hydrogen storage materials.

Science.gov (United States)

Hur, Tae Hong; Han, Jeong Seb; Kim, Jin Ho; Kim, Byung Kwan

2011-07-01

In order to investigate the influence of HCS on the hydrogen occupation site of Mg2Ni alloy, the thermal desorption technique has been applied to Mg2Ni hydride made by hydriding combustion synthesis (HCS). Mg2Ni was made under low temperature in a short time by the HCS compared to conventional melting process. At various initial hydride wt% from 0.91 to 3.52, the sample was heated to 623 K at a rate of 1.0 K/min. The starting temperature of the evolution of hydrogen goes higher as the initial hydride wt% increases. Only one peak is shown in the case of the small initial hydride wt%. But two peaks appeared with increasing initial hydride wt%. The activation energies obtained by the first and second peaks are 113.0 and 99.5 kJ/mol respectively. The two site occupation model by Darriet et al. was proved. The influence of HCS on the hydrogen occupation site of Mg2Ni alloy is nonexistent.

Hydrogen storage and microstructure investigations of La{sub 0.7-x}Mg{sub 0.3}Pr{sub x}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} alloys

Energy Technology Data Exchange (ETDEWEB)

Galdino, G.S.; Casini, J.C.S.; Ferreira, E.A.; Faria, R.N.; Takiishi, H., E-mail: agsgaldino@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (DM/IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Dept. de Metalurgia

2010-07-01

The effects of substitution of Pr for La in the hydrogen storage capacity and microstructures of La{sub 0.7-x}Pr{sub x}Mg{sub 0.3}Al{sub 0.3}Mn{sub 0.4}Co{sub 0.5}Ni{sub 3.8} (x=0, 0.1, 0.3, 0.5, 0.7) alloys electrodes have been studied. X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectrometry (EDS) and electrical tests were carried out in a the alloys and electrodes. Cycles of charge and discharge have also been carried out in the Ni/MH (Metal hydride) batteries based on the alloys negative electrodes. (author)

Evolución de las propiedades mecánicas con la temperatura de cintas amorfas Mg10Ni10Y

Directory of Open Access Journals (Sweden)

Torrijos, M. A.

2006-02-01

Full Text Available The mechanical behaviour by tensile strength test from room temperature to 350 ºC in the rapidly solidified Mg-10Ni-10Y (at. % ribbon has been studied. To determine the effect of yttrium additions the results are compared with those of Mg-11Ni studied in a previous work. Before studding the mechanical behavior of the material the thermal stability of the amorphous ribbon and the crystallization reactions were determined by DSC experiments. Results show that yttrium stabilizes the amorphous phase but it has not reinforcement effect. The tensile strength and elongation to failure values of the ternary alloy are lower than those of Mg-11Ni

El objetivo de este estudio es la caracterización mecánica, mediante ensayos de tracción, desde temperatura ambiente hasta 350 °C, de una aleación amorfa de composición Mg-10Ni-10Y (% at. obtenida mediante solidificación rápida por la técnica de la rueda. Se analiza la influencia de la adición de itrio al Mg-Ni para lo cual los resultados se comparan con los de la aleación binaria Mg-11Ni estudiada previamente. Antes de iniciar la caracterización mecánica del material, se realizó un estudio mediante calorimetría diferencial de barrido para comprobar la naturaleza amorfa de la cinta, analizar su estabilidad térmica y conocer las transformaciones que experimenta hasta la cristalización. Los resultados indican que el itrio es un estabilizador de la fase amorfa pero no mejora las propiedes mecánicas de la cinta binaria. Los valores de resistencia mecánica y alargamiento a rotura medidos en la cinta con itrio son menores que los obtenidos para la aleación binaria.

Non-equilibrium magnetic properties of melt-spun Nd60Fe30Al10 alloys

International Nuclear Information System (INIS)

Sato Turtelli, R.; Sinnecker, J.P.; Steiner, W.; Wiesinger, G.; Groessinger, R.; Triyono, D.

2003-01-01

The temperature, frequency and DC-field dependence of the AC-susceptibility has been investigated on melt-spun Nd 60 Fe 30 Al 10 . The temperature dependence of the AC-susceptibility shows an anomalous behavior, which depends strongly on the applied heat treatment and exhibits a cluster-like characteristic. Similar to the time dependence of the coercivity, a magnetic after-effect is present for temperatures higher than 50 K. 57 Fe Moessbauer spectra can be analyzed by two hyperfine field distributions pointing to two phases with quite different magnetic moments on the Fe sites

Microstructure, mechanical and functional properties of NiTi-based shape memory ribbons

International Nuclear Information System (INIS)

Mehrabi, K.; Bruncko, M.; Kneissl, A.C.

2012-01-01

Highlights: ► Melt-spun samples exhibited martensite structure and shape memory effects immediately after processing at room temperature. ► Using a new etchant and interference contrast, it is possible to reveal the fine microstructures and grain boundaries. ► The martensite structure in NiTi is very fine, and nano-sized twin boundaries could be revealed using TEM only. ► Two-way effects have been successfully introduced by different thermomechanical training methods in NiTi, NiTiCu and NiTiW alloys, which can be used for several applications, e.g. microsensors and microactuators. - Abstract: The present work has been aimed to study the microstructures, functional properties and the influence of different thermomechanical training methods on the two-way shape memory effect in NiTi-based melt-spun ribbons. In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. Their fracture and elasticity characteristics have been determined, as well as shape memory properties by thermomechanical cycling. The ribbons were trained under tensile and bending deformation by thermal cycling through the phase transformation temperature range. The results displayed that all different training methods were effective in developing a two-way shape memory effect (TWSME). The influence of copper (5–25 at.% Cu) and tungsten (2 at.% W) on the microstructure, and the functional and mechanical behavior of NiTi thin ribbons was also investigated. All samples show a shape memory effect immediately after processing without further heat treatment. The melt-spun ribbons were trained under constant strain (bending and tensile deformation) by thermal cycling through the phase transformation temperature range. The addition of copper was effective to narrow the transformation hysteresis. The W addition has improved the TWSME stability of the NiTi alloys and mechanical properties. Results about

Synthesis and hydrogen storage of La23Nd7.8Ti1.1Ni33.9Co32.9Al0.65 alloys

Directory of Open Access Journals (Sweden)

Priyanka Meena

2018-04-01

Full Text Available The present work investigates structural and hydrogen storage properties of first time synthesized La23Nd7.8Ti1.1Ni33.9Co32.9Al0.65 alloy by arc melting process and ball milled to get it in nano structure form. XRD analysis of as-prepared alloy showed single phased hexagonal LaNi5-type structure with 52 nm average particle size, which reduces to about 31 nm after hydrogenations. Morphological studies by SEM were undertaken to investigate the effect of hydrogenation of nanostructured alloy. EDX analysis confirmed elemental composition of the as-prepared alloy. Activation energy for hydrogen desorption was studied using TGA analysis and found to be −76.86 kJ/mol. Hydrogenation/dehydrogenation reactions and absorption kinetics were measured at temperature 100 °C. The equilibrium plateau pressure was determined to be 2 bar at 100 °C giving hydrogen storage capacity of about 2.1 wt%. Keywords: Hydrogen storage, La23Nd7.8Ti1.1Ni33.9Co32.9Al0.65 alloy, SEM, EDS, TGA, Hydrogenation/dehydrogenation

Development of the dentistry alloy Ni-Cr-Nb; Desenvolvimento de ligas odontologicas Ni-Cr-Nb

Energy Technology Data Exchange (ETDEWEB)

Souza, M.A.; Ramos, A.S.; Hashimoto, T.M., E-mail: mari_sou@hotmail.co [UNESP/FEG, Guaratingueta, SP (Brazil). Fac. de Engenharia. Dept. de Materiais e Tecnologia

2010-07-01

This work reports on the structural characterization of Ni-Cr-Mo and Ni-Cr-Nb alloys produced by arc melting. Samples were characterized by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and EDS analysis. Results indicated that the arc melting process was efficient to produce homogeneous structures in Ni-Cr-Mo and Ni-Cr-Nb alloys. The nickel dissolved large amounts of Cr, Mo and Nb, which was detected by EDS analysis and X-ray diffraction. The alloy containing molybdenum indicated the presence of structure based on Ni{sub SS}, while that the alloys containing niobium presented primary grains of Ni{sub SS} and precipitates formed by the simultaneous transformation of the Ni and Ni{sub 3}Nb phases. (author)

Ferromagnetic bulk glassy alloys

International Nuclear Information System (INIS)

Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

2000-01-01

This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

Hydriding properties of an Mg-Al-Ni-Nd hydrogen storage alloy

International Nuclear Information System (INIS)

Duarte, G.I.; Bustamante, L.A.C.; Miranda, P.E.V. de

2007-01-01

This work presents the development of an Mg-Al-Ni-Nd alloy for hydrogen storage purposes. The hydrogen storage properties of the alloy were analyzed using pressure-composition isotherms and hydrogen desorption kinetic curves at different temperatures. The characterization of the microstructures, before and after hydrogenation, was performed using X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometry. Hydrogenation caused significant changes in the alloy microstructure. Two pressure plateaus were observed. The maximum hydrogen storage reversible capacity measured was 4 wt.% at 573 K

Magnesium-Nickel alloy for hydrogen storage produced by melt spinning followed by cold rolling

Directory of Open Access Journals (Sweden)

Daniel Rodrigo Leiva

2012-10-01

Full Text Available Severe plastic deformation routes (SPD have been shown to be attractive for short time preparation of magnesium alloys for hydrogen storage, generating refined microstructures and interesting hydrogen storage properties when compared to the same materials processed by high-energy ball milling (HEBM, but with the benefit of higher air resistance. In this study, we present results of a new processing route for Mg alloys for hydrogen storage: rapid solidification followed by cold work. A Mg97Ni3 alloy was processed by melt spinning (MS and by extensive cold rolling (CR. Submitting Mg97Ni3 ribbons between steel plates to cold rolling has shown to be a viable procedure, producing a thin cold welded foil, with little material waste. The as-processed material presents a high level of [002] fiber texture, a sub microcrystalline grain structure with a high density of defects, and also a fine dispersion of Mg2Ni nanoparticles. This refined microstructure allied to the developed texture resulted in enhanced activation and H-sorption kinetics properties.

A Review of Selective Laser Melted NiTi Shape Memory Alloy

Science.gov (United States)

Khoo, Zhong Xun; Shen, Yu Fang

2018-01-01

NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed. PMID:29596320

Effect of P addition on glass forming ability and soft magnetic properties of melt-spun FeSiBCuC alloy ribbons

International Nuclear Information System (INIS)

Xu, J.; Yang, Y.Z.; Li, W.; Chen, X.C.; Xie, Z.W.

2016-01-01

The dependency of phosphorous content on the glass forming ability, thermal stability and soft magnetic properties of Fe 83.4 Si 2 B 14−x P x Cu 0.5 C 0.1 (x=0,1,2,3,4) alloys was investigated. The experimental results showed that the substitution of B by P increased the glass forming ability in this alloy system. The Fe 83.4 Si 2 B 10 P 4 Cu 0.5 C 0.1 alloy shows a fully amorphous character. Thermal stability of melt-spun ribbons increases and temperature interval between the first and second crystallization peaks enlarges with the increase of P content. And the saturation magnetic flux density (Bs) shows a slight increase with the increase of P content. The Fe 83.4 Si 2 B 11 P 3 Cu 0.5 C 0.1 nanocrystalline alloy exhibits a high Bs about 200.6 emu/g. The Bs of fully amorphous alloy Fe 83.4 Si 2 B 10 P 4 Cu 0.5 C 0.1 drops dramatically to 172.1 emu/g, which is lower than that of other nanocrystallines. Low material cost and excellent soft magnetic properties make the FeSiBPCuC alloys promise soft magnetic materials for industrial applications. - Highlights: • Partial substituting B by P helps to improve the glass forming ability of the alloy. • The addition of P content reduces the thermal stability and improves heat treatment temperature region for these alloys. • The Fe 83.4 Si 2 B 11 P 3 Cu 0.5 C 0.1 nanocrystalline alloy exhibits a high saturation magnetic density of 200.6 emu/g.

Microstructure and magnetic properties of melt-spun Alnico-5 alloys

International Nuclear Information System (INIS)

Löwe, Konrad; Dürrschnabel, Michael; Molina-Luna, Leopoldo; Madugundo, Rajasekhar; Frincu, Bianca; Kleebe, Hans-Joachim; Gutfleisch, Oliver; Hadjipanayis, George C.

2016-01-01

The aim of this work is to investigate the effect of very fine grain sizes on the spinodal decomposition in the Alnico system. Commercial Alnico 5 was melted and melt-spun with varying copper wheel speeds, which led to a grain size of 1–2 µm. This value was further reduced to sub-micrometer size by a small addition of Boron (1 at%). The spinodal decomposition was induced through a two-step annealing treatment under magnetic field in the range of 600–900 °C. It was found that the size of the spinodal structures is not influenced much by increased wheel speeds but becomes smaller with the addition of Boron. However, the difference in coercivity between the samples with and without Boron is only 50 Oe (4 kA/m). To study the influence of the annealing treatment two sets of samples are compared, one with the highest coercivity (366 Oe/29 kA/m) and the other one with lower coercivity (180 Oe/14.5 kA/m). We found with Scanning transmission electron microscopy Energy-dispersive X-ray spectroscopy (STEM EDX) a much sharper chemical interface between the α1 and α2 precipitates in the former sample, which we attribute to be the main reason for the higher coercivity. - Highlights: • The influence of various parameters on spinodal decomposition in Alnico is studied. • Through addition of Boron the spinodal features became significantly smaller. • High coercivity samples show a sharp chemical contrast between α1 and α2 lamellae.

Magnetic domains in martensite of Ni-Mg-Ga alloy

International Nuclear Information System (INIS)

Kokorin, V.V.; Babij, O.M.; Dubinko, S.V.; Prokopov, A.R.

2006-01-01

The structural changes attendant on intermartensitic transformation in a Ni-Mg-Ga shape memory alloy are considered using magneto-optical visualization with the help of ferrite-garnet monocrystalline films. It is established that on the intermartensitic transformation the complete reorganization of martensite macrostructure fails. Martensite crystals resulted from the basic transformation change somewhat their sizes on intermartensitic transition. The existence of large-scale labyrinth magnetic domain structure is revealed [ru

Nickel-metal hydride (Ni-MH) battery using Mg{sub 2}Ni-type hydrogen storage alloy

Energy Technology Data Exchange (ETDEWEB)

Cui, N.; Luo, J.L.; Chuang, K.T. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical Engineering

2000-04-28

The performance of a sealed prismatic prototype Ni-MH battery having a Mg-Ni-Y-Al alloy anode was investigated. The materials were characterized using X-ray diffraction (XRD). The laboratory tests run on this prototype battery as well as the single electrode was compared. The electrochemical behavior was determined using electrochemical impedance spectroscopy (EIS). The battery has a good dischargeability but a high self-discharge rate during storage at open-circuit state. (orig.)

Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy

Directory of Open Access Journals (Sweden)

Deng Zhenghua

2013-03-01

Full Text Available Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in the formation of surface oxide film. In this present work, the ignition temperature and the surface tension of Mg-9wt.%Al alloy with different Ce concentrations were studied. Surface tensions was measured using the maximum bubble pressure method (MBPM. Ignition temperature was measured using NiCr-NiSi type thermocouples and was monitored and recorded via a WXT-604 desk recording device. The results show that the ignition point of Mg-9wt.%Al alloy can be effectively elevated by adding Ce. The ignition temperature reaches its highest point of 720 ℃ when the addition of Ce is 1wt.%. The surface tension of the molten Mg-9wt.%Al alloy decreases exponentially with the increase of Ce addition at the same temperature. Similarly, the experiment also shows that the surface tension of Mg-9wt.%Al alloy decreases exponentially with the increase of temperature.

Effect of rare-earth elements on nanophase evolution, crystallization ...

Indian Academy of Sciences (India)

scattered image of Al87Ni8La5 ingot, the phases are marked. Figure 2. XRD patterns of as-melt-spun Al–Ni–RE amorphous ribbons on the air-cooled side. temperature axis change with alloy composition. Two or three exothermic peaks.

Electrochemical kinetic performances of electroplating Co–Ni on La–Mg–Ni-based hydrogen storage alloys

Energy Technology Data Exchange (ETDEWEB)

Li, Yuan; Tao, Yang; Ke, Dandan; Ma, Yufei [Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Han, Shumin, E-mail: hanshm@ysu.edu.cn [Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2015-12-01

Graphical abstract: - Highlights: • The Co–Ni composite coating was prepared by electroplating. • The alloy treated at 10 mA/cm{sup 2} has superior kinetic performances. • The Co–Ni layer accelerates the charge transfer rate on the surface of the alloy. - Abstract: Electroplating Co–Ni treatment was applied to the surface of the La{sub 0.75}Mg{sub 0.25}Ni{sub 3.48} alloy electrodes in order to improve the electrochemical and kinetic performances. The Scanning electron microscope-Energy dispersive spectroscopy and X-ray diffraction results showed that the electrodes were plated with a homogeneous Co–Ni alloy film. The alloy coating significantly improved the high rate dischargeability of the alloy electrode, and the HRD value increased to 57.5% at discharge current density 1875 mA/g after the Co–Ni-coating. The exchange current density I{sub 0}, the limiting current density I{sub L} and the oxidation peak current also increased for the coated alloy. The improvement of overall electrode performances was attributed to an enhancement in electro-catalytic activity and conductivity at the alloy surface, owing to the precipitation of the Co–Ni layer.

Phase formation in as-solidified and heat-treated Al-Si-Cu-Mg-Ni alloys: Thermodynamic assessment and experimental investigation for alloy design

Energy Technology Data Exchange (ETDEWEB)

Farkoosh, A.R., E-mail: amir.rezaeifarkoosh@mail.mcgill.ca [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada); Javidani, M. [Laval University, Department of Mining, Metallurgy and Materials Engineering, Aluminum Research Center - REGAL, 1065 Ave de la Medecine, Quebec, Canada G1V 0A6 (Canada); Hoseini, M. [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada); Larouche, D. [Laval University, Department of Mining, Metallurgy and Materials Engineering, Aluminum Research Center - REGAL, 1065 Ave de la Medecine, Quebec, Canada G1V 0A6 (Canada); Pekguleryuz, M. [Department of Mining and Materials Engineering, McGill University, 3610 University, Aluminum Research Center - REGAL, Montreal, Quebec, Canada H3A 2B2 (Canada)

2013-02-25

Highlights: Black-Right-Pointing-Pointer Phase formation in Al-Si-Ni-Cu-Mg-Fe system have been investigated. Black-Right-Pointing-Pointer T-Al{sub 9}FeNi, {gamma}-Al{sub 7}Cu{sub 4}Ni, {delta}-Al{sub 3}CuNi and {epsilon}-Al{sub 3}Ni are formed at different Ni levels. Black-Right-Pointing-Pointer Thermally stable Ni-bearing precipitates improved the overaged hardness. Black-Right-Pointing-Pointer It was found that Ni:Cu and Ni:Fe ratios control the precipitation. Black-Right-Pointing-Pointer {delta}-Al{sub 3}CuNi phase has more contribution to strength compare to other precipitates. - Abstract: Thermodynamic simulations based on the CALPHAD method have been carried out to assess the phase formation in Al-7Si-(0-1)Ni-0.5Cu-0.35Mg alloys (in wt.%) under equilibrium and non-equilibrium (Scheil cooling) conditions. Calculations showed that the T-Al{sub 9}FeNi, {gamma}-Al{sub 7}Cu{sub 4}Ni, {delta}-Al{sub 3}CuNi and {epsilon}-Al{sub 3}Ni phases are formed at different Ni levels. By analyzing the calculated isothermal sections of the phase diagrams it was revealed that the Ni:Cu and Ni:Fe ratios control precipitation in this alloy system. In order to verify the simulation results, microstructural investigations in as-cast, solution treated and aged conditions were carried out using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, cooling curve analysis (CCA) was also performed to determine the freezing range of the new alloys and porosity formation during solidification. Hardness measurements of the overaged samples showed that in this alloy system the {delta}-Al{sub 3}CuNi phase has a greater influence on the overall strength of the alloys compared to the other Ni-bearing precipitates.

Improved mechanical properties of near-eutectic Al-Si piston alloy through ultrasonic melt treatment

Energy Technology Data Exchange (ETDEWEB)

Jung, Jae-Gil; Lee, Sang-Hwa [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Lee, Jung-Moo, E-mail: jmoolee@kims.re.kr [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Cho, Young-Hee [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Kim, Su-Hyeon [Metal Materials Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of); Yoon, Woon-Ha [Implementation Research Division, Korea Institute of Materials Science (KIMS), Changwon 51508 (Korea, Republic of)

2016-07-04

The effects of ultrasonic melt treatment (UST) on the microstructure and mechanical properties of Al-12.2Si-3.3Cu-2.4Ni-0.8Mg-0.1Fe (wt%) piston alloy were systematically investigated. Rigid colonies consisting of primary Si, eutectic Si, Mg{sub 2}Si and various aluminides (ε-Al{sub 3}Ni, δ-Al{sub 3}CuNi, π-Al{sub 8}FeMg{sub 3}Si{sub 6}, γ-Al{sub 7}Cu{sub 4}Ni, Q-Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and θ-Al{sub 2}Cu) were observed in the as-cast alloys. The sizes of the secondary phases, eutectic cell and grain were significantly decreased by UST because of the enhanced nucleation of each phase under ultrasonic irradiation. The yield strength, tensile strength and elongation at 25 °C were significantly improved by UST mainly because of the refinement of the microstructures. Both tensile strength and elongation at 350 °C were also improved by UST despite the unchanged yield strength.

Revisiting Mg–Mg2Ni System from Electronic Perspective

Directory of Open Access Journals (Sweden)

Zhao Qian

2017-11-01

Full Text Available Both Mg and Mg2Ni are promising electrode materials in conversion-type secondary batteries. Earlier studies have shown their single-phase prospects in electro-devices, while in this work, we have quantitatively reported the electronic properties of their dual-phase materials, that is, Mg–Mg2Ni alloys, and analyzed the underlying reasons behind the property changes of materials. The hypoeutectic Mg–Mg2Ni alloys are found to be evidently more conductive than the hypereutectic Mg–Mg2Ni system. The density functional theory (DFT calculations give the intrinsic origin of electronic structures of both Mg2Ni and Mg. The morphology of quasi-nanoscale eutectics is another factor that can affect the electronic properties of the investigated alloy system; that is, the electrical property change of the investigated alloys system is due to a combination of the intrinsic property difference between the two constituting phases and the change of eutectic microstructures that affect electron scattering. In addition, regarding the Mg–Mg2Ni alloy design for device applications, the electronic property and mechanical aspect should be well balanced.

Diffusion dynamics in liquid and undercooled Al-Ni alloys

Energy Technology Data Exchange (ETDEWEB)

Stueber, Sebastian

2009-10-05

This work presents data on Ni self-diffusion in binary Al-Ni alloys with high precision. For this, we combined two techniques: containerless electromagnetic levitation to position the samples, and neutron time-of-flight spectroscopy to measure the decay of the self-correlation. This combination offers new measurement ranges, especially at low temperatures, several hundreds of Kelvin below the liquidus temperature. Because without container, the primary cristallization seeds for the metallic melt are avoided. But it is also possible to measure reactive samples, and at very high temperatures at and above 2000K, as problematic reactions with the containing cask won't occur. Furthermore this technique also enables measurements at higher momentum transfer q, as one does not have to limit the q-range of the measurement to avoid Bragg peaks of the solid container material. By this time-of-flight spectroscopy on levitated metallic melts, it is possible to determine the Ni self-diffusion in these alloys directly and on an absolute scale. The dependence of the Ni self-diffusion coefficient on temperature and concentration was studied in pure Ni and binary Al-Ni alloys. In a temperature range of several hundred degrees, we always found Arrhenius-like temperature dependence of the diffusion, irrespective of possible undercooling. In the context of these measurements, we also studied the interdependence between diffusivity in the metallic melt and its quasielastic structure factor. Time-of-flight spectroscopy made it also possible to derive the dynamic partial structure factors of the binary alloy Al{sub 80}Ni{sub 20}. All this to enable a better understanding of the atomic processes in the metallic melt, especially of the undercooled melt, as an alloy is always formed out of the (undercooled) melt of its stoichiometric compounds. For this, material transport and diffusion are immensely important. The final goal would be materials design from the melt, i.e. the prediction

Diffusion dynamics in liquid and undercooled Al-Ni alloys

International Nuclear Information System (INIS)

Stueber, Sebastian

2009-01-01

This work presents data on Ni self-diffusion in binary Al-Ni alloys with high precision. For this, we combined two techniques: containerless electromagnetic levitation to position the samples, and neutron time-of-flight spectroscopy to measure the decay of the self-correlation. This combination offers new measurement ranges, especially at low temperatures, several hundreds of Kelvin below the liquidus temperature. Because without container, the primary cristallization seeds for the metallic melt are avoided. But it is also possible to measure reactive samples, and at very high temperatures at and above 2000K, as problematic reactions with the containing cask won't occur. Furthermore this technique also enables measurements at higher momentum transfer q, as one does not have to limit the q-range of the measurement to avoid Bragg peaks of the solid container material. By this time-of-flight spectroscopy on levitated metallic melts, it is possible to determine the Ni self-diffusion in these alloys directly and on an absolute scale. The dependence of the Ni self-diffusion coefficient on temperature and concentration was studied in pure Ni and binary Al-Ni alloys. In a temperature range of several hundred degrees, we always found Arrhenius-like temperature dependence of the diffusion, irrespective of possible undercooling. In the context of these measurements, we also studied the interdependence between diffusivity in the metallic melt and its quasielastic structure factor. Time-of-flight spectroscopy made it also possible to derive the dynamic partial structure factors of the binary alloy Al 80 Ni 20 . All this to enable a better understanding of the atomic processes in the metallic melt, especially of the undercooled melt, as an alloy is always formed out of the (undercooled) melt of its stoichiometric compounds. For this, material transport and diffusion are immensely important. The final goal would be materials design from the melt, i.e. the prediction of alloy

Amorphous and nanocrystalline Fe-Ni-Zr-B ribbons as sensing elements in magnetic field sensors

International Nuclear Information System (INIS)

Vertesy, G.; Idzikowski, B.

2006-01-01

Fe 81-x Ni x Zr 7 B 12 (x=20, 30, 40) melt-spun alloys were investigated as potential new material applied as a sensing element of a fluxgate-type high-sensitivity magnetic field sensor. The sensitivity of the magnetometer was increased by about 60% by using the amorphous or nanocrystalline Fe 41 Ni 40 Zr 7 B 12 alloy, compared with a standard reference sensing material. Application of this material can also extend the temperature range of the operation of the device

Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final Report Ph.D. Thesis

Science.gov (United States)

Ellis, David L.; Michal, Gary M.

1989-01-01

A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

Microstructure and mechanical properties of Cu-Ni-Si alloys

International Nuclear Information System (INIS)

Monzen, Ryoichi; Watanabe, Chihiro

2008-01-01

The microstructure and mechanical properties of 0.1 wt.% Mg-added and Mg-free Cu-2.0 wt.% Ni-0.5 wt.% Si alloys aged at 400 deg. C have been examined. The addition of Mg promotes the formation of disk-shaped Ni 2 Si precipitates. The Cu-Ni-Si-Mg alloy exhibits higher strength and resistance to stress relaxation than the Cu-Ni-Si alloy. The higher strength or stress relaxation resistance is attributable to the reduction in inter-precipitate spacing by the Mg addition or the drag effect of Mg atoms on dislocation motion. The Cu-Ni-Si alloy with a large grain size of 150 μm shows higher stress relaxation resistance than the alloy with a small grain size of 10 μm because of a lower density of mobile dislocations in the former alloy

Microstructure and mechanical properties of Cu-Ni-Si alloys

Energy Technology Data Exchange (ETDEWEB)

Monzen, Ryoichi [Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanzawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)], E-mail: monzen@t.kanazawa-u.ac.jp; Watanabe, Chihiro [Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanzawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)

2008-06-15

The microstructure and mechanical properties of 0.1 wt.% Mg-added and Mg-free Cu-2.0 wt.% Ni-0.5 wt.% Si alloys aged at 400 deg. C have been examined. The addition of Mg promotes the formation of disk-shaped Ni{sub 2}Si precipitates. The Cu-Ni-Si-Mg alloy exhibits higher strength and resistance to stress relaxation than the Cu-Ni-Si alloy. The higher strength or stress relaxation resistance is attributable to the reduction in inter-precipitate spacing by the Mg addition or the drag effect of Mg atoms on dislocation motion. The Cu-Ni-Si alloy with a large grain size of 150 {mu}m shows higher stress relaxation resistance than the alloy with a small grain size of 10 {mu}m because of a lower density of mobile dislocations in the former alloy.

Studies on MgNi-Based Metal Hydride Electrode with Aqueous Electrolytes Composed of Various Hydroxides

Directory of Open Access Journals (Sweden)

Jean Nei

2016-08-01

Full Text Available Compositions of MgNi-based amorphous-monocrystalline thin films produced by radio frequency (RF sputtering with a varying composition target have been optimized. The composition Mg52Ni39Co3Mn6 is identified to possess the highest initial discharge capacity of 640 mAh·g−1 with a 50 mA·g−1 discharge current density. Reproduction in bulk form of Mg52Ni39Co3Mn6 alloy composition was prepared through a combination of melt spinning (MS and mechanical alloying (MA, shows a sponge-like microstructure with >95% amorphous content, and is chosen as the metal hydride (MH alloy for a sequence of electrolyte experiments with various hydroxides including LiOH, NaOH, KOH, RbOH, CsOH, and (C2H54N(OH. The electrolyte conductivity is found to be closely related to cation size in the hydroxide compound used as 1 M additive to the 4 M KOH aqueous solution. The degradation performance of Mg52Ni39Co3Mn6 alloy through cycling demonstrates a strong correlation with the redox potential of the cation in the alkali hydroxide compound used as 1 M additive to the 5 M KOH aqueous solution. NaOH, CsOH, and (C2H54N(OH additions are found to achieve a good balance between corrosion and conductivity performances.

Influences of alloying elements and oxygen on the stability and elastic properties of Mg17Al12

International Nuclear Information System (INIS)

Dai, Jianhong; Song, Yan; Yang, Rui

2014-01-01

Highlights: • Most alloying elements stabilize Mg 17 Al 12 with negative occupation energy. • The alloying element and oxygen co-existed Mg 17 Al 12 are stable. • Strong bonding interactions existed between alloying element and host atoms. - Abstract: Influence of alloying elements (Ca, Mn, Ni, Cu, Zn, Zr, Sn, and La) and oxygen on stability and elastic properties of Mg 17 Al 12 has been studied by first principles total energy calculations. The occupation preferences of oxygen and alloying elements in Mg 17 Al 12 are identified. Ca, Zr, and La tend to substitute for Mg atoms, Zn, Cu, and Ni prefer to occupy Al site, and Mn and Sn show positive occupation energy for substituting both Mg and Al atoms. The impurity oxygen prefers to occupy interstitial sites surrounded by four Mg atoms regardless the presence of alloying elements in this system. Elastic constants were estimated to evaluate the mechanical stability of alloyed systems. The results show that alloys which own negative occupation energy also satisfy the mechanical stability criteria. Electronic structures were analyzed to clarify the intrinsic mechanisms of how alloying elements and oxygen influence the stability of Mg 17 Al 12 . The stabilization effect of alloying elements and oxygen was found to originate from the strong bonding interaction with the matrix

Formation of long-period stacking ordered structures in Mg88M5Y7 (M = Ti, Ni and Pb) casting alloys

International Nuclear Information System (INIS)

Jin, Qian-Qian; Fang, Can-Feng; Mi, Shao-Bo

2013-01-01

Highlights: •Apart from 18R-LPSO, 14H-LPSO structure was determined in the Mg-Ni-Y alloys. •The appearance of twin-related structure in 18R-LPSO structure results from the stacking faults in the stacking sequence of the closely packed planes. •A new (Pb, Mg) 2 Y phase with a body-centered orthorhombic structure was determined in the Mg-Pb-Y alloy. •No LPSO structures were found in the Mg-Pb-Y and Mg-Ti-Y casting alloys. -- Abstract: Formation of long-period stacking ordered (LPSO) structures is investigated in Mg 88 M 5 Y 7 (M = Ti, Ni and Pb) casting alloys by means of electron microscopy and X-ray diffraction. In the Mg 88 Ni 5 Y 7 casting alloy, 14H-LPSO structure is observed in a small amount, which coexists with 18R-LPSO structure. The appearance of stacking faults in 18R-LPSO structure results in twin-related structure in the stacking sequence of the closely packed planes. A new (Pb, Mg) 2 Y phase with a body-centered orthorhombic structure is determined in the Mg 88 Pb 5 Y 7 alloy. No LPSO structures are found in the Mg 88 Pb 5 Y 7 and Mg 88 Ti 5 Y 7 casting alloys. In terms of the atomic radius and heat of mixing, the formation ability of LPSO structure in the present alloys is discussed

Fabrication and heat treatment of high strength Al-Cu-Mg alloy processed using selective laser melting

Science.gov (United States)

Zhang, Hu; Zhu, Haihong; Nie, Xiaojia; Qi, Ting; Hu, Zhiheng; Zeng, Xiaoyan

2016-04-01

The proposed paper illustrates the fabrication and heat treatment of high strength Al-Cu-Mg alloy produced by selective laser melting (SLM) process. Al-Cu-Mg alloy is one of the heat treatable aluminum alloys regarded as difficult to fusion weld. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers with a focused laser beam. The process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling. In this research, 3D Al-Cu-Mg parts with relative high density of 99.8% are produced by SLM from gas atomized powders. Room temperature tensile tests reveal a remarkable mechanical behavior: the samples show yield and tensile strengths of about 276 MPa and 402 MPa, respectively, along with fracture strain of 6%. The effect of solution treatment on microstructure and related tensile properties is examined and the results demonstrate that the mechanical behavior of the SLMed Al-Cu-Mg samples can be greatly enhanced through proper heat treatment. After T4 solution treatment at 540°C, under the effect of precipitation strengthening, the tensile strength and the yield strength increase to 532 MPa and 338 MPa, respectively, and the elongation increases to 13%.

Amorphous and nanocrystalline Fe-Ni-Zr-B ribbons as sensing elements in magnetic field sensors

Energy Technology Data Exchange (ETDEWEB)

Vertesy, G. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, H-1525 Budapest, P.O.B. 49 (Hungary)]. E-mail: vertesyg@mfa.kfki.hu; Idzikowski, B. [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, PL 60-179 Poznan (Poland)

2006-04-15

Fe{sub 81-x}Ni{sub x}Zr{sub 7}B{sub 12} (x=20, 30, 40) melt-spun alloys were investigated as potential new material applied as a sensing element of a fluxgate-type high-sensitivity magnetic field sensor. The sensitivity of the magnetometer was increased by about 60% by using the amorphous or nanocrystalline Fe{sub 41}Ni{sub 40}Zr{sub 7}B{sub 12} alloy, compared with a standard reference sensing material. Application of this material can also extend the temperature range of the operation of the device.

Effects of air melting on Fe/0.3/3Cr/0.5Mo/2Mn and Fe/0.3C/3Cr/0.5Mo/2Ni structural alloy steels

International Nuclear Information System (INIS)

Steinberg, B.

1979-06-01

Changing production methods of a steel from vacuum melting to air melting can cause an increase in secondary particles, such as oxides and nitrides, which may have detrimental effects on the mechanical properties and microstructure of the alloy. In the present study a base alloy of Fe/0.3C/3Cr/0.5Mo with either 2Mn or 2Ni added was produced by air melting and its mechanical properties and microstructure were compared to an identical vacuum melted steel. Significant differences in mechanical behavior, morphology, and volume fraction of undissolved inclusions have been observed as a function of composition following air melting. For the alloy containing manganese, all properties remained very close to vacuum melted values but the 2Ni alloy displayed a marked loss in Charpy impact toughness and plane strain fracture toughness. This loss is attributed to an increase in volume fraction of secondary particles in the nickel alloy, as opposed to both the Mn alloy and vacuum melted alloys, as well as to substaintially increased incidence of linear coalescence of voids. Microstructural features are discussed

Laser alloyed Al-Ni-Fe coatings

CSIR Research Space (South Africa)

Pityana, SL

2008-10-01

Full Text Available The aim of this work was to produce crack-free thin surface layers consisting of binary (Al-Ni, Al-Fe) and ternary (Al-Ni-Fe) intermetallic phases by means of a high power laser beam. The laser surface alloying was carried out by melting Fe and Ni...

Impact of beryllium additions on thermal and mechanical properties of conventionally solidified and melt-spun Al–4.5 wt.%Mn–x wt.%Be (x = 0, 1, 3, 5) alloys

International Nuclear Information System (INIS)

Öz, Turan; Karaköse, Ercan; Keskin, Mustafa

2013-01-01

Highlights: • Thermal and mechanical properties of Al–Mn–Be alloys were investigated. • IQC Al–Mn–Be alloys were synthesized by the CS and MS techniques. • The volume fraction of IQC increases continuously with Be content. • The melting points of the QC i-phase were determined between 652 °C and 675 °C. • The maximum H V and σ values were found to be 124 kg/mm 2 and 458 MPa with the addition of 5% Be. - Abstract: The influence of beryllium (Be) addition on the quasicrystal-forming ability, thermal and mechanical properties of Al–4.5 wt.%Mn–x wt.%Be (x = 0, 1, 3, 5) alloys was investigated in this study. Quasicrystalline Al–Mn–Be alloys were synthesized by the conventionally casting and melt spinning techniques. The microstructures of the samples were characterized by scanning electron microscopy (SEM) and the phase composition was identified by X-ray diffractometry (XRD). The phase transition during the solidification process was studied by differential scanning calorimetry (DSC) and differential thermal analysis (DTA) under an Ar atmosphere. The mechanical properties of the conventionally solidified (CS) and melt-spun (MS) samples were measured by a Vickers micro-hardness indenter and tensile-strength tests. The Al–4.5 wt.%Mn alloy has a hexagonal structure and minor dendritic icosahedral quasicrystalline phase (IQC) precipitates surrounded by an α-Al matrix. Addition of Be into the Al–4.5 wt.%Mn alloy generates intermetallic Be 4 AlMn and IQC phases with the extinction of the hexagonal phase, and the fraction of IQC increases continuously with the increase in Be content. A considerable improvement in microhardness and tensile strength values was observed due to the addition of Be in different percentages into the composition

Composition dependency of the glass forming ability (GFA) in Mg-Ni-Si system by mechanical alloying

International Nuclear Information System (INIS)

Xie Haowen; Lin Jianguo; Li Yuncang; Hodgson, Peter D.; Wen Cuie

2007-01-01

The pure elemental powder mixtures with the compositions of Mg 65 Ni x Si 35-x (x = 10, 20, 25, 33 at.%) were subject to high-energy ball mill, and the structures of the mixtures at different intervals of milling were characterised by X-ray diffraction (XRD). The compositional dependency of the glass forming ability (GFA) in Mg-Ni-Si system was evaluated based on the experimental results and the theoretical calculation. The compositional dependency of GFA in Mg-Ni-Si system can be understood well by comparing the enthalpies of the crystalline and amorphous phases based on the Miedema's theory for the formation enthalpy of alloys. Increasing the Ni/Mg ratio and/or decreasing Si content can improve the amorphous formability. The calculation results might be of great help in optimising the composition with high GFA in Mg-Ni-Si system

Mechanical and shape memory properties of porous Ni50.1Ti49.9 alloys manufactured by selective laser melting.

Science.gov (United States)

Taheri Andani, Mohsen; Saedi, Soheil; Turabi, Ali Sadi; Karamooz, M R; Haberland, Christoph; Karaca, Haluk Ersin; Elahinia, Mohammad

2017-04-01

Near equiatomic NiTi shape memory alloys were fabricated in dense and designed porous forms by Selective Laser Melting (SLM) and their mechanical and shape memory properties were systematically characterized. Particularly, the effects of pore morphology on their mechanical responses were investigated. Dense and porous NiTi alloys exhibited good shape memory effect with a recoverable strain of about 5% and functional stability after eight cycles of compression. The stiffness and residual plastic strain of porous NiTi were found to depend highly on the pore shape and the level of porosity. Since porous NiTi structures have lower elastic modulus and density than dense NiTi with still good shape memory properties, they are promising materials for lightweight structures, energy absorbers, and biomedical implants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solubility of hydrogen in LaNi{sub 5}-, LaCo{sub 5}- und LaNi{sub 5-x}Co{sub x}-alloys; Die Wasserstoff-Loeslichkeit in LaNi{sub 5}-, LaCo{sub 5}- und LaNi{sub 5-x}Co{sub x}-Legierungen

Energy Technology Data Exchange (ETDEWEB)

Schlotfeld, K.

2004-07-01

Hydrogen absorption isotherms of the alloys LaNi{sub 5}, LaNi{sub 4}Co, LaNi{sub 3}Co{sub 2} and LaCo{sub 5} were measured with an electronic microbalance between 313 and 533 K and between 0.01 and 120 bar. The unit cells of the binary alloys LaNi{sub 5} and LaCo{sub 5} contain a large number of interstitial sites of various kinds, which have to be considered for the occupation with hydrogen. Initially, the larger sites, which require the lowest energy, are filled. At rising concentrations the smaller sites associated with higher energy are successively entered. However, even at the highest hydrogen pressures of 1000 bar applied so far, most interstitial sites remain empty, due to an empirical rule which is theoretically well understood, that the dissolved hydrogen atoms cannot approach each other closer than the minimal distance of 0.21 nm. These conditions lead to a maximal hydrogen/metal ratio of 1.5 at 1000 bar and of roughly 1.2 at 150 bar. A statistical description of the two binary alloys has already been presented by Brodowsky, Yasuda, and Itagaki, which includes the energy differences of hydrogen in the various classes of sites. For the interpretation of the miscibility gaps below a critical temperature the influence of the volume expansion of the dissolved hydrogen on the excess functions was taken into account, similarly the shift of the Fermi energy of the system. In the ternary alloys, there is the complication that the energy of the sites is not is not equal within each group but that the levels have a distribution according to the number of Ni or Co atoms, respectively, around a particular interstitial site. Although this splitting up of the energy levels could not be treated quantitatively, it was very evident in the juxtaposition of the absorption isotherms of the various alloys. The measurements have shown, that the plateau pressure, which is important for the practical application of these alloys, is lowered in steps in the transition from LaNi

Usage of ATND method to determination of mechanical properties of AlMg10 alloy with complex additive of SbNiCr

Directory of Open Access Journals (Sweden)

J. Pezda

2009-07-01

Full Text Available Aluminum alloys with magnesium are commonly used in foundry industry due to lower density and higher corrosion resistance, comparing with silumins. Complicated shapes of produced alloys, differences in wall thickness and operation under changing loads require performing quality control as early as in stage of their preparation (melting. To register crystallization processes and monitor a phenomena arisen in result of the crystallization, are implemented methods based on analysis of temperature change (ATD, DTA. In the paper is present an attempt of usage of the ATND method (Thermal-Voltage-Derivative Analysis to registration of crystallization process of the investigated alloy. Obtained results concern registration of the crystallization process, strength and fatigue tests of the material, and visual observation of morphology of alloy’s fracture after static tensile test. Performed regression analysis has enabled implementation of changeable values of characteristic points of the ATND method to estimation of mechanical properties of the AlMg10 alloy with SbNiCr additive.

Amorphous phase formation in intermetallic Mg2Ni alloy synthesized by ethanol wet milling

International Nuclear Information System (INIS)

Wang, H.-W.; Chyou, S.-D.; Wang, S.-H.; Yang, M.-W.; Hsu, C.-Y.; Tien, H.-C.; Huang, N.-N.

2009-01-01

The hydriding/dehydriding properties of an intermetallic Mg 2 Ni alloy synthesized by wet ball milling in ethanol have been investigated. The appearance of the particle surface after different milling methods is one obvious difference. The alloyed powders prepared by either dry milling or wet milling under ethanol were characterized for phase content by X-ray diffractometer (XRD). The results show that two broad diffuse peaks, which are an ionic-organic-Mg amorphous material, appear in addition to the nickel element peaks. This unexpected amorphous phase has the special hydrogen absorbing/desorbing features.

Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys.

Science.gov (United States)

Tong, L B; Zhang, Q X; Jiang, Z H; Zhang, J B; Meng, J; Cheng, L R; Zhang, H J

2016-09-01

Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electrochemical corrosion behavior of Ni-containing hypoeutectic Al-Si alloy

Directory of Open Access Journals (Sweden)

Abul Hossain

2015-12-01

Full Text Available Electrochemical corrosion characteristics of the thermally treated 2 wt % Ni-containing Al-6Si-0.5Mg alloy were studied in NaCl solutions. The corrosion behavior of thermally treated (T6 Al-6Si-0.5Mg (-2Ni alloys in 0.1 M NaCl solution was investigated by electrochemical potentiodynamic polarization technique consisting of linear polarization method using the fit of Tafel plot and electrochemical impedance spectroscopy (EIS techniques. Generally, linear polarization experiments revealed a decrease of the corrosion rate at thermal treated Al-6Si-0.5Mg-2Ni alloy. The EIS test results showed that there is no significant change in charge transfer resistance (Rct after addition of Ni to Al-6Si-0.5Mg alloy. The magnitude of the positive shift in the open circuit potential (OCP, corrosion potential (Ecorr and pitting corrosion potential (Epit increased with the addition of Ni to Al-6Si-0.5Mg alloy. The forms of corrosion in the studied Al-6Si-0.5Mg alloy (except Al-6Si-0.5Mg-2Ni alloy are pitting corrosion as obtained from the scanning electron microscopy (SEM study.

An AC impedance study of self-discharge mechanism of nickel-metal hydride (Ni-MH) battery using Mg{sub 2}Ni-type hydrogen storage alloy anode

Energy Technology Data Exchange (ETDEWEB)

Cui, N.; Luo, J.L. [University of Alberta, Edmonton, Alberta (Canada). Department of Chemical and Materials Engineering

2000-07-01

The self-discharge mechanism during storage in open-circuit states of a Ni-MH battery using a Mg{sub 2}Ni-type hydrogen storage alloy anode was investigated by electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD). The loss of discharge capacity for this battery can be ascribed to two causes: (i) desorption of hydrogen from the Mg{sub 1.95}Y{sub 0.05}Ni{sub 0.92}Al{sub 0.08} hydride anode; and (ii) anode surface degradation resulting from oxidation of the magnesium alloy in the electrolyte. At the higher open-circuit voltages (OCV), the former was mainly responsible for a high self-discharge rate, while the latter might dominate the loss of capacity at the lower OCV. XRD results confirmed that Mg(OH){sub 2} formed on the magnesium alloy anode after storage in an open-circuit condition for 20 days. (author)

Wear behavioral study of as cast and 7 hr homogenized Al25Mg2Si2Cu4Ni alloy at constant load

Science.gov (United States)

Harlapur, M. D.; Sondur, D. G.; Akkimardi, V. G.; Mallapur, D. G.

2018-04-01

In the current study, the wear behavior of as cast and 7 hr homogenized Al25Mg2Si2Cu4Ni alloy has been investigated. Microstructure, SEM and EDS results confirm the presence of different intermetallic and their effects on wear properties of Al25Mg2Si2Cu4Ni alloy in as cast as well as aged condition. Alloying main elements like Si, Cu, Mg and Ni partly dissolve in the primary α-Al matrix and to some amount present in the form of intermetallic phases. SEM structure of as cast alloy shows blocks of Mg2Si which is at random distributed in the aluminium matrix. Precipitates of Al2Cu in the form of Chinese script are also observed. Also `Q' phase (Al-Si-Cu-Mg) be distributed uniformly into the aluminium matrix. Few coarsened platelets of Ni are seen. In case of 7 hr homogenized samples blocks of Mg2Si get rounded at the corners, Platelets of Ni get fragmented and distributed uniformly in the aluminium matrix. Results show improved volumetric wear resistance and reduced coefficient of friction after homogenizing heat treatment.

Depth-Sensing Microindentation Studies of Melt Spun Al-12wt%Si-0.5wt%Sb Alloys

International Nuclear Information System (INIS)

Uzun, O.

2004-01-01

In this study, the indentation load-penetration depth curves of melt spun ribbons were measured under different peak load levels. The unloading segments of these curves were analyzed using widely adopted Oliver and Pharr method. It was found that both hardness and Youngs modulus exhibit significant peak load dependence. Empirical approaches were then proposed to determine the load independent hardness, H0, and modulus. The load independent hardness (1135.07 and 756.72 MPa) and modulus (13.4 and 7.2 GPa) values were then calculated for wheel and air side of the ribbon, respectively. The results showed that the reduced elastic modulus increases with increasing hardness

Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K

Science.gov (United States)

Manghnani, M. H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.

2008-04-01

We report NiK -edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90° with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth’s core.

Effect of TiC additions to the microstructure and magnetic properties of Nd9.5Fe84.5B6 melt-spun ribbons

International Nuclear Information System (INIS)

Kramer, M.J.; Li, C.P.; Dennis, K.W.; McCallum, R.W.; Sellers, C.H.; Branagan, D.J.; Lewis, L.H.; Wang, J.Y.

1998-01-01

Rapidly solidified samples of Nd 9.5 Fe 84.5 B 6 with and without 3 at.% TiC were prepared by melt spinning and melt extraction and then annealed in vacuum (3x10 -6 Torr) at temperatures from 600 to 750 degree C. For alloys melt spun under similar conditions, the overquenched state was achieved at wheel speeds >10 m/s for the TiC added alloy while >20 m/s was necessary without TiC. The overquenched samples contained a smaller fraction of α-Fe in smaller grains than the undercooled samples where Fe dendrites formed near the free surface during solidification. These Fe dendrites were not removed by annealing. In addition, large orientated 2-14-1 grains nucleated on the Fe dendrites. This combination is detrimental to the magnetic properties. The addition of TiC results in improved control of the microstructure over a larger fraction of the ribbon volume enhancing the magnetic properties. copyright 1998 American Institute of Physics

Crystal structure and magnetic properties of a nitrogenated melt-spun Sm[sub 2]Fe[sub 17] compound

Energy Technology Data Exchange (ETDEWEB)

Yang, Choong-Jin [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of); Lee, Woo-Young [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of); Choi, Seung-Duck [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of)

1994-05-15

Sm[sub 2]Fe[sub 17]N[sub 2.9] compound powders were prepared from parent alloys of Sm[sub 2]Fe[sub 17] which were made by both arc melting and rapid solidification processes. The cast Sm[sub 2]Fe[sub 17] contained mixed phases of SmFe[sub 3] and [alpha]-Fe, and correspondingly formed less Sm[sub 2]Fe[sub 17]N[sub x] with a rather large amount of residual [alpha]-Fe after nitrogenation. The melt-spun Sm[sub 2]Fe[sub 17] compound, however, was single phase and exhibited a negligible amount of residual [alpha]+Fe after nitrogenation. The residual amount of free iron was found to increase as a function of milling time and to impede the development of promising permanent magnetic properties. The melt-spun Sm[sub 2]Fe[sub 17]N[sub x] compound powders exhibited a coercivity value [sub i]H[sub c] of 5 kOe, which is double that of the as-cast Sm[sub 2]Fe[sub 17]N[sub x] powders and a high remanence B[sub r]=60 e.m.u. g[sup -1]. The average magnetic moment of Fe atoms in the crystal is estimated to be 2.29 [mu][sub B] and the Fe atom in the 6c site exhibits the highest magnetic moment of 2.65 [mu][sub B]. The expansion in the c axial direction of the nitrogenated crystal was found to be mainly due to extension of Sm(6c)-Fe(c) and Fe(18f)-Fe(18f) distances. ((orig.))

Investigation on the thermodynamic analysis, preparation and characterization of LaNi5 - hydrogen storage alloy by magnesiothermic reduction diffusion process

Directory of Open Access Journals (Sweden)

Giresan G.

2016-01-01

Full Text Available The present investigation focuses on the preparation of LaNi5 intermetallic compound by “Metallothermic reduction diffusion process”. Experiments were carried out using oxides and chlorides of La and Ni metal powders as the raw materials with granular Mg powder as the reductant. The thermal reduction process was carried out at 900 ºC for 9 hrs in Ar atmosphere. After the completion of reaction, the contents were purified by treating with dilute acetic acid followed by de-ionized water. Thermodynamic feasibility studies were carried out to determine the probabilistic nature of formation of the desired compound. Thermal analysis was carried out to find the dissociation and decomposition temperature of the reactants. The phase purity and the elemental composition of the alloy were assessed by XRD and EDX analyses. The morphological features of the prepared powders were examined by SEM. From this study, it has been concluded that LaNi5 alloy can be prepared with an appreciable purity by the Metallothermic reduction diffusion process.

Exchange bias behavior in Ni{sub 50.0}Mn{sub 35.5} In{sub 14.5} ribbons annealed at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Sanchez, T. [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Sato Turtelli, R.; Groessinger, R. [Institut fur Festkoerperphysik, Technische Universitaet Wien, Wiedner Hauptstr. 8-10, 1040 Vienna (Austria); Sanchez, M.L.; Santos, J.D.; Rosa, W.O.; Prida, V.M. [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Escoda, Ll.; Sunol, J.J. [Campus de Montilivi, Universidad de Girona, edifici PII, Lluis Santalo s/n. 17003 Girona (Spain); Koledov, V. [Kotelnikov Institute of Radio Engineering and Electronics, RAS, Moscow 125009 (Russian Federation); Hernando, B., E-mail: grande@uniovi.es [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

2012-10-15

Heusler alloy Ni{sub 50.0}Mn{sub 35.5}In{sub 14.5} ribbons were prepared by melt-spinning technique. Several short time annealings were carried out in order to enhance the exchange bias effect in this alloy ribbon. The magnetic transition temperature increases with the annealing, compared to the as-spun sample, however no significant differences in respective Curie temperatures were observed for austenite and martensite phases in such annealed samples. Exchange bias effect is observed at low temperatures for all samples and practically vanishes at 60 K for the as-spun sample, whereas for the annealed ribbons it vanishes at 100 K.

Grain refining effect of magnetic field on Mg2Ni0.8Mn0.2 hydrogen storage alloys during rapid quenching

International Nuclear Information System (INIS)

Jiang, Chenxi; Wang, Haiyan; Chen, Xiangrong; Tang, Yougen; Lu, Zhouguang; Wang, Yazhi; Liu, Zuming

2013-01-01

The effect of static magnetic field treatment for synthesis of Mg 2 Ni 0.8 Mn 0.2 alloys during rapid quenching was investigated in this paper. X-ray diffraction (XRD) and scanning electron microscope (SEM) results show that the transversal static magnetic field can effectively refine the grain size, producing nanocrystalline inside. This distinct phenomenon is probably attributed to the Lorentz force suppressing the crystallization of the hydrogen storage alloys and the thermoelectric effect. Mainly due to the grain refinement, the discharge capacity of Mg 2 Ni 0.8 Mn 0.2 alloy is raised from 79 to about 200 mA h g −1 . It is confirmed that Mg 2 Ni 0.8 Mn 0.2 alloy by magnetic field assisted approach possesses enhanced electrochemical kinetics and relatively high corrosion resistance against the alkaline solution, thus resulting in higher electrochemical properties

Modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy

International Nuclear Information System (INIS)

Wu Yuying; Liu Xiangfa; Jiang Binggang; Huang Chuanzhen

2009-01-01

Modification effect of Ni-38 wt.%Si on the Al-12 wt.%Si alloy has been studied by differential scanning calorimeter, torsional oscillation viscometer and liquid X-ray diffraction experiments. It is found that there is a modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy, i.e. primary Si can precipitate in the microstructure of Al-12 wt.%Si alloy when Ni and Si added in the form of Ni-38 wt.%Si, but not separately. Ni-38 wt.%Si alloy brings 'genetic materials' into the Al-Si melt, which makes the melt to form more ordering structure, promotes the primary Si precipitated. Moreover, the addition of Ni-38 wt.%Si, which decreases the solidification supercooling degree of Al-12 wt.%Si alloy, is identical to the effect of heterogeneous nuclei.

Modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy

Energy Technology Data Exchange (ETDEWEB)

Wu Yuying [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China)], E-mail: wyy532001@163.com; Liu Xiangfa [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602, Shandong (China); Jiang Binggang [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Ji' nan 250061 (China); Huang Chuanzhen [School of Mechanical Engineering, Shandong University, Jinan 250061 (China)

2009-05-27

Modification effect of Ni-38 wt.%Si on the Al-12 wt.%Si alloy has been studied by differential scanning calorimeter, torsional oscillation viscometer and liquid X-ray diffraction experiments. It is found that there is a modification effect of Ni-38 wt.%Si on Al-12 wt.%Si alloy, i.e. primary Si can precipitate in the microstructure of Al-12 wt.%Si alloy when Ni and Si added in the form of Ni-38 wt.%Si, but not separately. Ni-38 wt.%Si alloy brings 'genetic materials' into the Al-Si melt, which makes the melt to form more ordering structure, promotes the primary Si precipitated. Moreover, the addition of Ni-38 wt.%Si, which decreases the solidification supercooling degree of Al-12 wt.%Si alloy, is identical to the effect of heterogeneous nuclei.

Vacuum Arc Melting Processes for Biomedical Ni-Ti Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Tsai De-Chang

2015-01-01

Full Text Available This study primarily involved using a vacuum arc remelting (VAR process to prepare a nitinol shape-memory alloy with distinct ratios of alloy components (nitinol: 54.5 wt% to 57 wt%. An advantage of using the VAR process is the adoption of a water-cooled copper crucible, which effectively prevents crucible pollution and impurity infiltration. Optimising the melting production process enables control of the alloy component and facilitates a uniformly mixed compound during subsequent processing. This study involved purifying nickel and titanium and examining the characteristics of nitinol alloy after alloy melt, including its microstructure, mechanical properties, phase transition temperature, and chemical components.

Understanding the effect of compositions on electronegativity, atomic radius and thermal stability of Mg-Ni-Y amorphous alloy

Science.gov (United States)

Deshmukh, A. A.; Kuthe, S. A.; Palikundwar, U. A.

2018-05-01

In the present paper, the consequences of variation in compositions on the electronegativity (ΔX), atomic radius difference (δ) and the thermal stability (ΔTx) of Mg-Ni-Y bulk metallic glasses (BMGs) are evaluated. In order to understand the effect of variation in compositions on ΔX, δ and ΔTx, regression analysis is performed on the experimentally available data. A linear correlation between both δ and ΔX with regression coefficient 0.93 is observed. Further, compositional variation is performed with δ and then it is correlated to the ΔTx by deriving subsequent equations. It is observed that concentration of Mg, Ni and Y are directly proportional to the δ with regression coefficients 0.93, 0.93 and 0.50 respectively. The positive slope of Ni and Y stated that ΔTx will increase if it has more contribution from both Ni and Y. On the other hand negative slope stated that composition of Mg should be selected in such a way that it will have more stability with Ni and Y. The results obtained from mathematical calculations are also tested by regression analysis of ΔTx with the compositions of individual elements in the alloy. These results conclude that there is a strong dependence of ΔTx of the alloy on the compositions of the constituting elements in the alloy.

Magnetic properties of nanocrystallized Fe-Pt-B melt-spun ribbons

International Nuclear Information System (INIS)

Yamamoto, Tokujiro; Omori, Akihiro; Kimura, Hisamichi; Inoue, Akihisa

2007-01-01

L1 0 FePt nanoparticles have been prepared by etching grain boundaries of heat-treated melt-spun Fe-19Pt-25B (at.%) alloy ribbons. It is revealed that an L1 0 FePt nanocrystalline phase is directly formed from the Fe-Pt-B amorphous ribbons by long-time heat treatment at low temperatures in the vicinity of 723 K. With increasing heat treatment time, dimensions of the nanocrystallized FePt grains increase, accompanied by a change from soft ferromagnetic to hard ferromagnetic. The ribbon crystallized at 723 K for 1.8 ks consists of only an FePt L1 0 phase and its coercivity is as low as 0.381 kA/m. However, it increases to 372 kA/m with increasing grain size of precipitated L1 0 phase to about 30 nm by heat treatment for 86.4 ks, while the saturation magnetic flux density remains constant at about 0.4 T. Etching boundaries in heat-treated ribbons has been performed to obtain ferromagnetic L1 0 FePt nanoparticles and several particles were observed by means of transmission electron microscopy

Hydrogen storage in MgH2 - LaNi5 nanocomposites produced by cold rolling under inert atmosphere

International Nuclear Information System (INIS)

Marquez, J.J.; Silva, W.B.; Leiva, D.R.; Ishikawa, T.T.; Kiminami, C.S.; Botta, W.J.; Floriano, R.

2016-01-01

In this study, the effects of the addition of LaNi5 in magnesium hydride H-sorption/desorption behavior was addressed. MgH 2 - X mol.% LaNi 5 (X=0.67; 1.50 and 2.54) mixtures were processed by cold rolling (CR) inside a glove box under controlled atmosphere, with oxygen and moisture contents below 0.1 ppm. Structural characterization showed that during the H-absorption/desorption cycles, a mixture of phases consisting of MgH 2 , LaH 3 and Mg 2 NiH 4 is formed, which has an important role in the hydrogen storage kinetic properties. The mixture MgH 2 -1.50 mol.% LaNi 5 was able to absorb/desorb 4.0 wt.% H 2 in less than 15 min at 100 and 280 °C respectively. The DSC analysis showed that the LaNi 5 additive lowers the temperature at which the H-desorption starts in cold rolled MgH 2 by around 50 °C. (author)

Pressure effects on Al89La6Ni5 amorphous alloy crystallization

DEFF Research Database (Denmark)

Zhuang, Yanxin; Jiang, Jianzhong; Zhou, T. J.

2000-01-01

The pressure effect on the crystallization of the Al89La6Ni5 amorphous alloy has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crystallizes in two steps in the pressure range studied (0-4 GPa). The first p...

Influence of postdrawing temperature on mechanical properties of melt-spun isotactic polypropylene

NARCIS (Netherlands)

Schimanski, T.; Peijs, A.A.J.M.; Lemstra, P.J.; Loos, J.

2004-01-01

Mech. properties of melt-spun and postdrawn isotactic polypropylene (iPP) are studied to examine the dependence on the temp. in the postdrawing stage. In accordance with the literature, the Young's modulus is uniquely detd. by the applied draw ratio. However, we found that the overall mech. behavior

Effects of Alloying Elements on Room and High Temperature Tensile Properties of Al-Si Cu-Mg Base Alloys =

Science.gov (United States)

Alyaldin, Loay

result of the presence of both Mg and Cu. These alloy types display excellent strength values at both low and high temperatures. Additions of Zr, Ni, Mn and Sc would be expected to maintain the performance of these alloys at still higher temperatures. Six alloys were prepared using 0.2 wt% Ti grain-refined 354 alloy, comprising alloy R (354 + 0.25wt% Zr) considered as the base or reference alloy, and five others, viz., alloys S, T, U, V, and Z containing various amounts of Ni, Mn, Sc and Zr, added individually or in combination. For comparison purposes, another alloy L was prepared from 398 (Al-16%Si) alloy, reported to give excellent high temperature properties, to which the same levels of Zr and Sc additions were made, as in alloy Z. Tensile test bars were prepared from the different 354 alloys using an ASTM B-108 permanent mold. The test bars were solution heat treated using a one-step or a multi-step solution heat treatment, followed by quenching in warm water, and then artificial aging employing different aging treatments (T5, T6, T62 and T7). The one-step (or SHT 1) solution treatment consisted of 5 h 495 °C) and the multi-step (or SHT 2) solution treatment comprised 5 h 495°C + 2 h 515°C + 2 h 530°C. Thermal analysis of the various 354 alloy melts was carried out to determine the sequence of reactions and phases formed during solidification under close-to-equilibrium cooling conditions. The main reactions observed comprised formation of the alpha-Al dendritic network at 598°C followed by precipitation of the Al-Si eutectic and post-eutectic beta-Al5FeSi phase at 560°C; Mg2Si phase and transformation of the beta-phase into pi-Al8Mg 3FeSi6 phase at 540°C and 525°C; and lastly, precipitation of Al2Cu and Q-Al5Mg8Cu2Si 6 almost simultaneously at 498°C and 488°C. Larger sizes of AlFeNi and AlCuNi phase particles were observed in T alloy with its higher Ni content of 4 wt%, when compared to those seen in S alloy at 2% Ni content. Mn addition in Alloy U helps

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.

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.

Thermodynamic properties of liquid alloys systems Fe - Ni - O - Me - Si

Directory of Open Access Journals (Sweden)

Н.О. Шаркіна

2008-01-01

Full Text Available  In the isoperabelic calorimeter at 1870 are determined partial and integral enthalpies of mixture of liquid alloys of systems Fe – Ni – O - Me and Fe – Ni – O – Me – Si, where Me – IVb-, Vb-, VIb-metals. The basis of alloy was served invars with the contents of oxygen by 0,06 %. Established, that the melts of systems Fe – Ni – O – IVb- (Vb--metals are characterized by strong interparticle interplay. The components of the maiden portions IVb- (Vb--metals in Fe – Ni – O melts are accompanied by very large exothermal effects (from – 400 up to – 1000 kJ/mol, which one considerably surpass those in double melts Fe(Ni – Me. The subsequent portions IVb- (Vb--metals caused smaller allocation of a heat (in limits from – 100 up to – 30 kJ/mol, that is conditioned by a decrease of the contents of dissolved oxygen. The partial enthalpies of mixture of molybdenum and tungsten in melts Fe – Ni – O are close to those in a nickel, and for a chromium exceed them. Is rotined, that D` HSi in liquid alloys Fe – Ni – O – Mo (– 450 kJ/mol considerably surpass that are characteristic for a nickel (– 50 kJ/mol. It is explained by interplay of silicon with the stayed dissolved oxygen in initial melts of a system Fe – Ni – O – Mo.

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

A novel method for producing magnesium based hydrogen storage alloys

International Nuclear Information System (INIS)

Walton, A.; Matthews, J.; Barlow, R.; Almamouri, M.M.; Speight, J.D.; Harris, I.R.

2003-01-01

Conventional melt casting techniques for producing Mg 2 Ni often result in no stoichiometric compositions due to the excess Mg which is added to the melt in order to counterbalance sublimation during processing. In this work a vapour phase process known as Low Pressure Pack Sublimation (LPPS) has been used to coat Ni substrates with Mg at 460-600 o C producing layers of single phase Mg 2 Ni. Ni substrates coated to date include powder, foils and wire. Using Ni-Fe substrates it has also been demonstrated that Fe can be distributed through the Mg 2 Ni alloy layer which could have a beneficial effect on the hydrogen storage characteristics. The alloy layers formed have been characterised by XRD and SEM equipped with EDX analysis. Hydrogen storage properties have been evaluated using an Intelligent Gravimetric Analyser (IGA). LPPS avoids most of the sintering of powder particles during processing which is observed in other vapour phase techniques while producing a stoichiometric composition of Mg 2 Ni. It is also a simple, low cost technique for producing these alloys. (author)

Microstructure analysis of magnesium alloy melted by laser irradiation

International Nuclear Information System (INIS)

Liu, S.Y.; Hu, J.D.; Yang, Y.; Guo, Z.X.; Wang, H.Y.

2005-01-01

The effects of laser surface melting (LSM) on microstructure of magnesium alloy containing Al8.57%, Zn 0.68%, Mn0.15%, Ce0.52% were investigated. In the present work, a pulsed Nd:YAG laser was used to melt and rapidly solidify the surface of the magnesium alloy with the objective of changing microstructure and improving the corrosion resistance. The results indicate that laser-melted layer contains the finer dendrites and behaviors good resistance corrosion compared with the untreated layer. Furthermore, the absorption coefficient of the magnesium alloy has been estimated according to the numeral simulation of the thermal conditions. The formation process of fine microstructure in melted layers was investigated based on the experimental observation and the theoretical analysis. Some simulation results such as the re-solidification velocities are obtained. The phase constitutions of the melted layers determined by X-ray diffraction were β-Mg 17 Al 12 and α-Mg as well as some phases unidentified

Analysis of hydrogen distribution on Mg-Ni alloy surface by scanning electron-stimulated desorption ion microscope (SESDIM)

International Nuclear Information System (INIS)

Yamaga, Atsushi; Hibino, Kiyohide; Suzuki, Masanori; Yamada, Masaaki; Tanaka, Kazuhide; Ueda, Kazuyuki

2008-01-01

Hydrogen distribution and behavior on a Mg-Ni alloy surface are studied by using a time-of-flight electron-stimulated desorption (TOF-ESD) microscopy and a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). The desorbed hydrogen ions are energy-discriminated and distinguished into two characters in the adsorbed states, which belong to Mg 2 Ni grains and the other to oxygen-contaminated Mg phase at the grain boundaries. Adsorbed hydrogen is found to be stable up to 150 deg. C, but becomes thermally unstable around at 200 deg. C

Microstructure formation in partially melted zone during gas tungsten arc welding of AZ91 Mg cast alloy

International Nuclear Information System (INIS)

Zhu Tianping; Chen, Zhan W.; Gao Wei

2008-01-01

During gas tungsten arc (GTA) welding of AZ91 Mg cast alloy, constitutional liquid forms locally in the original interdendritic regions in the partially melted zone (PMZ). The PMZ re-solidification behaviour has not been well understood. In this study, the gradual change of the re-solidification microstructure within PMZ from base metal side to weld metal side was characterised. High cooling rate experiments using Gleeble thermal simulator were also conducted to understand the morphological change of the α-Mg/β-Mg 17 Al 12 phase interface formed during re-solidification after partial melting. It was found that the original partially divorced eutectic structure has become a more regular eutectic phase in most of the PMZ, although close to the fusion boundary the re-solidified eutectic is again a divorced one. Proceeding the eutectic re-solidification, if the degree of partial melting is sufficiently high, α-Mg re-solidified with a cellular growth, resulting in a serrated interface between α-Mg and α-Mg/β-Mg 17 Al 12 in the weld sample and between α-Mg and β-Mg 17 Al 12 (fully divorced eutectic) in Gleeble samples. The morphological changes affected by the peak temperature and cooling rate are also explained

Identification of a new pseudo-binary hydroxide during calendar corrosion of (La, Mg)2Ni7-type hydrogen storage alloys for Nickel-Metal Hydride batteries

Science.gov (United States)

Monnier, J.; Chen, H.; Joiret, S.; Bourgon, J.; Latroche, M.

2014-11-01

To improve the performances of Nickel-Metal Hydride batteries, an important step is the understanding of the corrosion processes that take place in the electrode material. In particular, the present study focuses for the first time on the model (La, Mg)2Ni7 system. The calendar corrosion in 8.7 M KOH medium was investigated from 6 h to 16 weeks immersion. By a unique combination of structural and elemental characterisations, the corrosion products are evidenced in those systems. In particular, we demonstrate that Ni and Mg combine in a pseudo-binary hydroxide Mg1-xNix(OH)2 whereas La corrodes into nanoporous La(OH)3 needles with inner hollow nanochannels.

Laser melting treatment of Ni-P surface alloys on mild steel. Influence of initial coating thickness and laser scanning rate

Directory of Open Access Journals (Sweden)

García-Alonso, M. C.

1997-08-01

Full Text Available Different thickness Ni-P coatings deposited on mild steel are submitted to laser surface melting at different scanning rates. The microstructure of the alloys is characterized by optical and scanning electron microscopy and microprobe analysis. It is shown that both the initial coating thickness and the laser scanning rate have an influence on the shape, extent and size of the different structures resulting from the solidification process. Thus, when the laser scanning rate increases a progressive refinement of the structure takes place that could even totally block the dendritic growth produced during solidification for a high initial coating thickness.

Recubrimientos de Ni-P, con distinto espesor, depositados sobre un acero microaleado fueron tratados con láser a diferentes velocidades de barrido. La microestructura, tanto del recubrimiento como del acero base, ha sido caracterizada por microscopía óptica y electrónica y por microanálisis. En el proceso de solidificación se han obtenido distintas estructuras que varían en cuanto a la forma, extensión y tamaño dependiendo del espesor inicial de recubrimiento y de la velocidad de barrido del haz láser. A medida que la velocidad del haz aumenta, se produce un refinamiento progresivo de la microestructura dendrítica y, en casos extremos de alto espesor de recubrimiento y velocidades grandes, este crecimiento dendrítico se bloquea.

Comparing the dynamic and thermodynamic behaviors of Al{sub 86}Ni{sub 9}-La{sub 5}/(La{sub 0.5}Ce{sub 0.5}){sub 5} amorphous alloys

Energy Technology Data Exchange (ETDEWEB)

Li, G.H. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Wang, W.M. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China)], E-mail: weiminw@sdu.edu.cn; Bian, X.F.; Zhang, J.T.; Li, R.; Wang, L. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China)

2009-06-10

The dynamic viscosities and thermodynamic dilatometric behaviors of Al{sub 86}Ni{sub 9}La{sub 5} and Al{sub 86}Ni{sub 9}(La{sub 0.5}Ce{sub 0.5}){sub 5} amorphous alloys were investigated using viscometer, differential scanning calorimetry (DSC) and conventional dilatometer. Comparing with Al{sub 86}Ni{sub 9}La{sub 5} alloy, Al{sub 86}Ni{sub 9}(La{sub 0.5}Ce{sub 0.5}){sub 5} alloy exhibits a larger viscosity and a larger average thermal expansion coefficient in the linear expansion zone ({alpha}{sub exp}). The viscosity and thermal expansion data suggest that the partial substitution La by Ce decreases the quantity of free volume in Al-Ni-La system by improving the continuous degree of atomic size, which leads to the improvement of glass forming ability.

Crystal growth velocity in deeply undercooled Ni-Si alloys

Science.gov (United States)

Lü, Y. J.

2012-02-01

The crystal growth velocity of Ni95Si5 and Ni90Si10 alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T L ≈ 1505 and 1387 K for Ni95Si5 and Ni90Si10 alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni-Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10 at.% Si, resulting in the remarkable decrease of growth velocity.

Fate of half-metallicity near interfaces: The case of NiMnSb/MgO and NiMnSi/MgO

KAUST Repository

Zhang, Ruijing

2014-08-27

The electronic and magnetic properties of the interfaces between the half-metallic Heusler alloys NiMnSb, NiMnSi, and MgO have been investigated using first-principles density-functional calculations with projector augmented wave potentials generated in the generalized gradient approximation. In the case of the NiMnSb/MgO (100) interface, the half-metallicity is lost, whereas the MnSb/MgO contact in the NiMnSb/MgO (100) interface maintains a substantial degree of spin polarization at the Fermi level (∼60%). Remarkably, the NiMnSi/MgO (111) interface shows 100% spin polarization at the Fermi level, despite considerable distortions at the interface, as well as rather short Si/O bonds after full structural optimization. This behavior markedly distinguishes NiMnSi/MgO (111) from the corresponding NiMnSb/CdS and NiMnSb/InP interfaces. © 2014 American Chemical Society.

Influence of heat treatment on the mechanical and electrical characteristics of Ni0.5Ti0.5 alloy prepared by electron-beam melting

International Nuclear Information System (INIS)

Ammar, A.H.; Al-Buhairi, M.; Farag, A.A.M.; Al-Wajeeh, N.M.M.

2013-01-01

Nickel titanium alloys (Ni 0.5 Ti 0.5 ) were successfully produced from elemental Ni/Ti powders by electron-beam melting method and then subjected to annealing and aging treatment. Microstructure of the alloys was examined by XRD and SEM. The mechanical properties of the alloyed surface were examined. The microhardness was studied as a function of annealing temperature and time. It was found that the microhardness decreases with increasing annealing temperature until 660 °C after which the microhardness increases. Electrical resistance measurements were carried out in order to study the transformation behavior. The electrical measurements point out the importance of temperature dependence of Ni 0.5 Ti 0.5 electrical resistance for the identification of particular transformation. The influence of aging on the development of electrical resistivity was also investigated

Shock Compression and Melting of an Fe-Ni-Si Alloy: Implications for the Temperature Profile of the Earth's Core and the Heat Flux Across the Core-Mantle Boundary

Science.gov (United States)

Zhang, Youjun; Sekine, Toshimori; Lin, Jung-Fu; He, Hongliang; Liu, Fusheng; Zhang, Mingjian; Sato, Tomoko; Zhu, Wenjun; Yu, Yin

2018-02-01

Understanding the melting behavior and the thermal equation of state of Fe-Ni alloyed with candidate light elements at conditions of the Earth's core is critical for our knowledge of the region's thermal structure and chemical composition and the heat flow across the liquid outer core into the lowermost mantle. Here we studied the shock equation of state and melting curve of an Fe-8 wt% Ni-10 wt% Si alloy up to 250 GPa by hypervelocity impacts with direct velocity and reliable temperature measurements. Our results show that the addition of 10 wt% Si to Fe-8 wt% Ni alloy slightly depresses the melting temperature of iron by 200-300 (±200) K at the core-mantle boundary ( 136 GPa) and by 600-800 (±500) K at the inner core-outer core boundary ( 330 GPa), respectively. Our results indicate that Si has a relatively mild effect on the melting temperature of iron compared with S and O. Our thermodynamic modeling shows that Fe-5 wt% Ni alloyed with 6 wt% Si and 2 wt% S (which has a density-velocity profile that matches the outer core's seismic profile well) exhibits an adiabatic profile with temperatures of 3900 K and 5300 K at the top and bottom of the outer core, respectively. If Si is a major light element in the core, a geotherm modeled for the outer core indicates a thermal gradient of 5.8-6.8 (±1.6) K/km in the D″ region and a high heat flow of 13-19 TW across the core-mantle boundary.

Effect of substitution of 1 at% Ni for Zn on the microstructure and mechanical properties of Mg{sub 94}Y{sub 4}Zn{sub 2} alloy

Energy Technology Data Exchange (ETDEWEB)

Liu, Huan, E-mail: liuhuanseu@hotmail.com [Jiangsu Key Lab of Advanced Metallic Materials, School of Material Science and Engineering, Southeast University, Nanjing 211189 (China); Xue, Feng, E-mail: xuefeng@seu.edu.cn [Jiangsu Key Lab of Advanced Metallic Materials, School of Material Science and Engineering, Southeast University, Nanjing 211189 (China); Bai, Jing; Zhou, Jian [Jiangsu Key Lab of Advanced Metallic Materials, School of Material Science and Engineering, Southeast University, Nanjing 211189 (China); Liu, Xiaodao [Nanjing Yunhai Special Metals Co., Ltd., Nanjing 211200 (China)

2013-11-15

The microstructure and mechanical properties of Mg{sub 94}Y{sub 4}Zn{sub 2} and Mg{sub 94}Y{sub 4}Zn{sub 1}Ni{sub 1} alloys have been systematically investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and an electronic universal testing machine. The as-cast WZ42 alloy is composed of α-Mg matrix, 18R LPSO (long period stacking ordered) phase and a small fraction of Mg{sub 24}(Y,Zn){sub 5} phases. With the replacement of 1 at% Ni atoms, the phase structures in WZN411 alloy remain unchanged, but their chemical compositions vary obviously. A great number of stacking faults exist in α-Mg grains of WZ42 alloy, while they are barely observed in WZN411 alloy. After annealing at 500 °C for 12 h, there are plenty of 14H LPSO lamellas formed in WZ42 alloy and many nano-scale α-Mg slices generated between 18R phases. In contrast, the 18R in WZN411 alloy is thermally stable, and both the formation of α-Mg slices and 14H lamellas are restricted for annealed WZN411 alloy. Tensile tests indicate that the as-extruded WZ42 alloy exhibits ultimate tensile strength of 390 MPa, tensile yield strength of 246 MPa and elongation of 2.8% at room temperature. With the replacement of 1 at% Ni, the UTS and TYS of WZN411 alloy increase by 20 MPa and the ductility improves as well. The improvement of comprehensive mechanical properties could be ascribed to the substitution of 1 at% Ni element, which could enhance the degree of solid-solution strengthening and stimulate the thermal stability of 18R phase during annealing and extrusion processes.

Structural characteristics and corrosion behavior of biodegradable Mg-Zn, Mg-Zn-Gd alloys.

Science.gov (United States)

Kubásek, J; Vojtěch, D

2013-07-01

In this research, binary Mg-Zn (up to 3 wt% Zn) and ternary Mg-Zn-Gd (up to 3 wt% Gd, 3 wt% Zn) alloys were prepared by induction melting in an argon atmosphere. The structures of these alloys were characterized using light and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and X-ray fluorescence. In addition, Brinell hardness measurements were taken to supplement these studies. Corrosion behavior was evaluated by immersion tests and potentiodynamic measurements in a physiological solution (9 g/l NaCl). Depending on the composition, structures of the as-cast alloys contained α-Mg dendrites, MgZn, Mg5Gd and Mg3Gd2Zn3 phases. Compared to pure Mg, zinc improved the corrosion resistance of binary Mg-Zn. Gadolinium also improved the corrosion resistance in the case of Mg-1Zn-3Gd alloy. The highest corrosion rate was observed for Mg-3Zn-3Gd alloy. Our results improve the understanding of the relationships between the structure and corrosion behavior of our studied alloy systems.

Production of Magnesium and Aluminum-Magnesium Alloys from Recycled Secondary Aluminum Scrap Melts

Science.gov (United States)

Gesing, Adam J.; Das, Subodh K.; Loutfy, Raouf O.

2016-02-01

An experimental proof of concept was demonstrated for a patent-pending and trademark-pending RE12™ process for extracting a desired amount of Mg from recycled scrap secondary Al melts. Mg was extracted by electrorefining, producing a Mg product suitable as a Mg alloying hardener additive to primary-grade Al alloys. This efficient electrorefining process operates at high current efficiency, high Mg recovery and low energy consumption. The Mg electrorefining product can meet all the impurity specifications with subsequent melt treatment for removing alkali contaminants. All technical results obtained in the RE12™ project indicate that the electrorefining process for extraction of Mg from Al melt is technically feasible. A techno-economic analysis indicates high potential profitability for applications in Al foundry alloys as well as beverage—can and automotive—sheet alloys. The combination of technical feasibility and potential market profitability completes a successful proof of concept. This economical, environmentally-friendly and chlorine-free RE12™ process could be disruptive and transformational for the Mg production industry by enabling the recycling of 30,000 tonnes of primary-quality Mg annually.

Moessbauer study of Mg-Ni(Fe) alloys processed as materials for solid state hydrogen storage

Energy Technology Data Exchange (ETDEWEB)

Palade, P.; Principi, G., E-mail: giovanni.principi@unipd.it; Sartori, S.; Maddalena, A. [Universita di Padova, Settore Materiali, DIM (Italy); Lo Russo, S. [Universita di Padova, Dipartimento di Fisica (Italy); Schinteie, G.; Kuncser, V.; Filoti, G. [National Institute for Materials Physics, Solid State Magnetism Department (Romania)

2006-02-15

Mg-Ni-Fe magnesium-rich intermetallic compounds were prepared following two distinct routes. A Mg{sub 88}Ni{sub 11}Fe{sub 1} sample (A) was prepared by melt spinning Mg-Ni-Fe pellets and then by high-energy ball milling for 6 h the obtained ribbons. A (MgH{sub 2}){sub 88}Ni{sub 11}Fe{sub 1} sample (B) was obtained by high-energy ball milling for 20 h a mixture of Ni, Fe and MgH{sub 2} powders in the due proportions. A SPEX8000 shaker mill with a 10:1 ball to powder ratio was used for milling in argon atmosphere. The samples were submitted to repeated hydrogen absorption/desorption cycles in a Sievert type gas-solid reaction controller at temperatures in the range 520 - 590 K and a maximum pressure of 2.5 MPa during absorption. The samples were analysed before and after the hydrogen absorption/desorption cycles by X-ray diffraction and Moessbauer spectroscopy. The results concerning the hydrogen storage properties of the studied compounds are discussed in connection with the micro-structural characteristics found by means of the used analytical techniques. The improved kinetics of hydrogen desorption for sample A, in comparison to sample B, has been ascribed to the different behaviour of iron atoms in the two cases, as proved by Moessbauer spectroscopy. In fact, iron results homogeneously distributed in sample A, partly at the Mg{sub 2}Ni grain boundaries, with catalytic effect on the gas-solid reaction; in sample B, instead, iron is dispersed inside the hydride powder as metallic iron or superparamagnetic iron.

Studies on Al-Cu-Li-Mg-Ag-Zr alloy processed through vacuum induction melting (VIM) technique

International Nuclear Information System (INIS)

Nayan, Niraj; Govind; Nair, K. Suseelan; Mittal, M.C.; Sudhakaran, K.N.

2007-01-01

A new technique of lithium addition has been adapted for the processing of Al-Cu-Li-Ag-Mg-Zr alloy, which gives more than 90% recovery of lithium throughout the billet. Processing studies on this alloy include casting, three step homogenization, to avoid incipient melting, and mechanical working particularly forging and rolling. The products in the form of sheets were subjected to various T6 (solution treatment + water quenching + aging) tempers. Mechanical properties were evaluated at room temperature and correlated with microstructure. Characterizations using optical microscope and post-fracture analysis have been carried out using Scanning electron microscope (SEM). Experimental investigation shows highest mechanical properties for the Al-1.3%Li alloy in T6 (500 deg. C/1 h + WQ + 190 deg. C/24 h) condition

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.

Magnetic studies of melt spun NdFeAl-C alloys

International Nuclear Information System (INIS)

Rodriguez Torres, C.E.; Cabrera, A.F.; Sanchez, F.H.; Billoni, O.V.; Urreta, S.E.; Fabietti, L.M.

2004-01-01

Alloys with compositions Nd 60-x C x Fe 30 Al 10 (x=0, 1, 5 and 10) were processed by melt spinning at a tangential speed of 5 m/s. The as-cast ribbons were characterized by X-ray diffraction, Moessbauer Effect spectroscopy and their room temperature hysteresis loops. The substitution of Nd by C is found to affect the phase selection, from mainly DHCP-Nd for x=0 to DHCP-Nd /FCC-Nd for the other ones. Moessbauer spectra of all the as-cast samples indicate that Fe is present in crystalline magnetic phases as well as in a paramagnetic one. The major crystalline phase was identified as a μ-type (or A1) metastable phase, which is reported to have a large anisotropy field and a relatively high saturation polarization. Interstitial C stabilizes the μ-type phase and improves its average hyperfine field. The magnetic measurements display an increase of coercivity and remanence with the C concentration

Surface Roughness of a 3D-Printed Ni-Cr Alloy Produced by Selective Laser Melting: Effect of Process Parameters.

Science.gov (United States)

Hong, Min-Ho; Son, Jun Sik; Kwon, Tae-Yub

2018-03-01

The selective laser melting (SLM) process parameters, which directly determine the melting behavior of the metallic powders, greatly affect the nanostructure and surface roughness of the resulting 3D object. This study investigated the effect of various laser process parameters (laser power, scan rate, and scan line spacing) on the surface roughness of a nickel-chromium (Ni-Cr) alloy that was three-dimensionally (3D) constructed using SLM. Single-line formation tests were used to determine the optimal laser power of 200 W and scan rate of 98.8 mm/s, which resulted in beads with an optimal profile. In the subsequent multi-layer formation tests, the 3D object with the smoothest surface (Ra = 1.3 μm) was fabricated at a scan line spacing of 60 μm (overlap ratio = 73%). Narrow scan line spacing (and thus large overlap ratios) was preferred over wide scan line spacing to reduce the surface roughness of the 3D body. The findings of this study suggest that the laser power, scan rate, and scan line spacing are the key factors that control the surface quality of Ni-Cr alloys produced by SLM.

Trace element control in binary Ni-25Cr and ternary Ni-30Co-30Cr master alloy castings

Energy Technology Data Exchange (ETDEWEB)

Detrois, Martin [National Energy Technology Lab. (NETL), Albany, OR (United States); Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); Jablonski, Paul D. [National Energy Technology Lab. (NETL), Albany, OR (United States);

2017-10-23

Electro-slag remelting (ESR) is used for control of unwanted elements in commercial alloys. This study focuses on master alloys of Ni-25Cr and Ni-30Co-30Cr, processed through a combination of vacuum induction melting (VIM) and electro-slag remelting (ESR). Minor additions were made to control tramp element levels and modify the melting characteristics. Nitrogen and sulfur levels below 10 ppm and oxygen levels below 100 ppm were obtained in the final products. The role of the alloy additions in lowering the tramp element content, the resulting residual inclusions and the melting characteristics were determined computationally and confirmed experimentally. Additions of titanium were beneficial to the control of oxygen levels during VIM and nitrogen levels during ESR. Aluminum additions helped to control oxygen levels during remelting, however, aluminum pickup occurred when excess titanium was present during ESR. The usefulness of these master alloys for use as experimental remelt stock will also be discussed.

Calculation of glass forming ranges in Al-Ni-RE (Ce, La, Y) ternary alloys and their sub-binaries based on Miedema's model

International Nuclear Information System (INIS)

Sun, S.P.; Yi, D.Q.; Liu, H.Q.; Zang, B.; Jiang, Y.

2010-01-01

Research highlights: → A method based on semi-empirical Miedema's and Toop's model for predicting glass forming range of ternary alloy system has been systematically described. → The method is superior to conventional models by considering the effect of the thermodynamic asymmetric component when dealing with a ternary alloy system. → The glass forming ranges of Al-Ni-RE (Al-Ni-Ce, Al-Ni-Y and Al-Ni-La) systems and their sub-binaries have been successfully calculated. → The present calculations using the method are in well agreement with experiments. → This model is especially useful for predicting the glass forming range of ternary alloy system because the calculations do not require experimental data. - Abstract: A method based on the semi-empirical Miedema's and Toop's model for calculating the glass forming range of a ternary alloy system was systematically described. The method is superior to conventional models by considering the effect of the thermodynamic asymmetric component when dealing with a ternary alloy system. Using this method, the glass forming ranges of Al-Ni-RE (Ce, La, Y) systems and their sub-binaries were successfully predicted. The mixing enthalpy and mismatch entropy were calculated, and their effects on the glass forming abilities of Al-Ni-RE (Ce, La, Y) systems were also discussed. The glass forming abilities of Al-Ni-Ce, Al-Ni-La and Al-Ni-Y are found to be close. The calculated glass forming ranges agree with experiments well. Meanwhile, the enthalpy change from amorphous phase to solid solution in the glass forming ranges was calculated, and the results suggest that those alloys close to the Ni-RE sub-binary system have higher glass forming abilities.

Thermophysical properties of a highly superheated and undercooled Ni-Si alloy melt

Science.gov (United States)

Wang, H. P.; Cao, C. D.; Wei, B.

2004-05-01

The surface tension of superheated and undercooled liquid Ni-5 wt % Si alloy was measured by an electromagnetic oscillating drop method over a wide temperature range from 1417 to 1994 K. The maximum undercooling of 206 K (0.13TL) was achieved. The surface tension of liquid Ni-5 wt % Si alloy is 1.697 N m-1 at the liquidus temperature 1623 K, and its temperature coefficient is -3.97×10-4 N m-1 K-1. On the basis of the experimental data of surface tension, the other thermophysical properties such as the viscosity, the solute diffusion coefficient, and the density of liquid Ni-5 wt % Si alloy were also derived.

Characterization of oxide layers on amorphous Mg-based alloys by Auger electron spectroscopy with sputter depth profiling

Energy Technology Data Exchange (ETDEWEB)

Baunack, S.; Wolff, U. [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung Dresden, Postfach 270016, 01171, Dresden (Germany); Subba Rao, R.V. [Indira Ghandi Centre for Atomic Research, 603 102, Kalpakkam, Tamil Nadu (India)

2003-04-01

Amorphous ribbons of Mg-Y-TM-[Ag](TM: Cu, Ni), prepared by melt spinning, were subjected to electrochemical investigations. Oxide layers formed anodically under potentiostatic control in different electrolytes were investigated by AES and sputter depth profiling. Problems and specific features of characterization of the composition of oxide layers and amorphous ternary or quaternary Mg-based alloys have been investigated. In the alloys the Mg(KL{sub 23}L{sub 23}) peak exhibits a different shape compared to that in the pure element. Analysis of the peak of elastically scattered electrons proved the absence of plasmon loss features, characteristic of pure Mg, in the alloy. A different loss feature emerges in Mg(KL{sub 23}L{sub 23}) and Cu(L{sub 23}VV). The system Mg-Y-TM-[Ag] suffers preferential sputtering. Depletion of Mg and enrichment of TM and Y are found. This is attributed mainly to the preferential sputtering of Mg. Thickness and composition of the formed oxide layer depend on the electrochemical treatment. After removing the oxide by sputtering the concentration of the underlying alloy was found to be affected by the treatment. (orig.)

Powder metallurgy Al–6Cr–2Fe–1Ti alloy prepared by melt atomisation and hot ultra-high pressure compaction

International Nuclear Information System (INIS)

Dám, Karel; Vojtěch, Dalibor; Průša, Filip

2013-01-01

Al--6Cr--2Fe--1Ti alloy was prepared by melt atomisation into rapidly solidified powder. The powder was compacted using uniaxial hot compression at an ultra-high pressure (6 GPa). The samples were pressed at 300, 400 and 500 °C. The structure, mechanical properties and thermal stability were examined and compared with those of the commercially available Al--12Si--1Cu--1Mg--1Ni casting alloy, which is considered thermally stable. It was shown that the hot compression at ultra-high pressure results in a compact and pore-free material with excellent mechanical properties. The elevated pressing temperatures were found to be effective at increasing the mechanical stability after applying the ultra-high pressure. The results of thermal stability testing revealed that the mechanical properties do not change significantly at high temperature, even after 100 h of annealing at 400 °C. In addition, the Al--6Cr--2Fe--1Ti alloy exhibited very good creep resistance. A comparison between the commercial Al--12Si--1Cu--1Mg--1Ni alloy and the powder metallurgy alloy shows that this alloy has significantly better mechanical properties and thermal stability.

Powder metallurgy Al-6Cr-2Fe-1Ti alloy prepared by melt atomisation and hot ultra-high pressure compaction

Energy Technology Data Exchange (ETDEWEB)

Dam, Karel, E-mail: Karel.Dam@vscht.cz [Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Vojtech, Dalibor; Prusa, Filip [Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technicka 5, 166 28 Prague 6 (Czech Republic)

2013-01-10

Al--6Cr--2Fe--1Ti alloy was prepared by melt atomisation into rapidly solidified powder. The powder was compacted using uniaxial hot compression at an ultra-high pressure (6 GPa). The samples were pressed at 300, 400 and 500 Degree-Sign C. The structure, mechanical properties and thermal stability were examined and compared with those of the commercially available Al--12Si--1Cu--1Mg--1Ni casting alloy, which is considered thermally stable. It was shown that the hot compression at ultra-high pressure results in a compact and pore-free material with excellent mechanical properties. The elevated pressing temperatures were found to be effective at increasing the mechanical stability after applying the ultra-high pressure. The results of thermal stability testing revealed that the mechanical properties do not change significantly at high temperature, even after 100 h of annealing at 400 Degree-Sign C. In addition, the Al--6Cr--2Fe--1Ti alloy exhibited very good creep resistance. A comparison between the commercial Al--12Si--1Cu--1Mg--1Ni alloy and the powder metallurgy alloy shows that this alloy has significantly better mechanical properties and thermal stability.

Electron Backscatter Diffraction Studies on the Formation of Superlattice Metal Hydride Alloys

Directory of Open Access Journals (Sweden)

Shuli Yan

2017-12-01

Full Text Available Microstructures of a series of La-Mg-Ni-based superlattice metal hydride alloys produced by a novel method of interaction of a LaNi5 alloy and Mg vapor were studied using a combination of X-ray energy dispersive spectroscopy and electron backscatter diffraction. The conversion rate of LaNi5 increased from 86.8% into 98.2%, and the A2B7 phase abundance increased from 42.5 to 45.8 wt % and reduced to 39.2 wt % with the increase in process time from four to 32 h. During the first stage of reaction, Mg formed discrete grains with the same orientation, which was closely related to the orientation of the host LaNi5 alloy. Mg then diffused through the ab-phase of LaNi5 and formed the AB2, AB3, and A2B7 phases. Diffusion of Mg stalled at the grain boundary of the host LaNi5 alloy. Good alignments in the c-axis between the newly formed superlattice phases and LaNi5 were observed. The density of high-angle grain boundary decreased with the increase in process time and was an indication of lattice cracking.

Indications of the formation of an oversaturated solid solution during hydrogenation of Mg-Ni based nanocomposite produced by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Guzman, D. [Departamento de Ingenieria en Metalurgia, Facultad de Ingenieria, Universidad de Atacama y Centro Regional de Investigacion y Desarrollo Sustentable de Atacama, CRIDESAT, Av. Copayapu 485, Copiapo (Chile); Ordonez, S. [Departamento de Ingenieria Metalurgica, Facultad de Ingenieria, Universidad de Santiago de Chile, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Fernandez, J.F.; Sanchez, C. [Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid (Spain); Serafini, D. [Departamento de Fisica, Facultad de Ciencias, Universidad de Santiago de Chile and Center for Interdisciplinary Research in Materials, CIMAT, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Rojas, P.A. [Escuela de Ingenieria Mecanica, Facultad de Ingenieria, Av. Los Carrera 01567, Quilpue, Pontificia Universidad Catolica de Valparaiso, PUCV (Chile); Aguilar, C. [Instituto de Materiales y Procesos Termomecanicos, Facultad de Ciencias de la Ingenieria, Universidad Austral de Chile, Av. General Lagos 2086, Valdivia (Chile)

2009-07-15

An oversaturated solid solution of H in a nanocomposite material formed mainly by nanocrystalline Mg{sub 2}Ni, some residual nanocrystalline Ni and an Mg rich amorphous phase has been found for the first time. The nanocomposite was produced by mechanical alloying starting from Mg and Ni elemental powders, using a SPEX 8000D mill. The hydriding characterization of the nanocomposite was carried out by solid-gas reaction method in a Sievert's type apparatus. The maximum hydrogen content reached in a period of 21 Ks without prior activation was 2.00 wt.% H under hydrogen pressure of 2 MPa at 363 K. The X-ray diffraction analysis showed the presence of an oversaturated solid solution between nanocrystalline Mg{sub 2}Ni and H without any sign of Mg{sub 2}NiH{sub 4} hydride formation. The dehydriding behaviour was studied by differential scanning calorimetry and thermogravimetry. The results showed the existence of two desorption peaks, the first one associated with the transformation of the oversaturated solid solution into Mg{sub 2}NiH{sub 4}, and the second one with the Mg{sub 2}NiH{sub 4} desorption. (author)

Thermodynamic and surface properties of liquid Co–Cr–Ni alloys

International Nuclear Information System (INIS)

Costa, C.; Delsante, S.; Borzone, G.; Zivkovic, D.; Novakovic, R.

2014-01-01

Highlights: • The liquid phases of Co–Cr, Co–Ni and Cr–Ni were modelled by the Quasi Chemical Approximation for regular solutions. • The excess Gibbs free energy of mixing of the liquid Co–Cr–Ni phase is estimated by the three thermodynamic models. • Prediction of structure can compensate the lack of structural data of Co–Cr, Co–Ni and Cr–Ni melts. • Thermodynamic modelling of the surface properties of Co–Cr–Ni melts. • Weak effects of short range ordering among nearest neighbours in Co–Cr, Co–Ni and Cr–Ni liquid alloys can be deduced. -- Abstract: Direct measurements of bulk and surface properties of liquid alloys at elevated temperatures are often technically difficult or even impossible, and therefore, theoretical models can be used to estimate missing property values. The energetics of mixing in liquid Co–Cr, Cr–Ni and Co–Ni systems has been analysed through the study of the concentration dependence of various thermodynamic, surface (surface tension and surface composition) and structural properties (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) by the first or the Quasi-Chemical Approximation (QCA) for regular solutions, developed by Bhatia and Singh, in the framework of statistical mechanical theory in conjunction with the Quasi-Lattice Theory (QLT). The results obtained for these binary systems have been extended to study the thermodynamics and surface properties of ternary Co–Cr–Ni liquid alloys

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...

Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material.

Science.gov (United States)

Gu, X N; Li, X L; Zhou, W R; Cheng, Y; Zheng, Y F

2010-06-01

Rapidly solidified (RS) Mg–3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s(-1), 30 m s(-1) and 45 m s(-1) with the as-cast Mg–3Ca alloy ingot as a raw material. The RS45 Mg–3Ca alloy ribbon showed a much more fine grain size feature (approximately 200–500 nm) in comparison to the coarse grain size (50–100 μm)of the original as-cast Mg–3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg–3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds(1.43 mm yr(-1) for RS15, 0.94 mm yr(-1) for RS30 and 0.36 mm yr(-1) for RS45). The RS Mg–3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg–3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg–3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells,whereas the as-cast Mg–3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg–3Ca alloy ribbons than that of the as-cast Mg–3Ca alloy ingot.

Electrochemical hydrogen-storage properties of La{sub 0.78}Mg{sub 0.22}Ni{sub 2.67}Mn{sub 0.11}Al{sub 0.11}Co{sub 0.52}-M1Ni{sub 3.5}Co{sub 0.6}Mn{sub 0.4}Al{sub 0.}-5 composites

Energy Technology Data Exchange (ETDEWEB)

Huang, Hongxia, E-mail: hhxhunan@126.com [Key Lab of New Processing Technology for Nonferrous Metals and Materials Ministry of Education, Guilin University of Technology, Guilin (China); Li, Guohui [Guangxi Scientific Experiment Center of Mining, Metallurgy and Environment, College of Chemistry and Bioengineering, Guilin University of Technology, Guilin (China); Zhuang, Shuxin [School of Material Science and engineering, Xiamen University of Technology, Xiamen (China)

2013-07-15

For improving the electrochemical properties of nonstoichiometric AB{sub 3} -type La{sub 0.7}8Mg{sub 0.22}Ni{sub 2.67}Mn{sub 0.11}Al{sub 0.11}Co{sub 0.52} alloy as negative electrode of Ni-MH battery, its related composites La{sub 0.78}Mg{sub 0.22}Ni{sub 2.67}Mn{sub 0.11}Al{sub 0.11}Co{sub 0.52}-x wt.% M1Ni{sub 3.5}Co{sub 0.6}Mn{sub 0.4}Al{sub 0.5} (x = 0, 10, 20, 30) were prepared. Analysis by X-ray diffractometry (XRD) revealed that the composites consist mainly of LaNi{sub 5} and La{sub 2}Ni{sub 7} phases. Despite the small decrease in the maximum discharge capacity, the cycle performance was significantly enhanced. Linear polarization (LP), anodic polarization (AP) and potential step discharge experiments revealed that the electrochemical kinetics increases first and then decreases with increasing x. (author)

Properties of cemented carbides alloyed by metal melt treatment

International Nuclear Information System (INIS)

Lisovsky, A.F.

2001-01-01

The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

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.

Improved Mg-based alloys for hydrogen storage

Energy Technology Data Exchange (ETDEWEB)

Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J. [Energy Conversion Devices, Inc., Troy, MI (United States)

1998-08-01

The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a sample having a higher plateau pressure.

Application of Al-2La-1B Grain Refiner to Al-10Si-0.3Mg Casting Alloy

Science.gov (United States)

Jing, Lijun; Pan, Ye; Lu, Tao; Li, Chenlin; Pi, Jinhong; Sheng, Ningyue

2018-05-01

This paper reports the application and microstructure refining effect of an Al-2La-1B grain refiner in Al-10Si-0.3Mg casting alloy. Compared with the traditional Al-5Ti-1B refiner, Al-2La-1B refiner shows better performances on the grain refinement of Al-10Si-0.3Mg alloy. Transmission electron microscopy analysis suggests that the crystallite structure features of LaB6 are beneficial to the heterogeneous nucleation of α-Al grains. Regarding the mechanical performances, tensile properties of Al-10Si-0.3Mg casting alloy are prominently improved, due to the refined microstructures.

Electrochemical hydrogen storage alloys and batteries fabricated from Mg containing base alloys

Science.gov (United States)

Ovshinsky, Stanford R.; Fetcenko, Michael A.

1996-01-01

An electrochemical hydrogen storage material comprising: (Base Alloy).sub.a M.sub.b where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca; b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a+b=100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.

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.

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.

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.

Vacuum Arc Melting Processes for Biomedical Ni-Ti Shape Memory Alloy

OpenAIRE

Tsai De-Chang; Chiang Chen-Hsueh

2015-01-01

This study primarily involved using a vacuum arc remelting (VAR) process to prepare a nitinol shape-memory alloy with distinct ratios of alloy components (nitinol: 54.5 wt% to 57 wt%). An advantage of using the VAR process is the adoption of a water-cooled copper crucible, which effectively prevents crucible pollution and impurity infiltration. Optimising the melting production process enables control of the alloy component and facilitates a uniformly mixed compound during subsequent processi...

Features of Crystallization of Rapidly Quenched Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 Alloys from Melt with High-Temperature Shape Memory Effect

Science.gov (United States)

Pushin, A. V.; Pushin, V. G.; Kuntsevich, T. E.; Kuranova, N. N.; Makarov, V. V.; Uksusnikov, A. N.; Kourov, N. I.

2017-12-01

A comparative study of the structure and the chemical and phase composition of Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 amorphous alloys obtained by fast-quenching of melt stream by spinning has been carried out by transmission and scanning electron microscopy and X-ray diffraction. The critical temperatures of their devitrification were determined by the data of temperatures measurements of electrical resistance. The features of the formation of ultrafine structure and the phase transformation at the vitrification depending on the regimes of heat treatment and chemical composition of alloy have been established.

Heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-Si alloys investigated by entrained droplet technique and DSC

International Nuclear Information System (INIS)

Li, J H; Schumacher, P; Albu, M; Hofer, F; Ludwig, T H; Arnberg, L

2016-01-01

Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed. This can be attributed to the formation of phosphide compounds having a lower free energy and hence may preferentially form compared to AlP. Only a trace P addition was found to have a profound effect on the nucleation process. The nucleation kinetics is discussed on the basis of the classical nucleation theory and the free growth model, respectively. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur within the droplets, which strongly indicates that the nucleation of Si on an AlP patch or AlP particle is a limiting step for free growth. The maximum nucleation site density within one droplet is directly related to the size distribution of AlP particles or AlP patches for Si nucleation, but is independent of the cooling rates. Although the nucleation conditions were optimized in entrained droplet experiments, the observed mechanisms are also valid at moderate cooling conditions, such as in shape casting. (paper)

Mechanical behavior of Ti-Ta-based surface alloy fabricated on TiNi SMA by pulsed electron-beam melting of film/substrate system

Science.gov (United States)

Meisner, S. N.; Yakovlev, E. V.; Semin, V. O.; Meisner, L. L.; Rotshtein, V. P.; Neiman, A. A.; D'yachenko, F.

2018-04-01

The physical-mechanical properties of the Ti-Ta based surface alloy with thickness up to ∼2 μm fabricated through the multiple (up to 20 cycles) alternation of magnetron deposition of Ti70Ta30 (at.%) thin (50 nm) films and their liquid-phase mixing with the NiTi substrate by microsecond low-energy, high current pulsed electron beam (LEHCPEB: ≤15 keV, ∼2 J/cm2) are presented. Two types of NiTi substrates (differing in the methods of melting alloys) were pretreated with LEHCPEB to improve the adhesion of thin-film coating and to protect it from local delimitation because of the surface cratering under pulsed melting. The methods used in the research include nanoindentation, transmission electron microscopy, and depth profile analysis of nanohardness, Vickers hardness, elastic modulus, depth recovery ratio, and plasticity characteristic as a function of indentation depth. For comparison, similar measurements were carried out with NiTi substrates in the initial state and after LEHCPEB pretreatment, as well as on "Ti70Ta30(1 μm) coating/NiTi substrate" system. It was shown that the upper surface layer in both NiTi substrates is the same in properties after LEHCPEB pretreatment. Our data suggest that the type of multilayer surface structure correlates with its physical-mechanical properties. For NiTi with the Ti-Ta based surface alloy ∼1 μm thick, the highest elasticity falls on the upper submicrocrystalline layer measuring ∼0.2 μm and consisting of two Ti-Ta based phases: α‧‧ martensite (a = 0.475 nm, b = 0.323 nm, c = 0.464 nm) and β austenite (a = 0.327 nm). Beneath the upper layer there is an amorphous sublayer followed by underlayers with coarse (>20 nm) and fine (<20 nm) average grain sizes which provide a gradual transition of the mechanical parameters to the values of the NiTi substrate.

Effect of cooling rate on the phase transformation behavior and mechanical properties of Ni-rich NiTi shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Motemani, Y. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Nili-Ahmadabadi, M. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, 14395-731 Tehran (Iran, Islamic Republic of); Tan, M.J. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)], E-mail: mmjtan@ntu.edu.sg; Bornapour, M.; Rayagan, Sh. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, 14395-731 Tehran (Iran, Islamic Republic of)

2009-02-05

TiNi alloy is a well-known shape memory alloy and has been widely used for bio-medical, mechanical and electrical applications. In this study, a Ni-rich NiTi alloy was prepared by vacuum arc melting in a water-cooled copper crucible. Three samples of this alloy were heated to 1000 deg. C and cooled in three media: furnace, water, and dry-ice bath. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), hardness measurement and tensile test were carried out to investigate the effect of cooling rate on transformation temperature and mechanical properties. The results show that Ni{sub 3}Ti intermetallic compounds have a great influence on martensitic phase transformation temperature. These tests clearly showed the correlation between cooling rate and properties of the alloy.

On the Selective Laser Melting (SLM of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties

Directory of Open Access Journals (Sweden)

Francesco Trevisan

2017-01-01

Full Text Available The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM technique known as Selective Laser Melting (SLM. This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

On the Selective Laser Melting (SLM) of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties.

Science.gov (United States)

Trevisan, Francesco; Calignano, Flaviana; Lorusso, Massimo; Pakkanen, Jukka; Aversa, Alberta; Ambrosio, Elisa Paola; Lombardi, Mariangela; Fino, Paolo; Manfredi, Diego

2017-01-18

The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting (SLM). This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

Influence of heat treatment on the mechanical and electrical characteristics of Ni{sub 0.5}Ti{sub 0.5} alloy prepared by electron-beam melting

Energy Technology Data Exchange (ETDEWEB)

Ammar, A.H. [Thin Film Laboratory, Physics Department, Faculty of Education, Ain Shams University (Egypt); Physics Department, Faculty of Science and Arts, Al-Ola, Taibah University (Saudi Arabia); Al-Buhairi, M. [Physics Department, Faculty of Science, Taiz University (Yemen); Farag, A.A.M., E-mail: alaafaragg@yahoo.com [Thin Film Laboratory, Physics Department, Faculty of Education, Ain Shams University (Egypt); Al-Wajeeh, N.M.M. [Physics Department, Faculty of Science, Taiz University (Yemen)

2013-06-15

Nickel titanium alloys (Ni{sub 0.5}Ti{sub 0.5}) were successfully produced from elemental Ni/Ti powders by electron-beam melting method and then subjected to annealing and aging treatment. Microstructure of the alloys was examined by XRD and SEM. The mechanical properties of the alloyed surface were examined. The microhardness was studied as a function of annealing temperature and time. It was found that the microhardness decreases with increasing annealing temperature until 660 °C after which the microhardness increases. Electrical resistance measurements were carried out in order to study the transformation behavior. The electrical measurements point out the importance of temperature dependence of Ni{sub 0.5}Ti{sub 0.5} electrical resistance for the identification of particular transformation. The influence of aging on the development of electrical resistivity was also investigated.

Fe-15Ni-13Cr austenitic stainless steels for fission and fusion reactor applications. I. Effects of minor alloying elements on precipitate phases in melt products and implication in alloy fabrication

International Nuclear Information System (INIS)

Lee, E.H.; Mansur, L.K.

2000-01-01

In an effort to develop alloys for fission and fusion reactor applications, 28Fe-15Ni-13Cr base alloys were fabricated by adding various combinations of the minor alloying elements, Mo, Ti, C, Si, P, Nb, and B. The results showed that a significant fraction of undesirable residual oxygen was removed as oxides when Ti, C, and Si were added. Accordingly, the concentrations of the latter three essential alloying elements were reduced also. Among these elements, Ti was the strongest oxide former, but the largest oxygen removal (over 80%) was observed when carbon was added alone without Ti, since gaseous CO boiled off during melting. This paper recommends an alloy melting procedure to mitigate solute losses while reducing the undesirable residual oxygen. In this work, 14 different types of precipitate phases were identified. Compositions of precipitate phases and their crystallographic data are documented. Finally, stability of precipitate phases was examined in view of Gibbs free energy of formation

Effect of postdrawing temperature on structure, morphology and mechanical properties of melt-spun isotactic polypropylene tapes

NARCIS (Netherlands)

Loos, J.; Schimanski, T.

2005-01-01

Structure, morphology, and mechanical properties of melt-spun and postdrawn isotactic polypropylene (iPP) tapes are analyzed to study the effect of postdraw temperature applied. For affine drawing conditions, i.e., no effective relaxation of the molecules occurs during postdrawing, the Young's

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.

Study on the Ni Mo alloy nano crystals

International Nuclear Information System (INIS)

Goncalves, Lidice A. Pereira; Pontes, Luiz Renato de Araujo

1996-01-01

Materials with nanocrystalline microstructures are solids that contain such a high density of defects, with the spacings between neighboring defects approaching interatomic distances. As result, nanocrystalline solids exhibit physical and chemical properties different from those usually found in normal crystalline s or amorphous materials with the same chemical composition. In this work, the nanocrystalline Ni Mo alloy was prepared by melt-spinning method. The novelly synthesized nanocrystalline Ni Mo alloy was characterized by X-ray diffraction (XRD), differential scanning calorimetry (D S C) and microscopy. The estimated average crystalline size by the Debye-Scherrer formulas was 20 nm. (author)

Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

International Nuclear Information System (INIS)

Zhuang, Y. X.; Jiang, J. Z.; Lin, Z. G.; Mezouar, M.; Crichton, W.; Inoue, A.

2001-01-01

The phase evolution with the temperature and time in the process of crystallization of Al 89 La 6 Ni 5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi) 11 La 3 -like phase, were identified after the first crystallization reaction, revealing a eutectic reaction instead of a primary reaction suggested in the literature. Time-dependent nucleation in the amorphous alloy is detected and the experimental data can be fitted by both the Zeldovich's and Kashchiev's transient nucleation models with transient nucleation times of 220 and 120 min, respectively. Copyright 2001 American Institute of Physics

Pengaruh Penambahan Ni, Cu, dan Al dan Waktu Milling pada Mechanical Alloying Terhadap Sifat Absorpsi dan Desorpsi Mg sebagai Material Penyimpan Hidrogen

Directory of Open Access Journals (Sweden)

Febrian Budi Pratama

2012-09-01

Full Text Available Mg merupakan salah satu material yang digunakan sebagai material penyimpan hidrogen dengan membentuk MgH2. Sifat absorpsi dan desorpsi hidrogen dari suatu metal hidrida salah satunya tergantung  pada bahan, unsur penambah, dan metode pembuatannya. Pada penelitian kali ini Mg sebagai material penyimpan hidrogen dihasilkan melalui metode mechanical alloying dengan unsur penambah Ni, Cu, dan Al dan variasi waktu milling 10, 20, 30 jam. Selanjutnya sampel dilakukan pengujian SEM, XRD, DSC, dan Uji hidrogenisasi. Dari data uji diperoleh bahwa meningkatnya waktu milling menurunkan ukuran partikel sehingga meningkatkan wt% hidrogen terabsorb dan menurunkan temperatur onset desorpsi. Namun efek aglomerasi dan coldwelding yang berlebih pada proses mechanical alloying mengakibatkan ukuran partikel menjadi lebih besar. Unsur pemadu Al dan Cu berfungsi sebagai katalis, sedangkan Ni berfungsi sebagai pemadu yang ikut bereaksi dengan hidrogen. Mg10wt%Al dengan waktu milling 20 jam mempunyai nilai weight percent terbaik H2 yaitu 0.38% dalam temperatur hidrogenisasi 2500C, tekanan 3 atm, dan waktu tahan 1 jam. Sedangkan Mg10wt%Al dengan waktu milling 30 jam memiliki temperatur onset paling rendah yaitu 341.490C Kata Kunci— Absorpsi, Desorpsi, Material Penyimpan Hidrogen, Mechanical Alloying, Mg

Application of rapid solidification powder metallurgy to the fabrication of high-strength, high-ductility Mg-Al-Zn-Ca-La alloy through hot extrusion

Energy Technology Data Exchange (ETDEWEB)

Ayman, Elsayed, E-mail: ayman@jwri.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Junko, Umeda; Katsuyoshi, Kondoh [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2011-01-15

The microstructure and mechanical properties of hot extruded Mg-7Al-1Zn-1Ca powder alloys with an addition of 1.5% La or 3.3% La were investigated. Both rapidly solidified powders, produced via spinning water atomization process, and cast billets were extruded at 573, 623 and 673 K to optimize the processing conditions for obtaining better mechanical response. Powders were consolidated using both cold compaction and spark plasma sintering. The tensile properties of the extruded alloys were then evaluated and correlated to their microstructures. The results showed that the use of rapidly solidified Mg-7Al-1Zn-1Ca alloy powders with La additions could lead to effective grain refinement and super saturation of alloying elements, which in turn resulted in the improved mechanical response. The Mg-7Al-1Zn-1Ca-1.5La alloy extruded at 573 K attained ultimate tensile strength of 450 {+-} xx MPa and elongation of 17 {+-} xx%, superior to the Mg-7Al-1Zn-1Ca-3.3La alloy and other Mg alloys like Mg-Al-Mn-Ca. This may help extend the application of Mg alloys to higher load-carrying parts while maintaining the excellent advantage of light weight.

Comparative study of the microstructures and mechanical properties of direct laser fabricated and arc-melted Al{sub x}CoCrFeNi high entropy alloys

Energy Technology Data Exchange (ETDEWEB)

Joseph, Jithin, E-mail: jithin@deakin.edu.au [Institute for Frontier Materials, Deakin University, Waurn Ponds 3216 (Australia); Jarvis, Tom; Wu, Xinhua [Monash Centre for Additive Manufacturing, Monash University, Clayton 3168 (Australia); Stanford, Nicole; Hodgson, Peter; Fabijanic, Daniel Mark [Institute for Frontier Materials, Deakin University, Waurn Ponds 3216 (Australia)

2015-05-01

High entropy alloys (HEA) are a relatively new metal alloy system that have promising potential in high temperature applications. These multi-component alloys are typically produced by arc-melting, requiring several remelts to achieve chemical homogeneity. Direct laser fabrication (DLF) is a rapid prototyping technique, which produces complex components from alloy powder by selectively melting micron-sized powder in successive layers. However, studies of the fabrication of complex alloys from simple elemental powder blends are sparse. In this study, DLF was employed to fabricate bulk samples of three alloys based on the Al{sub x}CoCrFeNi HEA system, where x was 0.3, 0.6 and 0.85 M fraction of Al. This produced FCC, FCC/BCC and BCC crystal structures, respectively. Corresponding alloys were also produced by arc-melting, and all microstructures were characterised and compared longitudinal and transverse to the build/solidification direction by x-ray diffraction, glow discharge optical emission spectroscopy and scanning electron microscopy (EDX and EBSD). Strong similarities were observed between the single phase FCC and BCC alloys produced by both techniques, however the FCC/BCC structures differed significantly. This has been attributed to a difference in the solidification rate and thermal gradient in the melt pool between the two different techniques. Room temperature compression testing showed very similar mechanical behaviour and properties for the two different processing routes. DLF was concluded to be a successful technique to manufacture bulk HEA's.

XPS study on Mg0.9-xTi0.1PdxNi (x = 0.04, 0.06, 0.08, 0.1) hydrogen storage electrode alloys after charge-discharge cycles

International Nuclear Information System (INIS)

Tian Qifeng; Zhang Yao; Wu Yuanxin

2009-01-01

The passive film composition of Mg 0.9-x Ti 0.1 Pd x Ni (x = 0.04, 0.06, 0.08, 0.1) hydrogen storage alloys after 40 charge-discharge cycles has been investigated by means of X-ray photoelectron spectroscopy (XPS) in combination with Ar + sputtering technology. With the XPSPEAK software, high resolution spectra of alloy elements and oxygen were deconvolved into individual peaks. Composites formed by metal elements and their relative contents were also deduced. It was found that the composites originated from Mg and Ni were mainly in the form of their oxides and hydroxides, which existed at the top surface of alloys. With the increase of sputtering depth, the hydroxides of Mg and Ni gradually disappeared while corresponding oxides dominated their passive products. According to the analysis results of oxygen spectra, the elemental segregation of Mg and Ni was influenced by the substitution of Pd because the addition of Pd slightly enhanced the surface energy of the alloys and suppressed the formation of Mg hydroxide and oxide. Ti and Pd presented multiple-oxides from the surface to the inner alloys and metallic Pd appeared in the sub-layers of the alloys' surface. The possible mechanisms of the formation of passive products were suggested on the basis of the discussion in the paper.

Study on the surface reaction of LaNi{sub 5} alloy during discharge process in KOH solution

Energy Technology Data Exchange (ETDEWEB)

Tan Zuxian [Department of Chemistry, Wuhan University, Wuhan 430072 (China); Yang Yifu [Department of Chemistry, Wuhan University, Wuhan 430072 (China)]. E-mail: yang-y-f1@vip.sina.com; Jiang Fengshan [Department of Chemistry, Wuhan University, Wuhan 430072 (China); Shao Huixia [Department of Chemistry, Wuhan University, Wuhan 430072 (China)

2006-10-05

A new method for studying surface reaction of LaNi{sub 5} absorbing alloy in KOH solution (pH 12) was established. It is based on tip-substrate voltammetry of scanning electrochemical microscopy (SECM) where the tip faradic current is recorded while scanning the substrate potential. The Pt electrode is selected as tip electrode, and the Pt oxide formation-reduction is used as a pH-dependent reaction while the tip potential is held at a constant value. As substrate surface reactions proceed, the pH of solution can be changed, and then the tip faradic current is recorded. The mechanism of discharge process of LaNi{sub 5} alloy was analyzed by comparing the tip current (I {sub tip}) versus substrate potential (E {sub sub}) curve, which reflects the exchange of H{sup +} or OH{sup -} between the alloy surface and the solution, with the substrate current (I {sub sub}) versus substrate potential (E {sub sub}) curve, which reflects the exchange of electron on the LaNi{sub 5} alloy surface. The results showed that the OH{sup -} adsorption process is occurred before the electron transfer process during discharge process, and the adsorptive OH{sup -} helps the oxidation of adsorbed hydrogen atom on the alloy surface. A quantitative assessment for the maximum changes of pH during discharge process is also proposed, and the variation as large as 2.65 pH unit was detected.

Study on the surface reaction of LaNi{sub 5} alloy during discharge process in KOH solution

Energy Technology Data Exchange (ETDEWEB)

Tan, Zuxian; Yang, Yifu; Jiang, Fengshan; Shao, Huixia [Wuhan University, Wuhan (China). Department of Chemistry

2006-10-05

A new method for studying surface reaction of LaNi{sub 5} absorbing alloy in KOH solution (pH 12) was established. It is based on tip-substrate voltammetry of scanning electrochemical microscopy (SECM) where the tip faradic current is recorded while scanning the substrate potential. The Pt electrode is selected as tip electrode, and the Pt oxide formation-reduction is used as a pH-dependent reaction while the tip potential is held at a constant value. As substrate surface reactions proceed, the pH of solution can be changed, and then the tip faradic current is recorded. The mechanism of discharge process of LaNi{sub 5} alloy was analyzed by comparing the tip current (I{sub tip}) versus substrate potential (E{sub sub}) curve, which reflects the exchange of H{sup +} or OH{sup -} between the alloy surface and the solution, with the substrate current (I{sub sub}) versus substrate potential (E{sub sub}) curve, which reflects the exchange of electron on the LaNi{sub 5} alloy surface. The results showed that the OH{sup -} adsorption process is occurred before the electron transfer process during discharge process, and the adsorptive OH{sup -} helps the oxidation of adsorbed hydrogen atom on the alloy surface. A quantitative assessment for the maximum changes of pH during discharge process is also proposed, and the variation as large as 2.65 pH unit was detected. (author)

Mechanism of formation of corrosion layers on nickel and nickel-based alloys in melts containing oxyanions--a review

International Nuclear Information System (INIS)

Tzvetkoff, Tzvety; Gencheva, Petia

2003-01-01

A review of the corrosion of Ni and Ni-based alloys in melts containing oxyanions (nitrate, sulphate, hydroxide and carbonate) is presented, emphasising the mechanism of growth, the composition and structure of the passivating oxide films formed on the material in such conditions. First, the thermodynamical background involving solubility and point defect chemistry calculations for oxides formed on Ni, Cr and Ni-Cr alloys in molten salt media is briefly commented. The main passivation product on the Ni surface has been reported to be cubic NiO. In the transition stage, further oxidation of the compact NiO layer has been shown to take place in which Ni(III) ions and nickel cation vacancies are formed. Transport of nickel cation vacancies has been proposed to neutralise the charges of the excess oxide ions formed in the further oxidation reaction. Ex situ analysis studies reported in the literature indicated the possible formation of Ni 2 O 3 phase in the anodic layer. During the third stage of oxidation, a survey of the published data indicated that oxygen evolution from oxyanion melts is the predominant reaction taking place on the Ni/NiO electrode. This has been supposed to lead to a further accumulation of oxygen ions in the oxide lattice presumably as oxygen interstitials, and a NiO 2 phase formation has been also suggested. Literature data on the composition of the oxide film on industrial Ni-based alloys and superalloys in melts containing oxyanions are also presented and discussed. Special attention is paid to the effect of the composition of the alloy, the molten salt mixture and the gas atmosphere on the stability and protective ability of corrosion layers

Effect of stretching on the mechanical properties in melt-spun poly(butylene succinate)/microfibrillated cellulose (MFC) nanocomposites.

Science.gov (United States)

Zhou, Mi; Fan, Mao; Zhao, Yongsheng; Jin, Tianxiang; Fu, Qiang

2016-04-20

In order to prepare poly(butylene succinate)/microfibrillated cellulose composites with high performance, in this work, microfibrillated cellulose (MFC) was first treated by acetylchloride with ball-milling to improve its interfacial compatibility with poly(butylene succinate) (PBS). Then melt stretching processing was adopted to further improve the dispersion and orientation of MFC in as-spun PBS fiber. And the effect of MFC on the crystalline structure and mechanical properties were systematically investigated for the melt-spun fibers prepared with two different draw ratios. The dispersion, alignment of the MFC and interfacial crystalline structure in the composite fibers are significantly influenced by the stretching force during the melt spinning. The possible formation of nanohybrid shish kebab (NHSK) superstructure where aligned MFC as shish and PBS lamellae as kebab has been suggested via SEM and SAXS in the composite fibers prepared at the high draw ratio. Large improvement in tensile strength has been realized at the high draw ratio due to the enhanced orientation and dispersion of MFC as well as the formation of NHSK. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

DEFF Research Database (Denmark)

Zhuang, Yanxin; Jiang, Jianzhong; Lin, Z. G.

2001-01-01

The phase evolution with the temperature and time in the process of crystallization of Al89La6Ni5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi)(11...

Microstructure of bonding zones in laser-clad Ni-alloy-based composite coatings reinforced with various ceramic powders

International Nuclear Information System (INIS)

Pei, Y.T.; Ouyang, J.H.; Lei, T.C.

1996-01-01

Microstructure of the bonding zones (BZs) between laser-clad Ni-alloy-based composite coatings and steel substrates was studied by means of scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. Observations indicate that for pure Ni-alloy coating the laser parameters selected for good interface fusion have no effect on the microstructure of the BZ except for its thickness. However, the addition of ceramic particles (TiN, SiC, or ZrO 2 ) to the Ni alloy varies the compositional or constitutional undercooling of the melt near the solid/liquid interface and consequently leads to the observed changes of microstructure of the BZs. For TiN/Ni-alloy coating the morphology of γ-Ni solid solution in the BZ changes from dendritic to planar form with increasing scanning speed. A colony structure of eutectic is found in the BZ of SiC/Ni-alloy coating in which complete dissolution of SiC particles takes place during laser cladding. The immiscible melting of ZrO 2 and Ni-alloy powders induces the stratification of ZrO 2 /Ni-alloy coating which consists of a pure ZrO 2 layer fin the upper region and a BZ composed mainly of γ-Ni dendrites adjacent to the substrate. All the BZs studied in this investigation have good metallurgical characteristics between the coatings and the substrates

Thermodynamics of oxygen solutions in Fe-40% Ni-15% Cr melts containing Mn, Si, Ti, Al

International Nuclear Information System (INIS)

Dashevskij, V.Ya.; Makarova, N.N.; Grigorovich, K.V.; Kashin, V.I.; Polikarpova, N.V.

2000-01-01

Thermodynamic analysis and experimental studied are performed for oxygen solutions in Fe-40% Ni-15% Cr melts where Mn, Si, Ti, Al are used as reducing agents. It is revealed that in the alloys studied the affinity of reducing agents to oxygen essentially lower than in liquid iron, nickel and Fe-40% Ni alloy. This is explained by the fact that the oxygen activity in melts noticeably decreases due to a high chromium content whereas the activity of reducing elements increases in a rather less degree. The agreement between analytical and experimental results confirms the validity of the calculation technique [ru

Reduction of Oxidative Melt Loss of Aluminum and Its Alloys

Energy Technology Data Exchange (ETDEWEB)

Dr. Subodh K. Das; Shridas Ningileri

2006-03-17

This project led to an improved understanding of the mechanisms of dross formation. The microstructural evolution in industrial dross samples was determined. Results suggested that dross that forms in layers with structure and composition determined by the local magnesium concentration alone. This finding is supported by fundamental studies of molten metal surfaces. X-ray photoelectron spectroscopy data revealed that only magnesium segregates to the molten aluminum alloy surface and reacts to form a growing oxide layer. X-ray diffraction techniques that were using to investigate an oxidizing molten aluminum alloy surface confirmed for the first time that magnesium oxide is the initial crystalline phase that forms during metal oxidation. The analytical techniques developed in this project are now available to investigate other molten metal surfaces. Based on the improved understanding of dross initiation, formation and growth, technology was developed to minimize melt loss. The concept is based on covering the molten metal surface with a reusable physical barrier. Tests in a laboratory-scale reverberatory furnace confirmed the results of bench-scale tests. The main highlights of the work done include: A clear understanding of the kinetics of dross formation and the effect of different alloying elements on dross formation was obtained. It was determined that the dross evolves in similar ways regardless of the aluminum alloy being melted and the results showed that amorphous aluminum nitride forms first, followed by amorphous magnesium oxide and crystalline magnesium oxide in all alloys that contain magnesium. Evaluation of the molten aluminum alloy surface during melting and holding indicated that magnesium oxide is the first crystalline phase to form during oxidation of a clean aluminum alloy surface. Based on dross evaluation and melt tests it became clear that the major contributing factor to aluminum alloy dross was in the alloys with Mg content. Mg was

Influence of substitution of La by Ce on the glass forming ability and crystallization behavior of Al–Ni–La alloys

International Nuclear Information System (INIS)

Zhang, Z.; Xiong, X.Z.; Zhou, W.; Li, J.F.

2013-01-01

Highlights: •Wedge-shaped samples were suction cast with casting conditions controlled. •Partial substitution of La by Ce decreases the GFA of Al 85.5 Ni 9.5 La 5 . •Partial substitution of La by Ce increases the GFA of other Al–Ni–La alloys. •The GFA was analyzed from the thermodynamic and topological points of view. -- Abstract: Wedge-shaped samples of Al–Ni–(La–Ce) alloys were suction cast under an identical preparation condition, and their glass forming abilities (GFAs) and crystallization behaviors were compared. It was revealed that the partial substitution of La by Ce decreases the GFA of Al 85.5 Ni 9.5 La 5 alloy but increases the GFAs of Al 87.5 Ni 7.5 La 5 , Al 86.5 Ni 8.5 La 5 , Al 86 Ni 9 La 5 and Al 86 Ni 9.5 La 4.5 alloys. Meantime the crystallization behavior significantly changes. The optimal substitution content of La for glass formation depends on the composition of the base alloy. The lower the Ni content in the base alloy, the more the La content to be substituted. The GFA change with the substitution content is determined by the atomic packing efficiencies of the La (Ce)-centered clusters

The dry-heat loss effect of melt-spun phase change material fibres.

Science.gov (United States)

Tjønnås, Maria Suong; Færevik, Hilde; Sandsund, Mariann; Reinertsen, Randi E

2015-01-01

Phase change materials (PCM) have the ability to store latent heat when they change phases, a property that gives clothing that incorporates PCM its cooling effect. This study investigated the effect of dry-heat loss (cooling) of a novel melt-spun PCM fibre on the basis of the area covered, mass, the latent heat of fusion and melting temperature, compared to a known PCM clothing product. PCM fibres with melting temperatures of 28.4 and 32.0°C and PCM packs with melting temperatures of 28.0 and 32.0°C were studied. The results showed that the PCM fibres had a larger initial peak cooling effect than that of the PCM packs. The duration of the cooling effect of PCM fibres was primarily dependent on the PCM mass and the latent heat of fusion capacity, and secondly on the covered area and melting temperature of the PCM. This study investigates the cooling effect of PCM fibres on a thermal manikin. The PCM fibres had a high but short-lasting cooling effect. This study contributes to the knowledge of how the body's temperature regulation may be affected by the cooling properties of clothing that incorporates PCM.

Study on glass formation and crystallization of Zr54.5Cu20Al10Ni8Ti75 alloy

International Nuclear Information System (INIS)

Neogy, S.; Tewari, R.; Srivastava, D.; Dey, G.K.; Banerjee, S.; Vaibhaw, K.

2009-01-01

The microstructure of Zr 54.5 Cu 20 Al 10 Ni 8 Ti 75 alloy has been examined after solidification involving three different techniques viz., copper mould casting, suction casting and melt spinning. The bulk glass microstructure of the alloy obtained through copper mould casting was found to comprise of big cube Zr 2 Ni phase in a dendritic morphology and tetragonal Zr 2 Ni phase in a faulted morphology besides the amorphous phase. High-resolution electron microscopy (HREM) was carried out to examine the internal structure and interface structure of the phases. The dendritic phase was found to consist of primary and secondary dendrite arms with faceted as well rounded interfaces with the amorphous phase. Ledges were noticed at either of the interfaces with higher density at the rounded interfaces. The presence of the faulted phase was noticed in between dendritic arms. The faulted phase was found to consist of different domains corresponding to different orientations. A variety of interfaces could be noticed between these individual domains and also within a single domain itself. At least three different kinds of faulted region were identified to coexist in a single domain. The melt spun ribbon and bulk glass made through suction casting was found to be fully amorphous. The amorphous phase obtained from the three different techniques showed different degrees of medium range order as revealed by the fluctuation microscopy technique. Crystallization behavior of as solidified structures has been examined by comparing the crystallization kinetics and microstructure. Crystallization led to the transformation of the amorphous phase to nanocrystals in all the cases. The crystallization event was found to be singular in the case of copper mold cast bulk glass and multiple in the case of suction cast bulk glass and ribbon. The phase forming on crystallization was found to be the same faulted tetragonal Zr 2 Ni that was encountered during solidification. Multiple domains

Microstructural evidence of presence of beryllium in Ni-Cr alloys for dental prostheses

International Nuclear Information System (INIS)

Alkmin, L.B.; Nunes, C.A.; Santos, C.

2010-01-01

This study aimed to characterize the microstructure of commercial Ni-Cr alloys for dental prosthesis, with special focus on those containing Be. For this, the materials were characterized in terms of chemical composition, phases and melting point temperature. The following techniques were used: X-ray fluorescence, ICP-OES, scanning electron microscopy, electron probe microanalysis, X-ray diffraction and differential thermal analysis. The results clearly showed the presence of a typical eutectic, formed by the Ni ss and NiBe phases in those alloys containing Be, which can be considered a 'fingerprint' of the presence of this element in these alloys. (author)

Glass forming ability of Al–Ni–La alloys with Si addition

International Nuclear Information System (INIS)

Yi, J.J.; Xiong, X.Z.; Inoue, A.; Kong, L.T.; Li, J.F.

2015-01-01

(Al_8_5_._5Ni_9_._5La_5)_1_0_0_−_xSi_x, (Al_8_6Ni_9La_5)_1_0_0_−_xSi_x, (Al_8_6Ni_9_._5La_4_._5)_1_0_0_−_xSi_x, (Al_8_6Ni_1_0La_4)_1_0_0_−_xSi_x and (Al_8_6Ni_1_0_._5La_3_._5)_1_0_0_−_xSi_x alloys, where x = 0.0, 0.2, 0.5, 1.0, 1.5 and 2.0, were cast under the same suction casting conditions into a wedge-shaped copper mold for investigating the effect of Si addition on the glass-forming ability (GFA). The GFA of the Al–Ni–La base alloys, except for the optimal glass former (Al_8_5_._5Ni_9_._5La_5), is enhanced when a proper content of Si is added. The largest content of Si up to which GFA can be enhanced changes in the following order of the base alloys: Al_8_6Ni_9La_5, Al_8_6Ni_9_._5La_4_._5, Al_8_6Ni_1_0La_4 and Al_8_6Ni_1_0_._5La_3_._5. The enhancement of GFA due to Si addition becomes more significant as the La content decreases. This is presumably because more free Al atoms are present in the base alloy. - Highlights: • 0.2–2.0 at. % Si was added to each ternary base alloy. • Wedge-shaped samples were suction cast to obtain the glass-forming ability (GFA). • The GFA of the ternary non-optimal glass formers can be enhanced by Si addition. • The number of free-Al atoms dominates the best Si addition.

Effect of rare-earth elements and quenching wheel speed on the structure, mechanical and thermal properties of rapidly solidified AZ91 Mg melt-spun ribbons

Energy Technology Data Exchange (ETDEWEB)

Ekrami, A. [Iran University of Industries & Mines, Faculty of Engineering & High-Technology (Iran, Islamic Republic of); Shahri, F., E-mail: fshahri@irost.ir [Iranian Research Organization for Science & Technology, Department of Advanced Materials & Renewable Energy (Iran, Islamic Republic of); Mirak, A. [Iran University of Industries & Mines, Faculty of Engineering & High-Technology (Iran, Islamic Republic of)

2017-01-27

In this work, an attempt is made to study the effects of rare-earth elements as an additive (2 wt% of Ce base misch-metal) and various quenching wheel speeds (10–40 m/s) on the microstructure, thermal and mechanical properties of rapidly solidified AZ91 alloy prepared by single roller melt-spinning process. In this respect, all of the samples were studied using various techniques such as x-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC) and mechanical properties such as microhardness and tensile tests. The finding bore witness to proposed hypothesis in this study illustrating due to high affinity between Al and RE by adding 2 wt% rare-earth elements in the AZ91alloy, thermally stable Al{sub x}RE{sub y} intermetallic compounds are precipitated and the formation of β-Mg{sub 17}Al{sub 12} phases is reduced. DSC results revealed that by adding RE to AZ91 alloy, AlRE phases got stable up to 500 °C, while for the AZ91 sample, β-Mg{sub 17}Al{sub 12} phase was formed at temperature about 180 °C and then with increasing of temperature dissolved at 410 °C in the α-Mg matrix. Further it has been observed that the higher was the quenching wheel speed, the smaller was the grain size which in turn gives rise to a higher tensile properties (from 406 MPa for quenching wheel speed of 10 m/s to 510 MPa for 40 m/s) for the MM-added alloys. Tensile strength of 386 MPa was obtained for the AZ91 pure alloy which is prepared at wheel speed of 40 m/sec.

Influence of Mn incorporation for Ni on the magnetocaloric properties of rapidly solidified off-stoichiometric NiMnGa ribbons

Energy Technology Data Exchange (ETDEWEB)

Dey, Sushmita; Singh, Satnam; Roy, R.K.; Ghosh, M.; Mitra, A.; Panda, A.K., E-mail: akpanda@nmlindia.org

2016-01-01

The present investigation addresses the magnetocaloric behaviour in a series of Ni{sub 77−x}Mn{sub x}Ga{sub 23} (x=23, 24, 25, 27 and 29) rapidly solidified alloys prepared in the form of ribbons by melt spinning technique. The approach of the study is to identify the off-stoichiometric composition wherein room temperature magneto-structural transformation is achieved. The alloy chemistry was tailored through Mn incorporation for Ni such that the magnetic and structural transitions were at close proximity to achieve highest entropy value of ΔS equal to 8.51 J Kg{sup −1} K{sup −1} for #Mn{sub 24} ribbon measured at an applied field of 3 T. When such transitions are more staggered as in #Mn{sub 29} the entropy value of ribbon reduced to as low as 1.61 J Kg{sup −1} K{sup −1}. Near room temperature transformations in #Mn{sub 24} ribbon have been observed through calorimetric and thermomagnetic evaluation. Reverse martensitic transformation (martensite→autstenite) temperature indicates not only distinct change in the saturation flux density but also an inter-martensitic phase. Microstructural analysis of #Mn{sub 24} alloy ribbon revealed structural ordering with the existence of plate morphology evidenced for martensitic phase. - Highlights: • Magnetocaloric effect in a series of melt spun NiMnGa ribbon is addressed. • The alloy series revealed austenitic state as well as its presence with martensite. • The morphology of the ribbons has been shown and discussed through phase analysis. • Influence of magnetising field on entropy and relative cooling power is discussed. • Influence of intermartensitic state on magnetization plots have also been shown.

Influence of substitution of La by Ce on the glass forming ability and crystallization behavior of Al–Ni–La alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang, Z.; Xiong, X.Z.; Zhou, W.; Li, J.F., E-mail: jfli@sjtu.edu.cn

2013-11-05

Highlights: •Wedge-shaped samples were suction cast with casting conditions controlled. •Partial substitution of La by Ce decreases the GFA of Al{sub 85.5}Ni{sub 9.5}La{sub 5}. •Partial substitution of La by Ce increases the GFA of other Al–Ni–La alloys. •The GFA was analyzed from the thermodynamic and topological points of view. -- Abstract: Wedge-shaped samples of Al–Ni–(La–Ce) alloys were suction cast under an identical preparation condition, and their glass forming abilities (GFAs) and crystallization behaviors were compared. It was revealed that the partial substitution of La by Ce decreases the GFA of Al{sub 85.5}Ni{sub 9.5}La{sub 5} alloy but increases the GFAs of Al{sub 87.5}Ni{sub 7.5}La{sub 5}, Al{sub 86.5}Ni{sub 8.5}La{sub 5}, Al{sub 86}Ni{sub 9}La{sub 5} and Al{sub 86}Ni{sub 9.5}La{sub 4.5} alloys. Meantime the crystallization behavior significantly changes. The optimal substitution content of La for glass formation depends on the composition of the base alloy. The lower the Ni content in the base alloy, the more the La content to be substituted. The GFA change with the substitution content is determined by the atomic packing efficiencies of the La (Ce)-centered clusters.

Unusual morphology of the omega phase in a Zr-1.75 At. pct Ni alloy

International Nuclear Information System (INIS)

Srivastava, D.; Mukhopadhyay, P.; Ramadasan, E.; Banerjee, S.

1993-01-01

The observations reported in the present communication were made in the course of a microstructural investigation on dilute Zr-Ni alloys. The alloys were prepared from nuclear-grade sponge zirconium and high-purity nickel by nonconsumable arc melting. Repeated melting was carried out to enhance homogeneity. A master alloy was used in the preparation of very dilute alloys. The observations reported here clearly indicate that the formation of the ω phase on β quenching, can occur in the binary Zr-Ni system at very low solute concentrations, suggesting that nickel is a strong ω stabilizer. Such a situation is known to obtain in the binary Zr-Mo system also. However, the unusual ω morphology observed in the present work has not been reported in the context of dilute Zr-Mo alloys. The appearance of sharp ω reflections and the absence of streaking and diffuse distributions in the selected area electron diffraction (SAD) patterns suggest that the Zr-1.75 at. pct Ni composition lies toward the solute lean end of the composition range associated with the formation of the athermal ω phase in the binary Zr-Ni system. In a more dilute Zr-Ni alloy (Zr-1.30 at. pct Ni), no athermal ω could be observed in β quenched specimens. The absence of streaking is also consistent with the fact that the ω phase in the β quenched Zr-1.75 at. pct Ni alloy did not occur in the form of very fine precipitates. The unusual ω morphology encountered in this work merits further investigation

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

Behavior and effect of Ti2Ni phase during processing of NiTi shape memory alloy wire from cast ingot

International Nuclear Information System (INIS)

Bhagyaraj, J.; Ramaiah, K.V.; Saikrishna, C.N.; Bhaumik, S.K.; Gouthama

2013-01-01

Highlights: •Ti 2 Ni second phase particles forms in different sizes and shapes in cast ingot. •TEM evidences showed shearing/fragmentation of Ti 2 Ni during processing. •Matrix close to Ti 2 Ni experienced severe plastic deformation lead to amorphisation. •Ti 2 Ni interfaces were mostly faceted and assist in nucleation of martensite. •Heterogeneity of microstructure observed near to and away from Ti 2 Ni. -- Abstract: Binary NiTi alloy is one of the commercially successful shape memory alloys (SMAs). Generally, the NiTi alloy composition used for thermal actuator application is slightly Ti-rich. In the present study, vacuum arc melted alloy of 50.2Ti–Ni (at.%) composition was prepared and characterized using optical, scanning and transmission electron microcopy. Formation of second phase particles (SPPs) in the cast alloy and their influence on development of microstructure during processing of the alloy into wire form has been investigated. Results showed that the present alloy contained Ti 2 Ni type SPPs in the matrix. In the cast alloy, the Ti 2 Ni particles form in varying sizes (1–10 μm) and shapes. During subsequent thermo-mechanical processing, these SPPs get sheared/fragmented into smaller particles with low aspect ratio. The presence of SPPs plays a significant role in refinement of the microstructure during processing of the alloy. During deformation of the alloy, the matrix phase around the SPPs experiences conditions similar to that observed in severe plastic deformation of metallic materials, leading to localized amorphisation of the matrix phase

Effect of CeLa addition on the microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy

International Nuclear Information System (INIS)

Du, Jiandi; Ding, Dongyan; Xu, Zhou; Zhang, Junchao; Zhang, Wenlong; Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua; Chen, Renzong; Huang, Yuanwei; Tang, Jinsong

2017-01-01

Development of high strength lithium battery shell alloy is highly desired for new energy automobile industry. The microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy with different CeLa additions were investigated through optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rietveld refinement and tensile testing. Experimental results indicate that Al 8 Cu 4 Ce and Al 6 Cu 6 La phases formed due to CeLa addition. Addition of 0.25 wt.% CeLa could promote the formation of denser precipitation of Al 20 Cu 2 Mn 3 and Al 6 (Mn, Fe) phases, which improved the mechanical properties of the alloy at room temperature. However, up to 0.50 wt.% CeLa addition could promote the formation of coarse Al 8 Cu 4 Ce phase, Al 6 Cu 6 La phase and Al 6 (Mn, Fe) phase, which resulted in weakened mechanical properties. - Highlights: •Al-Cu-Mn-Mg-Fe alloys with different CeLa addition were fabricated through casting and rolling. •Al 8 Cu 4 Ce and Al 6 Cu 6 La phases formed after CeLa addition. •Addition of 0.25 wt.% CeLa promoted formation of denser precipitates of Al 20 Cu 2 Mn 3 and Al 6 (Mn, Fe). •Mechanical properties of the alloy was improved after 0.25 wt.% CeLa addition.

Scale up of NiTi shape memory alloy production by EBM

Science.gov (United States)

Otubo, J.; Rigo, O. D.; Moura Neto, C.; Kaufman, M. J.; Mei, P. R.

2003-10-01

The usual process to produce NiTi shape memory alloy is by vacuum induction melting (VIM) using a graphite crucible, which causes contamination of the melt with carbon. Contamination with oxygen originates from the residual oxygen inside the melting chamber. An alternative process to produce NiTi alloys is by electron beam melting (EBM) using a water-cooled copper crucible that eliminates carbon contamination, and the oxygen contamination would be minimal due to operation in a vacuum of better than 10^{-2} Pa. In a previous work, it was demonstrated that the technique is feasible for button shaped samples weighing around 30g. The present work presents the results on the scale up program that enables the production of larger samples/ingots. The results are very promising in terms of chemical composition homogeneity as well as in terms of carbon contamination, the latter being four to ten times lower than the commercially-produced VIM products, and in terms of final oxygen content which is shown to depend primarily on the starting raw materials.

Influence of micro-additions of bismuth on structures, mechanical and electrical transport properties of rapidly solidified Sn-3.5% Ag Alloy from melt

International Nuclear Information System (INIS)

El Bahay, M.M.; Mady, H.A.

2005-01-01

The present study was undertaken to investigate the influence of the Bi addition in the Sn-3.5 Ag rapidly solidified binary system for use as a Pb-free solder. The resulting properties of the binary system were extended to the Sn based ternary systems Sn 9 6.5-X Ag 3 .5 Bi x (0≤ X ≤ 2.5) solder. The structure and electrical resistivity of rapidly solidified (melt spun) alloys have been investigated. With the addition of up to 2.5 mass % Bi, the melting temperature decreases from 221.1 to 214.8 degree C. Wetting contact angle of the six alloys on Cu Zn 3 0 substrate are carried out at 573 K. Microhardness evaluations were also performed on the Sn-Ag-Bi alloys. The measured values and other researcher's results were compared with the calculated data

Effect of Ga substitution on the crystallization behaviour and glass forming ability of Zr-Al-Cu-Ni alloys

International Nuclear Information System (INIS)

Singh, Devinder; Yadav, T.P.; Mandal, R.K.; Tiwari, R.S.; Srivastava, O.N.

2010-01-01

The crystallization behaviour of melt spun Zr 69.5 Al 7.5-x Ga x Cu 12 Ni 11 (x = 0-7.5; in at.%) metallic glasses has been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The DSC traces showed changes in crystallization behaviour with substitution of Ga. Formation of single nano-quasicrystalline phase by controlled crystallization of glasses has been found only for 0 ≤ x ≤ 1.5. Further increase of Ga content gives rise to formation of the quasicrystals together with Zr 2 Cu type crystalline phase. In addition to this, the substitution of Ga influences the size and shape of nano-quasicrystals. The glass forming abilities (GFAs) of these metallic glasses were assessed by the recognition of glass forming ability indicators, i.e. reduced glass transition temperature (T rg ) and supercooled liquid region (ΔT x ). The glass transition temperature (T g ) has been observed for all the melt spun ribbons.

Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

Science.gov (United States)

Sengupta, Pranesh; Rogalla, Detlef; Becker, Hans Werner; Dey, Gautam Kumar; Chakraborty, Sumit

2011-08-15

Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt. Copyright © 2011 Elsevier B.V. All rights reserved.

A FeNiMnC alloy with strain glass transition

Directory of Open Access Journals (Sweden)

Hui Ma

2018-02-01

Full Text Available Recent experimental and theoretical investigations suggested that doping sufficient point defects into a normal ferroelastic/martensitic alloy systems could lead to a frozen disordered state of local lattice strains (nanomartensite domains, thereby suppressing the long-range strain-ordering martensitic transition. In this study, we attempt to explore the possibility of developing novel ferrous Elinvar alloys by replacing nickel with carbon and manganese as dopant species. A nominal Fe89Ni5Mn4.6C1.4 alloy was prepared by argon arc melting, and XRD, DSC, DMA and TEM techniques were employed to characterize the strain glass transition signatures, such as invariance in average structure, frequency dispersion in dynamic mechanical properties (storage modulus and internal friction and the formation of nanosized strain domains. It is indicated that doping of Ni, Mn and C suppresses γ→α long-range strain-ordering martensitic transformation in Fe89Ni5Mn4.6C1.4 alloy, generating randomly distributed nanosized domains by strain glass transition. Keywords: Strain glass transition, Elinvar alloys, Point defects, Nanosized domains

Glass forming ability of Al–Ni–La alloys with Si addition

Energy Technology Data Exchange (ETDEWEB)

Yi, J.J.; Xiong, X.Z. [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Inoue, A. [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); WPI-Advanced Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Kong, L.T. [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, J.F., E-mail: jfli@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-11-25

(Al{sub 85.5}Ni{sub 9.5}La{sub 5}){sub 100−x}Si{sub x}, (Al{sub 86}Ni{sub 9}La{sub 5}){sub 100−x}Si{sub x}, (Al{sub 86}Ni{sub 9.5}La{sub 4.5}){sub 100−x}Si{sub x}, (Al{sub 86}Ni{sub 10}La{sub 4}){sub 100−x}Si{sub x} and (Al{sub 86}Ni{sub 10.5}La{sub 3.5}){sub 100−x}Si{sub x} alloys, where x = 0.0, 0.2, 0.5, 1.0, 1.5 and 2.0, were cast under the same suction casting conditions into a wedge-shaped copper mold for investigating the effect of Si addition on the glass-forming ability (GFA). The GFA of the Al–Ni–La base alloys, except for the optimal glass former (Al{sub 85.5}Ni{sub 9.5}La{sub 5}), is enhanced when a proper content of Si is added. The largest content of Si up to which GFA can be enhanced changes in the following order of the base alloys: Al{sub 86}Ni{sub 9}La{sub 5}, Al{sub 86}Ni{sub 9.5}La{sub 4.5}, Al{sub 86}Ni{sub 10}La{sub 4} and Al{sub 86}Ni{sub 10.5}La{sub 3.5}. The enhancement of GFA due to Si addition becomes more significant as the La content decreases. This is presumably because more free Al atoms are present in the base alloy. - Highlights: • 0.2–2.0 at. % Si was added to each ternary base alloy. • Wedge-shaped samples were suction cast to obtain the glass-forming ability (GFA). • The GFA of the ternary non-optimal glass formers can be enhanced by Si addition. • The number of free-Al atoms dominates the best Si addition.

Effect of CeLa addition on the microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy

Energy Technology Data Exchange (ETDEWEB)

Du, Jiandi [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Dongyan, E-mail: dyding@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Zhou; Zhang, Junchao; Zhang, Wenlong [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua [Huafon NLM Al Co., Ltd, Shanghai 201506 (China); Chen, Renzong; Huang, Yuanwei; Tang, Jinsong [Shanghai Huafon Materials Technology Institute, Shanghai 201203 (China)

2017-01-15

Development of high strength lithium battery shell alloy is highly desired for new energy automobile industry. The microstructures and mechanical properties of Al-Cu-Mn-Mg-Fe alloy with different CeLa additions were investigated through optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rietveld refinement and tensile testing. Experimental results indicate that Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed due to CeLa addition. Addition of 0.25 wt.% CeLa could promote the formation of denser precipitation of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe) phases, which improved the mechanical properties of the alloy at room temperature. However, up to 0.50 wt.% CeLa addition could promote the formation of coarse Al{sub 8}Cu{sub 4}Ce phase, Al{sub 6}Cu{sub 6}La phase and Al{sub 6}(Mn, Fe) phase, which resulted in weakened mechanical properties. - Highlights: •Al-Cu-Mn-Mg-Fe alloys with different CeLa addition were fabricated through casting and rolling. •Al{sub 8}Cu{sub 4}Ce and Al{sub 6}Cu{sub 6}La phases formed after CeLa addition. •Addition of 0.25 wt.% CeLa promoted formation of denser precipitates of Al{sub 20}Cu{sub 2}Mn{sub 3} and Al{sub 6}(Mn, Fe). •Mechanical properties of the alloy was improved after 0.25 wt.% CeLa addition.

Minor-alloyed Cu-Ni-Si alloys with high hardness and electric conductivity designed by a cluster formula approach

Directory of Open Access Journals (Sweden)

Dongmei Li

2017-08-01

Full Text Available Cu-Ni-Si alloys are widely used due to their good electrical conductivities in combination with high strength and hardness. In the present work, minor-alloying with M = (Cr, Fe, Mo, Zr was conducted for the objective of further improving their hardness while maintaining their conductivity level. A cluster-plus-glue-atom model was introduced to design the compositions of M-alloyed Cu-Ni-Si alloys, in which an ideal composition formula [(Ni,Si,M-Cu12]Cu3 (molar proportion was proposed. To guarantee the complete precipitation of solute elements in fine δ-Ni2Si precipitates, the atomic ratio of (Ni,M/Si was set as 2/1. Thus the designed alloy series of Cu93.75(Ni/Zr3.75Si2.08(Cr/Fe/Mo0.42 (at% were arc-melted into ingots under argon atmosphere, and solid-solutioned at 950 °C for 1 h plus water quenching and then aged at 450 °C for different hours. The experimental results showed that these designed alloys exhibit high hardness (HV > 1.7 GPa and good electrical conductivities (≥ 35% IACS. Specifically, the quinary Cu93.75Ni3.54Si2.08(Cr/Fe0.42Zr0.21 alloys (Cu-3.32Ni-0.93Si-0.37(Cr/Fe−0.30Zr wt% possess both a high hardness with HV = 2.5–2.7 GPa, comparable to the high-strength KLFA85 alloy (Cu-3.2Ni-0.7Si-1.1Zn wt%, HV = 2.548 GPa, and a good electrical conductivity (35–36% IACS.

Microstructure and mechanical properties of Al-20Si-5Fe-2X (X = Cu, Ni, Cr) alloys produced by melt-spinning

International Nuclear Information System (INIS)

Rajabi, M.; Simchi, A.; Davami, P.

2008-01-01

Al-20Si-5Fe-2X (X = Cu, Ni and Cr) ribbons were produced by melt-spinning and consolidated by hot pressing at 400 deg. C for 60 min. The microstructure of the ribbons and the consolidated alloys was investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometry (XRD) method, and transmission electron microscopy (TEM). The hardness and compressive strength of the specimens at ambient and elevated temperatures were examined. The microstructure of the ribbons exhibited featureless and dendritic zones. Results of XRD and TEM showed formation of spherically shaped Si particles with an average diameter of 20 nm. Ultrafine Si (110-150 nm) and iron-containing intermetallic particles were noticed in the microstructure of the consolidated ribbons. An improved strength was achieved by alloying of Al-20Si-5Fe with Cu, Ni, and Cr. Nickel was found to be the most effective element in increasing the maximum stress, particularly at elevated temperatures

Purification of melt-spun metallurgical grade silicon micro-flakes through a multi-step segregation procedure

Science.gov (United States)

Martinsen, F. A.; Nordstrand, E. F.; Gibson, U. J.

2013-01-01

Melt-spun metallurgical grade (MG) micron dimension silicon flakes have been purified into near solar grade (SG) quality through a multi-step melting and re-solidification procedure. A wet oxidation-applied thermal oxide maintained the sample morphology during annealing while the interiors were melted and re-solidified. The small thickness of the flakes allowed for near elimination of in-plane grain boundaries, with segregation enhanced accumulation of impurities at the object surface and in the few remaining grain boundaries. A subsequent etch in 48% hydrofluoric acid (HF) removed the impure oxide layer, and part of the contamination at the oxide-silicon interface, as shown by electron dispersive spectroscopy (EDS) and backscattered electron imaging (BEI). The sample grains were investigated by electron back-scattered diffraction (EBSD) after varying numbers of oxidation-annealing-etch cycles, and were observed to grow from ˜5 μm to ˜200 μm. The concentration of iron, titanium, copper and aluminium were shown by secondary ion mass spectroscopy (SIMS) and inductively coupled plasma mass spectroscopy (ICPMS) to drop between five and six orders of magnitude. The concentration of boron was observed to drop approximately one order of magnitude. A good correlation was observed between impurity removal rates and segregation models, indicating that the purification effect is mainly caused by segregation. Deviations from these models could be explained by the formation of oxides and hydroxides later removed through etching.

Hydrogen sorption and corrosion properties of La{sub 2}Ni{sub 9}CoSn{sub 0.2} alloy

Energy Technology Data Exchange (ETDEWEB)

Giza, Krystyna; Adamczyk, Lidia [Czestochowa Univ. of Technology (Poland). Faculty of Production Engineering and Materials Technology; Drulis, Henryk; Hackemer, Alicja [Institute of Low Temperatures and Structure Research PAS, Wroclaw (Poland)

2018-02-15

The hydrogenation and corrosion behaviour of La{sub 2}Ni{sub 9} . CoSn{sub 0.2} alloy was analysed in respect of its use in Ni-MH batteries. It has been proved that the presence of tin in the alloy causes a decrease in hydrogen equilibrium pressure. In the electrochemical studies several techniques, such as chronopotentiometry, multi-potential steps, linear sweep voltammetry and the potentiokinetic polarization were applied to characterize the electrochemical properties of a La{sub 2}Ni{sub 9}CoSn{sub 0.2} powder composite electrode. During long cycling, powder particles undergo micro-cracking or other forms of surface development causing a progressive increase in the exchange current density of the H{sub 2}O/H{sub 2} system, but, on the other hand, this increase favours corrosion processes such as the electrode material's oxidation. This is also reflected in the capacity loss values.

Three-dimensional hole transport in nickel oxide by alloying with MgO or ZnO

Science.gov (United States)

Alidoust, Nima; Carter, Emily A.

2015-11-01

It has been shown previously that the movement of a hole in nickel oxide is confined to two dimensions, along a single ferromagnetic plane. Such confinement may hamper hole transport when NiO is used as a p-type transparent conductor in various solar energy conversion technologies. Here, we use the small polaron model, along with unrestricted Hartree-Fock and complete active space self-consistent field calculations to show that forming substitutional MxNi1-xO alloys with M = Mg or Zn reduces the barrier for movement of a hole away from the ferromagnetic plane to which it is confined. Such reduction occurs for hole transfer alongside one or two M ions that have been substituted for Ni ions. Furthermore, the Mg and Zn ions do not trap holes on O sites in their vicinity, and NiO's transparency is preserved upon forming the alloys. Thus, forming MxNi1-xO alloys with M = Mg or Zn may enhance NiO's potential as a p-type transparent conducting oxide, by disrupting the two-dimensional confinement of holes in pure NiO.

Comparative microstructural and corrosion development of VCrNiCoFeCu equiatomic multicomponent alloy produced by induction melting and spark plasma sintering

Science.gov (United States)

Fazakas, É.; Heczel, A.; Molnár, D.; Varga, B.; Zadorozhnyy, V.; Vida, Á.

2018-03-01

The present study focuses on the corrosion behavior of a single-phase FCC high entropy alloy (VCrNiCoFeCu) casted by two different methods: induction melting and spark plasma sintering. The corrosion resistance has been evaluated using immersion tests in 3.5% NaCl solution, the potentiodynamic polarization measurements and the results are compared how is dependent the corrosion rate as a function of the production methods. Our results show that induction melted sample is stable in salty environment. On the other hand, based on the changes of polarization curves, there must be an evolution of oxide films on the SPSed sample until reaching the stable oxide layer.

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

International Nuclear Information System (INIS)

Lee, Kee Ahn; Kim, Yong Chan; Kim, Jung Han; Lee, Chong Soo; Namkung, Jung; Kim, Moon Chul

2007-01-01

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

Energy Technology Data Exchange (ETDEWEB)

Lee, Kee Ahn [School of Advanced Materials Engineering, Andong National University, Andong 760-749 (Korea, Republic of)]. E-mail: keeahn@andong.ac.kr; Kim, Yong Chan [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Jung Han [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Lee, Chong Soo [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Namkung, Jung [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Moon Chul [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of)

2007-03-25

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys.

Thermomechanical characterization of Ni-rich NiTi fabricated by selective laser melting

International Nuclear Information System (INIS)

Saedi, Soheil; Turabi, Ali Sadi; Karaca, Haluk; Andani, Mohsen Taheri; Haberland, Christoph; Elahinia, Mohammad

2016-01-01

This study presents the shape memory behavior of as-fabricated and solution annealed Ni 50.8 Ti 49.2 alloys fabricated using the selective laser melting (SLM) technique. Results were compared to the initial ingot that was used to fabricate powders. Optical microscopy was employed to reveal the microstructure. The shape memory effect under constant compressive stress and isothermal compressive stress cycling tests were utilized to investigate the shape memory characteristics of the initial ingot and fabricated alloys. It was revealed that the SLM method and post heat treatments can be used to tailor the microstructure and shape memory response. Partial superelasticity was observed after the SLM process. Solutionizing the fabricated samples increased the strength and improved the superelasticity but slightly decreased the recoverable strain. (paper)

Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} Alloys

Energy Technology Data Exchange (ETDEWEB)

Kim, Jonghyun, E-mail: joindoc@kumamoto-u.ac.jp [Department of Material Science, Magnesium Research Center (MRC), Kumamoto University, Kumamoto, 860-8555 (Japan); Kawamura, Y. [Department of Material Science, Magnesium Research Center (MRC), Kumamoto University, Kumamoto, 860-8555 (Japan)

2013-06-20

Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} (RE=La, Ce, Nd and Sm, at. %) alloys were prepared by high-frequency induction melting in an Ar atmosphere. Rods were extruded at 623 K and a ram speed of 2.5 mm·s{sup −1} using a circular die with an extrusion ratio of 10. The microstructure and mechanical properties of the extruded alloys were investigated. The Mg{sub 97}Zn{sub 1}Y{sub 1}Nd{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Sm{sub 1} alloys consisted of only two phases: α-Mg and a Mg-RE intermetallic compound. The Mg{sub 97}Zn{sub 1}Y{sub 1}La{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Ce{sub 1} alloys consisted of three phases: α-Mg, a Mg-RE intermetallic compound, and a Mg{sub 12}ZnY phase with a long-period stacking ordered (LPSO) phase. Additionally, after extrusion, the three-phase Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} alloys, i.e., those with an LPSO phase, had a stratified microstructure and exhibited better mechanical properties than those without an LPSO. At room temperature, the yield strength and ultimate tensile strength of the three-phase Mg{sub 97}Zn{sub 1}Y{sub 1}La{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Ce{sub 1} alloys were 381–384 MPa and 427–429 MPa, respectively, and yield strengths greater than 280 MPa were observed at the elevated temperature of 523 K.

Structural and Electrical Properties Characterization of Sb1.52Bi0.48Te3.0 Melt-Spun Ribbons

Directory of Open Access Journals (Sweden)

Viktoriia Ohorodniichuk

2017-06-01

Full Text Available Melt-spinning (MS has been reported as a promising tool to tailor the microstructure of bulk thermoelectric materials leading to enhanced thermoelectric performances. Here, we report on a detailed characterization of p-type Bi0.48Sb1.52Te3 ribbons produced by melt-spinning. The microstructure of the melt-spun ribbons has been studied by means of X-ray diffraction, scanning and transmission electron microscopy (TEM. The analyses indicate that the ribbons are highly-textured with a very good chemical homogeneity. TEM reveals clear differences in the microstructure at large and short-range scales between the surface that was in contact with the copper wheel and the free surface. These analyses further evidence the absence of amorphous regions in the melt-spun ribbons and the precipitation of elemental Te at the grain boundaries. Low-temperature electrical resistivity and thermopower measurements (20–300 K carried out on several randomly-selected ribbons confirm the excellent reproducibility of the MS process. However, the comparison of the transport properties of the ribbons with those of bulk polycrystalline samples of the same initial composition shows that MS leads to a more pronounced metallic character. This difference is likely tied to changes in deviations from stoichiometry due to the out-of-equilibrium conditions imposed by MS.

Effects in Mg-Zn-based alloys strengthened by quasicrystalline phase

International Nuclear Information System (INIS)

Vlček, M; Čížek, J; Lukáč, F; Melikhova, O; Hruška, P; Procházka, I; Vlach, M; Stulíková, I; Smola, B; Jäger, A

2016-01-01

Magnesium Mg-based alloys are promising lightweight structural materials for automotive, aerospace and biomedical applications. Recently Mg-Zn-Y system attracted a great attention due to a stable icosahedral phase (I-phase) with quasicrystalline structure which is formed in these alloys. Positron lifetime spectroscopy and in situ synchrotron X-ray diffraction were used to study thermal stability of I-phase and precipitation effects in Mg-Zn-Y and Mg- Zn-Al alloys. All alloys containing quasicrystalline I-phase exhibit misfit defects characterized by positron lifetime of ∼ 300 ps. These defects are associated with the interfaces between I- phase particles and Mg matrix. The quasicrystalline I-phase particles were found to be stable up to temperatures as high as ∼ 370°C. The W-phase is more stable and melts at ∼ 420°C. Concentration of defects associated with I-phase decreases after annealing at temperatures above ∼ 300°C. (paper)

EXAFS investigation on microstructure of La-based alloy deuteride

CERN Document Server

Chen Bo Fei; Xie Chao Mei; Chen Xi Ping; Liu Li Juan; Xie Ya Ning; Hu Tian Dou; Zhang Jing

2002-01-01

Extended X-ray absorption fine structure (EXAFS) spectra were measured to investigate the microstructure of La-based alloy deuteride. The radial structural functions of LaNi sub 4 sub . sub 2 sub 5 Al sub 0 sub . sub 7 sub 5 D sub x samples were obtained and the comparisons among different samples were performed. The results show that removal of deuterium is fast in La-Ni-Al hydrogen storage alloys under non-airtight condition

Fabrication and tensile properties of rapidly solidified Cu-10wt. %Ni alloy. [Cu-10Ni

Energy Technology Data Exchange (ETDEWEB)

Baril, D; Angers, R; Baril, J [Dept. of Mining and Metallurgy, Laval Univ., Ste-Foy, Quebec (Canada)

1992-10-15

Cu-10wt.%Ni ribbons were produced by melt spinning and cut into small particles with a blade cutter mill. The powders were then hot consolidated to full density by hot pressing followed by hot extrusion. Tensile properties of the resulting pieces were measured. Cu-10wt.%Ni cast ingots were also hot extruded and mechanically tested to compare with the rapidly solidified alloy and to evaluate the possible benefits brought by the rapid solidification process.

Producing a particle-reinforced AlCuMgMn alloy by means of mechanical alloying; Herstellung einer partikelverstaerkten AlCuMgMn-Legierung durch mechanisches Legieren

Energy Technology Data Exchange (ETDEWEB)

Nestler, D.; Wielage, B. [TU Chemnitz, Institut fuer Werkstoffwissenschaft und Werkstofftechnik (Germany); Siebeck, S.

2012-07-15

High-energy ball milling (HEM) with subsequent consolidation is a suitable method to produce particle-reinforced aluminium materials. The task of HEM is to distribute the reinforcement particles as homogeneously as possible. A further application of HEM is mechanical alloying (MA). This paper deals with the combination of both applications. Pure metallic powders (Al, Cu, Mg, Mn) were milled together with SiC particles up to 10 h. The composition of the metallic powder corresponds to that of the alloy AA2017 (3.9% Cu, 0.7% Mg, 0.6% Mn). In previous experiments [1], this alloy was used in the form of atomized powder. The changes in microstructure during the formation of the composite powder have been studied by light microscopy, SEM, EDXS and XRD. The results show that the production of composite powders in a single step is possible. This not only allows the economical production of such powders, but also facilitates the use of alloy compositions that are not producible via the melting route, or only producible with difficulty via the melting route. It's possible to produce tailor-made-alloys. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Features of Pd-Ni-Fe solder system for vacuum brazing of low alloy steels

International Nuclear Information System (INIS)

Radzievskij, V.N.; Kurochko, R.S.; Lotsmanov, S.N.; Rymar', V.I.

1975-01-01

The brazing solder of the Pd-Ni-Fe alloyed with copper and lithium, in order to decrease the melting point and provide for a better spreading, when soldered in vacuum ensures a uniform strength of soldered joints with the base metal of low-alloyed steels of 34KHNIM-type. The properties of low-alloyed steel joints brazed with the Pd-Ni-Fe-system solder little depend on the changes in the soldering parameters. The soldered joint keeps a homogeneous structure after all the stages of heat treatment (annealing, quenching and tempering)

Grain refinement of DC cast magnesium alloys with intensive melt shearing

International Nuclear Information System (INIS)

Zuo, Y B; Jiang, B; Zhang, Y; Fan, Z

2012-01-01

A new direct chill (DC) casting process, melt conditioned DC (MC-DC) process, has been developed for the production of high quality billets/slabs of light alloys by application of intensive melt shearing through a rotor-stator high shear device during the DC casting process. The rotor-stator high shear device provides intensive melt shearing to disperse the naturally occurring oxide films, and other inclusions, while creating a microscopic flow pattern to homogenize the temperature and composition fields in the sump. In this paper, we report the grain refining effect of intensive melt shearing in the MC-DC casting processing. Experimental results on DC casting of Mg-alloys with and without intensive melt shearing have demonstrated that the MC-DC casting process can produce magnesium alloy billets with significantly refined microstructure. Such grain refinement in the MC-DC casting process can be attributed to enhanced heterogeneous nucleation by dispersed naturally occurring oxide particles, increased nuclei survival rate in uniform temperature and compositional fields in the sump, and potential contribution from dendrite arm fragmentation.

Magnesium–Gold Alloy Formation by Underpotential Deposition of Magnesium onto Gold from Nitrate Melts

Directory of Open Access Journals (Sweden)

Vesna S. Cvetković

2017-03-01

Full Text Available Magnesium underpotential deposition on gold electrodes from magnesium nitrate –ammonium nitrate melts has been investigated. Linear sweep voltammetry and potential step were used as electrochemical techniques. Scanning electron microscopy (SEM, energy dispersive spectrometry (EDS and X-ray diffraction (XRD were used for characterization of obtained electrode surfaces. It was observed that reduction processes of nitrate, nitrite and traces of water (when present, in the Mg underpotential range studied, proceeded simultaneously with magnesium underpotential deposition. There was no clear evidence of Mg/Au alloy formation induced by Mg UPD from the melt made from eutectic mixture [Mg(NO32·6H2O + NH4NO3·XH2O]. However, EDS and XRD analysis showed magnesium present in the gold substrate and four different Mg/Au alloys being formed as a result of magnesium underpotential deposition and interdiffusion between Mg deposit and Au substrate from the melt made of a nonaqueous [Mg(NO32 + NH4NO3] eutectic mixture at 460 K.

Structure and properties of melt-spun high acrylonitrile copolymer fibers via continuous zone-drawing and zone-annealing processes

International Nuclear Information System (INIS)

Wu Zongquan; Zhang Anqiu; Percec, Simona; Jin Shi; Jing, Alexander J.; Ge, Jason J.; Cheng, Stephen Z.D.

2003-01-01

Continuous zone-drawing and zone-annealing processes have been utilized to probe improvements in mechanical performance of melt-spun high acrylonitrile copolymer fibers (AMLON TM ). The as-spun fibers were zone-drawn at different ratios in a narrow temperature range of 100-105 deg. C and then zone-annealed. As a result of these processes, the fibers show substantial increases in tensile strength and tensile modulus (about three times) and significant improvements in elongation-at-break (about two times) after zone annealing. The thermal transition behavior, dimensional stability and dynamic relaxation properties of the as-spun, zone-drawn and zone-annealed fibers have been studied using differential scanning calorimetry, thermal mechanical and dynamic mechanical experiments. Their mechanical and thermal property changes after the zone-drawing and zone-annealing processes can be associated with the microscopic structural evolution including crystallinity, crystal orientation and apparent crystallite size detected by wide angle X-ray diffraction experiments

Effect of process parameters on formability of laser melting deposited 12CrNi2 alloy steel

Science.gov (United States)

Peng, Qian; Dong, Shiyun; Kang, Xueliang; Yan, Shixing; Men, Ping

2018-03-01

As a new rapid prototyping technology, the laser melting deposition technology not only has the advantages of fast forming, high efficiency, but also free control in the design and production chain. Therefore, it has drawn extensive attention from community.With the continuous improvement of steel performance requirements, high performance low-carbon alloy steel is gradually integrated into high-tech fields such as aerospace, high-speed train and armored equipment.However, it is necessary to further explore and optimize the difficult process of laser melting deposited alloy steel parts to achieve the performance and shape control.This article took the orthogonal experiment on alloy steel powder by laser melting deposition ,and revealed the influence rule of the laser power, scanning speed, powder gas flow on the quality of the sample than the dilution rate, surface morphology and microstructure analysis were carried out.Finally, under the optimum technological parameters, the Excellent surface quality of the alloy steel forming part with high density, no pore and cracks was obtained.

Effect of annealing treatment on structure and electrochemical performance of quenched MmNi4.2Co0.3Mn0.4Al0.3Mg0.03 hydrogen storage alloy

International Nuclear Information System (INIS)

Zhou Zenglin; Song Yueqing; Cui Shun; Huang Changgeng; Qian Wenlian; Lin Chenguang; Zhang Yongjian; Lin Yulin

2010-01-01

MmNi 4.2 Co 0.3 Mn 0.4 Al 0.3 Mg 0.03 hydrogen storage alloy was prepared by single-roll rapid quenching followed by different annealing treatments for 8 h at 1133 K, 1173 K, 1213 K, and 1253 K, respectively. Alloy structure, phase composition, pressure-composition-temperature (PCT) properties, and electrochemical performance of different annealed alloys have been investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), energy dispersion spectrometer (EDS), automatic Sieverts-type apparatus, and electrochemical experiments. Electrochemical experiments indicate that the annealing treatment at 1213 K extends cycle life from 193 cycles to 358 cycles, increases the maximum discharge capacity, and slightly decreases the activation behavior. Alloy structure analyses show that the improvement in cycle life is attributed to the formation of a single CaCu 5 -type structure or the relief of an Mg-containing AlMnNi 2 -type second phase. Pressure composition isotherms results illustrate that both the hydrogen absorption capability and the dehydriding equilibrium pressure go up with increased annealing temperature. For its good performance/cost ratio, the Mg-added low-Co alloy annealed at 1213 K would be a promising substitution for MmNi 4.05 Co 0.45 Mn 0.4 Al 0.3 alloy product.

Microstructural evolution of direct chill cast Al-15.5Si-4Cu-1Mg-1Ni-0.5Cr alloy during solution treatment

OpenAIRE

He Kezhun; Yu Fuxiao; Zhao Dazhi

2011-01-01

Heat treatment has important influence on the microstructure and mechanical properties of Al-Si alloys. The most common used heat treatment method for these alloys is solution treatment followed by age-hardening. This paper investigates the microstructural evolution of a direct chill (DC) cast Al-15.5Si-4Cu-1Mg-1Ni-0.5Cr alloy after solution treated at 500, 510, 520 and 530℃, respectively for different times. The major phases observed in the as-cast alloy are α-aluminum dendrite, primary Si p...

Additive Manufacturing of NiTiHf High Temperature Shape Memory Alloy

Science.gov (United States)

Benafan, Othmane; Bigelow, Glen S.; Elahinia, Mohammad; Moghaddam, Narges Shayesteh; Amerinatanzi, Amirhesam; Saedi, Soheil; Toker, Guher Pelin; Karaca, Haluk

2017-01-01

Additive manufacturing of a NiTi-20Hf high temperature shape memory alloy (HTSMA) was investigated. A selective laser melting (SLM) process by Phenix3D Systems was used to develop components from NiTiHf powder (of approximately 25-75 m particle fractions), and the thermomechanical response was compared to the conventionally vacuum induction skull melted counterpart. Transformation temperatures of the SLM material were found to be slightly lower due to the additional oxygen pick up from the gas atomization and melting process. The shape memory response in compression was measured for stresses up to 500 MPa, and transformation strains were found to be very comparable (Up to 1.26 for the as-extruded; up to 1.52 for SLM).

Grain refinement of Ca addition in a twin-roll-cast Mg-3Al-1Zn alloy

Energy Technology Data Exchange (ETDEWEB)

Jiang Bin, E-mail: jiangbinrong@cqu.edu.cn [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030 (China); College of Materials Science and Engineering, Chongqing University, Chongqing 400030 (China); Liu Wenjun [College of Materials Science and Engineering, Chongqing University, Chongqing 400030 (China); Qiu Dong; Zhang Mingxing [Division of Materials, School of Mechanical and Mining Engineering, University of Queensland, St Lucia, QLD 4072 (Australia); Pan Fusheng [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030 (China)

2012-04-16

Highlights: Black-Right-Pointing-Pointer Grain refinement of Ca addition in a twin-roll-cast Mg-3Al-1Zn alloy was investigated. Black-Right-Pointing-Pointer Addition of 0.08 wt% Ca into Mg melts can significantly reduce the grain size to 30 {mu}m from 100 {mu}m. Black-Right-Pointing-Pointer Al{sub 2}Ca intermetallic particles have high potency to act as heterogeneous nucleation sites for {alpha}-Mg. - Abstract: Addition of 0.08 wt% Ca into AZ31 melts significantly reduces the average grain size of thin strips produced by twin-roll-cast to 30 {mu}m from 100 {mu}m. Like Zr, due to the high chemical activity, the Ca added into the melts reacts with Al and forms Al{sub 2}Ca intermetallic compound. X-ray diffraction result approves the existence of Al{sub 2}Ca in the thin strips, which formed in the melts. Crystallographic examination of relationship between Al{sub 2}Ca and Mg using the edge-to-edge matching model indicates that Al{sub 2}Ca particles are effective inoculants for heterogeneous nucleation of Mg. It is considered that Al{sub 2}Ca is a potential and effective grain refiner for Mg alloys and the grain refinement through addition of Ca in the AZ31 alloy is attributed to the inoculation effect of Al{sub 2}Ca particles formed in the melts.

Electrochemical properties of LaNi{sub 4.2}Co{sub 0.4}Zn{sub 0.1}Al{sub 0.3} and LaNi{sub 4.3}Co{sub 0.4}Zn{sub 0.1}Al{sub 0.2} alloys as anode materials for Ni-MH batteries

Energy Technology Data Exchange (ETDEWEB)

Giza, Krystyna [Czestochowa Univ. of Technology (Poland). Faculty of Production Engineering and Materials Technology

2017-07-01

The galvanostatic charge and discharge technique was used for the evaluation of the changes in electrochemical parameters of the tested metal hydride electrodes during the repeated hydrogen absorption and desorption processes. Higher development of the effective surface area during hydrogenation has been obtained for LaNi{sub 4.3}Co{sub 0.4}Zn{sub 0.1}Al{sub 0.2} composite electrode. For the conditions of current ± 0.5 C, the discharge capacities of LaNi{sub 4.2}Co{sub 0.4}Zn{sub 0.1}Al{sub 0.3} and LaNi{sub 4.3}Co{sub 0.4}Zn{sub 0.1}Al{sub 0.2} alloys are 240 and 316 mAh x g{sup -1}, respectively. From the point of view of improving the kinetics of the process of charge transfer at the electrode/electrolyte interface as well as a resistance to self-discharging, a partial substitution of nickel with zinc in the LaNi{sub 4.3}Co{sub 0.4}Al{sub 0.3} alloy is not favorable.

Grain refining mechanism of Al-containing Mg alloys with the addition of Mn-Al alloys

International Nuclear Information System (INIS)

Qin, Gaowu W.; Ren Yuping; Huang Wei; Li Song; Pei Wenli

2010-01-01

Graphical abstract: Display Omitted Research highlights: The ε-AlMn phase acts as the heterogeneous nucleus of α-Mg phase during the solidification of the AZ31 Mg alloy, not the γ-Al 8 Mn 5 phase. The grain refinement effect is very clear with the addition of only 0.5 wt% Mn-28Al alloy (pure ε-AlMn). The grain refinement does not deteriorate up to the holding time of 60 min at 740 o C. - Abstract: The effect of manganese on grain refinement of Al-containing AZ31 Mg alloy has been investigated by designing a series of Mn-Al alloys composed of either pure ε-AlMn, γ 2 -Al 8 Mn 5 or both of them using optical microscopy and X-ray diffraction. It is experimentally clarified that the grain refinement of the AZ31 Mg alloy is due to the existence of the ε-AlMn phase in the Mn-Al alloys, not the γ 2 -Al 8 Mn 5 phase. The grain size of AZ31 Mg alloy is about 91 μm without any addition of Mn-Al alloys, but remarkably decreases to ∼55 μm with the addition of either Mn-34 wt% Al or Mn-28 wt% Al. With a minor addition of 0.5 wt% Mn-28Al alloy, the grain size of AZ31 alloy decreases to ∼53 μm, and the Mn-28Al alloy can be active as grain refiner for holding time up to 60 min for the melt AZ31 alloy at 750 o C.

In-situ investigation of the hydrogen release mechanism in bulk Mg2NiH4