Vascular changes, the angioarchitecture of renal glomerular fine vessels in early diabetic KK-Ay mice of 4 months of age were examined by scanning electron microscopy of corrosion casts. Histologically, enlargement of glomeruli and dilation of glomerular capillaries were found. In resin cast specimens, glomeruli with diabetes were larger than normal, and an increase in diameter of the glomerular vessels was found in diabetic mice. No capillary proliferation, distortion of glomerular vessels and destruction of glomerular capillary loops were found in diabetic mice. The increased vascular diameter may explain the increase in blood flow in the glomeruli, affecting kidney function in early diabetes.   

Canine bronchoalveolar and vascular corrosion casts were prepared using unfixed tissue and Dow-Corning Room Temperature Vulcanizing Silastic 734. The casts were observed using stereo light microscopy and scanning electron microscopy. The casts show the relationship between the vasculature and airway and demonstrate intricate microanatomical details. Also, microvasculature filling was enhanced using unfixed tissue as compared to my previously described technique using fixed tissue. Prewashing the microvasculature with cold phosphate buffered saline appeared to facilitate microvascular filling with silicone rubber. The described method is useful for rapidly making durable models for studying the normal respiratory airway and microvasculature. It should be useful in future studies of diseased pulmonary tissue as well as other normal and diseased tissues where microanatomical relationships between microvasculature and adjacent luminal structures are relevant. PMID:9854861

The vasculature of the hemal node (HN) from bovine cervical region was investigated using a combination of vascular corrosion casting and scanning electron microscopy. A dense vessel network of capsule was found surrounding the cast of HN parenchyma and had no connection with subcapsular sinus, these vessels converged and exited the HN via the hilar vein. Within the HN, many anastomoses were found between the capillary networks and the surrounding sinuses in the follicular zone and deep cortex. The sinusoid pathway in the HN was characterized by subcapsular sinuses, which were continuous with the trabecular sinuses and tubular sinuses over the parenchyma, and these sinuses finally entered into the medullary veins. In our study, direct communications between cortical capillaries and subcapsular sinuses were identified. This may explain the origin of numerous erythrocytes in the HN sinusoids and help to understand lymphocyte migration of HN.   

Abstract Corrosion casting was utilized to examine the development of gill vasculature in embryonic yellow stingrays, Urobatis jamaicensis (formerly Urolophus jamaicensis). The most marked changes in vascular configuration of the gills occur in the earliest castable stages of gestation. These changes included development of afferent external gill filament vessels and progression from paired dorsal aortae to a single fused dorsal aorta. Internal gill vasculature was found to nearly match that of an adult by the time the external gill filaments had fully regressed and yolk sac had been exhausted (>47 mm disc width). Examination of embryo casts also revealed characteristics of the branchial vasculature not previously reported in adult specimens. These include the presence of pre-lamellar sphi...

  Cast irons are thought to be superior in corrosion resistance to plain steels. The differences between cast iron and plain steel are mainly in the existence of graphite and the amount of silicon. The graphite nobility for the matrix results in the electric potential difference between graphite and matrix. Thus the study of the effect of graphite morphology on corrosion resistance in cast irons under mild corrosive environments is needed. In this study, ductile cast irons with different graphite nodule size are austempered, their corrosion potentials are measured and their anodic polarization tests are carried out in 0.01N HCl aq. . The results show that : (1) In ductile cast irons, the smaller is the graphite nodule size, the lower is the corrosion resistance. In ADI, however, the graphite nodule size has a littIe effect on the corrosion resistance. (2) In ADI, the amount of retained austenite and the corrosion resistance decrease as the austempering time increases.   

It is not known whether eNOS deficiency in the mother or the conceptus (ie, placenta and fetus) causes fetal growth restriction in mice lacking the endothelial NO synthase gene (eNOS knockout [KO]). We hypothesized that eNOS sustains fetal growth by maintaining low fetoplacental vascular tone and promoting fetoplacental vascularity and that this is a conceptus effect and is independent of maternal genotype. We found that eNOS deficiency blunted fetal growth, and blunted the normal increase in umbilical blood flow and umbilical venous diameter and the decrease in umbilical arterial Resistance Index in late gestation (14.5-17.5 days) in eNOS KO relative to C57Bl/6J controls. On day 17.5, fetoplacental capillary lobule length and capillary density in vascular corrosion casts were reduced in eNOS KO placentas. Reduced vascularization may be a result of decreased vascular endothelial growth factor mRNA and protein expression in eNOS KO placentas at this stage. These factors, combined with significant anemia found in eNOS KO fetuses, would be anticipated to reduce fetal oxygen delivery and contribute to the fetal tissue hypoxia that was detected in the heart, lung, kidney, and liver by immunohistochemistry using pimonidazole. Although maternal eNOS deficiency impairs uteroplacental adaptations to pregnancy, maternal genotype was not a significant factor affecting growth in heterozygous conceptuses. This indicates that fetal growth restriction was primarily caused by conceptus eNOS deficiency. In mice, placental hemodynamic and vascular changes with gestation and growth restriction showed strong parallels with human pregnancy. Thus, the eNOS KO model could provide insights into the pathogenesis of human intrauterine growth restriction. PMID:23150513

The microvascular bed of the stomach of Xenopus laevis and the changes it undergoes when the herbivorous tadpole becomes a carnivorous adult were studied by scanning electron microscopy of vascular corrosion casts and light microscopy of stained tissue sections. In tadpoles an upper and a lower gastric artery supplied, and upper, middle and lower medial and lateral gastric veins drained the vertically extending stomach. During metamorphosis, the stomach gained a horizontal cranio-caudal extension and vessels accordingly become dorsal and ventral gastric arteries, and anterior, middle and posterior gastric veins, respectively. Up to stage 64 (late climax) mucosal capillaries formed a polygonal network of wide immature-looking capillaries ensheathing gastric glands in a basket-like manner. F...

Non-alcoholic fatty liver disease can progress to steatohepatitis and fibrosis, and is also associated with impaired liver regeneration. The pathophysiology remains elusive. We recently showed that severe steatosis is associated with an increase in portal pressure, suggesting liver flow impairment. The objective of this study is to directly assess total intrahepatic resistance and its potential functional and structural determinants in an in situ perfusion model. Male Wistar rats fed a control (n=30) or a methionine–choline-deficient (MCD) diet (n=30) for 4 weeks were compared. Liver tissue and serum analysis, in vivo haemodynamic measurements, in situ perfusion experiments and vascular corrosion casts were performed. The MCD group showed severe steatosis without inflammation or fibr...

A wide range of disorders are associated with alterations of the central and peripheral vascular system. Modified vascular corrosion casting using a newly developed polymer, allows for the first time hierarchical assessment of 3D vessel data in animals down to the level of capillaries. Imaging of large volumes of vasculature at intermediate resolution (16 ?m) was performed using a desktop micro-computed tomography system. Subsequently regions of interest were identified for additional high resolution imaging (1.4 ?m) at the X-ray Tomographic Microscopy (XTM) station of the Swiss Light Source (SLS). A framework for systematic hierarchical imaging and quantification was developed. Issues addressed included enhanced XTM data acquisition, introduction of local tomography, sample navigation, advanced post processing, and data combination. In addition to visual assessment of qualitative changes, morphometrical and architectural indices were determined using direct 3D morphometry software developed in house. Vessel specific parameters included thickness, surface, connectivity, and vessel length. Reconstructions of cerebral vasculature in mutant mice modeling Alzheimer's disease revealed significant changes in vessel architecture and morphology. In the future, a combination of these techniques may support drug discovery. Additionally, future ultra-high-resolution in vivo systems may even allow non-invasive tracking of temporal alterations in vascular morphology.

Duplex stainless steels (DSS) are being specified for chloride containing environments due to their enhanced pitting and stress corrosion cracking resistance. They exhibit improved corrosion performance over the austenitic stainless steels. Duplex stainless steels also offer improved strength properties and are available in various wrought and cast forms. Selected grades of duplex stainless steel castings and their welds, in comparison with their wrought counterparts, were evaluated, regarding corrosion performance and mechanical properties and weldability. Multiple heats of cast duplex stainless steel were evaluated in the as-cast, solution annealed (SA) static cast and SA centrifugal cast conditions, while their wrought counterparts were characterized in the SA condition and in the form of as-rolled plate. Welding, including extensive assessment of autogenous welds and a preliminary study of composite welds (shielded metal arc weld (SMAW)), was performed. The evaluations included critical pitting temperature (CPT) testing, intergranular corrosion (IGC) testing, ASTM A923 (Methods A, B and C), Charpy impact testing, weldability testing (ASTM A494), ferrite measurement and microstructural evaluations. In the study, the corrosion performances of DSS castings were characterized and assessed, including the wrought counterparts for comparison. The evaluation filled the pore of lack of data for cast duplex stainless steels compared to wrought materials. A database of the pitting corrosion and IGC behavior of cast and wrought materials was generated for a greater depth of understanding for the behavior of cast duplex stainless steel. In addition, improved evaluation methods for DSS castings were developed according to ASTM A923, A262, G48 and A494. The study revealed that when properly heat treated according to the specification, (1) DSS castings have equal or better pitting and intergranular corrosion resistance than their wrought counterparts; (2) Welding reduces the pitting and intergranular corrosion resistance for both the wrought and cast duplex alloys; (3) Castings generally have better toughness than their wrought counterparts in the temperature range of -80 C to +20 C; (4) All shield metal arc (SMA) test welds in DSS castings, with recommended or over matching filler metal, indicate that welding is not a significant factor when considering DSS applications.

To elucidate the morphological background of physiological differences between bovine and buffalo gestation forty-two placentae ranging from the 3rd to 10th month of pregnancy were used to study the microvascular architecture of the fetal cotyledons in the buffalo. The tissues were prepared for light and scanning electron microscopy by paraformaldehyde fixation and corrosion casting of the fetal cotyledonary vascular system. Histology and vascular casts revealed the buffalo fetal cotyledons to consist of a series of conical villous trees changing from a wide to slender shape during pregnancy, and with a base strictly facing the fetal side. The branches of these trees, intermediate and terminal villi, projected radially from the stem, thus representing a rough type of villous tree. A second type of tree lacked these branches and was therefore termed smooth villus. The rough type was most prevalent, and the intermediate and terminal villi showed capillary complexes arranged in stories by the 4th to 5th month of gestation. The stories became broader and denser with the progress of pregnancy (6th to 7th month of gestation), due to extensive growth of new capillaries and simultaneous development of convolutions causing the vascular ridges of the terminal villi to appear bushy. Near term (9th to 10th month) the capillary system became very dense, particularly at the margin of the vascular ridges, leaving only narrow spaces for the corresponding maternal septal tissue. In detail, at its base the trunk of each villous tree contained a single central stem artery which originated from the allantochorionic arterial system, and 1-3 parallel peripheral stem veins. When approaching the cone tip, these vessels branched into new stem arteries and veins, each giving rise to arterioles and venules according to the principle vascularization of the stem villus first, followed by intermediate and terminal villi. The capillary complex of the terminal villi consisted of arterial capillary limbs, capillary loops with sinusoidal dilatations and anastomoses, and venous capillary limbs. The latter converged into venules of terminal and intermediate villi which joined stem veins leading into allantochorionic veins. In conclusion, the fetal vasculature of the buffalo placentome was greatly increased from early pregnancy to near term. This was denoted by the general development of stem villous trees and an increase in the volume and density of the capillary system of the terminal villi, reflecting the increasing need of materno-fetal substance exchange in the buffalo placenta, particularly near term. PMID:12924470

on the effects of gravity on solidification mechanisms and cast iron .... small amount of gold incorporated into one .... ROLE OF CONVECTION IN PROCESSES (ELECTROKINETIC SEPARATION, ELECTROPLATING, CORROSION, ETC.1 ...

Magnesium alloy AP65 was prepared by melting and casting. The corrosion behavior of the as-cast and solid solution (T4)-treated AP65 alloys in 3.5% sodium chloride solution was investigated by corrosion morphology observation, immersion test, and electrochemical measurements. The results show that the second phase Mg17Al12 surrounded by a lead-enriched area distributes discontinuously along the grain boundaries in the as-cast AP65 alloy. The lead-enriched areas with high activity are susceptible to be attacked during immersion test and can act as places for preferential anodic dissolution. The corrosion resistance of the as-cast AP65 alloy can be improved after T4 treatment and the T4-treated alloy suffers general corrosion.

Coronary Angioplasty Stent Placement Shawnee Mission Heart & Vascular Center, Shawnee Mission, Kansas February 19, 2009 Welcome to this OR-Live westbound cast presentation, live from Shawnee Mission Medical Center ...

The microvascular anatomy of the large intestine of the adult South African Clawed Toad, Xenopus laevis (Daudin), was studied by scanning electron microscopy (SEM) of vascular corrosion casts (VCCs) and correlative light microscopy. Observations showed the large intestine to be supplied by the haemorrhoidal artery and the posterior mesenteric artery and drain via the posterior haemorrhoidal vein into either the left or right posterior abdominal vein. Both arteries and veins showed a bipinnate supply/draining pattern with branches running circumferentially. Vessels embraced the gut wall while arteries and veins in most cases alternated along the gut length. Many short terminal arterioles arose from the circumferential arteries at almost acute angles and capillarized after a short distance. Capillary lengths were short and continued into numerous postcapillary venules which merged either in a leaf vein-like formation or in a rosette-like formation with up to four draining sites per supplying arteriole. The microvasculature was found to be well adapted 1) to sustain blood flow under different amounts of feces in the gut and 2) to provide optimal conditions for the resorption of water and salts from the gut lumen into the blood vascular system by the high number of venules and their conspiciouos rosette-like and leaf vein-like patterns.   

The lymphatic system plays important roles in maintaining tissue fluid homeostasis, immune surveillance of the body, and the taking up dietary fat and fat-soluble vitamins A, D, E and K. The lymphatic system is involved in many pathological conditions, including lymphedema, inflammatory diseases, and tumor dissemination. A clear understanding of the organization of the lymphatic vessels in normal conditions would be critically important to develop new treatments for diseases involving the lymphatic vascular system. Therefore, the present paper reviews the organization of the lymphatic vascular system of a variety of organs, including the thyroid gland, lung and pleura, small intestine, cecum and colon in the rat, the diaphragm in the rat, monkey, and human, Peyer's patches and the appendix in the rabbit, and human tonsils. Methods employed include scanning electron microscopy of lymphatic corrosion casts and tissues with or without treatment of alkali maceration technique, transmission electron microscopy of intact tissues, confocal microscopy in conjunction with immunohistochemistry to some lymphatic-specific markers (i.e., LYVE-1 and VEGFR-3), and light microscopy in conjunction with enzyme-histochemistry to 5'-nucleotidase. Some developmental aspects of the lymphatic vessels and lymphedema are also discussed.   

Recent results show that bone vasculature is a major contributor to local tissue porosity, and therefore can be directly linked to the mechanical properties of bone tissue. With the advent of third generation synchrotron radiation (SR) sources, micro-computed tomography (?CT) with resolutions in the order of 1 ?m and better has become feasible. This technique has been employed frequently to analyze trabecular architecture and local bone tissue properties, i.e. the hard or mineralized bone tissue. Nevertheless, less is known about the soft tissues in bone, mainly due to inadequate imaging capabilities. Here, we discuss three different methods and applications to visualize soft tissues. The first approach is referred to as negative imaging. In this case the material around the soft tissue provides the absorption contrast necessary for X-ray based tomography. Bone vasculature from two different mouse strains was investigated and compared qualitatively. Differences were observed in terms of local vessel number and vessel orientation. The second technique represents corrosion casting, which is principally adapted for imaging of vascular systems. The technique of corrosion casting has already been applied successfully at the Swiss Light Source. Using the technology we were able to show that pathological features reminiscent of Alzheimer"s disease could be distinguished in the brain vasculature of APP transgenic mice. The third technique discussed here is phase contrast imaging exploiting the high degree of coherence of third generation synchrotron light sources, which provide the necessary physical conditions for phase contrast. The in-line approach followed here for phase contrast retrieval is a modification of the Gerchberg-Saxton-Fienup type. Several measurements and theoretical thoughts concerning phase contrast imaging are presented, including mathematical phase retrieval. Although up-to-now only phase images have been computed, the approach is now ready to retrieve the phase for a large number of angular positions of the specimen allowing application of holotomography, which is the three-dimensional reconstruction of phase images.

In order to study the wear of cylinder bore fundamentally, a reciprocating friction tester was produced and utilized. The friction between a cast iron and a piston-ring and the wear of the cast iron were examined under the corrosive oil with sulphuric acid. The findings indicate that the friction and wear around TDC and BDC was confirmed to be greater than between these reversal points and the friction and wear around the reversal points increased with the sulphuric acid which has caused the deficiency of oil film and the corrosion of the cast iron.

  Nowadays, spheroidal graphite cast iron is widely used for metal tubes buried under ground or soil and structural materials. However, a kind of special soil called marine clay may acidify in such uses, causing corrosion of the metal tubes and structural materials. This research considered the effects of pH on the corrosion behavior of spheroidal graphite cast iron in simulated groundwater using polarization curve and immersing test. The results showed that while pH is 3.5 or less in the immersing experiment, the corrosion rate increases markedly. Thus, the following two factors can be considered as the reason why spheroidal graphite cast iron generates extensive corrosion in acid solution. One reason is the pearlite colony boundary where phosphorous and sulfur segregate dissolves intensely preferentially, and the other is spheroidal graphite and cementite in pearlite promote hydrogen evolution reaction.   

In previous corrosion studies performed in salt brines, unalloyed steels, Ti 99.8-Pd and Hastelloy C4 have proved to be the most promising materials for long-term resistant packagings to be used in heat-generating waste (vitrified HLW, spent fuel) disposal in rock-salt formations. Investigations of the iron-base materials Ni-Resist D2 and D4, cast iron and Si-cast iron have also been carried out in order to complete the results available to date. The three steels (fine-grained steel, low-carbon steel, cast steel) investigated and Ti 99.8-Pd resisted pitting and crevice corrosion as well as stress-corrosion cracking under all test conditions. Gamma dose-rates of 1 Gy/h - 100 Gy/h or H{sub 2}S concentrations in the brines as well as welding and explosion plating did not influence noticeably the corrosion behaviour of the materials. Furthermore, the determined corrosion rates of the steels (50 {mu}m/a-250 {mu}m/a, depending on the test conditions) are intercomparable and imply technically acceptable corrosion allowances for the thick-walled containers discussed. For Ti 99.8-Pd no detectable corrosion was observed. By contrast, Hastelloy C4 proved susceptible to pitting and crevice corrosion at gamme dose-rates higher than 1 Gy/h and in the presence of H{sub 2}S (25 mg/l) in Q-brine. The materials Ni Resist D2 and D4, cast iron and Si-cast iron corroded at negligible rates in the in-situ experiments performed in rock salt/limited amounts of NaCI-brine. Nevertheless, these materials must be ruled out as container materials because they have proved to be susceptible to pitting and intergranular corrosion in previous laboratory studies conducted with MgCI{sub 2}-rich brine (Q-brine) in excess. 15 refs.; 29 figs.; 7 tabs.

In general, aluminum alloys provide the most significant part of all shaped casting manufactured. An optimum range of properties can be obtained as a function of different cooling rate processes, such as sand, plaster, investment, permanent molds and die castings. It is well known that the dendritic network affects not only the mechanical properties but also the corrosion resistance. However, the literature is scarce on reports concerning the influences of dendrite arm spacing on corrosion resistance and mechanical behavior. The aim of this study is to investigate the influence of as-cast microstructure features, i.e., dendrite arm spacing and solute redistribution on the corrosion resistance of samples of aluminum alloys. In order to investigate the electrochemical behavior of solute and solvent of different aluminum systems, samples with the same order of magnitude of dendritic spacings were analyzed to permit comparison between Al-10 wt% Sn and Al-20 wt% Zn alloys. A casting water-cooled assembly promoting upward directional solidification was used in order to obtain controlled casting samples of these alloys. In order to characterize the dendritic structure, longitudinal sections from the directionally solidified specimens were analyzed by using optical and electronic microscopy techniques. The corrosion resistance was analyzed by both the electrochemical impedance spectroscopy technique and Tafel extrapolation method conducted in a 3% NaCl solution at room temperature. Although both systems present an Al-rich dendritic matrix, different responses to corrosive action as a function of dendritic spacing have been detected.

Corrosion resistance of step castings of Al-2.5%Li-1.2%Cu-0.7%Mg alloys and Al-2.5%Li-2%Mg alloys with or without 0.15% Zr and 0.12% Ti were examined using salt spray tests. Corrosion resistance of the as-cast materials in the middle part and near surface part was almost same as that of the Al-7%Si-0.4%Mg alloy (AC4C). The corrosion resistance was good in spite of existence of unstable non-equilibrium crystal phase {delta}. This is due to formation of Na(ClCN), Cu3(CO3)2(OH)2 and Al(OH)3 on the surface of castings in the initial stage of corrosion, which work as a barrier over a corrosive environment. After T6 heat treatment of the alloys at 453 K and 36 ks, corrosion resistance of the near surface part of the casting was better than that of the middle part, and was almost equal to that of AC4C. This is considered due to more precipitation of the metastable phases:{delta}prime, Sprime and T1 in the middle part. 8 refs., 11 figs., 1 tab.

An apparatus was constructed to measure the expansion caused by the anaerobic corrosion of steel and cast iron whilst under representative compressive loads. The detection of hydrogen and the identification of magnetite on the surface of the specimens demonstrated the occurrence of anaerobic corrosion, but no expansion was observed after over two years' exposure, suggesting that the corrosion product is too soft and deformable to cause jacking of the walls of canisters used for encapsulating spent nuclear fuel. The use of natural analogues to examine the potential for expansion caused by anaerobic corrosion in confined spaces over long time periods is discussed. (authors)

It is commonly believed that high alloy steel castings have inferior corrosion resistance to their wrought counterparts as a result of the increased amount of microsegregation remaining in the as-cast structure. Homogenization and dissolution heat treatments are often utilized to reduce or eliminate the residual microsegregation and dissolve the secondary phases. Detailed electron probe microanalysis (EPMA) and light optical microscopy (LOM) were utilized to correlate the amount of homogenization and dissolution present after various thermal treatments with calculated values and with the resultant corrosion resistance of the alloys.The influence of heat treatment time and temperature on the homogenization and dissolution kinetics were investigated using stainless steel alloys CN3MN and CK3MCuN. The influence of heat treatment time and temperature on the impact toughness and corrosion reistance of cast stainless steel alloys CF-3, CF-3M, CF-8, and CF-8M was also investigated.

The present conference on state-of-the-art cast MMCs discusses topics on their fundamental microstructural and mechanical properties, the method of MMC 'squeeze casting', the thermomechanical behavior of cast MMCs, and the tribology, damping, corrosion and erosion properties of cast MMCs. Attention is given to the kinetics of fiber preform infiltration, the bonding of SiC and Al, a chemical analysis of the fiber-matrix interface in model Al-matrix MMCs, porosity in vortex method-produced foundry MMCs, the solidification of Al and Zn alloys containing discontinuous SiC fibers, the liquid pressure forming of MMCs, and the strengthening of P/M vs melted SiC/Al MMCs. Also discussed are the deformation-mechanism mapping of SiC/Al MMCs, the thermal cycling of alumina (FP)/Mg-alloy MMCs, the corrosion properties of MMCs, and the damping capacity of Al-alloy matrix MMCs.

The fatigue properties of the aluminium cast alloys AlSi7Mg and AlSi10Mg, magnesium high pressure die-cast AZ91 hp and AM60 hp, as well as low-pressure permanent mould casting AZ91 hp were determined at numbers of cycles to failure between 10{sup 5} and 10{sup 9} in ambient air and in saltwater spray. The investigations were performed at constant amplitudes and in addition at varying load amplitudes for aluminium cast alloy AlSi10Mg and low-pressure permanent mould casting AZ91 hp with a high-frequency testing facility (20 kHz ultrasound). The SN-curves of the aluminium cast alloys and of the magnesium low-pressure permanent mould casting are steeper in corrosive environment than in laboratory air. No endurance limit could be detected up to 10{sup 9} cycles in both environments. The magnesium high pressure die-cast alloys do not have an endurance limit in saltwater spray, whereas an endurance limit could be detected in laboratory air. The life time curves for in-service loading conditions are about parallel to the SN-curves for ambient air, but steeper for corrosive environment. The reason for the reduced fatigue properties in corrosive environment are accelerated crack initiation and higher crack propagation rates. Material defects may lead to a large scatter of the fatigue data for testing in air as well as in saltwater spray. Corrosion pits are formed on the surface of both light-weight alloys at higher number of cycles. They become crack initiation sites. (orig.) 10 refs.

One effect of high purification is to delay {sigma} phase formation in high Cr steel. This report presents the application trial of this concept to a practical material, namely 45Cr-30Ni cast steel used for boiler burner parts in fossil power plants, which are exposed to a severe hot-corrosion atmosphere. Conventionally, a Ni content of 30 mass % has been required in order to prevent {sigma} phase formation in this cast steel. However, it is desirable to reduce the amount of Ni in order to improve anti-hot corrosion properties. The research reported here considers the possibility of lowering the amount of Ni in this cast steel through the reduction of silicon and manganese as impurities. Aging and hot-corrosion behavior of 45Cr-30Ni and 45Cr-20Ni cast steels with both conventional and small amounts of silicon and manganese were investigated. It was found that reduction of these impurities greatly impeded the formation of the {sigma} phase, even in 45Cr-20Ni cast steel conventionally characterized by {sigma} phase formation. Also, with the decrease in Ni content, anti-hot corrosion performance was substantially improved in a heavy oil combustion atmosphere. (authors)

The microstructures and corrosion behavior of AM60B magnesium alloys, produced by both high-pressure die casting (HPDC) and super vacuum die casting (SVDC) processes, were investigated by a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), and slow positron beam technique. XRD confirmed that calcium carbonate (CaCO3) deposited on the surface of alloys during the early stages of corrosion, and the deposition rate of CaCO3 for SVDC with corrosion time was slower than that of HPDC. SEM observation found that the ?-phases in the skin surface of SVDC alloy had a greater volume fraction and more continuous distribution than that of HPDC alloy, leading to lower volume fraction of CaCO3 deposited on surface of SVDC alloy for the same corrosion time. The slow positron beam...

Magnesium alloys are often used in as-cast conditions. So, the aim of this work is to characterize the corrosion protection of as-cast AZ91D alloys coated with simple chemical conversion (phosphate-permanganate, and cerium-based coatings). With the two coatings, the electrochemical measurements show that the corrosion protection is due to both the inhibition of cathodic and anodic reactions, because of the presence of stable CeO{sub 2} or manganese oxides in basic pH. Nevertheless, the non-electrochemical tests of corrosion are required to bring to light the healing effect of phosphate-permanganate coating compared to Ce-coating and to describe the corrosion behaviour completely. Finally phosphoric and soda pickling associated to phosphate-permanganate conversion treatment or cerium coating are ecologically efficient alternatives to fluoride-based pickling and the chromating treatment.

The field tests were conducted under reducing and oxidizing conditions. Corrosion rates with zero oxygen were about 1.1 mils per year (mpy) for both copper and steel coupons, which is quite low for carbon steel. There was a problem controlling the oxygen level in the oxygenated experiments; however, it was found that corrosion rates increased with the presence of oxygen. Corrosion rates for the steel and copper coupons were 4 and 2 mpy, respectively; copper coupled to cast iron corroded at 8 mpy. Commercial corrosion rate measuring equipment determined the general corrosion rate of carbon steel farily well but overestimated copper corrosion rates. The redox electrode was a very sensitive indicator of the entry of oxygen.

The corrosion and corrosion-abrasion resistance of some stainless steels in industrial phosphoric acid 30% P{sub 2}O{sub 5} has been studied using electrochemical techniques. The corrosion rate of materials increases with the increase of temperature. Alloys which contain chromium, molybdenum and nitrogen in sufficient quantities present the best behaviour. In the abrasion-corrosion conditions, the experimental device set up allowed to follow continually samples electrochemical behaviour. Under dynamic conditions and without solid particles, the increase of acid projection speed has no effect on the alloys corrosion behaviour. The adding of abrasive leads to a general increase of corrosion rate and to a decrease of material resistance. Under these conditions, materials attack is controlled by synergistic effect between the abrasion and the impurities. The cast 30% Cr shows good resistance according to his high chromium content.

The research explored ways of improving corrosion behaviour of AZ91D magnesium alloy through heat treatment for degradable biocompatible implant application. Corrosion resistance of heat-treated samples is studied in simulated body fluid at 37degreeC using immersion and electrochemical testing. Heat treatment significantly affected microgalvanic corrosion behaviour between cathodic b-Mg17Al12 phase and anodic a-Mg matrix. In T4 microstructure, dissolution of the b-Mg17Al12 phase decreased the cathode-to-anode area ratio, leading to accelerated corrosion of a-Mg matrix. Fine b-Mg17Al12 precipitates in T6 microstructure facilitated intergranular corrosion and pitting, but the rate of corrosion was less than those of as-cast and T4 microstructures.

During the past 20 years, lead acid batteries manufacturers have modified grid manufacturing processes and the chemical composition of the used alloys in order to decrease battery grid weight as well as to reduce the production costs, and to increase the battery life-time cycle and the corrosion resistance. The aim of this study was to evaluate the effects of cellular and dendritic microstructures of two different Pb-Sb alloys on the resultant corrosion behavior. A water-cooled unidirectional solidification system was used to obtain cellular and dendritic structures. Macrostructural and microstructural aspects along the casting have been characterized by optical microscopy and SEM techniques. Electrochemical impedance spectroscopy and potentiodynamic polarization curves were used to analyze the corrosion resistance of samples in a 0.5 M H{sub 2}SO{sub 4} solution at 25 C. For cellular microstructures the corrosion rate decreases with increasing cell spacing. In contrast, finer dendritic spacings exhibit better corrosion resistance than coarser ones. The microstructural pre-programming may be used as an alternative way to produce Pb alloy components in conventional casting, rolled-expanded, and continuous drum casting with better corrosion resistance. (author)

The corrosion behaviour of investment cast and friction stir (FS) processed Ti-6Al-4V alloy was studied in HCl solution. FS processing was performed with the peak temperatures both above and below the {beta} transus. All of the samples exhibited active-passive transitions in deaerated 5% HCl at room temperature, but the {beta} FS processed samples exhibited superior corrosion behaviour. The corrosion morphology after immersion in 20% HCl was rationalized on the basis of a difference in partitioning of the alloying elements, which controls the composition of the {alpha} and {beta} phases.

Although well known, corrosion processes are still a problem for technical constructions. Although different coating technologies and materials have been developed and approved to prevent base metals from being destroyed, industrial applications dealing with aggressive atmospheres, require new material concepts to protect them. Using the example of two different applications, on the one hand heat exchangers in waste incineration plants and on the other hand permanent-molds used for casting non-ferrous metals, innovative material concepts for corrosion protection are given. Heat exchangers in waste incineration plants are exposed to highly corrosive atmospheres especially due to high temperatures in combination with chlorine containing atmospheres. Wire arc sprayed coatings made of iron-bas...

The effects of disinfection and biofilm on the corrosion of cast iron pipe in a model reclaimed water distribution system were studied using annular reactors (ARs). The corrosion scales formed under different conditions were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), while the bacterial characteristics of biofilm on the surface were determined using several molecular methods. The corrosion scales from the ARs with chlorine included predominantly ?-FeOOH and Fe2O3, while CaPO3(OH)·2H2O and ?-FeOOH were the predominant phases after chloramines replaced chlorine. Studies of the consumption of chlorine and iron release indicated that the formation of dense oxide layers and biofilm inhibited iron corrosion, causing stable lower chlorine decay. It was verified that iron-oxidizing bacteria (IOB) such as Sediminibacterium sp., and iron-reducing bacteria (IRB) such as Shewanella sp., synergistically interacted with the corrosion product to prevent further corrosion. For the ARs without disinfection, ?-FeOOH was the predominant phase at the primary stage, while CaCO3 and ?-FeOOH were predominant with increasing time. The mixed corrosion-inducing bacteria, including the IRB Shewanella sp., the IOB Sediminibacterium sp., and the sulfur-oxidizing bacteria (SOB) Limnobacter thioxidans strain, promoted iron corrosion by synergistic interactions in the primary period, while anaerobic IRB became the predominant corrosion bacteria, preventing further corrosion via the formation of protective layers. PMID:22209261

corrosion) and that the leading edge inside the wall was the distress ... The assumed blade material was cast IN 100 alloy. .... Corn pu t ed ai r fo i I I ead i ng- edg e-s t ag n at i on-poi n t , ..... mined from a ductility exhaustion approach. 2.

The mechanical, fatigue, thermal fatigue, stress rupture, oxidation and hot-salt corrosion properties of two cobalt based alloys were assessed. Fulmalloy C1, a casting alloy with a nominal composition of 20Cr, 7W, 5Al 0.2C, has good fatigue, oxidation and...

The comparison of mechanical properties, fracture toughnes, fatigue properties, corrosion resistance and technological efficiency during casting, deformation and quenching, as well as the structure of 1933 alloy commercial die forgings with the die forgings of B93 {Pi}h and 7050 alloys was carried out. (orig.)

A simple to employ corrosion protecting coating based on sol-gel derived new nanocomposites for Al alloys has been developed. This composite coating reacts to the Al surface by formation of a thermodynamically stabilized interface. Moreover, for pressure cast Al, the coating process can be used for ...

fatigue cracking. Thermal shrinkage, particularly of aluminum impellers on steel ... in fretting corrosion. Radial piloting has been ensured by use of interference .... 2014-T6. 6061 -T6. 7075-T73. 7079. Steel. AM 350. 304L (cast). 304L. 310 ...

This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy. PMID:21244518

The objective of the present study was to characterize the short-term biomechanical properties of cast micro/macroporous poly(caprolactone) (PCL) tubes intended for application as tissue integrating blood vessel substitutes. Micro/macroporous PCL vascular grafts (5.5 mm internal diameter, 7.5 mm ext...

  Although boronizing is known as a useful surface-improving treatment for spheroidal graphite cast iron (SG iron) , the corrosion resistance of boronized SG iron has seldom been reported. Graphite configuration, however, seems to affect on the morphology of boride layer and the corrosion resistance in SG iron. Anodic polarization measurements are performed on 0.01NHCl solution to study the effect of boronizing on the corrosion resistance of SG irons with identical chemical composition and different graphite nodule sizes or counts. The results show that : (1) Boronizing improves corrosion resisitance in SG iron, and FeB is more effective than Fe2B. (2) Increasing the graphite nodule size decreases the corrosion resistance of boronized specimens, as well as untreated and oil-quenched specimens.   

Carbon steels may be used for borehole liners in a potential high-level nuclear waste repository in tuff in Nevada. Borehole liners are needed to facilitate emplacement of the waste packages and to facilitate retrieval of the packages, if required. Corrosion rates of low carbon structural steels AISI 1020 and ASTM A-36 were determined in J-13 well water and in saturated steam at 100{sup 0}C. Tests were conducted in air-sparged J-13 water to attain more oxidizing conditions representative of irradiated aqueous environments. A limited number of irradiation corrosion and stress corrosion tests were performed. Chromium-molybdenum alloy steels and cast irons were also tested. These materials showed lower general corrosion but were susceptible to stress corrosion cracking when welded. 4 references, 4 tables.

In oxidizing environments, most tin-based lead (Pb)-free alloys form a tin oxide that is easily eroded or mechanically damaged, affecting corrosion resistance and thus reliability of the soldered joints. In this study, the effect of microstructure heterogeneity on corrosion behavior of Pb-free solder candidate systems has been investigated on the example of as-cast and heat-treated alloys. The research was focused on a comparison between the corrosion resistance of binary Sn-Zn and ternary Sn-Zn-Cu alloys. Accelerated corrosion tests were performed by means of electrochemical methods in the sodium sulfate solution (VI), Na2SO4, of about 0.5 M concentration, pH adjusted to 2 by means of concentrated H2SO4 acid. In these tests, the corrosion potentials as well as polarization curves were determined for the selected alloys in as-cast state and after their heat treatment using different combinations of processing parameters. The measurements of basic electrochemical characteristics were made, i.e., the corrosion current ( i corr ?A/cm2) and Tafel coefficients, both cathodic ( b c V/dec) and anodic ( b a V/dec) ones. Detailed structural characterization of as-cast and heat-treated alloys before and after accelerated corrosion tests has been made under a wide range of magnifications using light microscopy and scanning electron microscopy observations. The results showed that structural heterogeneity of the examined alloys, attributed to the presence of secondary phases, and affected by their size and distribution, significantly influences the behavior of the examined Pb-free Sn-Zn-based alloys in the corrosive environment.

Cast NiAl alloyed with Cr, Pt, Pd, Ir and Ru was tested in 1-h cycles at 950 C under hot corrosion conditions and at 1150 C in oxygen. For comparison, Hf-doped NiAl variants and a cast NiPtAl alloy resembling the composition of commercial aluminide coatings were included. Cr was the only element that reduced hot corrosion attack of NiAl significantly. However, at higher temperatures, addition of Cr to Hf-doped NiAl accelerated the alumina scale growth rate and promoted spallation of the oxide scale. The results from initial detailed characterization indicate that rejection of chromium at the metal-oxide interface gives rise to the formation of chromium-rich precipitates in the alloy, which apparently modify its oxidation behavior. This suggests that for NiAl-based substrates, hot corrosion resistance and exceptional scale spallation resistance may be mutually incompatible goals. (orig.)

Humid-air and aqueous general and pitting corrosion models (including their uncertainties) for the carbon steel outer containment barrier were developed using the corrosion data from literature for a suite of cast irons and carbon steels which have similar corrosion behaviors to the outer barrier material. The corrosion data include the potential effects of various chemical species present in the testing environments. The atmospheric corrosion data also embed any effects of cyclic wetting and drying and salts that may form on the corroding specimen surface. The humid-air and aqueous general corrosion models are consistent in that the predicted humid-air general corrosion rates at relative humidities between 85 and 100% RH are close to the predicted aqueous general corrosion rates. Using the expected values of the model parameters, the model predicts that aqueous pitting corrosion is the most likely failure mode for the carbon steel outer barrier, and an earliest failure (or initial pit penetration) of the 100-mm thick barrier may occur as early as about 500 years if it is exposed continuously to an aqueous condition at between 60 and 70{degrees}C.

It is commonly held that the caudal mesenteric artery (CaMA, or inferior mesenteric artery in humans) arises in the same manner as the celiac and cranial mesenteric artery (CrMA, or superior mesenteric artery in humans), i.e., from the remodeling of the vitelline system of arteries that surrounds and supports the yolk sac. Conflicting evidence about the precise manner in which the CaMA arises was presented in studies of the luxate syndrome (Carter: J. Genet. 1954;52:1-35) and sirenomelia (Schreiner and Hoornbeek: J. Morphol. 1973;141:345-358) in the mouse. These studies suggested that the CaMA arises from the remodeling of the medial umbilical arterial roots. Later studies of blood vessel development in the hindlimb of the Dominant hemimelic mouse (Gest: Anat. Rec. 1984;208:296; Anat. Rec. 1987;218:49A; Gest and Roden: Anat. Rec. 1988;220:37-38A) also supported the results of the previous studies. The present investigation tests the hypothesis that the CaMA arises as a result of the regression and remodeling of the medial umbilical arterial roots. Vascular corrosion casts of 9.5-13.5-day-old mouse embryos were observed by scanning electron microscopy (SEM). The results of the present investigation agree with the aforementioned studies. The medial umbilical roots initially conduct the blood to the placenta. On days 10-12 the medial umbilical roots regress and remodel into the CaMA, while the lateral umbilical roots take over the blood supply to the placenta. On the basis of our results, we conclude that the CaMA arises from the medial umbilical roots and not from the remodeling of the vitelline system of arteries, as previously assumed. PMID:12552635

The placental vasculature is critical for nutrient, gas, and waste exchange between the maternal and fetal systems. Its development depends on the proper expression and interaction of angiogenesis and associated growth factors. Heme oxygenase (HMOX), the enzyme for heme degradation, plays a role in angiogenesis and is highly expressed in the placenta. To evaluate the role of maternal HMOX1, the inducible HMOX isozyme, on placental vasculature formation, mice with a partial deficiency in Hmox1 (Hmox1(+/-)) were used. Three-dimensional images of placental vasculatures as well as spiral arteries from Hmox1(+/+) or Hmox1(+/-) placentas were created by vascular corrosion casting technique and imaged by micro-computerized tomography (microCT). The structures and morphologies of fetomaternal interfaces were observed by histological staining and the ultrastructure of uterine natural killer (uNK) cells, a major regulator in spiral artery remodeling, was analyzed by transmission electron microscopy. A group of growth factors and angiogenic factors from the decidua/mesometrial lymphoid aggregate of pregnancy (MLAp) as well as labyrinth regions were quantified using an angiogenesis PCR array kit and compared between Hmox1(+/+) or Hmox1(+/-) placentas. In conclusion, a partial deficiency of maternal Hmox1 resulted in the malformation of fetomaternal interface, insufficiency of spiral artery remodeling, and alteration of uNK cell differentiation and maturation. These changes were independent of the fetal genotype, but relied on the maternal HMOX1 level, which determined the balance of expression levels of pro- and antiangiogenic factors in the decidua/MLAp region. These results implied that Hmox1 polymorphisms among the human population might contribute to some unexplained cases of pregnancy disorders, such as fetal growth retardation and preeclampsia. PMID:21778140

Corrosion tests were performed with various construction materials, such as carbon steel, cast iron, stainless steels, nickel and nickel-based alloys, copper and its alloys, aluminum alloy, zirconium alloy, and tantalum, exposed to wet-process superphosphoric acids (approximately 70% P{sub 2}O{sub 5}) from all the suppliers in the United States and to a technical-grade (55% P{sub 2}O{sub 5}) acid made by the electric furnace process. The study was conducted in response to reports from pipe-reactor users of excessive corrosion by superphosphoric acids and electric furnace acid. Test temperatures were ambient (approximately 21{degrees}C or 70{degrees}F), 66{degrees}C (150{degrees}F), and 93{degrees}C (200{degrees}F). Test results showed that temperature was a significant factor in acid corrosivity. Electric furnace acid was more corrosive than the superphosphoric acids. Carbon steel, cast iron, and aluminum alloy were not resistant to either the superphosphoric acids or the electric furnace acid. Nickel-chromium (Ni-Cr) and nickel-molybdenum (Ni-Mo) based alloys and tantalum exhibited adequate corrosion resistance in the superphosphoric acids and the electric furnace acid. Stainless steels performed well in all test acids at all test temperatures with some exceptions in the electric furnace acid at 93{degrees}C. Zirconium alloy, copper and its alloys, pure nickel, and Monel 400 provided adequate corrosion resistance to all test acids at ambient temperature only.

A study has been undertaken into the corrosive wear of marine diesel engine piston ring cast iron pin specimens against cylinder lining grey cast iron disc specimens during reciprocating sliding in mixtures of base lubricating oil and 10% sulphuric acid solution. Wear is low in the base-oil environment. The presence of 5% or 10% acid in the oil is sufficient to disrupt partially the hydrodynamic oil film, giving significant periods of metal-metal contact. The dispersed nature of the acid droplets in the oil restricts corrosion to localized sites on the metal surfaces and wear damage is mainly due to mechanical processes. As the volume of acid in oil is increased to 20% and 40%, the hydrodynamic oil film is disrupted almost completely and the aqueous phase becomes almost continuous. This increases the contribution of electrochemical corrosion to the corrosive wear phenomenon as the products of corrosion are removed rapidly from the contacting surfaces by the sliding action. In this situation, both corrosive and mechanical processes contribute to the overall wear damage.

In organs, the correct architecture of vascular and ductal structures is indispensable for proper physiological function, and the formation and maintenance of these structures is a highly regulated process. The analysis of these complex, 3-dimensional structures has greatly depended on either 2-dimensional examination in section or on dye injection studies. These techniques, however, are not able to provide a complete and quantifiable representation of the ductal or vascular structures they are intended to elucidate. Alternatively, the nature of 3-dimensional plastic resin casts generates a permanent snapshot of the system and is a novel and widely useful technique for visualizing and quantifying 3-dimensional structures and networks. A crucial advantage of the resin casting system is the ability to determine the intact and connected, or communicating, structure of a blood vessel or duct. The structure of vascular and ductal networks are crucial for organ function, and this technique has the potential to aid study of vascular and ductal networks in several ways. Resin casting may be used to analyze normal morphology and functional architecture of a luminal structure, identify developmental morphogenetic changes, and uncover morphological differences in tissue architecture between normal and disease states. Previous work has utilized resin casting to study, for example, architectural and functional defects within the mouse intrahepatic bile duct system that were not reflected in 2-dimensional analysis of the structure(1,2), alterations in brain vasculature of a Alzheimer's disease mouse model(3), portal vein abnormalities in portal hypertensive and cirrhotic mice(4), developmental steps in rat lymphatic maturation between immature and adult lungs(5), immediate microvascular changes in the rat liver, pancreas, and kidney in response in to chemical injury(6). Here we present a method of generating a 3-dimensional resin cast of a mouse vascular or ductal network, focusing specifically on the portal vein and intrahepatic bile duct. These casts can be visualized by clearing or macerating the tissue and can then be analyzed. This technique can be applied to virtually any vascular or ductal system and would be directly applicable to any study inquiring into the development, function, maintenance, or injury of a 3-dimensional ductal or vascular structure. PMID:23128398

The ability to properly apply casts and splints is a technical skill easily mastered with practice and an understanding of basic principles. The initial approach to casting and splinting requires a thorough assessment of the injured extremity for proper diagnosis. Once the need for immobilization is ascertained, casting and splinting start with application of stockinette, followed by padding. Splinting involves subsequent application of a noncircumferential support held in place by an elastic bandage. Splints are faster and easier to apply; allow for the natural swelling that occurs during the acute inflammatory phase of an injury; are easily removed for inspection of the injury site; and are often the preferred tool for immobilization in the acute care setting. Disadvantages of splinting include lack of patient compliance and increased motion at the injury site. Casting involves circumferential application of plaster or fiberglass. As such, casts provide superior immobilization, but they are more technically difficult to apply and less forgiving during the acute inflammatory stage; they also carry a higher risk of complications. Compartment syndrome, thermal injuries, pressure sores, skin infection and dermatitis, and joint stiffness are possible complications of splinting and casting. Patient education regarding swelling, signs of vascular compromise, and recommendations for follow-up is crucial after cast or splint application. PMID:19145960

The electrochemical behavior of titanium and dental casting alloys in modelling oral conditions With applying dental implants in the oral cavity the direct contact of various metals (titanium and other casting alloys) is unavoidable. Considering the electrolyte characteristic of the saliva, the chances are given that electrochemical processes might occur under such circumstances. The aim of this study was to investigate the electrochemical behavior of titanium and other dental alloys being in direct contact with the oral environment. Nickel-chromium, cobalt-chromium, high palladium content and gold alloys as well as CP grade I titanium cast samples respectively were involved in the study. Test models were made from these metals. As an electrolyte solution (set to pH 4) artificial saliva and 0.9 % NaCl solution were used. The type and the rate of corrosion were assessed with laboratory immersion test and electrochemical polarization method. In case of polarization method a three-electrode measuring-cell was applied. Laboratory exposure tests revealed that titanium resisted corrosion; there was no sign of corrosion at all. The high palladium content alloy and gold alloy behaved similarly. The nickel-chromium and cobalt-chromium alloys showed some signs of corrosion, especially in sites with damaged surface or inhomogeneities on the surface. Results of the laboratory electrochemical experiments correlated with immersion studies graphically illustrated in the paper. PMID:16468487

Abstract in portuguese O objetivo deste trabalho foi analisar a distribuição dos vasos arteriais nos testículos em caprinos com diferentes graus de divisão escrotal. A configuração escrotal foi classificada da seguinte forma: Grupo I: constituído por caprinos com escroto único, Grupo II: com escroto separado até a metade do testículo e Grupo III: com separação escrotal estendendo-se além da metade do testículos. As artérias foram injetadas e coradas com solução de acetado de vi (more) nil, sendo os orgãos (30 pares) submetidos à corrossão para obtenção dos moldes vasculares. As artérias testiculares emergem da aorta abdominal, com trajeto retilíneo, atravessam o canal inguinal, apresentam-se espiraladas e envolvidas parcialmente pelo plexo pampiniforme. Próximo à extremidade caudada do testículo, dividem-se mais freqüentemente nos ramos cranial e caudal, os quais emitem vasos colaterais, de onde emergem ramos penetrantes. Os testículos dos animais com nível intermediário de divisão escrotal (Grupo II) apresentam menor quantidade destes ramos, sendo os quadrantes mais povoados o ventrolateral e o dorsolateral. Conclui-se que a origem, o trajeto e a distribuição das artérias testiculares não apresentam variações relacionadas ao grau de divisão escrotal em caprinos. Abstract in english The objective of this study was to describe the distribution of testicular arterial vessels in caprines with different degrees of scrotal division. Scrotal configurations were classified as follows; Group I: scrotum without bipartition; Group II: scrotum showing a ventral division until the middle of the testis; and, Group III: scrotal separation extended beyond the middle of the testis. A colored vinyl acetate solution was injected into 60 testicular arteries (30 pairs). (more) After, the samples were submitted to corrosion cast method to obtain tubular vascular models for macroscopic analysis. We observed that the testicular arteries emerge from the abdominal aorta, cross the inguinal canal to become coiled and involved by the pampiniform plexus. Close to the caudal extremity of the testis, the arteries become divided in cranial and caudal branches that emit collateral vessels to originate emerging branches. Testicles with intermediate level of scrotal division (group II) showed a smaller amount of those branches than the others, being the most populated the ventrolateral and the dorsolateral quadrants. The origin, distribution and localization of the testicular arteries did not show any differences related to the degree of scrotal division in caprines.

This paper brings together and analyzes recent work based on the interpretation of the electrochemical measurements made on a modified micro-abrasion-corrosion tester used in several research programmes. These programmes investigated the role of abradant size, test solution pH in abrasion-corrosion of biomaterials, the abrasion-corrosion performance of sintered and thermally sprayed tungsten carbide surfaces under downhole drilling environments and the abrasion-corrosion of UNS S32205 duplex stainless steel. Various abrasion tests were conducted under two-body grooving, three-body rolling and mixed grooving-rolling abrasion conditions, with and without abrasives, on cast F75 cobalt–chromium–molybdenum (CoCrMo) alloy in simulated body fluids, 2205 in chloride containing solu...

The effects of disinfection and biofilm on the corrosion of cast iron pipe in a model reclaimed water distribution system were studied using annular reactors (ARs). The corrosion scales formed under different conditions were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), while the bacterial characteristics of biofilm on the surface were determined using several molecular methods. The corrosion scales from the ARs with chlorine included predominantly a-FeOOH and Fe2O3, while CaPO3(OH)2H2O and a-FeOOH were the predominant phases after chloramines replaced chlorine. Studies of the consumption of chlorine and iron release indicated that the formation of dense oxide layers and biofilm inhibited iron corrosion, causing stab...

The in vitro electrochemical behaviour of a new titanium based a-alloy (Ti-0.5wt% Si-0.65wt% C), fabricated via casting and rapid cooling route, was determined using linear, Tafel, potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS), complemented with ex situ SEM-EDS analysis to evaluate the corrosion mechanism. The experimental results revealed that silicon and carbon, in addition to titanium, resulted in the enhancement of mechanical properties. The polarization tests confirmed that Ti-Si-C alloy possessed excellent corrosion resistance (a low corrosion current density of 0.033mAcm^-^2), comparable to cp Ti and better than Ti6Al4V in phosphate buffered saline (PBS). The mechanism of corrosion was identified as selective dissolution of titanium solid soluti...

Abstract There is a clear trend in industry to eliminate fluorine from metallurgical slags. Regarding the continuous casting process, fluorine in mould powders is undesirable due to the following reasons: (i) evolves easily from slags producing health-injurious gaseous substances like hydrofluoric acid, (ii) creates problems for storage and utilization of solid waste, and (iii) causes machinery corrosion. A collaboration among universities, mould powder supplier, and steel producer was established, aiming for the development of a new F-free mould powder for billet casting. Firstly, technological parameters for a particular composition were determined: melting characteristics, viscosity, melting behavior, and crystallization tendency. Afterwards, industrial trials were performed in a Brazil...

A method for creating tough, flexible, bronchoalveolar casts from formalin-fixed canine lung is described. A lung was washed using simple methods and fixed in 10% neutral-buffered formalin. While still wet with formalin, an intact lobe was injected with silicone sealant, Silastic 734 RTV (Room Temperature Vulcanizing), using a caulk gun. Following digestion with protease and corrosion with potassium hydroxide, a bronchoalveolar cast was recovered giving detail as shown using scanning electron microscopy or conveniently seen by stereo light microscopy. This method should be useful for micro-anatomy studies of normal and diseased lungs. PMID:8393308

Ultrathin poly(epsilon-caprolactone) (PCL) films were fabricated through biaxially drawn films made from three different methods, namely, spin casting, 2-roll milling, and solution casting. Biaxial drawn spin cast films yield thickness of 1.2 microm which is 9 and 12 times thinner that 2-roll mill and solvent cast films, respectively. The films fabricated were found to exhibit different drawing ratios. 2-roll mill film exhibits the highest drawing ratio of 4 x 4 while spin cast films can only draw up to a ratio of 2 x 2. The morphology of the films, studied using a polarized microscope and atomic force microscope, showed fine fibrillar networks of different thicknesses. Biaxially drawn 2-roll mill and solvent cast films showed thicker fibrils as compared to those for the spin cast films. Such a difference can be attributed to larger spherulites caused by slower cooling rates during melt pressing for both 2-roll mill and solvent cast films and smaller spherulites because of fast cooling during evaporation for spin cast films. Thermal analysis through differential scanning calorimetry revealed a slight increase in the peak-melting temperature after biaxial drawing. A drop in percentage crystallinity was also noted. The result of the water vapor transmission rate (WVTR) was found to be dependent on fabrication techniques that determine the spherulites formation. It was also found that the WVTR was inversely proportional to the thickness of the films. Tensile strength and modulus of the films showed significant improvements after biaxial stretching. By identifying the unique strengths of each individual PCL film produced via different techniques, it is possible to apply to different areas of membrane tissue engineering such as dermatology, ophthalmology, vascular graft engineering, and soft tissue regeneration. PMID:17274653

Superalloys are those alloys based on Group VIIIA-base elements developed for elevated temperature service in virtue of their combination of mechanical strength with surface stability in such corrosive environments as those of aircraft and industrial gas turbines, coal conversion plants, etc. An updated account is presently given of the genesis and character of superalloys; superalloys' impact on gas turbine design; precipitation- and dispersion-strengthening, and precipitation-hardening; representative Ni-, Co-, and Ni-Fe-base alloys; directionally solidified superalloys; phase composition prediction, mechanical behavior, and fatigue; high temperature oxidation, hot corrosion, and protective coatings; investment-cast, wrought, and P/M alloys; and prospective competition for superalloys from nonmetallic materials.

A Ni3Si-Cr7C3 composite coating was fabricated on AISI 1020 steel substrate by self-propagating high-temperature synthesis (SHS) casting route. Phase composition, microhardness and dry sliding wear behavior of the coating were studied. The results indicated that the coating was mainly consisted of Ni3Si and Cr7C3. The microhardness of coating is about 900HV. The friction and wear tests showed that although the friction coefficient had no obvious change, the wear resistance of the AISI 1020 steel matrix was improved greatly. Also, the corrosion test result showed that the coating had an excellent corrosion resistance.

Die Casting dies are subject to severe service conditions during the die casting operation. While these severe conditions are necessary to achieve high production rates, they cause the dies which are commonly made of H13 die steel, to suffer frequent failures. The major die failure mechanisms are erosion or washout, Heat checking, soldering and corrosion. Due to their geometrical complexity, die casting dies are very expensive (some dies cost over a million dollars), and thus a large number of parts have to be produced by a die, to justify this cost and leverage the advantages of the die casting process (high production rates, low manpower costs). A potential increase in the die service life, thus has a significant impact on the economics of the die; casting operation. There are many ways to extend die life: developing new wear resistant die materials, developing new surface treatments including coatings, improving heat treatment of existing H13 dies, using better lubricants that can protect the die material, or modifying the die geometry and process parameters to reduce the intensity of wear. Of these the use of coatings to improve the wear resistance of the die surface has shown a lot of promise. Consequently, use of coatings in the die casting industry and their wide use to decrease die wear can improve significantly the productivity of shop operations resulting in large savings in material and energy usage.

The paper presents the properties of the author`s company`s proprietary super duplex stainless steel. Work is presented showing the development of a more realistic laboratory solution representing typical limestone slurries found in real flue gas desulfurization (FGD) systems. The importance of additions of metal ions such as Fe{sup 3+} and Mn{sup 2+} as well as partially oxidized sulfur species is demonstrated. Results are presented comparing the crevice corrosion resistance of super duplex stainless steel in these slurries with other commonly used wrought and cast stainless steels, for both simulated anthracite and lignite type slurries. Data from loop tests on the erosion resistance of a range of alloys in simulated FGD slurries is presented. The results clearly show the superior resistance of super duplex stainless steel to both crevice corrosion and erosion in FGD slurries. Finally the experiences in UK FGD systems with both cast and wrought super duplex stainless steel are presented.

Electrochemical techniques using both ac and dc as well as surface analyses approach were used to investigate the corrosion inhibition characteristics of polyacrylic acid (PAA) for pure cast aluminium in 0.5 M H2SO4 at 30???1 ?C. The effect of iodide ion additives was also studied. The results obtained indicate that PAA inhibited the corrosion of pure cast aluminium in the acid medium by adsorption onto the metal surface following Frumkin adsorption isotherm model. Inhibition efficiency increases with an increase in PAA concentration and synergistically enhanced by the addition of iodide ions. A mixed inhibition mechanism is proposed for the inhibitive effects of PAA as revealed by potentiodynamic polarisation technique. Synergism parameter evaluated was found to be greater than unity, ind...

The susceptibility to hot corrosion of four nickel-base, cast superalloys has been studied at 900 and 1000 C. The test consisted of coating alloy samples with known amounts of Na2SO4 and oxidizing the coated samples isothermally in 1 atmosphere of slowly flowing oxygen, the weight-gain being monitored on a sensitive recording microbalance. Susceptibility to hot corrosion decreased in the order of decreasing molybdenum content of the alloys. Preoxidation of samples before hot-corrosion testing markedly increased the induction period observed prior to the inception of hot corrosion for all alloys tested. X-ray diffraction analyses of the oxide scales were made. All samples that underwent hot corrosion showed the presence of a (Ni,Co)MoO4 layer near the alloy-oxide interface. Several specimens displayed resistance to hot corrosion and these showed NaTaO3 as a prominent feature in their oxide scale. Our results may be interpreted as indicating that molybdenum in an alloy is detrimental, with respect to hot corrosion, while tantalum is beneficial.

A specific composition range and process sequence are described for the production of single crystal superalloy articles which have an exceptional combination of high temperature mechanical properties and resistance to oxidation and hot corrosion. The nominal composition is 6% Ta, 9% Cr, 5% Co, 1% Ti, 1% Mo, 7% W, 5.5% Al, 0.15% Hf balance essentially nickel. Material of this composition is cast and solidifed in single crystal form and heat treated to produce an optimum microstructure.

The development of an iron-base alloy that can meet the requirements of automotive Stirling engine cylinders and regenerator housings is described. Alloy requirements are as follows: a cast alloy, stress for 5000-hr rupture life of 200 MPa (29 ksi) at 775 C (1427 F), oxidation/corrosion resistance comparable to that of N-155, compatibility with hydrogen, and an alloy cost less than or equal to that of 19-9DL. The preliminary screening and evaluation of ten alloys are described.

An aluminum-cast statue, representing an open-armed Madonna, was positioned in 1938 on the memorial for the victims of World War I built in Lido di Venezia (Italy). Due to the severe exposure conditions (marine industrial atmosphere), the statue suffered extensive deterioration and fell down in summer 2003. In 2009, a restoration project started, with the aim of repairing and conserving the statue, at the time badly fragmented. In the present work, the results of investigations on (i) degradation factors and (ii) potential conservation strategies, are presented. In particular, in the first part of the study composition and microstructure of the cast alloy were determined, pointing out the influence of casting defects on the intrinsic brittleness of the statue. The corrosion products on the...

Filling trace, filling time and temperature distribution during the die-casting process were simulated using commercial software (MAGMA). The surface microstructure and phase distribution in thin-walled AZ91D magnesium components cast on a hot-chamber die-casting machine were investigated by means of optical microscopy and scanning electron microscopy. The depth profile of alloying elements was examined using a glow discharge optical emission spectrometer. The outer skin microstructure consists of more ?-phase and less eutectic ?-phase than the interior region. The elemental content of C, Si, and Fe in the outer skin increased along the filling trace, and they decreased with increasing distance from the surface to the interior region, while the Al had an inverse trend. The corrosion resistance decreased along the filling trace.

The objective of this research was to investigate the effect of mold temperature on grain interior and grain boundary reactions in a14-karat gold alloy. The alloy (Au-15%Ag-3%Pd-24 mass%Cu) was cast into an investment with different mold temperatures (22, 250,400, and 700°C) and then analyzed using SEM, X-ray diffraction, and potentiodynamic polarization tests. Lower mold temperatures(22 and 250°C) retarded a grain boundary reaction evidently present when using higher mold temperatures (400 and 700°C). Phase separation, which was manifested as a dual phase grain boundary nodular formation, was observed at a higher degree at 400°C mold temperature than at 700°C. The corrosion potentials of alloys cast at lower mold temperatures were more noble than those cast at higher mold temperatures, suggesting improved corrosion properties. Results of this study showed that the microstructure, crystalline phases present, and corrosion properties of 14-karat gold alloy were keenly influenced by the mold temperature, which controls and influences the cooling rate.   

Nowadays, lead-acid battery grids are manufactured mostly from low-antimony and lead-calcium alloys. A variable corrosion resistance of battery grids is caused by either battery operation conditions, purity of used alloy components, an alloy makeup, and the castings quality. Such compositions as usual lead-antimony alloy, low-antimony lead-arsenious alloy and lead-calcium alloy with moderate content of tin today may be regarded as the most studied ones. A significant share of published works has been devoted to low-antimony lead-tin alloys. In the present article, results of corrosion tests of the samples made with application of cadmium as the second component of low-antimony alloy, has been represented. Several samples were extra-alloyed by selenium and silver. Samples of lead-calcium and usual antimony alloys as well as pure lead samples were being tested simultaneously. Upon termination of polarization, weight of anodic films referred to a unit of the sample surface has been determined. Thus, the film covering lead-antimony alloy sample has the maximal weight, whereas the oxidation products on the pure lead surface have the lowest one. Among low-antimony alloys, the highest corrosion resistance has been found out with the samples alloyed by a low amount of silver. The microstructure of the castings surface has been analysed. Process of corrosion has been considered in connection with size of grains. (author)

This paper examines the application of the acryl plastic injection to the preparation of vascular corrosion microcasts for scanning electron microscopy (SEM). The original injection method using acryl plastic was described by Taniguchi, Ohta et al. in 1952 and 1955, under the title of "New improved method for injection of acrylic resin". Three dimensional observations were undertaken in our laboratory on the angiology at the macro- and microscopic levels of various organs from various mammals employing the original method. Based on this extensive experience, an injection method for preparing corrosion microcasts for use in SEM was devised in our laboratory. Microcasts prepared by the present method were able to demonstrate the fine vascular architecture of each organ. In general, although applications for preparing vascular microcasts of isolated and parenchymal organs are not so difficult, the method can be used to be applicable for demonstrating the fine vascular architecture related to or within hard tissues, as well as for investigating the morphological relations between changes of vascular patterns and restorative changes in the surrounding tissues affected by experimental operations. SEM microphotographs are also presented to illustrate actual practical applications.   

HK steels are among the most used heat-resistant cast stainless steels, being corrosion-resistant and showing good mechanical properties at high service temperatures. These steels are widely used in reformer furnaces and as superheater tubes. During service, combustion gases leaving the burners come in contact with these tubes, resulting in corrosive attack and a large weight loss occurs due to the presence of vanadium, which forms low melting point salts, removing the protective oxide layer. In this work the external surface of a tube with dramatic wall thickness reduction was analyzed using light microscopy, scanning electron microscopy, and transmission electron microscopy. The identification of the phases was achieved by energy dispersive spectroscopy (EDS) analyses. The results showed oxides arising from the external surface. In this oxidized region vanadium compounds inside chromium carbide particles were also observed, due to inward vanadium diffusion during corrosion attack. A chemical reaction was proposed to explain the presence of vanadium in the metal microstructure.

Hydrogen-induced cracking (HIC) and CO{sub 2} corrosion of high-strength low-alloy (HSLA) steel were studied. Advanced technologies were developed on the basis of this study, including the manufacturing of clean steel, soft reduction for continuously cast slabs, accelerated cooling after plate rolling, and pipe seam welding. HSLA line pipes that were manufactured using a combination of these technologies showed excellent properties in sour environment or sweet CO{sub 2} environment. Basic research on the CO{sub 2} corrosion of low-alloy steel led to the discoveries that the addition of 0.6% Cr to the base material improved field weldability and low-temperature toughness, and that the addition of approximately 0.2% chromium to the weld metal in the base material was effective in preventing the preferential corrosion of the weld. 9 refs., 14 figs.; 6 tabs.

Abstract in english The present work aimed to study the transformation from as-cast structure of the Ti4Al-4V alloy, as a result of the Ti-6Al-4V recycling, after some rapid heat treatments based on martensitic reactions. The effects on mechanical properties were evaluated by Vickers hardness measurements, Charpy and monotonic tensile tests. The corrosion strength was tested by immersion during 4 months in artificial physiological solutions, to evaluate its possible use as a biomaterial. The (more) data pointed to: a) a reduction on corrosion strength for quenching above beta transus; b) significant increasing on hardness and mechanical strength; c) a maintenance of impact toughness; d) the corrosion strength for immersion in a NaCl 1%+ NaF 0,1% (m/m) was lower in all conditions, specially for those including heating to 900 °C.

Ni- and Cu-free Zr-Al-Co-Ag bulk metallic glasses (BMGs) were synthesized by copper mold casting. The effects of Ag addition for partially replacing Co of Zr53Al16Co31 BMG on the corrosion behavior, surface chemistry and in vitro biocompatibility of BMGs were investigated. The Zr-Al-Co-Ag BMGs are spontaneously passivated with low passive current densities in phosphate buffered saline (PBS) solution. Partial substitution of Co by Ag is effective in improving the corrosion resistance of the Zr-Al-Co BMG. X-ray photoelectron spectroscopy (XPS) measurements reveal that the Ag addition increases the concentration of Zr and decreases the concentration of Al in the surface passive film of BMGs, which is responsible for the enhanced corrosion resistance of Zr-Al-Co-Ag BMGs. Mouse MC3T3-E1 pre-ost...

In order to investigate the decay of bronzes exposed to acid wet depositions, a comparative study has been performed by following the corrosion behaviour of different sets of bronze specimens exposed either to natural rain or to a similar solution, without organic compounds, artificially reproduced in laboratory. The as cast G85 bronze specimens were exposed to aggressive solutions for different periods through a wet-dry technique. The pH trend of the solutions and the amount of metals transferred into the solutions were periodically monitored. OM, SEM, XRD, RAMAN analyses and ac electrochemical measurements were performed on the artificially weathered specimens. Preliminary results, showing the difference between the ageing in natural and synthetic rain, suggest the influence of the organic components on the corrosion process. In particular, the growth of a more uniform protective layer of corrosion products on the metal surface exposed to the natural rain could be attributed to these components.

Blood perfusion in organs has been shown to be heterogeneous in a number of cases. At the same time, a number of models of vascular structure and flow have been proposed that also generate heterogeneous perfusion. Although a relationship between local perfusion and vascular structure has to exist, no model has yet been validated as an accurate description of this relationship. A study of perfusion and three-dimensional (3D) arterial structure in individual rat kidneys is presented, which allows comparison between local measurements of perfusion and model-based predictions. High-resolution computed tomography is used to obtain images of both deposited microspheres and of an arterial cast in the same organ. Microsphere deposition is used as an estimate of local perfusion. A 3D cylindrical pipe model of the arterial tree is generated based on an image of the arterial cast. Results of a flow model are compared with local microsphere deposition. High correlation (r(2) > 0.94) was observed between measured and modeled flows through the vascular tree segments. However, the relative dispersion of the microsphere perfusion measurement was two- to threefold higher than perfusion heterogeneity calculated in the flow model. Also, there was no correlation in the residual deviations between the methods. This study illustrates the importance of comparing models of local perfusion with in vivo measurements of perfusion in the same biologically realistic vascular tree. PMID:16766647

Strip casting process combines casting and hot rolling into a single step, with advantages of low equipment cost, low running cost, energy saving and space saving. Protective gases, such as SF6 and NovecTM612, should be used in order to prevent the ignition of magnesium alloys during strip casting. However, protective gases have disadvantages such as global warming, high production cost and corrosion of steel based equipments. According to the recent study, the addition of CaO is the effective way to improve the ignition and oxidation resistance of magnesium alloy. CaO added AZ31 magnesium alloy strip casting could be manufactured with reduced protective gas during melting and without protective gas during strip casting. The minimum SF6 gas amount could be reduced under 50 ppm for 0.3 mass%CaO added AZ31 magnesium alloy both under sealed and unsealed conditions. The strips of CaO added AZ31 magnesium alloys were almost uniform in terms of microstructure and hardness.   

Embryonic development is associated with extensive vascular growth and remodeling. We used immunohistochemical, light and electron microscopical techniques, as well as vascular casting methods to study the developing chick embryo kidney with special attention to the interplay between sprouting and intussusceptive vascular growth modes. During inauguration at embryonic day 5 (E5), the early mesonephros was characterised by extensive microvascular sprouting. By E7, the vascular growth mode switched to intussusception, which contributed to rapid kidney vasculature growth up to E11, when the first obvious signs of vascular degeneration were evident. The metanephros underwent similar phases of vascular development inaugurating at E8 with numerous capillary sprouts and changing at E13 to intussusceptive growth, which was responsible for vascular amplification and remodeling. A phenomenal finding was that future renal lobules arose as large glomerular tufts, supplied by large vessels, which were split into smaller intralobular feeding and draining vessels with subsequent formation of solitary glomeruli. This glomerular duplication was achieved by intussusception, i.e., by formation of pillars in rows and their successive merging to delineate the vascular entities. Ultimately, the maturation of the vasculature was achieved by intussusceptive pruning and branching remodeling. An interesting finding was that strong VEGF expression was associated with the sprouting phase of angiogenesis while bFGF was upregulated during the phase of intussusceptive microvascular growth. We conclude that microvascular growth and remodeling in avian kidney follows an adroitly crafted pattern, which entails a precise spaciotemporal interplay between sprouting and intussusceptive angiogenic growth modes supported partly by VEGF and bFGF. PMID:16003781

In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 ?m. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. PMID:21783152

X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed a fully amorphous structure for as-cast bulk metallic glass (BMG) and melt-spun ribbons of Zr52Ti6Al10Cu18Ni14 prepared by copper mold casting and the melt-spinning technique, respectively. For melt-spun ribbons, the wheel-side surface contained a higher concentration of quenched-in defects (air pockets), whereas surface irregularities were noticed in the air side. Fluctuation microscopy indicated more medium-range order for the as-cast structure of BMG than for the melt-spun ribbon, whereas in the BMG, the medium-range order was located more in the central region than in the periphery. Macro- and microcell electrochemical experiments of the BMG along the cross section and macrocell experiments of each side of the ribbons in dilute acidic chloride environments indicated that the corrosion resistance of the BMG decreased with the increase in the medium-range order; the medium-range order, however, was less deleterious than either the surface irregularities or the quenched-in defects from the viewpoint of corrosion. A surface film formed on the metallic glasses in a dilute acidic chloride environment mainly consisted of oxide of zirconium, in which zirconium was present in the Zr+3, Zr+2, and Zr+1 state in the BMG and in the air-side and wheel-side surfaces, respectively.

Corrosion resistance of anodized surfaces on high-purity magnesium (99.95 mass%), rolled sheets of ASTM AZ31B (Mg-2.9Al-0.85Zn) magnesium alloy and die-cast plates of ASTM AZ91D (Mg-9.1Al-0.75Zn) magnesium alloy has been studied. Anodization was conducted by environment-friendly electrolysis whose electrolyte consists of phosphate and ammonium salt. The anodized surface was covered with amorphous film, and showed only discoloration during salt spray test where formation of corrosion product (magnesium hydroxide) was well suppressed within 605 ks. Even when the anodized surfaces were trenched with ceramic knife to form locally exposed substrate, corrosion was well suppressed by formation of new type of dense protective films for each substrate which consist of oxygen, magnesium, aluminum and phosphorus. Anodic polarization curves indicate that the anodized surfaces show sacrificial function due to the thermodynamically unstable state of phosphorus in the anodized layers and its resulting release of electrons. From the viewpoint of kinetics in corrosion on the anodzed surfaces, the curves show that the anodized layers dissolve quite slowly into the electrolyte compared with the case of the untreated substrates. The excellent corrosion protectivity obtained by the anodization is considered to be based on the formation of a dense protective film on the exposed area, as well as sacrificial function of the amorphous anodized layer.   

The proposed design for a final repository for spent fuel and other long-lived residues in Sweden is based on the multi-barrier principle. The waste will be encapsulated in sealed cylindrical canisters, which will then be placed in granite bedrock and surrounded by compacted bentonite clay. The canister design is based on a thick cast inner container fitted inside a corrosion-resistant copper canister. During fabrication of the outer copper canisters there will be some unavoidable grain growth in the welded areas. As grains grow they will tend to concentrate impurities within the copper at the new grain boundaries. The work described in this report was undertaken to determine whether there is any possibility of enhanced corrosion at grain boundaries within the copper canister. The potential for grain boundary corrosion was investigated by exposing copper specimens, which had undergone different heat treatments and hence had different grain sizes, to aerated artificial bentonite-equilibrated groundwater with two concentrations of chloride, for increasing periods of time. The degree of grain boundary corrosion was determined by atomic force microscopy (AFM) and optical microscopy. AFM showed no increase in grain boundary 'ditching' for low chloride groundwater. In high chloride groundwater the surface was covered uniformly with a fine-grained oxide. No increases in oxide thickness were observed. No significant grain boundary attack was observed using optical microscopy either. The work suggests that in aerated artificial groundwaters containing chloride ions, grain boundary corrosion of copper is unlikely to adversely affect SKB's copper canisters.

Silica is an important natural component of ground and surface waters, and is sometimes added as an inhibitor to control "red water" problems caused by corroding iron pipes. However, the effect of silicates on many aspects of iron corrosion has never been assessed. Experiments with water containing 0.5, 10, 25 or 50mg/L of SiO(2) demonstrated a significant interplay between aqueous silica and iron corrosion. During this 4-month experiment, higher levels of silica caused more iron release to the water and decreased the size of suspended iron particles. The process of iron corrosion also changed aqueous silica concentrations; silica was released into the water from the cast iron during corrosion and was removed from the water by incorporation into the scale layer. Silica also affected the type of scale that formed on the iron coupons. Scale at the lower silica concentrations was fairly uniform and easy to remove from the coupons, while the scale from the high silica reactors was more dense, and was more difficult to remove. Scale from the high concentration silica reactor also developed tall tubercles, and hydrogen gas-containing bubbles were channeled to solution through these tubercles. Iron corrosion occurring via the evolution was significant under all experimental conditions. PMID:12553983

This report summarizes the results of the General Electric Fireside Corrosion Task II Program. This program was designed to evaluate the erosion/corrosion behavior of gas turbine nozzle guide vane and rotor blade materials in both simulated and actual pressurized fluidized bed combustor (PFBC) environments. Simulation testing included exposing disc-shaped specimens in atmospheric pressure small burner rig test stands operated at 1600/sup 0/F (871/sup 0/C) for periods up to 1300 hours. PFBC evaluation testing consisted of exposing airfoil shaped specimens to the efflux from a PFBC in a turbine test section installed in the Exxon PFBC Miniplant facility at Linden, N.J. Candidate gas turbine materials included three cast vane and blade base alloys, FSX-414, IN-738, and U-700, and one protective coating system, platinum-chromium-aluminide (RT-22). Small burner rig testing consistently showed the nickel-base alloys U-700 and IN-738 most susceptible to corrosion/sulfidation, followed by the cobalt-base alloy FSX-414; the RT-22 coating on IN-738 was most resistant to hot corrosion attack. Parts life estimates have been made for the nickel and cobalt-base alloys based on corrosion rates determined from the PFBC testing.

The overall objective of the Long Term Materials Test (LTMT) Program is to identify promising corrosion-resistant materials for coal-fired gas turbine applications by exposing candidate turbine materials to a realistic pressurized fluidized bed combustor environment for up to 14,000 hours. This report is a summary of the material screening tests performed in conjunction with the LTMT Program. The testing was designed to provide preliminary performance data on a variety of alloys through a series of short-term screening tests in simulated PFB environments. Two types of screening tests under atmospheric pressure were performed; small burner rig tests and testing of airfoil-shaped specimens in a high-temperature, high-velocity, erosion/corrosion simulator. Candidate gas turbine materials evaluated in the simulator tests included a cast, cobalt-base vane alloy, FSX-414, and a cast, nickel-base blade alloy, IN-738. In addition, several protection systems were tested: CoCrAlY and FeCrAlY applied to IN-738 substrates by a physical vapor deposition (PVD) process, and M(Co,Fe)CrAlY materials of similar composition applied to IN-738 by a glass-HIP cladding process. In the simulator tests FSX-414 exhibited the highest susceptibility to erosion/corrosion degradation followed by IN-738; the PVD (Co,Fe)CrAlY alloys were somewhat more resistant and the two cladding alloy compositions were most resistant to erosion/corrosion. Of particular significance was the fact that the MCrAlY materials which appeared completely adequate at lower velocity (960 ft/s) and fine particle loading, became highly susceptible to deterioration at high velocity (1170 ft/s) and large particle erosion/corrosion conditions.

The effects of annealing treatments on the microstructure, elastic/mechanical properties, wear resistance and corrosion behavior of rod-shaped Ti40Zr10Cu38Pd12 bulk glassy alloys, synthesized by copper mold casting, are investigated. Formation of ultrafine crystals embedded in an amorphous matrix is observed for intermediate annealing temperatures, whereas a fully crystalline microstructure develops after heating to sufficiently high temperatures. The glassy alloy exhibits large hardness, relatively low Young's modulus, good wear resistance and excellent corrosion behavior. Nanoindentation measurements reveal that the sample annealed in the supercooled liquid region exhibits a hardness value of 9.4 GPa, which is 20% larger than in the completely amorphous state and much larger than the hardness of commercial Ti-6Al-4V alloy. The Young's modulus of the as-cast alloy (around 100 GPa, as determined from acoustic measurements) increases only slightly during partial devitrification. Finally, the anticorrosion performance of the Ti40Zr10Cu38Pd12 alloy in Hank's solution has been shown to ameliorate as crystallization proceeds and is roughly as good as in the commercial Ti-6Al-4V alloy. The outstanding mechanical and corrosion properties of the Ti40Zr10Cu38Pd12 alloy, both in amorphous and crystalline states, are appealing for its use in biomedical applications. PMID:22098871

Cobalt-base alloys may be generally described as non magnetic, wear, corrosion and heat-resistant (high strength even at elevated temperature). Many properties of the alloy originate from the crystallographic nature of cobalt, the solid-solution-strengthening effect of chromium and molybdenum, the formation of extremely hard carbides and the corrosion resistance imparted by chromium. Cobalt-base alloys are difficult to fabricate which is why their use has been limited, but continuous work led to the development of specialized casting methods. Due to its excellent resistance to degradation in the oral environment, the first medical use of cobalt-base alloys was in the cast of dental implants. Various in vitro and in vivo tests have shown that the alloys are biocompatible and suitable for use as surgical implants. Today, the use of Co alloys for surgical applications is mainly related to orthopaedic prostheses for the knee, shoulder and hip as well as to fracture fixation devices. Joint endoprostheses are typical long-term implants and the applied implant material must therefore meet extremely high requirements with regard to biocompatibility with the surrounding body tissue material and corrosion resistance to body fluids. PMID:11270075

The objective is to develop an Fe-base alloy that can meet the requirements of the automotive Stirling engine cylinders and regenerator housings. The scope of work was to test various alloys and select the one best demonstrating the following characteristics: It must be a cast alloy, using nonstrategic metals. It must withstand stresses for a 2500-hr rupture life at 200 MPa/775/degree/C. Oxidation/corrosion resistance must be comparable to that of N-155. It must be compatible with hydrogen. Fatigue properties must be superior to alloy XF 818. Cost must be less than or equal to that of 19-9DL. Major tests were designed to include the following: Selection, processing, and evaluation of candidate alloys within each alloy group system. Determination of casting parameters. Selection of a candidate alloy and establishment of a data base for this alloy. In the initial phase of the program designated as Round 1, a series of alloys representing each alloy system was cast and tested. In all there were 5 alloys of the nickel-manganese Group 1, 13 alloys of the nickel Group 2, and 3 alloys of the manganese Group 3. The aim was to maintain the chemistry of the major element(s) shown and vary the percentage of other elements to study their influence. Evaluation of results obtained from this series of tests enabled us to closely define the chemistry range for our candidate alloy, designated NASACC-1. A master heat was made to this composition. The heat was melted and poured under controlled casting conditions previously established and poured into investment shell molds. All castings and test bars were heat treated before actual testing. NASACC-1 proved to be an excellent alloy for casting. It could be melted in air and had good fluidity and fill characteristics. The alloy met or exceeded all program goals. 28 refs., 47 figs., 44 tabs.

Casting of titanium metals has been difficult due to their high chemical reactivity at elevated temperatures. Thus, special melting and mold materials are needed. This study investigated molds, Ti alloys, and porcelain applications, utilizing a new dental casting machine, Castmatic. It involved argon-arc melting and subsequent argon/vacuum pressurized casting. Special refractory oxides such as yttria or Zirconia A were utilized for a face coat under phosphate bonded silica investment. Studies of Ti alloys (Ti, Ti-6Al-4V, Ti-15V, Ti-20Cu and Ti-30Pd) involved metallography, phase identification (XRD), hardness, tensile tests, and electrochemical-corrosion tests. Preliminary porcelain studies included an experimental low fusing porcelain along with commercial low fusing porcelains. The bond was evaluated by three-point bending tests and SEM/EDX observations. The yttria face coat was inert, but lacked the necessary mechanical and thermal stability. The face coat, consisting of Zirconia A and zirconium acetate binder, was stable and resulted in less mold reactivity, good internal soundness, but slightly rough surfaces. Metallographs revealed quite larger grains in the cast structure, than in the wrought forms. XRD analysis showed that quasi-equilibrium phases present.

Extremely superheated liquid of high-melting-point NiAl-base intermetallic alloys have been produced and cast into a cylindrical bar using the reactive casting method, which is based on the exothermic self-propagating high-temperature synthesis (SHS) reaction between elemental liquids. When liquid aluminum of 1023?K and a molten nickel-cobalt alloy of 1773?K are mixed, they exothermically react and produce a cobalt-containing NiAl liquid with a temperature over 2300?K . The liquid solidifies into a B2-ordered ?-phase intermetallic alloy. When the cobalt concentration of the alloy increases, the density, hardness, wear resistance, coefficient of thermal expansion and corrosion resistance to hydrochloric acid increase, while the thermal conductivity decreases. The effect of cobalt concentration on the oxidation resistance of the alloy to hot air is negligible.   

Volume 3 is comprised of the Development of Qualification Standards for Cast Super Duplex Stainless Steel (A890-5A) which is equivalent to wrought 2507. The objective of this work was to determine the suitability of ASTM A923 ���¢��������Standard Test methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic-Ferritic Stainless Steels���¢�������� for 25 Cr Cast Super Duplex Stainless Steels (ASTM A890-5A). The various tests which were carried out were ASTM A923 Test Method A, B and C (Sodium Hydroxide Etch Test, Charpy Impact Test and Ferric Chloride Corrosion Test), ferrite measurement using Feritscope�������®, ASTM E562 Manual Point Count Method and X-Ray Diffraction, hardness measurement using Rockwell B and C and microstructural analysis using SEM and EDS.

A comparative experimental study of the electrochemical features of as-cast Pb-1wt.% Sn and Pb-1wt.% Sb alloys is carried out with a view to applications in the manufacture of lead-acid battery components. The as-cast samples are obtained using a water-cooled unidirectional solidification system. Pb-Sn and Pb-Sb alloy samples having similar coarse cell arrays are subjected to corrosion tests in order to assess the effect of Sn or Sb segregation in the cell boundary on the electrochemical performance. Electrochemical impedance spectroscopy (EIS) diagrams, potentiodynamic polarization curves and an equivalent circuit analysis are used to evaluate the electrochemical parameters in a 0.5M H2SO4 solution at 25^oC. Both the experimental and simulated EIS parameters evidence different kinetics of...

The structure, phase composition, and mechanical properties of an austenitic corrosion-resistant high-chromium nitrogen-bearing (???0.5% N) steel are studied in the as-cast state and after homogenizing heat treatment (HT) followed by quenching. The main structural constituents of the as-cast steel are austenite and the ?? phase (12%), which forms as an interdendritic metal during solidification, and ? ferrite and M 23C6-type chromium carbides are absent. Homogenizing HT at 1100???1200°C leads to the ?? ??? ? transformation through the stage of the formation of intermediate ? ferrite via the restructuring of the tetragonal into the bcc lattice. Upon long-term homogenizing HT, the chromium concentration in ferrite decreases due to diffusion chromium redistribution and the ? ??? ? trans...

The formulation of durable high performance polymer concrete materials was discussed. Polymer concrete is the generic term for the combination of thermo setting polymers such as epoxy or vinyl ester polymers, with mineral aggregates. Polymer concrete compositions contain no water and no Portland cement. There have been significant developments in polymer technology in the past 30 years in an effort to solve the problem of environmental and chemical attack of steel and concrete structures. Polymer concrete can be used as a cost effective pre-cast material for tanks and cell houses. Cell house environments generally pose a challenge in terms of protection of the concrete structure against the corrosive effects of acid. The use of polymer concrete technology for pre-cast components such as tanks and cells requires the correct polymer selection and also substantial information in aggregate technology to achieve the desired performance properties.

The effectiveness of 30 organic acids as inhibitors in engine coolants is reported. Tests include glassware corrosion of coupled and uncoupled metals. FORD galvanostatic and cyclic polarization electrochemistry for aluminum pitting, and reserve alkalinity (RA) measurements. Details of each test are discussed as well as some general conclusions. For example, benzoic acid inhibits coupled metals well but is ineffective on cast iron when uncoupled. In benzoic acid inhibits coupled metals well but is ineffective on cast iron when uncoupled. In general, the organic acids provide little RA when titrated to a pH of 5.5, titration to a pH of 4.5 can result in precipitation of the acid. Trends with respect to acid chain length are reported also.

OG Technologies, Inc. (OGT), developed a prototype of a Hot Billet Surface Qualifier (“Qualifier”) based on OGT’s patented HotEye™ technology and other proprietary imaging and computing technologies. The Qualifier demonstrated its ability of imaging the cast billets in line with high definition pictures, pictures capable of supporting the detection of surface anomalies on the billets. The detection will add the ability to simplify the subsequent process and to correct the surface quality issues in a much more timely and efficient manner. This is challenging due to the continuous casting environment, in which corrosive water, temperature, vibration, humidity, EMI and other unbearable factors exist. Each installation has the potential of 249,000 MMBTU in energy savings per year. This represents a cost reduction, reduced emissions, reduced water usage and reduced mill scale.

NASACC-1 is a castable iron-base alloy designed to replace the costly and strategic cobalt-base X-40 alloy used in the automotive Stirling engine cylinder/generator housing. Over 40 alloy compositions were evaluated using investment cast test bars for stress-rupture testing. Also, hydrogen compatibility and oxygen corrosion resistance tests were used to determine the optimal alloy. NASACC-1 alloy was characterized using elevated and room temperature tensile, creep-rupture, low cycle fatigue, heat capacity, specific heat, and thermal expansion testing. Furthermore, phase analysis was performed on samples with several heat treated conditions. The properties are very encouraging. NASACC-1 alloy shows stress-rupture and low cycle fatigue properties equivalent to X-40. The oxidation resistance surpassed the program goal while maintaining acceptable resistance to hydrogen exposure. The welding, brazing, and casting characteristics are excellent. Finally, the cost of NASACC-1 is significantly lower than that of X-40.

Objective This study was designed to establish guinea pigs as an animal model for uterine artery embolization (UAE) with tris-acryl gelatin microspheres (TAGM). Methods Twenty-five female adult guinea pigs were randomly divided into two groups, including a uterine artery casting mould group (n?=?10) and a UAE group (n?=?15). Pelvic angiography and vascular casting mould were performed in the first group. The anatomical characters of the pelvic cavity in guinea pigs were described. In the second group, the technical feasibility of performing UAE with TAGM in guinea pigs was investigated. The histopathological slides of the uterus of guinea pigs after UAE were examined to inspect the outcomes of UAE. Results The uterine artery springs from the internal iliac artery, ascends tortuously along ...

Duplex cast stainless steels, containing mainly austenite and some ferrite, is used for different components in light water reactors. These alloys have good mechanical properties, good weldability, and they are resistant to intergranular stress corrosion cracking (IGSCC). Examples of components where cast duplex stainless steel is used are pump housings, valves and pipe elbows. A model for the aging/embrittlement of these materials when used in light water reactors has been developed. The model is based on regression of a large data matrix. It is mainly the impact energy (Charpy V) that has been regarded. The model only requires knowledge of the chemical composition of the material but the prediction can be improved if additional data like initial impact properties and measured ferrite content are available. The model is also capable of predicting fracture toughness. The susceptibility to IGSCC in BWR environment is primarily determined by the amount of ferrite and the carbon content of the material. When the amount of ferrite exceeds 12%, IGSCC has not been observed regardless of the carbon content. At carbon contents lower than 0.035% in weld-sensitized material IGSCC was not observed regardless of the ferrite content. Data for corrosion fatigue in primary PWR and BWR environment are available. Under BWR conditions the crack propagation rate is decreased with decreasing corrosion potential, consequently also with decreasing oxygen content of the water. Some areas have been identified where additional work is needed. In all cases the efforts should focus on characterizing cast duplex stainless steel components removed from Swedish reactors. The characterization should include: Microstructure and chemical analysis, susceptibility to IGSCC, and a comparison with existing models for embrittlement. 24 refs, 12 figs.

Abstract in portuguese O objetivo deste trabalho foi avaliar o comportamento eletroquímico da liga Al-4,5%Cu solidificada em condições de fluxo de calor transitório. Esta evolução foi realizada através de análises de curvas de polarização e testes de espectroscopia de impedância eletroquímica (EIE), em solução de 0,5M de NaCl à 25°C. O perfil de segregação obtido no experimento de solidificação foi caracterizado por segregação positiva e negativa de cobre, respectivamente, (more) na base e no topo da amostra. Igualmente, na prática de fundição convencional, em um mesmo lingote podem ocorrer regiões de segregação de cobre positiva e negativa. O lingote pode apresentar diferentes respostas à corrosão em diferentes partes, como função do arranjo microestrutural. As influências na resistência à corrosão da redistribuição do soluto durante a solidificação, a magnitude dos espaçamentos dendríticos e a distribuição das partículas da fase rica em Al e Al2Cu ao longo do lingote, foram examinadas com coleta de amostras ao longo do lingote. A taxa de corrosão e parâmetros de impedância (obtidos de uma análise de circuito equivalente) são também discutidos. Abstract in english The purpose of this work was to evaluate the electrochemical behavior of an Al-4.5wt%Cu alloy solidified under unsteady-state heat flow conditions. This evaluation was carried out through the analysis of both potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) tests in a 0.5 M NaCl solution at 25ºC. The experimental segregation profile obtained in the solidification experiment was characterized by positive and negative copper content regi (more) ons at the bottom and the top of the casting, respectively. Likewise, in conventional foundry practice, in a same casting both positive and negative copper segregation regions may occur. Such casting can exhibit different corrosion responses at different locations. The influences of solute redistribution during solidification, the magnitude of dendritic spacing and hence of the Al-rich phase and of Al2Cu particles distribution along the casting on the corrosion resistance, were examined in samples collected along the casting length. The corrosion rate and impedance parameters (obtained from an equivalent circuit analysis) are also discussed.

Grid and active mass materials for maintenance free lead acid batteries with high cycle life are discussed. Alloys for casting and expanding materials for the grids were manufactured. With low grade Sb alloys ( 1,5 %) and PbCa alloys, energy densities of 50 Wh/kg are reached. Improved insulation, corrosion resisting alloys and inhibitors as well as suitable mass materials increase cycle life by 700. Manufacturing costs are similar to starting battery manufacturing costs. Expanded metal grids and plates of the most suitable alloys were produced.

Micro-porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.

Outstanding combination of mechanical, wear and corrosion performance has been achieved in Laves intermetallic materials, termed Tribaloy alloys. In these two-phase alloys the solid solution provides high mechanical strength and fracture toughness while the Laves intermetallic phase offers excellent wear resistance. However, conventional Tribaloy alloys usually have low tensile strength and fracture toughness compared with ductile materials due to the large volume fraction of Laves phase, which has limited their application in many cases. The present research is aimed at developing advanced Tribaloy alloys with increasing ductility. Two new cobalt base alloys were developed in this research. The specimens were fabricated with a centrifugal casting technique. The material characterization w...

A study was made on temperature conditions of heating ingots of corrosion resistant 08Kh18N10T, 12Kh18N10T and other steels and their effect on roted steel quality. Heating conditions, enabling to decrease the re ects caused by rough fissures on casts with 12-14% and more ..cap alpha..-phase content, down to the minimum during rolling are suggested The introduction of improved heating conditions decreases the duration of ingot heating and enables to obtain the sufficient economical benefit.

This paper summarizes the key properties of GTD-222 (Wood and Haydon, 1989), a new cast nickel-base nozzle alloy developed by GE for use in land-based gas turbines. GTD-222 is being introduced as a replacement for FSX-414 in second and third-stage nozzles of certain machines. Presented in this paper are comparisons of the tensile, creep-rupture, and fatigue properties of GTD-222 versus FSX-414. In addition, the results of a long-term thermal stability study, high-temperature oxidation, and hot corrosion evaluation as well as weldability results will be discussed.

Rod-shaped amorphous bulk Ni?Cr?Mo-22?at.%Ta-14?at.%Nb?P alloys resistant to concentrated hydrochloric acids were prepared by copper-mold casting. Alloys of amorphous single phase and mixture of nanocrystalline phases in the amorphous matrix were all spontaneously passive in 6 and 12?M HCl and were immune to corrosion in 6?M HCl, although the corrosion weight loss was detected for heterogeneous alloys in 12?M HCl. Spontaneous passivation is due to presence of stable air-formed films in which chromium was particularly concentrated in addition to enrichment of tantalum and niobium. The angle resolved X-ray photoelectron spectroscopy revealed that chromium and molybdenum are rich in the inner part of the film. The major molybdenum species is in the tetravalent state, although penta- and hexav...

The release of mercury vapor was determined from eleven different amalgams exposed to externally induced corrosion by galvanic contact with a dental casting gold alloy. The electrolyte was an artificial saliva solution at 37 degrees C. The corrosion rates of the amalgams could be divided into two groups corresponding to the grouping into conventional and high-copper materials. The mercury release rate decreased during the 24 h test period for all the amalgams except one containing indium. There was no significant difference in the total mercury release between the conventional and high-copper amalgams as groups. The same applied for the individual products, except the one containing indium, which released significantly more mercury vapor than the two products with the lowest release. PMID:8595850

Anodic polarization tests were performed in 0.9% NaCl and 1% lactic acid solutions to characterize the relationship between the corrosion behavior and the microstructures of cast Ti-Ag (5-40% Ag) alloys. The anodic polarization curves for the Ti-Ag alloys up to 17.5% Ag were similar to those for pure titanium in both solutions. On the other hand, an abrupt increase in the current density was observed for the alloys with more than 20% Ag in the NaCl solution and with more than 27.5% Ag in the lactic acid solution. The microstructures of the corroded alloy surfaces indicated the deterioration of precipitated intermetallic compounds along the grain boundaries. The Ti-Ag alloys up to 17.5% Ag had excellent corrosion resistance similar to that of pure titanium. The alloys with 20-25% Ag may be also used as dental alloys, since they passivated again immediately after preferential dissolution in the NaCl solution.   

The creep strength of battery grids, expanded from drum-cast low-antimony lead alloy tip, wa varied by heat-treatments at several temperature. Grid growth following potentiostatic corrosion was found to be highly anisotropic. In spite of an increase in length, there wa a decrease in width. A theoretical analysis indicated that growth of expanded grids consisted of two components: an increase in the wire length (wire elongation), and a change in the grid shape (grid shear). The rate of the wire elongation is the corrosion test was found to be inversely related to the grid creep strength, and the deformation mechanism was identified as power-law creep. It is shown that, in order to meaningfully compare grid growths, the geometrical environment of grid test samples must be carefully controlled.

Cracking of an air tube used for supplying air in rotary kiln of a sponge iron plant is investigated in this paper. The material of the air tube is ASTM A297 HK 40, a member of the heat-resistant cast alloy family (H series) steels widely used for enhanced high-temperature properties. Microstructural degradation occurring at high temperature affects mechanical and corrosion-resistance properties of the component. The failure analysis consists of visual observation, chemical analysis, examination of microstructures using optical and scanning electron microscopes, and characterization with energy-dispersive spectroscopy (EDS). Microstructural characterization reveals (i) intergranular corrosion at the cross section of tube wall, (ii) formation of severe chromium carbide network at the grain ...

Localized corrosion of duplex UNS S32550 stainless steel in seawater was investigated in the laboratory and in field trials for several surface finish conditions: polished, ground, and sandblasted. Electrochemical data obtained by polarization curves showed that the smoother, polished surface had better characteristics (higher pitting and protection potentials) than the ground or sandblasted surfaces. However, despite its high degree of roughness, the sandblasted surface was the most resistant in field conditions, exhibiting the lowest number of sites attacked. Internal compressive stresses created by sandblasting seem also to have an unsensitizing effect on sensitized zones that exist in cast steel (due to repairs of mold defects), reducing its susceptibility to microbiologically influenced corrosion (MIC). Such stresses are not generated in polished or ground surfaces, and localized MIC attack can occur.

This edition has been updated to include the latest developments in the field. For example, a chapter on vapor deposited coatings offers a summary of heretofore widely scattered data. In addition, the chapters on metallography, hard metals, friction and wear, corrosion, and soldering and brazing have been extensively revised. Major Sections: General Physical and Chemical Constants; X-Ray Analysis of Metallic Materials; Crystallography; Crystal Chemistry; Metallurgically Important Minerals; Thermochemical Data; Physical Properties of Molten Salts; Metallography; Equilibrium Diagrams; Gas-Metal Systems; Diffusion in Metals; General Physical Properties; Elastic Properties, Damping Capacity and Shape Memory Alloys; Temperature Measurement and Thermoelectric Properties; Electron Emission; Electrical Properties; Steels and Alloys with Special Magnetic Properties; Mechanical Testing; Mechanical Properties of Metals and Alloys; Hardmetals; Lubricants; Friction and Wear; Casting Alloys and Foundry Data; Refractory Materials; Fuels; Heat Treatment Environments; Laser Metal Working; Guide to Corrosion Control; Electroplating and Metal Finishing; Welding; Soldering and Brazing; Vapor Deposited Coatings; Superplasticity; Index.

The impact of orthophosphate addition on biofilm formation and water quality was studied in corrosion-resistant stainless steel (STS) pipe and corrosion-susceptible ductile cast iron (DCI) pipe using cultivation and culture-independent approaches. Sample coupons of DCI pipe and STS pipe were installed in annular reactors, which were operated for 9 months under hydraulic conditions similar to a domestic plumbing system. Addition of 5 mg/L of phosphate to the plumbing systems, under low residual chlorine conditions, promoted a more significant growth of biofilm and led to a greater rate reduction of disinfection by-products in DCI pipe than in STS pipe. While the level of THMs (trihalomethanes) increased under conditions of low biofilm concentration, the levels of HAAs (halo acetic acids) an...

The effect of Cr addition on the glass-forming ability (GFA), the magnetic properties, and corrosion resistance of (Fe0.76Si0.096B0.096P0.048)100?xCrx (x=0, 2, 4 and 6) bulk glassy alloys (BGAs) with high Fe contents was investigated. 4% Cr addition makes the alloy composition to approach towards a eutectic point, which could result in an increase in the GFA. The BGA rod with diameters up to 3 mm was produced by copper mold casting. These BGAs exhibit a rather high saturation magnetization of 1.10–1.50 T and lower coercive force of 1.4–2.4 A/m. A significant improvement in corrosion resistance was observed with increasing Cr content. Furthermore, these Fe-based BGAs exhibit super high strength of ?3.3 GPa and Young’s modulus of 168 GPa.   

Objective To demonstrate regeneration of muscle fascia appropriate for future harvest with the use of acellular porcine intestinal submucosa in a rat model. Study Design Animal cohort study. Setting Tertiary care academic medical center. Subjects and Methods Sixteen male Sprague-Dawley rats underwent excision of rectus abdominis muscle fascia. A sheet of acellular porcine intestinal submucosa was placed in the fascia harvest defect. Graft and underlying muscle were harvested at three-, six-, and nine-week intervals. Histologic examination, including immunohistology for anti-von Willebrand factor, was performed at each timepoint. Additional selected specimens were subjected to latex vascular perfusion casts to examine vessel growth patterns within the graft. Results Gross examination reveal...

Perivascular delivery of anti-proliferative agents is an attractive approach to inhibit hyperplasia that causes stenosis of synthetic hemodialysis grafts and other vascular grafts. Perivascular drug delivery systems typically release drugs to both the vascular wall and non-target extravascular tissue. The objective of this study was to develop a biodegradable, perivascular delivery system for localized, sustained and unidirectional drug release in the context of synthetic arteriovenous (AV) grafts used for chronic hemodialysis. To this end, a dense non-porous polymer barrier layer was laminated to either i) a drug-loaded non-porous polymer layer or ii) a porous polymer layer. To provide tunability, the porous layer could be loaded with drug during casting or later infused with a drug-loade...

We studied various types of surface treatments for magnesium alloys that involved the application of chromium or manganese by measuring their corrosion potential using X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and microscopic examination. The chromium-conversion coating is composed primarily of amorphous trivalent chromium oxide (or hydroxide) and a fluoride of magnesium and aluminum. The permanganate-conversion coatings, we obtained by adding HF to the immersion bath, consisted of a film that was composed primarily of manganese oxides and magnesium fluoride. We found that these films formed an amorphous composite coating. In addition, we examined the corrosion resistance of AZ91D magnesium alloy die-cast panels with various surface treatments. The exposure tests, we performed in Miyakojima, indicated that the anodic oxidation coating and the MX1-type surface treatment containing chromate, which result in relatively thick coatings, are superior in corrosion resistance. The corrosion resistance of permanganate chemical conversion coatings is comparable with that of chromium conversion coatings. (orig.)

An Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass with a diameter of 5 mm was prepared with the copper-mold-casting method. The corrosion resistance of this amorphous steel in sulfuric-acid solutions was determined by electrochemical measurements. The passive film formed on the surface of the alloy after immersion in the 0.5-mol/l H2SO4 solution for 1 week was analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical measurements show that the corrosion resistance of the amorphous steel in the 1 mol/l-H2SO4 solution is superior to a stainless steel (SUS 321), and is almost the same as Ti6Al4V, which shows that the amorphous steel has an excellent corrosion resistance in sulfuric-acid solutions. As the concentration of the sulfuric-acid solutions increases from 0.5 mol/l to 4 mol/l, the corrosion resistance of the amorphous steel decreases. The XPS result reveals that a bilayer structure of protective film formed on the surface of the amorphous steel in a H2SO4 solution. The compositions of the inner part of the film are MoO2, Cr2O3, CoO, and FeO, and those of the outer film are MoO3, Cr(OH)3, Co(OH)2, and Fe(OH)3.

Presently, one of the most interesting approaches to the generation of H{sub 2} is based on sulphur-based cycles, that however require structural components able to work in a corrosive environment at high temperature. Silicon carbide (SiC) is one of the most promising materials for this application, and to increase its limited toughness multilayered structures can be envisaged, since crack deviation and delamination increase energy adsorption during fracture. In this work tape casting and pressureless sintering were used to produce SiC samples consisting in alternating dense and porous layers, the porosity being realised by the insertion of pore forming agents during the preparation of the green ceramic. The mechanical properties of these materials were studied both at room temperature and at 1550 deg. C. The effect of corrosion at 850 deg. C by a mixture of H{sub 2}O, O{sub 2} and SO{sub 2} was studied by comparing microstructure and mechanical behaviour before and after long-term (1000 h) corrosion treatments. Corrosion resistance was very good, and flexural strength was strongly increased due to a combined effect of crack tip blunting and compressive residual stress formation. Concerning the architecture instead, the insertion of porous layers brings to a reduction of flexural strength, while Young's modulus remains almost constant.

Experiments were carried out with aluminum - plutoniunn alloys, containing up to 20 wt.% plutonium, to assess their potential value for water- cooled power reactors. Metallographic exanninations and hardness determinations were carried out on cast and annealed alloys and the densities of cast alloys were determined, for comparison with irradiated alloys. Interactions between Zircaloy-2 and aluminumplutonium alloys were studied by subjecting sheathed alloys to various thermal treatments. Liquation of the core alloys caused rapid sheath dissolution, 0.025 in./h at 660 deg C. Interaction was relatively slow at sub-solidus core temperatures, from 0.0015 to 0.006 in. in 26 hours at 636 deg C depending on the core composition. Interaction would be insignificant in water- cooled power reactors with core temperatures of 300 to 400 deg C. Corrosion rates of the bare alloys in 340 deg C de-ionized water in an AISI 316 stainlesssteel autoclave varied with composition. The 5 wt.% alloy corroded approximately 3 x 10/sup -3/ in./h, and the 20 wt.% alloy corroded only 1.5 x 10/sup -3/i in. in 6 3/4 days. The 10 and 15 wt.% alloys possessed intermediate rates. The 5 wt.% alloy in defected Zircaloy-2 cans underwent less attack than in the bare condition, approximately 2 x 10/sup -3/ in. in 20 hours. Anodically treated 5 and 10 wt.% alloys in defected sheaths showed no corrosive attack after 20 hours at 340 deg C. (auth)

Objectives: The purpose of this research was to determine the mechanical properties and corrosion behavior of 0.5% Co-DI before and after heat treatment and compare with commercial ductile iron. Methods: Molten metal of newly developed ductile iron which alloyed with 0.5% Cobalt produced through CO2 sand casting method. The specimens then performed preheat to 500°C in an hour then oil quenched. Specimens then performed annealing to 900°C in half an hour before oil quenched again. 500°C, 600°C and 700°C austempering temperature had been selected subjected to the specimens in half an hour before cooled to room temperature. The tests involved are microstructure analysis which included nodule count and phase analysis, polarization test, spectrometer test, density test, tensile test (ASTM E 8M), hardness test and impact test (ASTM A327) on as cast and austempered specimen. Results: 0.5% Cobalt alloyed austempered ductile iron with 500°C austempered temperature is the optimum temperature for 0.5% Co-ADI. It's not only increase the nodule count in the content, but also improve the mechanical properties such as impact toughness and tensile strength. Corrosion rate of 0.5% Co-DI also improved compare to unalloyed DI.

The laboratory immersion test system built and operated at ORNL was found to successfully screen samples from numerous refractory suppliers, including both commercially available and experimental materials. This system was found to provide an accurate prediction of how these materials would perform in the actual gasifier environment. Test materials included mullites, alumino-silicate bricks, fusion-cast aluminas, alumina-based and chrome-containing mortars, phosphate-bonded mortars, coated samples provided under an MPLUS-funded project, bonded spinels, different fusion-cast magnesia-alumina spinels with magnesia content ranging from 2.5% to about 60%, high-MgO castable and brick materials, spinel castables, and alkali-aluminate materials. This testing identified several candidate material systems that perform well in the New Bern gasifier. Fusion-cast aluminas were found to survive for nearly one year, and magnesia-alumina spinels have operated successfully for 18 months and are expected to survive for two years. Alkali-aluminates and high-MgO-content materials have also been identified for backup lining applications. No other material with a similar structure and chemical composition to that of the fusion-cast magnesium-aluminum spinel brick currently being used for the hot-face lining is commercially available. Other materials used for this application have been found to have inferior service lives, as previously discussed. Further, over 100 laboratory immersion tests have been performed on other materials (both commercial and experimental), but none to date has performed as well as the material currently being used for the hot-face lining. Operating experience accumulated with the high-temperature gasifier at New Bern, North Carolina, has confirmed that the molten alkali salts degrade many types of refractories. Fusion-cast alumina materials were shown to provide a great improvement in lifetime over materials used previously. Further improvement was realized with fusion-cast magnesia-alumina spinel refractory, which appears to be the most resistant to degradation found to date, exhibiting over a year of service life and expected to be capable of over two years of service life. Regarding the use of refractory mortar, it was found that expansion of the current chrome-alumina mortar when subjected to black liquor smelt is likely contributing to the strains seen on the vessel shell. Additionally, the candidate high-alumina mortar that was originally proposed as a replacement for the current chrome-alumina mortar also showed a large amount of expansion when subjected to molten smelt. A UMR experimental mortar, composed of a phosphate bonded system specifically designed for use with fusion-cast magnesium-aluminum spinel, was found to perform well in the molten smelt environment. Strain gauges installed on the gasifier vessel shell provided valuable information about the expansion of the refractory, and a new set of strain gauges and thermocouples has been installed in order to monitor the loading caused by the currently installed spinel refractory. These results provide information for a direct comparison of the expansion of the two refractories. Measurements to date suggest that the fusion-cast magnesia-alumina spinel is expanding less than the fusion-cast {alpha}/{beta}-alumina used previously. A modified liquor nozzle was designed and constructed to test a number of materials that should be more resistant to erosion and corrosion than the material currently used. Inserts made of three erosion-resistant metallic materials were fabricated, along with inserts made of three ceramic materials. The assembled system was sent to the New Bern mill for installation in the gasifer in 2005. Following operation of the gasifier using the modified nozzle, inserts should be removed and analyzed for wear by erosion/corrosion. Although no materials have been directly identified for sensor/thermocouple protection tubes, several of the refractory material systems identified for lining material applications may be applicable for use in this

A recent review by the U.S. Advanced Ceramics Association, the Aluminum Association, and the U.S. Department of Energy's Office of Industrial Technologies (DOE/OIT) described the status of advanced ceramics for aluminum processing, including monolithics, composites, and coatings. The report observed that monolithic ceramics (particularly oxides) have attractive properties such as resistance to heat, corrosion, thermal shock, abrasion, and erosion [1]. However, even after the developments of the past 25 years, there are two key barriers to commercialization: reliability and cost-effectiveness. Industry research is therefore focused on eliminating these barriers. Ceramic coatings have likewise undergone significant development and a variety of processes have been demonstrated for applying coatings to substrates. Some processes, such as thermal barrier coatings for gas turbine engines, exhibit sufficient reliability and service life for routine commercial use. Worldwide, aluminum melting and molten metal handling consumes about 506,000 tons of refractory materials annually. Refractory compositions for handling molten aluminum are generally based on dense fused cast silica or mullite. The microstructural texture is extremely important because an interlocking mass of coarser grains must be bonded together by smaller grains in order to achieve adequate strength. At the same time, well-distributed microscopic pores and cracks are needed to deflect cracks and prevent spalling and thermal shock damage [2]. The focus of this project was to develop and validate new classes of cost-effective, low-permeability ceramic and refractory components for handling molten aluminum in both smelting and casting environments. The primary goal was to develop improved coatings and functionally graded materials that will possess superior combinations of properties, including resistance to thermal shock, erosion, corrosion, and wetting. When these materials are successfully deployed in aluminum smelting and casting operations, their superior performance and durability will give end users marked improvements in uptime, defect reduction, scrap/rework costs, and overall energy savings resulting from higher productivity and yield. The implementation of results of this program will result in energy savings of 30 trillion Btu/year by 2020. For this Industrial Materials for the Future (IMF) project, riser tube used in the low-pressure die (LPD) casting of aluminum was selected as the refractory component for improvement. In this LPD process, a pressurized system is used to transport aluminum metal through refractory tubes (riser tubes) into wheel molds. It is important for the tubes to remain airtight because otherwise, the pressurized system will fail. Generally, defects such as porosity in the tube or cracks generated by reaction of the tube material with molten aluminum lead to tube failure, making the tube incapable of maintaining the pressure difference required for normal casting operation. Therefore, the primary objective of the project was to develop a riser tube that is not only resistant to thermal shock, erosion, corrosion, and wetting, but is also less permeable, so as to achieve longer service life. Currently, the dense-fused silica (DFS) riser tube supplied by Pyrotek lasts for only 7 days before undergoing failure. The following approach was employed to achieve the goal: (1) Develop materials and methods for sealing surface porosity in thermal-shock-resistant ceramic refractories; (2) Develop new ceramic coatings for extreme service in molten aluminum operations, with particular emphasis on coatings based on highly stable oxide phases; (3) Develop new monolithic refractories designed for lower-permeability applications using controlled porosity gradients and particle size distributions; (4) Optimize refractory formulations to minimize wetting by molten aluminum, and characterize erosion, corrosion, and spallation rates under realistic service conditions; and (5) Scale up the processing methods to full-sized components and perform field testing in commercial aluminum casting shops.

Aluminium alloys based on the aluminium-silicon system are popular for automotive and aerospace applications, thanks to their high strength to weight ratio, excellent castability, and corrosion resistance. Microporosity is widely acknowledged to affect both static and dynamic properties of structural aluminium alloy castings. Formation of microporosity is a complex phenomenon and depends upon various factors but mainly hydrogen content and melt cleanliness, i.e., oxide films and inclusions. In the past few decades numerous studies on microporosity formation have been reported. However, several aspects of this subject are not fully understood. The motivation of this doctoral thesis has been to improve the knowledge of porosity formation and its affect of the mechanical properties of the cast products. This study aimed at understanding the effect of hydrogen and defects on microporosity of aluminium-silicon based castings. A literature review of the theories of porosity formation, and previously reported results on the factors affecting the microporosity formation in aluminium alloys is reported briefly in order to establish a basis of the present study. The research presented in this thesis is divided in five phases. In the first phase, lab scale directional solidification experiments were carried out with an A 356 alloy. Six hydrogen levels from 0.48 to 0.07 mL/100 g melt were reached by various up-gassing and de-gassing treatments of the melt. The melt quality was assessed by porous disc filtration apparatus (PoDFA) and reduced pressure test (RPT) methods. Microporosity distribution in the castings was characterized by the Archmedian method, image analysis and X-ray radiography. The results show that the porosity distribution is strongly dependent on the cooling rate and hydrogen content in the presence of the oxide films type defects. In the next phase, casting experiments with an A356 melt were carried by using a step mould die and castings were produced with and without filtration. The experiments were divided into series I and series II. In the first series 70 kg of the A356 ingots were melted in an electric resistance furnace. Three hydrogen levels namely 0.1, 0.2, and 0.4 mL/100 g melt were reached first by Ar-degassing, and up-gassing with Ar-10 % H2 and Ar-water vapour mixture, respectively. In the second series of experiments similar procedure was applied to another melt but in the reverse order. The castings were characterized in terms of microporosity and mechanical properties distribution. In addition high pressure die casting of an A380 alloy was carried out with different processing parameters like plunger speed, commutation point between first and second phase and pouring temperature. The results shows that tensile properties in both gravity and high pressure die castings were affected by the amount and distribution of casting defects. A series of casting experiments were carried out with the same type of step mould and with two hydrogen levels, namely 0.1 and 0.2 mL/100 g melt, in the third phase of the project. The main focus of these trials was to carefully control the variables during melt preparation, casting and solidification and keep the variations at minimum. Experiments were performed in two different days in order to check the reproducibility of the measurements. For the low gas level (0.1 mL/100 g melt) higher porosity levels are observed in the thinnest step, while the trend is opposite with the medium gas level (0.2 mL/100 g melt) castings. The data obtained form these trials where casting variables were controlled in a reproducible way form a basis for evaluating the results of simulated microporosity distributions using recent modelling approaches. The reproducibility of the step mould used was calculated to be 10-15 %. In the fourth phase, a study in an automotive casting plant was targeted to address the problem of high rejection rate of a cylinder head casting made from an A354 alloy. In the foundry, the castings under investigation were usually made from the mixture of A 354 alloys from three different suppliers in uncontrolled proportions. In an attempt to solve this problem, a number of systematic experiments were carried out to assess the melt quality with RPT, and pressure filtration (PREFIL) tests. The results from these trials show that the bi-film index data from the RPT has a potential to be used in an industrial environment for routine melt quality control as the cause of high scrap was successfully identified with this technique. In the last phase of this work, state-of-the-art low pressure die casting (LPDC) experiments with an A356 melt were carried out using the same step mould die used in second and third phases. Castings were made with two hydrogen levels, namely 0.1 and 0.2 mL/100 g melt. There is not much reported on microporosity simulation under LPDC conditions and reliable experimental validation is needed.

The modified white metal casting method described in this article is especially useful for mounting brittle oxides and nitrides, such as those formed on the surface and within the structure of nickelbase alloys during high temperature corrosion, for examination by transmission electron microscopy (TEM). The specimens are cast in cylinders using a zinc pressure die casting alloy. These cylinders are then cut into discs which are then further prepared by dimple grinding and ion beam thinning. The specimens prepared in this way were used to quantify the precipitation behaviour of nitrides in nickel-base alloys by transmission electron microscopy. In addition to energy dispersive X-ray spectroscopy (EDS), the convergent diffraction of the electron beam (CBED) can also be used in particular to provide valuable information about the presence of local internal stresses. (orig.) [German] Speziell fuer die transmissionselektronenmikroskopische Untersuchung (TEM) sproeder Oxide und Nitride, die infolge von Hochtemperaturkorrosion auf und innerhalb von Nickelbasislegierungen entstehen, eignet sich die hier vorgestellte modifizierte Eingiessmethode. Dabei werden die Proben mit einer Zink-Druckgusslegierung zu Zylindern vergossen, von denen Scheiben als Ausgangsquerschnittspraeparate abgetrennt und mittels Muldenschleifen und Ionenduennen fertigpraepariert werden. Die so hergestellten Proben werden in dieser Arbeit dazu genutzt, transmissionselektronenmikroskopisch das Ausscheidungsverhalten innerer Nitride in Nickelbasislegierungen zu quantifizieren. Neben der energiedispersiven Roentgenspektroskopie (EDS) kann dabei insbesondere zum Nachweis lokaler Eigenspannungen die konvergente Elektronenbeugung (CBED) wertvolle Informationen liefern. (orig.)

An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and nickel-based materials, and are proving to have excellent wear properties, sufficient to warrant their use in earth excavation, drilling and tunnel boring applications. Large areas have been successfully coated with these materials, with thicknesses of approximately one centimeter. The observed corrosion resistance may enable applications of importance in industries such as: oil and gas production, refining, nuclear power generation, shipping, and others.

In Sweden and Finland the spent nuclear fuel is planned to be encapsulated in cast iron canisters that have an outer shield made of copper. The copper shield is responsible for the corrosion protection of the canister construction. General corrosion of the copper is not expected to be the limiting factor in the waste repository environment when estimating the life-time of the canister construction. However, different forms of localised corrosion, i.e. pitting, stress corrosion cracking, or environmentally assisted creep fracture may cause premature failure of the copper shield. Of the probable constituents in the groundwater, nitrites, chlorides, sulphides and carbonates have been suggested to promote localised corrosion of copper. The main assumption made in planning this research program is that the surface films forming on copper in the repository environment largely determine the susceptibility of copper to the different forms of localised corrosion. The availability of reactants, which also may become corrosion rate limiting, is investigated in several other research programs. This research program consists of a set of successive projects targeted at characterising the properties of surface films on copper in repository environment containing different detrimental anions. A further aim was to assess the significance of the anion-induced changes in the stability of the oxide films with regard to localised corrosion of copper. This report summarises the results from a series of investigations on properties of surface films forming on copper in water of pH = 8.9 at temperature of 80 deg C and pressure of 2 MPa. The main results gained so far in this research program are as follows: The surface films forming on copper in the thermodynamic stability region of monovalent copper at 80 deg C consist of a bulk part (about 1 mm thick) which is a good ionic and electronic conductor, and an outer, interfacial layer (0.001 - 0.005 mm thick) which shows p-type semiconductor properties. The thin outer layer controls the corrosion properties of copper, corrosion rate being limited by ionic transport through the layer and the charge transfer step of the film dissolution. Chlorides cause a breakdown of the oxide film in the stability region of divalent copper, but they seem to have no effect on the properties of the film in the stability region of monovalent copper; oxidising conditions with simultaneous exposure to chlorides are thus expected to subject copper to localised corrosion. Sulphides at the concentration of 10 ppm dissolved H{sub 2}S were found not to promote the formation of a three-dimensional film of Cu{sub 2}S (or other copper sulphides), thus the mechanisms of localised corrosion which operate under reducing conditions and are based on the formation of copper sulphides seem not to be valid. In the presence of 10 ppm H{sub 2}S the corrosion rate of copper is controlled by the charge transfer step of the dissolution of the outer layer 57 refs, 35 figs, 7 tabs

Inhibitors of angiogenesis and radiation induce compensatory changes in the tumor vasculature both during and after treatment cessation. To assess the responses to irradiation and vascular endothelial growth factor-receptor tyrosine kinase inhibition (by the vascular endothelial growth factor tyrosine kinase inhibitor PTK787/ZK222854), mammary carcinoma allografts were investigated by vascular casting; electron, light, and confocal microscopy; and immunoblotting. Irradiation and anti-angiogenic therapy had similar effects on the tumor vasculature. Both treatments reduced tumor vascularization, particularly in the tumor medulla. After cessation of therapy, the tumor vasculature expanded predominantly by intussusception with a plexus composed of enlarged sinusoidal-like vessels containing multiple transluminal tissue pillars. Tumor revascularization originated from preserved alpha-smooth muscle actin-positive vessels in the tumor cortex. Quantification revealed that recovery was characterized by an angiogenic switch from sprouting to intussusception. Up-regulated alpha-smooth muscle actin-expression during recovery reflected the recruitment of alpha-smooth muscle actin-positive cells for intussusception as part of the angio-adaptive mechanism. Tumor recovery was associated with a dramatic decrease (by 30% to 40%) in the intratumoral microvascular density, probably as a result of intussusceptive pruning and, surprisingly, with only a minimal reduction of the total microvascular (exchange) area. Therefore, the vascular supply to the tumor was not severely compromised, as demonstrated by hypoxia-inducible factor-1alpha expression. Both irradiation and anti-angiogenic therapy cause a switch from sprouting to intussusceptive angiogenesis, representing an escape mechanism and accounting for the development of resistance, as well as rapid recovery, after cessation of therapy. PMID:18787105

This work supports an experiment being conducted by Roland Schulze and Mary Ann Hill to study hydride formation, one of the most important forms of corrosion observed in uranium and uranium alloys. The study goals and objectives are described in Schulze and Hill (2008), and the work described here focuses on development of a statistical experiment plan being used for the study. The results of this study will contribute to the development of a uranium hydriding model for use in lifetime prediction models. A parametric study of the effect of hydrogen pressure, gap size and abrasion on hydride initiation and growth is being planned where results can be analyzed statistically to determine individual effects as well as multi-variable interactions. Input to ESC from this experiment will include expected hydride nucleation, size, distribution, and volume on various uranium surface situations (geometry) as a function of age. This study will also address the effect of hydrogen threshold pressure on corrosion nucleation and the effect of oxide abrasion/breach on hydriding processes. Statistical experiment plans provide for efficient collection of data that aids in understanding the impact of specific experiment factors on initiation and growth of corrosion. The experiment planning methods used here also allow for robust data collection accommodating other sources of variation such as the density of inclusions, assumed to vary linearly along the cast rods from which samples are obtained.

This investigation studies the effects of Cu content and ageing treatment on the microstructural, mechanical, corrosion and antibacterial properties of SUS 304 austenitic stainless steel. Cu was added respectively to SUS 304 stainless steels in proportions of 1.5, 2.5, 3.5, 4.5 and 5.5 wt.%. A vacuum arc remelting furnace was used to remelt SUS 304 stainless steel with various added Cu contents. These ingot alloys underwent hot rolling and various heat treatments, and were then cut into test specimens. A series of microstructural investigation, tensile tests, corrosion tests and antibacterial tests were conducted to study the properties of Cu-containing SUS 304 austenitic stainless steel. Microstructural observations reveal that the amount of retained {delta}-ferrite in the as-cast SUS 304 steel decreases as the Cu content increases. After hot rolling, the retained {delta}-ferrite disappears and {alpha}'-martensite forms in the austenitic matrix. The results of the tensile tests reveal that the ultimate tensile strength (UTS) declines as the Cu content increases below 2.5 wt.%. However, the ultimate tensile strength increases with the Cu content above 2.5 wt.%. X-ray diffraction analysis reveals that adding Cu suppresses the formation of strain-induced martensite ({alpha}'-martensite). The corrosion test indicates that the pitting potential declines as the Cu content in SUS 304 steels increases. The results of the antibacterial test reveal that adding a proper amount of Cu (such as 2 wt.%) gives SUS 304 stainless steel an excellent antibacterial property.

Currently, the excessive weight of the positive grid is a limiting factor to the increase of the specific energy of the lead/acid battery. With present alloys, a thickness of a few millimeters is a pre-requisite in the processing of a positive grid which is submitted to heavy corrosion during the charge and deep-discharge cycles usually encountered with electric vehicles. The search for a lighter battery approaching the ALABC`s goal of 50 Wh kg{sup -1} therefore requires the development of a new set of alloys that are able to withstand mechanical stress and corrosion experienced by a positive grid during the service life of an electric-vehicle battery. The work reported here shows that tin addition (to a level of 1.2 wt.%) or combined tin (to a level of 0.6 wt.%) and silver (to a level of 0.05 wt.%) additions increase considerably both the mechanical properties and the corrosion resistance of a Pb-0.08 wt.% Ca-0.013 wt.% Al alloy. Gravity casting trials reveal that the tin-rich alloy (1.2 wt.%) and the silver-rich alloy (0.05 wt.%) could be used directly in the industrial processing of batteries that use gel technology. Information is also given on the performances of these batteries when submitted to the international TC69 cycling test, as well as indications of the minimum grid thickness that could be achieved with these alloys without sacrificing battery cycle life. (orig.)

1.1 This guide covers conducting and evaluating galvanic corrosion tests to characterize the behavior of two dissimilar metals in electrical contact in an electrolyte under low-flow conditions. It can be adapted to wrought or cast metals and alloys. 1.2 This guide covers the selection of materials, specimen preparation, test environment, method of exposure, and method for evaluating the results to characterize the behavior of galvanic couples in an electrolyte. Note 1—Additional information on galvanic corrosion testing and examples of the conduct and evaluation of galvanic corrosion tests in electrolytes are given in Refs (1) through (7). 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicabil...

... moving. The outer layer is usually made of plaster or fiberglass. Fiberglass casts are made of fiberglass, ... color! These casts are lighter and stronger than plaster casts. Plaster casts are usually white and made ...

This study evaluated the effects of tooth preparation design on resistance to dislodgment of a resin-bonded fixed partial denture (RBFPD). The variations of tooth preparation tested included axial coverage, retentive grooves, and an occlusal rest. Patterns of the tooth preparation designs were prepared and cast in a base metal alloy. Retainer patterns were waxed to refractory casts of metal dies, cast, finished and then bonded to the dies. The complete assemblies were loaded to failure on an Instron mechanical testing machine, and analysis indicated that retainers with occlusal rests were the most resistant. Grooves provided no statistically significant increase in resistance to failure of the cement. Increased axial coverage did not increase resistance to dislodgment. Successful fixed partial dentures (FPDs) depend on cast retainers to resist displacement of the restoration during function. Introduction of resin-bonded restorations opened the possibility of FPDs with minimal reduction of abutments. Specific questions concerning long term success and tooth preparation designs were prominent concerns. The influence of resistance form on overall stability of a restoration was also of particular interest. Buonocore established the foundation for retention of composite resins to acid-pitted enamel. Rochette used this technology to bond perforated cast metal splints to periodontally compromised teeth. A mechanical interlock was created as composite resin engaged these perforations and sustained the cast splint to acid-etched enamel. Howe adapted this design for replacement of anterior teeth by adding porcelain to a metal ceramic framework and then bonding the framework to abutments without tooth preparations. The advantages of these procedures were their conservative nature, esthetics, and ease of rebonding after dislodgment. Livaditis and Thompson adapted the procedure proposed by Tanaka of corrosion-pitting the bonding surface of a base metal alloy. They increased the surface area to be bonded, eliminated the perforations to improve rigidity of the framework, and described tooth preparation modifications of the abutments. They suggested an occlusal rest, establishment of guide planes through axial reduction, and a proximal extension to the facial surface to resist lingual displacement. Simonson, et al., based their anterior tooth preparation design on the configuration suggested by Livaditis which included a slight chamfer finish line plus reduction of the lingual surface to provide a thicker metal framework. Barrack introduced an inlay type tooth preparation for the occlusal rest plus shallow vertical proximal grooves, and Meiers used grooves as an esthetic alternative to proximal extensions. Clinical studies and surveys have identified specific variables involved with success and failure, while in vitro studies have evaluated framework designs, bonding agents, and methods for pitting the metal surface. This study evaluated resistance of RBFPDs to dislodgment of different tooth preparation designs. PMID:11314309

Abstract in portuguese Nitreto de silício (Si3N4) é um material cerâmico covalente de elevada resistência à corrosão e estabilidade mecânica em temperaturas elevadas. Devido a essas propriedades, sua utilização em processos metalúrgicos, tais como em fundição de ligas metálicas, é crescente. Desta forma, a caracterização da interface entre Si3N4 e metais fundidos é de grande interesse para investigar possíveis interações as quais poderão deteriorar o material cerâmico e/ou (more) contaminar o metal. Nesse trabalho o uso de Si3N4 como material base de cadinhos para fundição de alumínio foi estudado, pela investigação do ataque corrosivo de Al líquido a 1150 ºC durante 30 dias, ao ar. A interface foi caracterizada por difração de raios X, microscopia eletrônica de varredura e espectroscopia de energia dispersiva. É encontrado que devido à oxidação superficial dois óxidos se formam - SiO2 no Si3N4 e Al2O3 no Al - os quais evitam possíveis reações sob as condições estudadas, conferindo alta resistência à corrosão aos cadinhos de Si3N4. Abstract in english Silicon nitride is a covalent ceramic material of high corrosion resistance and mechanical stability at elevated temperatures. Due to these properties, its use in metallurgical processes, such as the casting of alloys, is increasing. Therefore, the characterization of the interface between Si3N4 and the casted metal is of great importance to investigate possible interactions, which might deteriorate the ceramic mould or contaminate the metal. In this work, the use of Si3N (more) 4 as crucible material for Al-casting has been studied, by investigating the corrosion attack of liquid Al at a temperature of 1150 ºC during 30 days in air. The interface was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. It has been found that due to superficial oxidation two oxide layers form - SiO2 on Si3N4 and Al2O3 on Al - which effectively hinder further reactions under the conditions studied, confering high corrosion resistance to the Si3N4 crucible.

Abstract in portuguese No presente trabalho foram produzidos 30 moldes anatômicos de corações de vertebrados, visando contribuir para o estudo das artérias coronárias direita e esquerda de diferentes espécies: peixes, anfíbios, répteis, aves e mamíferos. Os corações foram injetados com acetato de vinil, submetidos a corrosão e semicorrosão pelo ácido clorídrico, a fim de evidenciar o padrão anatômico apresentado pelas artérias coronárias no tocante à evolução das espécies (more) e adaptações morfológicas (estrutura e arquitetura). Com base na morfologia das peças estudadas foram obtidas as seguintes conclusões: a técnica utilizando acetato de vinil, associada à corrosão, mostrou-se eficaz na produção de modelos de coração de diferentes espécies, apresentando detalhamento capaz de permitir visibilização dos ramos colaterais, quando existentes; o número de estruturas e a complexidade vascular cardíaca aumenta na medida em que os seres evoluem na escala zoológica. No réptil iguana iguana foi encontrado ventrículo duplo com tríplice via de saída, como único padrão evolutivo da anatomia dos ventrículos e grandes vasos da base ainda não descrito como cardiopatia congênita em humanos. Abstract in english Thirty anatomic models of vertebrate hearts were produced in order to study the right and left coronary arteries in different species such as fish, amphibians, reptiles, birds and mammals. The hearts were injected with vinyl acetate and then submited to corrosion and/or partial corrosion with hydrochloric acid to obtain the anatomical coronary artery model allowing correlation with the evolution of the species and its morphological adaptations. Based on these models we co (more) ncluded that: the technique using vinyl acetate associated to corrosion produced models of coronary vessels with enough details to visualize the branches; the number of structures and the vascular complexity increased as the species evolved in the zoological scale. In the reptile Iguana iguana a three outlet double ventricle was found, which has not yet been reported as a human congenital disease in the literature surveied.

Recent developments in multi-component Fe-based amorphous alloys have shown that these novel materials exhibit outstanding corrosion resistance compared to typical crystalline alloys such as high-performance stainless steels and Ni-based C-22 alloy. During the past decade, amorphous alloy synthesis has advanced to allow for the casting of bulk metallic glasses. In several Fe-based alloy systems it is possible to produce glasses with cooling rates as low as 100 K/s. At such low cooling rates, there is an opportunity to produce amorphous solids through industrial processes such as thermal spray-formed coatings. Moreover, since cooling rates in typical thermal spray processing exceed 1000 K/s, novel alloy compositions can be synthesized to maximize corrosion resistance (i.e. adding Cr and Mo) and to improve radiation compatibility (adding B) and still maintain glass forming ability. The applicability of Fe-based amorphous coatings in typical environments where corrosion resistance and thermal stability are critical issues has been examined in terms of amorphous phase stability and glass-forming ability through a coordinated computational analysis and experimental validation. For example, a wedge casting technique has been applied to examine bulk glass forming alloys by combining multiple thermal probes with a measurement based kinetics analysis and a computational thermodynamics evaluation to elucidate the phase selection competition and critical cooling rate conditions. Based upon direct measurements and kinetics modeling it is evident that a critical cooling rate range should be considered to account for nucleation behavior and that the relative heat flow characteristics as well as nucleation kinetics are important in judging ease of glass formation. Similarly, a novel computational thermodynamics approach has been developed to explore the compositional sensitivity of glass-forming ability and thermal stability. Also, the synthesis and characterization of alloys with increased cross-section for thermal neutron capture will be outlined to demonstrate that through careful design of alloy composition it is possible to tailor the material properties of the thermally spray-formed amorphous coating to accommodate the challenges anticipated in typical nuclear waste storage applications over tens of thousands of years in a variety of corrosive environments.

A major safety concern regarding the extension of the operating life of nuclear power plants is the gradual degradation of pressure boundary steel components and weldments beyond the present design life. The long-term effects of thermal aging, irradiation fluence, stress, and the corrosive environments of reactors must be properly understood and evaluated. These factors can act separately or, more often, synergistically to degrade the pressure boundary materials. Of particular concern is the capability to satisfactorily predict the fracture toughness properties of cast-duplex stainless steels (used in primary pipes, pumps, and valves) and pressure vessel steels (A302, A508, and A533) in long-term service (greater than or equal to 40 yr).

High chromium cast irons (HCCIs) are widely used in many industrial processes that require materials possessing high resistance to wear and corrosion. In the Alberta oil sands industry, HCCIs are extensively used in slurry pumping systems as well as other processing and handling equipments. However, due to the very harsh mining environment and severe working conditions, conventional HCCIs do not always perform satisfactorily. Great efforts have been made to identify optimum microstructures and chemical compositions in order to effectively tailor HCCIs for improved performance under various operating conditions and minimize maintenance costs. One proposal is to extend the chromium concentration of HCCIs to higher levels. In this work, six HCCIs containing 45wt.% of chromium and carbon conce...

Flaw detection and characterization by ultrasonic methods is particularly difficult for stainless steel. This paper focuses on two specific problem areas: (a) the inspection of centrifugally cast stainless steel (CCSS) and (b) the differentiation of intergranular stress-corrosion cracking (IGSCC) from geometrical reflectors such as the weld root. To help identify optimal conditions for the ultrasonic inspection of CCSS, the effect of frequency on propagation of longitudinal and shear waves was examined in both isotropic and anisotropic samples. Good results were obtained with isotropic CCSS and 0.5-MHz angle beam shear waves. The use of beam-scattering patterns (i.e. signal amplitude vs skew angle) as a tool for discriminating IGSCC from geometrical reflectors is also discussed.

Y/Cr-modified aluminide coatings were prepared on a Ni-base superalloy K417G using a hybrid slurry/pack cementation process. The coatings consisted of a NiAl layer with dissolved Cr and Y. The microstructures and high temperature corrosion behavior of the coatings were characterized using SEM/EDS, XRD, EPMA and SIMS. Cyclic oxidation tests at 1000??C for 200?h were carried out in air. The results indicated that specimens coated by either the Y/Cr-modified aluminide coatings or the simple aluminide coatings exhibited better oxidation resistances than the cast alloy. The Y/Cr-modified aluminide coatings possessed lower oxidation rates and better degradation resistance than the simple aluminide coatings during the oxidation tests. Furthermore, the alumina scales formed on the Y/Cr-modified al...

Die-cast plates of ASTM (American Society for Testing and Materials) AZ91D magnesium alloy were anodized by DC or AC electrolysis in a solution of phosphate and ammonium salt in which the anodized layer is formed by local discharge, followed by rapid solidification. Salt spray tests of the anodized specimens showed that AC electrolysis increases corrosion resistance and the anodized layers become denser compared with that for DC electrolysis. Tensile strength, elongation, and hardness were also improved by anodization, but higher anodizing bias and the resulting heating caused grain coarsening and a decrease in these properties. For the specimens that displayed remarkable improvement in mechanical properties, a decrease in network precipitates of the ? phase was observed. Improvement of mechanical properties is considered to be due to the fine precipitation of ? inside the grains of the ? phase at moderate temperature.   

The aim of this article is focused on a comparative experimental study of the electrochemical feature of as-cast Pb-2.2wt.% Sb alloy with cellular/dendritic transition for applications in the manufacturing of lead-acid battery parts. A water-cooled unidirectional solidification system is used to obtain the alloy samples. Electrochemical impedance spectroscopy (EIS) plots, potentiodynamic polarization curves and equivalent circuit analysis are used to evaluate corrosion resistance in a 0.5M H2SO4 solution at 25^oC. The cellular Pb-2.2wt.% Sb alloy is found to have a current density which is of about 3 times lower than that of the dendritic Pb-2.2wt.% Sb alloy. The Pb-2.2wt.% Sb alloy has lower current density than both the Pb-1wt.% Sb and the Pb-6.6wt.% Sb alloys evidencing its potential fo...

Grain Boundary Engineering can enhance the population of structurally-ordered "low S" Coincidence Site Lattice (CSL) grain boundaries in the microstructure. In some alloys, these "special" grain boundaries have been reported to improve overall resistance to corrosion, oxidation, and creep resistance. Such improvements could be quite beneficial for superalloys, especially in conditions which encourage damage and cracking at grain boundaries. Therefore, the effects of GBE processing on high-temperature mechanical properties of the cast and wrought superalloy Allvac 718Plus (Allvac ATI) were screened. Bar sections were subjected to varied GBE processing, and then consistently heat treated, machined, and tested at 650 C. Creep, tensile stress relaxation, and dwell fatigue crack growth tests were performed. The influences of GBE processing on microstructure, mechanical properties, and associated failure modes are discussed.

The use of Engineered Cementitious Composite (ECC), which has metal-like deformation and crack opening restriction ability, as a retrofit material for structures, has been the subject of high expectations. For this application, the direct spray method has been commonly accepted. This study focused on experimentally clarifying the fundamental properties of direct sprayed ECC containing high-performance polyvinyl alcohol fibers. The experiments that were performed demonstrated that direct sprayed ECC was successfully processed and showed pseudo-strain hardening performance comparable to that of traditionally cast ECC reported in the literature. Furthermore, test results simulating concrete cover cracking due to re-bar corrosion demonstrated that direct sprayed ECC has significant potential to prolong service life of R/C members in a heavy chloride environment.   

Corrosion-resistant weldable iron aluminide alloys are being developed for weld overlay cladding of conventional steels and alloys and possible structural applications. Weld hot cracking can be minimized by careful choice of alloying additions, and hot cracking resistance equivalent to commercial austenitic stainless steels has been achieved. Hydrogen-induced cold cracking, however, continues to be a problem with these alloys, both in monolithic weldments and weld overlay cladding applications. The authors have found that preheat and postweld heat treatment can reduce hydrogen cracking, and that composition is also an important variable. Experiments in controlled atmospheres have confirmed that a major source of hydrogen is provided by the reduction of water vapor from the environment, and that oxygen helps to reduce cracking sensitivity. Concurrently, they are developing filler metals using the aspiration-casting process, for use both as filler metals with the gas tungsten arc process, and as core wire for the production of shielded metal arc electrodes.

Cobalt-based alloy (Co-30Cr-5.5Mo) is produced by the investment casting process. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. SEM, XRD and microhardness tests are used to examine the mechanical properties of the material. The examined material exhibits the behaviour of indentation size effect (ISE). Our results reveal that Vickers and Knoop microhardness are dependent on indentation test load. The traditional Meyer's law, the proportional specimen resistance (PSR) model and the Hays-Kendall model (HK) are used to analyze the load dependence of the hardness. As a result, the Hays-Kendall model is found to be the most effective to determine the load-independent hardness HLI of CoCrMo alloy.

Hypereutectic Al?Si alloys are used in components that require high resistance wear and corrosion, good mechanical properties, low thermal expansion and less density. The size and morphology of hard primary silicon particles present in Al?Si alloys greatly influences the mechanical properties. Addition of Mg leads to formation of intermetallic Mg2Si phases, which contributes towards the properties of high silicon alloy as well as alters the nature and quantity of primary silicon formed. The high silicon alloy subjected to centrifugal casting leads to the formation of functionally gradient material, which provides variation in spatial and continuous distribution of primary phases in a definite direction exhibiting selective properties and functions within a component. The present study is t...

  To elucidate the composition and crystal structure of spheroidal vanadium carbides precipitated in high V-Cr-Ni cast iron that have exhibited excellent performance of anti-corrosive and anti-abrasive properties, alloys of Fe-V-C, Fe-Cr-V-C, Fe-Ni-V-C and Fe-Cr-Ni-V-C systems were prepared and the compositions and structures of vanadium carbides and/or other precipitates were investigated by using SEM, EPMA and XRD. The spheroidal compound was revealed to be a vanadium carbide with an atomic ratio M/C of more or less one and a crystal structure of V8C7 type. The composition and crystal structure of the vanadium carbide remain unchanged even if the alloy concentration or the morphology was varied.   

Abstract The documented data regarding the three-dimensional structure of the air capillaries (ACs), the ultimate sites of gas exchange in the avian lung is contradictory. Further, the mode of gas exchange, described as cross-current has not been clearly elucidated. We studied the temporal and spatial arrangement of the terminal air conduits of the chicken lung and their relationship with the blood capillaries (BCs) in embryos as well as the definitive architecture in adults. Several visualization techniques that included corrosion casting, light microscopy as well as scanning and transmission electron microscopy were used. Two to six infundibulae extend from each atrium and give rise to numerous ACs that spread centrifugally. Majority of the ACs are tubular structures that give off branch...

The harbor and marine structures made of concrete have many subjects to be discussed on structure design owing to construct under marine environment and execution conditions are very severe. This time, among these subjects, as for improvement of structure durability and saving labor of execution, it was paid attention and discussed. As for structure durability, structures degradation with the corrosion of steel material due to salt damage is cited. When CFRP using carbon fiber is applied instead of steel bar in the concrete structures such as piers and bridges, excellent durability is secured in marine environment. In this paper, results of loading test of composite beams and forms and design procedure of the super structures of the pier are described. As an example of field application, a composite pier deck was built using pre-cast CFRP reinforced concrete slab as a permanent form for the steel reinforced concrete deck floor. 12 refs., 29 figs., 10 tabs.

One of the key aspects in designing Spanish spent nuclear fuel canister for geological repository is selecting the inner material to be placed between the steel walls and the fuel assemblies. This material has to primarily avoid the possibility of a criticality event once the canister gets breached by corrosion and flooded by groundwater. A detailed set of requirements for a material to fulfil this role in that environment have been devised and presented in this paper. With these requirements in view, eight potentially interesting candidates were evaluated: cast iron or steel, borosilicate glass, spinel, depleted uranium, dehydrated zeolites, haematite, phosphates, and olivine. Among these, the first four materials or their families are found promising for this application.

Cast duplex and superaustenitic stainless steels are attractive alloys for applications that desire high strength and high corrosion resistance. Due to the large amounts of alloying additions present in these systems, a proper solution heat-treatment schedule is critical in ensuring that the alloys are able to meet the desired specifications. While studies to determine the phase transformation behavior of duplex and superaustenitic alloys have shown that the precipitation kinetics are comparatively slow when considering large amounts of precipitation, studies involving Charpy impact specimens have noted significant decreases in impact strength in materials improperly heat treated for times as short as 10?min, well before any significant amount of precipitation (<1?vol.%) has occurred. The ...

Au40Si17-20Cu28-30Ag5-7Pd5 glassy alloys showed a wide supercooled liquid region of 42–53 K and a large reduced glass transition temperature of 0.568–0.605, indicating high stabilization of supercooled liquid and high glass-forming ability (GFA). The best GFA was obtained from Au40Si20Cu28Ag7Pd5 alloy, and a fully glassy sample with a diameter of 6 mm could be fabricated by copper mold casting. The bulk glassy alloys exhibited very low Tg of 400–424 K, high fracture strength of over 1100 MPa, and corrosion resistance superior to SUS316L in 1 N H2SO4 solution.   

Selected physical and chemical properties and tribological data for a newly-developed, imidazolium-based ionic liquid (IL) are presented. The IL is soluble in the SAE 5W-30 oil up to a certain weight percentage, and is as a promising candidate for use in lubrication applications, either in its neat version or as an oil additive. Characterization of the IL included dynamic viscosity at different temperatures, corrosion effects on cast iron cylinder liners, and thermal stability analysis. The tribological performance was evaluated using a reciprocating ring-on-liner test arrangement. When used in neat version this IL demonstrated friction coefficient comparable to a fully formulated engine oil, and when used as an oil additive it produced less wear.

A zirconia microelectromechanical-system-based microthruster was fabricated through a newly developed fabrication route. Gel casting of homogenously dispersed zirconia suspension on polydimethylsiloxane soft mold was utilized to replicate the geometries of microthruster design onto a ceramic layer of about 1.2 mm thick. Lamination of the patterned ceramic layer to another flat ceramic layer and subsequent sintering produced the microthruster. Characterizations on the fabricated prototype showed good shape retention on the replicated geometries and good quality of lamination. Shrinkage of about 10-15% was noted after sintering. The current fabrication route is particularly promising for the development of high-performance micropropulsion systems which require their structural material to survive in an extreme environment which is corrosive, of high temperature and highly oxidative.

Titanium alloys were developed as an alternative to stainless steels and have been extensively used as biomaterials ever since. One of these alloys is Ti-13Nb-13Zr (TNZ), a near-beta phase alloy containing elements with excellent biocompatibility. The main advantage of the TNZ alloy, compared to other titanium alloys, such as Ti-6Al-4V and Ti-6Al-7Nb, widely used as biomaterials, is its low elasticity modulus, closer to that of bone, and the absence of aluminum and vanadium, which have been reported to cause long-term adverse effects. In this paper, the corrosion and electrochemical behavior of TNZ alloy (as cast and after oxygen charge) was studied in a PBS solution. The results showed that, with the oxygen load, there is a significant reduction of the anodic current in almost the whole p...

The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

The corrosion fatigue properties under sine wave loading in Eagle’s medium were compared among various metallic biomaterials: SUS-316L stainless steel, Co–Cr–Mo cast alloy and three types of vanadium-free titanium alloy, namely ?+? type Ti–6Al–7Nb, Ti–6Al–2Nb–1Ta and a variety of newly developed Ti–15Zr–4Ta–4Nb alloys. The number of cycles to failure for the SUS-316L stainless steel and Co–Cr–Mo cast alloy increased as the maximum stress decreased. The fatigue strengths of the SUS-316L stainless steel and Co–Cr–Mo cast alloy at 1×108 cycles were much lower than those of the titanium alloys. The fatigue strengths of the vanadium-free Ti–6Al–7Nb and Ti–6Al–2Nb–1Ta alloys at 1×108 cycles were approximately 600 and 720?MPa, respectively. The fatigue strengths of the Ti–15Zr–4Nb–4Ta alloys annealed at 700°C for 2?h were about 700?MPa at 1×108 cycles, and were not significantly affected by varying the frequency from 2 to 10?Hz. Aging of the Ti–15Zr–4Nb–4Ta alloy containing 0.2%O and 0.05%N after solution treatment increased its ultimate tensile strength to 1150?MPa, and the total elongation and reduction in the area were 15 and 50%, respectively. The fatigue strength of the Ti–15Zr–4Ta–4Nb alloy treated in this way was 880?MPa under sine wave loading of 10?Hz at 1×108 cycles. This strength proved to be nearly identical to that estimated for the human hip joint, following an analysis of its movements and the forces acting upon it in vivo. The fatigue strength ratios at 1×108 cycles to ultimate tensile strength of the SUS-316L stainless steel and Co–Cr–Mo cast alloy were about 50%. The fatigue strength ratio at 1×108 cycles to ultimate tensile strength of the Ti–6Al–2Nb–1Ta alloy was high at 75%. In the case of the Ti–15Zr–4Nb–4Ta alloy annealed or aged after solution treatment, the fatigue strength ratio to ultimate tensile strength was about 75%. Many striations and cracks caused by fatigue were visible on the fatigue-fractured surfaces of the SUS-316L stainless steel and Co–Cr–Mo cast alloy. Micro-cracks in dimples were also apparent on the fatigue-fractured surface of the titanium alloys.   

Abstract To identify the forces that may exist in the parabronchus of the avian lung and that which may explain the reported strengths of the terminal respiratory units, the air capillaries and the blood capillaries, the arrangement of the parabronchial collagen fibers (CF) of the lung of the domestic fowl, Gallus gallus variant domesticus was investigated by discriminatory staining, selective alkali digestion, and vascular casting followed by alkali digestion. On the luminal circumference, the atrial and the infundibular CF are directly connected to the smooth muscle fibers and the elastic tissue fibers. The CF in this part of the parabronchus form the internal column (the axial scaffold), whereas-the CF in the interparabronchial septa and those associated with the walls of the interparab...

Stroke-prone spontaneously hypertensive rats (SHRSP) are known to show necrosis of the femoral head with a frequency of about 50%. This rat has thus been used as an animal model for necrosis of the femoral head in many studies. In a detailed investigation of feeding vessel disorders that cause femoral head necrosis, we observed changes over time in the feeding vessels using scanning electron microscopy and transmission electron microscopy. In scanning electron microscopy of vascular casts, abnormal findings in feeding vessels of SHRSP with aging from the immature stage included contortion and bending in the lumen with overall narrowing. Under transmission electron microscopy, decreased numbers of smooth muscle cells and increased amounts of collagen fibers were marked, and these changes wi...

A key issue in developing strategies against diseases such as cancer is the analysis of the vessel tree in comparison to the healthy one. In the search for parameters that might be characteristic for tumor capillaries we study the vascularization in mice for cancerous and healthy tissues using synchrotron radiation-based micro computed tomography in absorption and phase contrast modes. Our investigations are based on absorption tomograms of casted healthy and cancerous tissues as well as a phase tomogram of a fixated tumor. We demonstrate how the voxel-based tomography data can be vectorized to assess the capillary networks quantitatively. The processing includes segmentation, skeletonization, and vectorization to finally extract the vessel parameters. The mean diameter of capillaries in h...

To ensure the safe encapsulation of spent nuclear fuel rods for geological disposal, SKB of Sweden are considering using the Copper-Iron Canister, which consists of an outer copper canister and a cast iron insert. Over the years a programme of laboratory work has been carried out to investigate a range of corrosion issues associated with the canister, including the possibility of expansion of the outer copper canister as a result of the anaerobic corrosion of the cast iron insert. Previous experimental work using stacks of test specimens has not shown any evidence of corrosion-induced expansion. However, as a further step in developing an understanding of the likely performance of the canister in a repository environment, Serco has set up a series of experiments in SKB's Aespoe Hard Rock Laboratory (HRL) using inactive model canisters, in which leaks were deliberately introduced into the outer copper canister while surrounded by bentonite, with the aim of obtaining information about the internal corrosion evolution of the internal environment. The experiments use five small-scale model canisters (300 mm long x 150 mm diameter) that simulate the main features of the SKB canister design (hence the project name, 'MiniCan'). The main aim of the work is to examine how corrosion of the cast iron insert will evolve if a leak is present in the outer copper canister. This report describes the progress on the five experiments running at the Aespoe Hard Rock Laboratory and the data obtained from the start of the experiments in late 2006 up to Winter 2010. The full details of the design and installation of the experiments are given in a previous report and this report concentrates on summarising and interpreting the data obtained to date. This report follows two earlier progress reports presenting results up to December 2009. The current document (progress report 3) describes work up to December 2010. The current report presents the results of the water analyses obtained in 2007 and 2008, including gas composition and microbial activity. These data show an increase in the dissolved iron concentration inside the support cage, together with a decrease in the pH. Both these observations may be due to microbial activity, but it is also possible that abiotic processes could have contributed to changes in the local chemistry. Microbial analysis has shown the presence of sulphate reducing bacteria (SRBs) and autotrophic acetogens. The presence of low density bentonite appears to stimulate the growth of SRBs, but recent studies reported in the literature indicate that high density fully compacted bentonite inhibits SRB activity. A further set of water samples was taken for analysis at the end of 2010, but the full set of results from this sampling campaign is not currently available and will be included in a subsequent report

This dictionary contains about 13.500 entries in each part of the following fields: Basic principles of corrosion (metals and their properties - electromotive series - passivity - lattice defects - corrodents - concepts of corrosion); Types of corrosion (corrosion of metals and non-metals - electrochemical corrosion - chemical corrosion - liquid-metal corrosion); Corrosion control (protection by influencing the state of a corroding system); Protection by coatings; Corrosion testing (field, plant, and laboratory testing - long-term and short-term tests). (orig./HP).

Solidification structures often determine the quality of final products. In this study, three different phenomena related to solidification processing, which are welding, hot-workability and investment casting, have been summarized.With non-filler welding of SUS836L strips by TIG, segregation of welded material deteriorated corrosion resistance at the bead because of lower Cr and Mo concentrations at the dendrite cores. Employing filler material with higher pitting resistance equivalent (PRE) improved this deterioration. Next, it was confirmed that hot-workability of a stainless steel containing 1.1 mass% boron that has eutectic solidification behavior was more excellent with CC slabs than ingots. This reason is attributed to the fact that the eutectoids consisting of austenite and boride with the CC slab are much finer. Cracks at the stem-like corners of investment casts were often found by the magnetic particle testing. It was considered that the cracks were caused with this position being hot spots. The cracking was improved by changing the size of sprues for molten steel not to hit the corners to prevent hot spots.As a summary, for high alloys, solidification process still depends on the way of try and error and experience base. Therefore far more investigations are expected to predict how molten steels solidify avoiding any defects and deterioration of every property.