Showing papers in "JOM in 1997"
TL;DR: Improvement has been made in the model descriptions in the CALPHAD method, the coupling of phase diagrams with kinetic process modeling, computer programs for easy access to phase diagram information, and the construction of databases used for calculating the phase diagrams of complex commercial alloys.
Abstract: Enormous progress has been made in the calculation of phase diagrams during the past 30 years. This progress will continue as model descriptions are improved and computational technology advances. Improvement has been made in the model descriptions in the CALPHAD method, the coupling of phase diagrams with kinetic process modeling, computer programs for easy access to phase diagram information, and the construction of databases used for calculating the phase diagrams of complex commercial alloys.
279 citations
TL;DR: In this article, the microstructure and mechanical properties of H13 alloy are described using the direct metal deposition (DMD) technique, which is the state-of-the-art for die and tool manufacturing.
Abstract: The rapid prototyping process has reached the stage of rapid manufacturing via the direct metal deposition (DMD) technique. The DMD process is capable of producing three-dimensional components from many of the commercial alloys of choice. H13 tool steel is a difficult alloy for deposition due to residual stress accumulation from martensitic transformation; however, it is the material of choice for the die and tool industry. This article reviews the state of the art of DMD and describes the microstructure and mechanical properties of H13 alloy deposited by DMD.
254 citations
TL;DR: In this article, the thermomechanical processing of ingot-metallurgy alpha/beta titanium alloys is summarized, with special emphasis on microstructure evolution and workability considerations.
Abstract: In this article, the thermomechanical processing of ingot-metallurgy alpha/beta titanium alloys is summarized, with special emphasis on microstructure evolution and workability considerations. Primary hot working dealing with the conversion of ingot structures to fine-equiaxed wrought structures is addressed. In this regard, the breakdown of lamellar microstructures, the occurrence of cavitation/wedge cracking, and the development of crystallographic texture are described. Secondary processes such as sheet rolling, superplastic forming, and closed-die forging are also reviewed.
193 citations
TL;DR: In this article, a review of developments in the molten processing of particulate Al-Si alloy composites and their respective properties are discussed, and the reinforcement phases in prominent R&D activities are identified.
Abstract: In the past ten years, materials R&D has shifted from monolithic to composite materials, adjusting to the global need for reduced weight, low cost, quality, and high performance in structural materials. This article reviews developments in the molten processing of particulate Al-Si alloy composites and their respective properties. Existing and emerging processing innovations are discussed, and the reinforcement phases in prominent R&D activities are identified. The vortex (or mixing) method continues to be the most popular processing method in use because of its ease of operation, total production cost, and suitability, while the infiltration, compocasting (or rheocasting), in-situ, and spray atomization and codeposition techniques receive less attention.
143 citations
TL;DR: In this article, fracture toughness, oxidation properties, high-temperature mechanical behavior, and lowtemperature fatigue properties of refractory metal-intermetallic composites are described and compared to air-craft-engine fundamental material property goals for the next millennium.
Abstract: There has been substantial progress in the development of properties in high-temperature in-situ composites during the last five years. For example, fracture-toughness values in excess of 20 MPa √m have been reported in silicide-based composites toughened by niobium-based metallic solid solutions. These composites also have oxidation resistances and rupture lives comparable to those of single-crystal superalloys for temperatures up to 1,150°C. In this article, fracture toughness, oxidation characteristics, high-temperature mechanical behavior, and low-temperature fatigue properties of refractory metal-intermetallic composites (RMICs) are described and compared to air-craft-engine fundamental material property goals for the next millennium. Further avenues toward the pursuit of these goals are outlined.
133 citations
TL;DR: In this article, an overview of the mechanical properties of metal-ceramic and intermetallicceramic composites produced by in-situ techniques is presented. Butler et al. emphasize systems for which the mechanisms controlling mechanical properties are known.
Abstract: Because in-situ composites offer such a wide selection of reinforcement types, size, and volume fractions, understanding the mechanisms controlling mechanical properties will allow more intelligent decisions to be made when tailoring a composite system for a specific application. This article provides an overview of the mechanical properties of discontinuously reinforced metal-ceramic and intermetallic-ceramic composites produced by in-situ techniques. Systems for which the mechanisms controlling mechanical properties are known are emphasized.
129 citations
TL;DR: In the absence of grain-refining additions to a melt or of any significant heterogeneous nuclei, equiaxed grains can only originate in a casting from primary dendrite fragments as mentioned in this paper.
Abstract: In the absence of grain-refining additions to a melt or of any significant heterogeneous nuclei, equiaxed grains can only originate in a casting from primary dendrite fragments. Thus, it is pertinent to understand how dendrites become fragmented and to explain why liquid stirring should appear to “break up” and refine the grain structure. Dendrite fragmentation occurs by local remelting, and fluid flow is important as a dispersal mechanism.
128 citations
TL;DR: In the past four years, a new process has been developed at McGill University for the immobilization of arsenic from metallurgical effluents and flue dusts by the controlled precipitation of scorodite under atmospheric pressure conditions as mentioned in this paper.
Abstract: In the past four years, a new process has been developed at McGill University for the immobilization of arsenic from metallurgical effluents and flue dusts by the controlled precipitation of scorodite under atmospheric-pressure conditions. So far, the process has been successfully tested in the laboratory with chloride and sulfate solutions containing arsenic and with As2O3 smelter flue dusts. It has been also tested with equal success at a copper smelter with industrial arsenic-containing sulfate effluents.
124 citations
TL;DR: The Kirkendall effect as mentioned in this paper was first observed in the diffusion of copper and zinc in interdiffusion between brass and copper in the early 1940s, and it is known as the KE.
Abstract: In the 1940s, it was a common belief that atomic diffusion took place via a direct exchange or ring mechanism that indicated the equality of diffusion of binary elements in metals and alloys. However, Ernest Kirkendall first observed inequality in the diffusion of copper and zinc in interdiffusion between brass and copper. This article reports how Kirkendall discovered the effect, now known as the Kirkendall Effect, in his short research career.
116 citations
TL;DR: The results of an investigation of granular and compact aluminum drosses are reported in this paper, where the bulk density and salt contents of the dross were measured by applying the leaching test DIN 38414-S4; the metal contents by the salt-melting process were measured on a laboratory scale.
Abstract: In this article, the results of an investigation of granular and compact aluminum drosses are reported. The bulk density of granular drosses was determined according to DIN 52110-B, while DIN 52102-RE-VA was applied to compact drosses. The salt contents of the drosses were measured by applying the leaching test DIN 38414-S4; the metal contents by the salt-melting process were measured on a laboratory scale. In addition to the density data, the particle-size analysis, the distribution of elements in the different fractions, composition, metal content of recovered alloys, and gas evolution were compiled in a dross identity card characterizing each dross and simplifying the preanalysis for recovery.
109 citations
TL;DR: Although it has been recognized for almost three decades that titanium-aluminide systems have the potential for significant weight reduction in jet engines, Ti−48Al−2Cr−2Nb has emerged as the first to enter commercial jet engine service as mentioned in this paper.
Abstract: Although it has been recognized for almost three decades that titanium-aluminide systems have the potential for significant weight reductions in jet engines, Ti−48Al−2Cr−2Nb has emerged as the first to enter commercial jet engine service. Cast gamma titanium aluminides are evolving from an intriguing idea into the next materials revolution for aircraft engines. Its potential appears to be similar to the changes caused by the introduction of cast titanium alloys in the 1970s.
TL;DR: In this article, a defect-controlled resistivity can be eliminated with an order-disorder transformation at a specific non-metal/metal ratio, which can be used to form interconnects and diffusion barriers in ultralarge scale integrated circuits.
Abstract: Compounds of transition metals from Groups IV and V with carbon, nitrogen, or boron (e.g., NbC, TiN, and ZrB2) are electronically conductive but are also very hard and have high melting points. These materials resist electromigration and prevent diffusion because their strong interatomic bonding makes the activation energy for diffusion very high. Carbides and nitrides form the NaCl crystal structure, but are nonstoichiometric with nonmetal atom vacancies that scatter electrons. This defect-controlled resistivity can be eliminated with an order-disorder transformation at a specific nonmetal/metal ratio. The diborides are essentially sentially stoichiometric and have low resistivities. These metallic ceramics can be deposited as thin films to form interconnects and diffusion barriers in ultralarge-scale integrated circuits.
TL;DR: In this paper, a system approach to the design of materials involves modeling the interactions of the processing-structure-property links, which leads to total optimization of properties both within and beyond the limits of any empirical approach.
Abstract: A systems approach to the design of materials involves modeling the interactions of the processing-structure-property links. This approach leads to total optimization of properties both within and beyond the limits of any empirical approach. The design of precipitation-strengthened, high-strength, high-electrical-conductivity alloys provides a unique opportunity for demonstrating the efficiency of this approach. Using this computer-aided design, a new class of alloys with improved strength-conductivity combinations can be designed.
TL;DR: In this article, the authors developed laser-based methods to obtain fully dense metallic components directly from a computer-aided design solid model, which holds great promise for applications; however, none have been developed into a commercial product.
Abstract: Direct fabrication technology, which utilizes computer-aided design solid models to automatically control the manufacture of functional piece parts, is rapidly gaining popularity as a means to significantly reduce the time to market of new concepts. Since the introduction of stereolithography in 1982, several different rapid prototyping technologies have evolved using surrogate rather than actual materials of construction. Most recently, researchers have begun to develop laser-based methods to obtain fully dense metallic components directly from a computer-aided design solid model. Each of these methods is unique, but possesses aspects that are similar to the others. Many of these methods hold a great deal of promise for applications; however, none have been developed into a commercial product.
TL;DR: The U.S. Army has been using more and more titanium to either increase armor or reduce the weight of current combat vehicles as mentioned in this paper, and future plans call for the development of combat vehicles that are 30 percent lighter.
Abstract: The U.S. Army has been using more and more titanium to either increase armor or reduce the weight of current combat vehicles. Future plans call for the development of combat vehicles that are 30 percent lighter. To achieve this target, the future-vehicle hull and turret will have to be manufactured using more ballistically efficient materials than rolled homogeneous steel armor. Lowcost titanium, with its good mechanical, ballistic, and corrosion properties and acceptable fabricability, offers the overall best afternative to achieving this objective.
TL;DR: Most of the rapid developments in (AlIn)GaN alloy system technology have occurred within the past few years, and the technology is still moving at a fast pace as discussed by the authors.
Abstract: Most of the rapid developments in (AlIn)GaN alloy system technology have occurred within the past few years, and the technology is still moving at a fast pace New performance records for light-emitting diodes and laser diodes are constantly being reported This article highlights the progression of the development of the (AlIn)GaN alloy system and describes the fabrication and performance of some of the light-emitting devices that have been produced to date
TL;DR: An overview of the methods developed during the past 30 years for solidification simulation on a microscopic scale, with a special emphasis on multicomponent alloys, can be found in this paper.
Abstract: Accurate predictions of microstructure and microsegregation in metallic alloys are highly important for applications such as process optimization and alloy development. This article gives an overview of the methods developed during the past 30 years for solidification simulation on a microscopic scale, with a special emphasis on multicomponent alloys. Analytical approaches as well as advanced numerical models coupled with greatly simplified phase diagrams and thermodynamically calculated phase diagrams have been critically reviewed. Factors that influence the predictions, such as solid-state diffusion, coarsening of dendrite arms, undercooling effects, and, most importantly, the accuracy of the phase diagram are discussed, and suggestions for further research are given.
TL;DR: This article shows that both well-known kinetic equations and new triple junctions motions fit in this context of gradient flow with respect to an inner product.
Abstract: Recent progress in variational methods helps to provide general principles for microstructural evolution. Especially when several processes are interacting, such general principles are useful to formulate dynamical equations and to specify rules for evolution processes. Variational methods provide new insight and apply even under conditions of nonlinearity, nondifferentiability, and extreme anisotropy. Central to them is the concept of gradient flow with respect to an inner product. This article shows, through examples, that both well-known kinetic equations and new triple junctions motions fit in this context.
TL;DR: In this article, the results of the preparation by suspension plasma spraying (SPS) of thick coatings and spherical powders of bioceramics, namely, hydroxyapatite, are reported.
Abstract: Suspension plasma spraying (SPS) is a single-step process for the preparation of thick coatings or for the production of powder using radio-frequency inductively coupled thermal plasma technology. SPS is based on a liquid suspension of very fine (<10 μm) or even ultrafine (,100 nm) powders axially fed into the radio-frequency plasma flame through an atomization probe. This article reports the results of the preparation by SPS of thick coatings and spherical powders of bioceramics, namely, hydroxyapatite. Characterization of the hydroxyapatite coatings and atomized powders are reported. Process variables are studied as a function of phase structure and crystallinity of the obtained hydroxyapatite material.
TL;DR: In this paper, the authors investigated the metallurgical aspects of fire gilding in the context of metalwork and found that it was the predominant technique for metalwork from 300 b.c. in China and 200 a.d. in Europe until the invention of electroplating in the 19th century.
Abstract: Fire gilding was the predominant technique for the gilding of metalwork from 300 b.c. in China and 200 a.d. in Europe until the invention of electroplating in the 19th century. This article investigates its metallurgical aspects based on studies of original objects, gilding replication experiments, and literary evidence.
TL;DR: In this paper, the authors report the results of a study to determine the effects of austenite stability, with respect to the strain-induced transformation to martensite, on the formability of 300 series stainless steels.
Abstract: This article reports the results of a study to determine the effects of austenite stability, with respect to the strain-induced transformation to martensite, on the formability of 300 series stainless steels. The effects were evaluated as a function of alloy content, deformation temperature, and deformation rate. Three stainless-steel alloys with different nickel contents were evaluated as commercially cold-rolled and annealed sheet products. Tensile tests were performed at temperatures between −60°C and +125°C and at strain rates from 0.00167 s−1 to 0.167 s−1. The combined effects of strain, strain state, deformation-induced temperature changes, and strain rate are considered to explain the interrelationships between martensite formation and limit strains as observed in forming-limit diagrams.
TL;DR: In this paper, the authors investigated the versatility of thermal spray techniques to perform spheroidization of HA powders, the preparation of HA-based biocomposite powders and coatings, and the deposition of HA coatings.
Abstract: In recent years, coated implants have been actively researched and put to use in many biomedical engineering applications. The coating used on the implants is hydroxyapatite (HA), a calcium-phosphate compound with attractive bioactive and biocompatible properties that can enhance the fixation process of biomedical implants. Thermal spraying provides a potent means for depositing the HA coatings on implants. Among the populat thermal-spray techniques are combustion-flame spray, plasma spray, and high-velocity oxy-fuel spray. This article investigates the versatility of thermal-spray techniques to perform spheroidization of HA powders, the preparation of HA-based biocomposite powders and coatings, and the deposition of HA coatings.
TL;DR: In this article, the composites are processed by conventional liquid-phase sintering of mixed powders as well as pressureless melt infiltration, and typical mechanical properties such as hardness, flexure strength, and fracture toughness are evaluated for composites containing different volume fractions of carbide or boride particulates.
Abstract: Iron-aluminide composites containing 30–90 vol. % carbides or borides can be processed to near full density (greater than 97% theoretical density). This wide range of ceramic contents enables the tailoring of the composite properties to a variety of applications requiring a combination of the corrosion and oxidation resistance of iron aluminides and the hardness and wear resistance of the ceramic phases. The composites are processed by conventional liquid-phase sintering of mixed powders as well as pressureless melt infiltration. Typical mechanical properties such as hardness, flexure strength, and fracture toughness were evaluated for composites containing different volume fractions of carbide or boride particulates. Furthermore, evaluations of the wear resistance, oxidation resistance, aqueous corrosion resistance, and thermal expansion of the iron-aluminide composites suggest many potential applications for these new materials.
TL;DR: In this paper, the influence of external load on the strain-induced austenite-to-martensite phase transformation for selected microstructures is investigated in an incremental formulation to a finite-element code.
Abstract: Low-alloyed transformation-induced plasticity steel (25 CrMo 4 and 15 CrNi 6) is produced by special heat treatments resulting in microstructures with variations in the content of retained austenite as well as the spatial arrangement of the austenitic grains. In this article, the influence of these variations on mechanical behavior is investigated. A continuum micromechanical unit-cell model is used to study the influence of external load on the strain-induced austenite-to-martensite phase transformation for selected microstructures. The model is implemented in an incremental formulation to a finite-element code.
TL;DR: In this article, the authors discuss the potential and challenges for the use of titanium in the family automobile and propose a solution to solve the problem of high cost for high-production-volume automotive applications.
Abstract: Titanium offers a number of attractive features for use in high-production-volume automobiles; however, high cost has been a barrier to application, thus far. This article discusses the potential and challenges for the use of titanium in the family automobile.
TL;DR: RuAl as discussed by the authors is a high-temperature structural intermetallics compound with a unique line-up of physical, chemical, and mechanical properties, and, provided that misconceptions that it is exotic and expensive can be addressed, it is bound to attract more attention in the future.
Abstract: Of the many intermetallic compounds identified to date, only a relatively small number are candidates suitable for further development as high-temperature structural intermetallics. Were it not for the relative scarcity of ruthenium, the B2 compound RuAl might have received considerably more development impetus from its unusual inherent combination of ductility, strength, and thermodynamic stability. Nevertheless, variations of this compound have received a great deal of attention. RuAl possesses an almost unique line-up of physical, chemical, and mechanical properties, and, provided that misconceptions that it is exotic and expensive can be addressed, it is bound to attract more attention in the future.
TL;DR: In this paper, a summary of selected experimental and theoretical studies aimed at understanding the convective transport processes both for a single grain and at the scale of a casting is presented, and the need for much additional research is emphasized.
Abstract: Modeling the development of micro- and macrosegregation patterns and grain structures in the equiaxed solidification of metal alloys under the combined influences of melt convection and the motion of free solid has been the subject of intense recent research efforts. This article presents a summary of selected experimental and theoretical studies aimed at understanding the convective transport processes both for a single grain and at the scale of a casting. The need for much additional research is emphasized.
TL;DR: In this article, the present understanding regarding the effects of microstructure, loading conditions, and environments on the fatigue behavior of nickel-based superalloys is reviewed, and a literature review is presented.
Abstract: In this literature review, the present understanding regarding the effects of microstructure, loading conditions, and environments on the fatigue behavior of nickel-based superalloys is reviewed.
TL;DR: In this paper, the fundamental aspects of an electronically mediated reaction (EMR) and its usefulness for titanium production are well delineated by reliable experimental evidence, and an alternative mechanism for magnesium transport along the titanium sponge/MgCl2 interface is also provided by EMR.
Abstract: The fundamental aspects of an electronically mediated reaction (EMR) and its usefulness for titanium production are well delineated by reliable experimental evidence. EMR provides an effective method for controlling the location and morphology of the metal deposit. An alternative mechanism for magnesium transport along the titanium sponge/MgCl2 interface is also provided by EMR. Exploitation of the full potential of EMR will aid the automation of extraction processes for reactive metals, with significant cost benefits.