Showing papers on "Alloy published in 1989"
TL;DR: In this article, the influence of cooling rate on the microstructure of stainless steel alloys was investigated and the conditions that lead to the many microstructural morphologies that develop during solidification.
Abstract: The microstructures that develop during the solidification of stainless steel alloys are related to the solidification conditions and the specific alloy composition. The solidification conditions are determined by the processing method,i.e., casting, welding, or rapid solidification, and by parametric variations within each of these techniques. One variable that has been used to characterize the effects of different processing conditions is the cooling rate. This factor and the chemical composition of the alloy both influence (1) the primary mode of solidification, (2) solute redistribution and second-phase formation during solidification, and (3) the nucleation and growth behavior of the ferrite-to-austenite phase transformation during cooling. Consequently, the residual ferrite content and the microstructural morphology depend on the cooling rate and are governed by the solidification process. This paper investigates the influence of cooling rate on the microstructure of stainless steel alloys and describes the conditions that lead to the many microstructural morphologies that develop during solidification. Experiments were performed on a series of seven high-purity Fe-Ni-Cr alloys that spanned the line of twofold saturation along the 59 wt pct Fe isopleth of the ternary alloy system. High-speed electron-beam surface-glazing was used to melt and resolidify these alloys at scan speeds up to 5 m/s. The resulting cooling rates were shown to vary from 7°C/s to 7.5×106°C/s, and the resolidified melts were analyzed by optical metallographic methods. Five primary modes of solidification and 12 microstructural morphologies were characterized in the resolidified alloys, and these features appear to be a complete “set” of the possible microstructures for 300-series stainless steel alloys. The results of this study were used to create electron-beam scan speedvs composition diagrams, which can be used to predict the primary mode of solidification and the microstructural morphology for different processing conditions. Furthermore, changes in the primary solidification mode were observed in alloys that lie on the chromium-rich side of the line of twofold saturation when they are cooled at high rates. These changes were explained by the presence of metastable austenite, which grows epitaxially and can dominate the solidification microstructure throughout the resolidified zone at high cooling rates.
399 citations
TL;DR: In this article, the authors investigated the corrosion behavior of mold-cast Mg alloy AZ91 in as-cast (F), homogenized (T4), and artificially-aged (T6) conditions in chloride media.
Abstract: Corrosion behavior of mold-cast Mg alloy AZ91 is investigated in as-cast (F), homogenized (T4), and artificially-aged (T6) conditions in chloride media. Heat treatment influences mainly th...
360 citations
15 Nov 1989-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the experimental evidence for the reactive element effect is summarized, and different models that have been proposed to account for one or more aspects of the REE are assessed in terms of this evidence.
Abstract: When small quantities (typically 1 wt.% or less) of a number of reactive elements are added to high-temperature alloys containing chromium or aluminum, a number of beneficial effects result. This is called the “reactive element effect” (REE). Some or all aspects of the REE can be developed when the reactive element is added as an alloy addition, when it is present as a dispersion of oxide particles in the alloy, when it is ion implanted into the surface, or when a coating of the reactive element oxide is applied to the surface of the alloy. In this paper, the experimental evidence is briefly summarized, and different models that have been proposed to account for one or more aspects of the REE are assessed in terms of this evidence.
313 citations
01 Jan 1989-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure of SiC-reinforced aluminium alloys produced by this method are considered and it is shown that the SiC stability in the melt is dependent on the matrix alloy involved and that only alloys with high silicon contents have a low reactivity with this reinforcement.
Abstract: When metal matrix composites are produced by molten metal methods there are some unique factors which have to be considered. In this paper, the microstructure of SiC-reinforced aluminium alloys produced by this method are considered. It is shown that the stability of SiC in the melt is dependent on the matrix alloy involved and that only alloys with high silicon contents have a low reactivity with this reinforcement. With other alloy matrices, SiC reacts to form Al 4 C 3 , and the nature of this reaction and its kinetics are considered in this paper. Initially, the reaction rates are very rapid but almost saturate after about 1 h. It is also shown that the distribution of the reinforcing particles is dependent on the solidification rate because particles are rejected and pushed ahead of the meniscus. At low solidification rates, and hence for large cell sizes, the reinforcing particles are clustered and form a network which delineates the cell walls. Because the SiC particles are in the interdendritic regions they will be associated with any coarse intermetallic particles present and this can influence the fracture behaviour.
225 citations
183 citations
TL;DR: In this paper, it has been shown that when the bond layer is thick, the bond strength is limited either by plastic flow or by ductile fracture in the metal, whereas when the layer is thin, failure occurs in the ceramic, limited by the strength of the ceramic.
171 citations
TL;DR: In this article, two Al-Si alloys (LM13 of near eutectic and LM30 of hypereutectical composition) were chosen as matrix alloys and composites were prepared by casting.
157 citations
TL;DR: In this paper, in situ and ex- situ characterizations of the surface of a bulk PtRu alloy in sulfuric acid solutions at room temperature were performed and the results showed that the surface composition of the alloy appears to be stable up to +1.0 V vs. RHE.
141 citations
TL;DR: Wetting phenomena in ceramic particulate/liquid Al-alloy systems were investigated experimentally using a new pressure infiltration technique developed by the authors in this article, which was performed on two different ceramic particulates, SiC and B4C, with four different liquid aluminum alloy matrices, pure Al, AlCu, Al-Si, and Al-Mg, tested with optical microscopy, SEM, EPMA, and Auger Electron Spectroscopy (AES).
Abstract: Wetting phenomena in ceramic particulate/liquid Al-alloy systems were investigated experimentally using a new pressure infiltration technique developed by the authors Studies were performed on two different ceramic particulates, SiC and B4C, with four different liquid aluminum alloy matrices, pure Al, Al-Cu, Al-Si, and Al-Mg Five major variables tested to study wetting phenomena in ceramic/Al-alloy systems were holding time, melt temperature, alloying element, gas atmosphere, and particulate Metal: ceramic interfaces were investigated with optical microscopy, SEM, EPMA, and Auger Electron Spectroscopy (AES) in order to understand better the wetting process The threshold infiltration pressure decreased with, temperature as well as with pressurization time for all the ceramic/metal systems A strong correlation was found between the alloying effect on the threshold pressure and the free energy of formation of oxide phase of the alloying element More reactive alloying elements were more effective in improving wettability In air atmospheres, the threshold pressure usually increased markedly as a result of a thick oxide layer formation on the liquid front Compacts of B4C particulates showed lower threshold pressures than those of SiC, particulates Fracture occurred in a generally brittle manner in infiltrated SiC, specimens AES element profiles on the fracture surfaces showed fast diffusion of Si, and pile-up of C at the metal∶SiC boundaries which promoted fracture through the carbon-rich layer The fracture surfaces of infiltrated B4C specimens indicated plastic deformation, hence a more ductile failure mode
141 citations
TL;DR: In this paper, a series of heat treatments were performed to study the sensitization and the stress corrosion cracking (SCC) behavior of INCONEL Alloy 690 for use as the steam generator (S/G) tubing material for PWR's.
Abstract: A series of heat treatments were performed to study the sensitization and the stress corrosion cracking (SCC) behavior of INCONEL Alloy 690. The microstructural evaluation and the chromium depletion near grain boundaries were carefully studied using analytical electron microscopy (AEM). The measured chromium depletion profiles were matched well to the calculated results from a thermodynamic/kinetic model. The constant extension rate test (CERT) was performed in the solution containing 0.001 M sodium thiosulfate (Na2S2O3) to study the SCC resistance of this alloy. The Huey test was also performed in a boiling 65 pct HNO3 solution for 48 hours to study the intergranular attack (IGA) resistance of this alloy. Both tests showed that INCONEL 690 has very good corrosion resistance. It is believed that the superior IGA and SCC resistances of this alloy are due to the high chromium concentration (≈30 wt pct). It is concluded in this study that INCONEL 690 may be a better alloy than INCONEL 600 for use as the steam generator (S/G) tubing material for pressurized water reactors (PWR's)
133 citations
TL;DR: In this paper, the structural and electronic properties of hydrogenated amorphous silicon-germanium alloys deposited by rf glow discharge from SiH4 and GeH4 in a diode reactor were investigated.
Abstract: We report on a detailed study of structural and electronic properties of hydrogenated amorphous silicon‐germanium alloys deposited by rf glow discharge from SiH4 and GeH4 in a diode reactor. The chemical composition of the alloys is related to the deposition conditions, with special emphasis on preferential incorporation of Ge into the solid phase and on the role of inert dilutant gases. Hydrogen bonding in the alloys is investigated with nuclear magnetic resonance and vibrational (Raman and infrared) spectroscopy. The optical properties of a‐SiGe:H samples deposited under optimal conditions are analyzed with the help of subgap absorption measurements and band‐tail luminescence for the entire range of alloy composi‐tions. A large part of the article describes an investigation of the electron‐spin‐resonance response of undoped alloys. The spin density associated with dangling bond defects localized on Si and Ge atoms has been measured as a function of alloy composition for optimized material. In addition, ...
TL;DR: In this paper, an isothermal kinetics of non-equilibrium grain-boundary segregation was developed both for segregation processes and for desegregation processes within a phenomenological theory.
Patent•
14 Sep 1989TL;DR: In this paper, a package (10) adapted to house an electronic device (12) such as a semiconductor integrated circuit, is described, which is comprised of aluminum or an aluminum based alloy.
Abstract: The present invention relates to a package (10) adapted to house an electronic device (12), such as a semiconductor integrated circuit. The package (10) components are comprised of aluminum or an aluminum based alloy. At least a portion of the surfaces of the package components are anodized to enhance corrosion resistance and increase bond strength. The aluminum based packages are characterized by lighter weight than copper based packages and better thermal conductivity than plastic based packages.
TL;DR: In this article, the ternary alloys of arc-melted, nearequiatomic TiAl alloys containing boron additions are analyzed and compared with those of binary Ti-Al and Ti-B alloys processed in a similar fashion.
Abstract: Solidification microstructures of arc-melted, near-equiatomic TiAl alloys containing boron additions are analyzed and compared with those of binary Ti-Al and Ti-B alloys processed in a similar fashion. With the exception of the boride phase, the matrix of the ternary alloy consists of the same α2 (DO19) and γ (Ll0) intermetallic phases found in the binary Ti-50 at. pct Al alloy. On the other hand, the boride phase, which is TiB (B27) in the binary Ti-B alloys, changes to TiB2 (C32) with the addition of Al. The solidification path of the ternary alloys starts with the formation of primary α (A3) for an alloy lean in boron (∼1 at. pct) and with primary TiB2 for a higher boron concentration (∼5 at. pct). In both cases, the system follows the liquidus surface down to a monovariant line, where both α and TiB2 are solidified concurrently. In the final stage, the α phase gives way to γ, presumably by a peritectic-type reaction similar to the one in the binary Ti-Al system. Upon cooling, the α dendrites order to α2 and later decompose to a lath structure consisting of alternating layers of γ and α2.
Patent•
10 Oct 1989
TL;DR: In this paper, thermal shock-resistant coatings for nickel base super alloys are obtained by applying to the base metal a thin bond coat of an alloy of chromium aluminum and yttrium with materials selected from the group consisting of iron, cobalt, nickel and nickel-cobalt.
Abstract: Adherent, thermal shock-resistant protective coatings for nickel base super alloys are obtained by applying to the base metal a thin bond coat of an alloy of chromium aluminum and yttrium with materials selected from the group consisting of iron, cobalt, nickel and nickel-cobalt and applying thereover a continuously graded mixture of this material with a zirconia-based ceramic, the concentration of zirconia-based ceramic increasing from the bond coat to the outer layer. The zirconia ceramic may be stabilized by the addition thereto of amounts of magnesium oxide or other materials.
TL;DR: In this article, the room temperature deformation behavior and microstructure of Ti 48 Al 52 and Ti 52 Al 48 alloys are compared and the possible reasons for the differences in micro-structure and mechanical behavior between these two alloys were discussed.
Abstract: The room temperature deformation behavior and microstructure of Ti 48 Al 52 and Ti 52 Al 48 alloys are compared. The material was fabricated by rapid solidification melt spinning, and examined in both as-cast and consolidated forms. The Ti 52 Al 48 alloy exhibited enhanced strength and ductility in both forms in bend tests compared with the Ti 48 Al 52 alloy. The microstructure of the Ti 52 Al 48 alloy was two-phase γ–TiAl and α 2 –Ti 3 Al. The Ti 48 Al 52 alloy was single-phase γ–TiAl and had a larger grain size than the previous alloy. The microstructure of the Ti 52 Al 48 alloy after room temperature deformation consisted primarily of {111} mechanical twins and a /2〈110〉 perfect dislocations. The comparable Ti 48 Al 52 alloy microstructure contained fewer twins, and many more a 〈101〉 and a /2〈112〉 superdislocations were present in addition to a /2〈110〉 dislocations. The superdislocations had dissociated and formed sessile faulted dipoles. The possible reasons for the differences in microstructure and mechanical behavior between these two alloys are discussed.
TL;DR: In this paper, the authors showed that the dissolution of additional ferromagnetic phases in the intergranular regions of sintered Fe-Nd-B magnets might be the positive effect of the 600 °C annealing.
Abstract: In the FeNd system an additional ferromagnetic phase with Tc = 245 ± 10 °C is found. In the ternary FeNdB system, magnetic analysis shows two ferromagnetic phases with Tc = 245 and 285 °C in as-cast alloys, in addition to Fe14Nd2B. Those phases are formed through the eutectic solidification of a neodymium-rich liquid at the boron-poor side of the system, suppressing the formation of Fe14Nd2B. An annealing at 600 °C dissolves the phase with Tc = 245 °C and develops Fe14Nd2B. This results in an Hci increase from 3.9 kOe in the as-cast to 14.1 kOe in the annealed condition for an Fe-80at.%Nd-5at.%B alloy. This suggests that the dissolution of additional ferromagnetic phases in the intergranular regions of sintered FeNdB magnets might be the positive effect of the 600 °C annealing.
TL;DR: A surface treatment with aqueous solutions of K2ZrF6 has been carried out to improve, in dramatic manner, the wetting of carbon (or SiC)-base ceramics by liquid light alloys at low temperatures as mentioned in this paper.
Abstract: A surface treatment with aqueous solutions of K2ZrF6 has been carried out to improve, in dramatic manner, the wetting of carbon (or SiC)-base ceramics by liquid light alloys at low temperatures (ie within the 700 to 900°C range) The mechanism which is thought to be responsible for the wetting improvement involves two steps: (i) K2ZrF6 reacts with aluminium with the formation of K3AlF6, other complex fluoride species and intermetallics, (ii) K3AlF6 dissolves the alumina thin layer, coating the liquid light alloy and enables the wetting of the ceramics The mechanism has been worked out from sessile drop experiments, solid state chemistry experiments and composite casting The K2ZrF6 surface treatment appears to be particularly suitable for processing composite materials made of carbon (or SiC) fibrous preforms and aluminium-base matrices according to techniques directly derived from the light alloy foundry
TL;DR: In this article, the formation of the protective scales on iron and nickel base alloys is discussed, with particular reference to the population densities of the initial nuclei of the oxide and the rates of growth and coalescence of these particles to develop the healing barrier layer.
Abstract: Some of the important principles of alloy oxidation are discussed, with emphasis on the formation of protective Cr2O3, Al2O3, and SiO2 scales on iron and nickel base alloys. The competition between internal and external oxidation is considered and it is shown how establishment of the protective layer is influenced by various parameters, including alloy interdiffusion coefficient, oxygen solubility and diffusivity in the alloy, and the relative growth rates of the various oxides. The importance of the transient stage of oxidation is emphasised, with particular reference to the population densities of the initial nuclei of the protective oxide and the rates of growth and coalescence of these particles to develop the healing barrier layer. Consideration is given to the effectiveness of the protective scales in service, with respect to transport processes and mechanical integrity. The influence of the minor alloying elements, manganese, titanium, aluminium, silicon, molybdenum, and niobium, on oxidati...
Patent•
28 Nov 1989
TL;DR: A titanium-based metal matrix microcomposite material was used in a process for cladding a macrocompositionite structure as mentioned in this paper, where the microcomposition material was formed by sintering at a temperature selected to preclude diffusion of TiB 2 into the matrix.
Abstract: A titanium-based metal matrix microcomposite material About 1% to about 25% by weight TiB 2 is substantially uniformly incorporated in a titanium-based alloy matrix The microcomposite material is formed by sintering at a temperature selected to preclude diffusion of TiB 2 into the matrix The microcomposite material may be used in a process for cladding a macrocomposite structure
Patent•
25 Aug 1989
TL;DR: A supported platinum alloy electrocatalyst for an acid electrolyte fuel cell was proposed in this paper, which consisted of an electrically conductive powdery carbon carrier and dispersed in, and deposited on, the carrier, an ordered platinum-iron-copper ternary alloy.
Abstract: A supported platinum alloy electrocatalyst for an acid electrolyte fuel cell, said electrocatalyst consisting essentially of an electrically conductive powdery carbon carrier and dispersed in, and deposited on, the carrier, an ordered platinum-iron-copper ternary alloy comprising 40 to 60 atomic percent of platinum, 13 to 40 atomic percent of iron and 13 to 40 atomic percent of copper. The electrocatalyst has much better initial activity and lifetime than conventional platinum alone or multi-components alloy electrocatalysts. A process for producing the supported platinum alloy electrocatalyst which comprises depositing copper on a previously formed platinum-iron supported binary ordered alloy, again subjecting the product to an alloying treatment, or depositing iron on the platinum-copper supported binary alloy and then again subjecting the product to an alloying treatment. An electrode for an acid electrolyte fuel cell having an excellent output performance and a long operating life is also provided which comprises the above supported platinum alloy electrocatalyst and a water-repellent binder which are bonded to an electrically conductive and acid-resistant supporting member.
TL;DR: In this article, the phase equilibria in eutectic systems are affected by the interaction of the liquid components, and the link between two apparently distinct types of alloy systems: one capable of exhibiting solid-state amorphization (SSA), in which there are compounds and a deep metastable eUTectic; the other not capable of SSA, but capable of glass formation by rapid liquid quenching.
Abstract: SOLID amorphous alloys can be made by a wide variety of techniques1. Of these, rapid liquid quenching and solid-state amorphization (SSA) in annealed multilayers can be most readily analysed according to a condensed-phase equilibrium diagram for the alloy. Here we consider how the phase equilibria in eutectic systems are affected by the interaction of the liquid components. We use such considerations to show the link between two apparently distinct types of alloy system: one capable of exhibiting SSA, in which there are compounds and a deep metastable eutectic; the other not capable of SSA, but capable of glass formation by rapid liquid quenching, in which there is only a stable eutectic. In alloys of intermediate type we propose that there exists a novel transformation, the inverse eutectic transition, which is a special case of a peritectoid transformation (two solid phases transforming to a single solid phase on cooling) in which the product phase is amorphous.
TL;DR: In this article, the microstructure of a series of as-quenched and aged Al-Li base alloys has been studied by high resolution transmission electron microscopy (HREM) and by X-ray diffraction.
TL;DR: Zinc alloy electrodeposits containing 0 to 25% of Ni or Co have been prepared in the laboratory and carefully characterised with respect to composition and structure as mentioned in this paper, and their corrosion behaviour has been investigated.
Abstract: Zinc alloy electrodeposits containing 0 to 25% of Ni or Co have been prepared in the laboratory and carefully characterised with respect to composition and structure. Corrosion behaviour has been s...
TL;DR: In this article, a review paper of high temperature (greater than 200°C) oxidation of steels with total alloying elements less than 3 wt% is presented.
Abstract: This is a review paper of high temperature (greater than 200° C) oxidation of steels with total alloying elements less than 3 wt%. Topics include the iron-oxygen phase diagram, the oxidation mechanism and kinetics as well as the effects of alloying elements, environmental atmospheres, and cold work.
TL;DR: In this article, an amorphous Ni-19P alloy prepared by rapid quenching of white heat melt showed a higher anodic dissolution current density in 1 N HCl in comparison with the same amorphized alloy prepared with red heat melt, showing that the difference in anodic behavior between these two as-quenched specimens seems due to the differences in the amounts of quenched-in defects.
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05 May 1989TL;DR: In this paper, the authors proposed the use of a ceramic-coated heat-resilient alloy member for improving the power efficiency of gas turbine plants used for power generation.
Abstract: A ceramic-coated heat resisting alloy member comprises a base metal (2) mainly composed of at least one of nickel, cobalt and iron; a mixture layer (4) which is deposited on the external surface of the base metal (2) and which comprises a ceramics and a metal; an alloy layer (3) which is formed between the mixture layer (4) and a ceramic coating layer (1) formed as an outermost layer and which comprises an alloy material exhibiting excellent resistance to high temperature oxidation and excellent resistance to high temperature corrosion. It is therefore possible to prevent any high temperature oxidation and high temperature corrosion of the mixture layer (4) and to enable the mixture layer (4) to have a satisfactory function of reducing the thermal stress produced between the ceramic coating layer (1) and the base metal (2). The ceramic coating (1) thus has a satisfactory thermal barrier effect on the base metal (2). In addition, it is therefore possible to provide the ceramic-coated heat resisting alloy member as a useful structural member for improving the power efficiency of gas turbine plants used for power generation.
TL;DR: Etude de la corrosion par piqure des alliages Al−Ti et Al−Cr dans une solution saline de NaCl as discussed by the authors is a classic example.
Abstract: Etude de la corrosion par piqure des alliages Al−Ti et Al−Cr dans une solution saline de NaCl