Showing papers in "JOM in 1995"
TL;DR: The first International Symposium on Gamma Titanium Aluminides (ISGTA) was held in conjunction with the TMS '95 Annual Meeting, 13-16 February 1995, Las Vegas, under the sponsorship of the Structural Materials Division--Titanium Committee as discussed by the authors, which covered almost the entire aspects of the current gamma technology such as fundamentals, alloy development and design, process development, microstructure and property evaluation, and applications.
Abstract: The first international symposium on gamma titanium aluminides (ISGTA) was held in conjunction with the TMS `95 Annual Meeting, 13--16 February 1995, Las Vegas, under the sponsorship of the TMS Structural Materials Division--Titanium Committee. The selected papers cover almost the entire aspects of the current gamma technology such as fundamentals, alloy development and design, process development, microstructure and property evaluation, and applications. The current status as well as the future of gamma titanium aluminide alloys are discussed, as an emerging engineering materials technology, including potential/real application areas of cast gamma alloys in turbine engines. The topics on environmental effects include oxidation resistance, coating, hydrogen effects and the effects of oxide scale on mechanical properties. Phase relations and transformations are discussed for alpha-phase decomposition, coarsening of lamellar structures, high temperature phase stability, and solidification. Deformation mechanisms are evaluated to explain the flow stress anomaly behavior. Deformation character, fracture behavior, fatigue and creep are evaluated for the lamellar structure of PST crystals. Advanced methodologies are evaluated for calculating the TiAl phase diagram as well as site preferences of various elements in the gamma phase. Studies on strengthening by solid solution as well as precipitation is reported. Measurements are reported of the solubilitiesmore » of oxygen and carbon as well as of the diffusivity and activation energies for various alloying elements in the gamma phase. Melting processes as well as methods for near-net-shaping are discussed. In summary, these proceedings confirm that gamma alloys are emerging as a new generation of structural materials. One hundred and two papers have been processed separately for inclusion on the data base.« less
680 citations
TL;DR: In this paper, the authors demonstrate that both stress and surface tension effects play major roles in determining the overall stability of a film to agglomeration, and that the formation of holes and/or hillocks may provide a means of stress relaxation in the film.
Abstract: Agglomeration is a common problem in all technological areas that depend on the integrity and continuity of films. The origin of agglomeration of thin films has been traced to its thermodynamic roots. This article demonstrates that both stress and surface tension effects play major roles in determining the overall stability of a film to agglomeration. However, complete agglomeration—uncovering the substrate and the formation of well-separated islands—will only occur if the operative surface and interfacial tensions favor dewetting or partial wetting. The formation of holes and/or hillocks may be favored by the commonplace large stresses in a film. Such holes and/or hillocks can provide a means of stress relaxation in the film.
151 citations
TL;DR: Gamma alloys, based on the gamma titanium aluminide (y-TiAl) intermetallic compound, are emerging as a revolutionary engineering material for high-temperature structural applications as mentioned in this paper.
Abstract: Gamma alloys, based on the gamma titanium aluminide (y-TiAl) intermetallic compound, are emerging as a revolutionary engineering material for high-temperature structural applications. This article discusses the historical background as well as the status and future prospects of gamma alloy technology in the areas of alloy development/ design, process development, and applications.
103 citations
TL;DR: In aluminum-silicon cast alloys, the shapes of the silicon phase and the general solidification pattern can be changed by the cooling conditions and by minor additions to the melt as mentioned in this paper.
Abstract: In aluminum-silicon cast alloys, the shapes of the silicon phase and the general solidification pattern can be changed by the cooling conditions and by minor additions to the melt. The minor additions either cause modification (sodium, strontium, and other metals) or refine the primary silicon in hypereutectic alloys (phosphorus and elements of Group V-B). Detailed examination of the modified microstructures and analysis of cooling curves are compatible with a modification mechanism involving growth rather than nucleation kinetics.
80 citations
TL;DR: The CMSX®-10 alloy as mentioned in this paper is a third-generation, single-crystal (SX), nickel-based casting alloy that is characterized by its 6 wt.% rhenium content, relatively high refractory element level (W+Ta + Re+Mo), and low level of chromium employment.
Abstract: The CMSX®-10 alloy is a third-generation, single-crystal (SX), nickel-based casting alloy that is characterized by its 6 wt.% rhenium content, relatively high refractory element level (W+Ta + Re+Mo), and low level of chromium employment. Based on published data, the alloy's high-temperature creep-rupture resistance is greater than all other nickel-based alloys (approximately 30 °C better than CMSX-4 and PWA1484). Moreover, the alloy's composition is balanced to provide an attractive blend of SX component castability, heat treatability, impact strength, fatigue strength, and resistance to environmental degradation. Most notably, the alloy provides extremely good bare hot corrosion resistance, despite its novel and relatively low (2–3 wt.%) chromium content.
77 citations
TL;DR: The fastest growing application for magnesium is the high-pressure die casting for automotive components, which represents approximately 70-80% of the magnesium casting shipments in recent years as mentioned in this paper, and the growth rate of magnesium casting in North America has averaged 16.6 percent per year over the last ten years.
Abstract: The growth rate of magnesium casting production in North America has averaged 16.6 percent per year over the last ten years.1−3 The fastest growing application for magnesium is the high-pressure die casting for automotive components, which represents approximately 70–80% of the magnesium casting shipments in recent years. This paper presents the latest developments in magnesium alloys, product design, casting technology, surface finishing, and magnesium-matrix composites. Current and future automotive applications of magnesium castings are also discussed.
76 citations
TL;DR: The average automobile currently produced in North America contains about 90 kg of aluminum and that figure is expected to grow, driven by environmental needs, the Partnership for a New Generation of Vehicles, safety mandates, consumer preferences, and an increasingly global marketplace.
Abstract: The average automobile currently produced in North America contains about 90 kg of aluminum. That figure is expected to grow, driven by environmental needs, the Partnership for a New Generation of Vehicles, safety mandates, consumer preferences, and an increasingly global marketplace. This paper examines those issues, along with current automotive applications for aluminum, the technology being developed to meet future demand, and the forces driving changes in technology.
71 citations
TL;DR: A number of pilot plant operations have been conducted, but thus far none of the processes have become operational as discussed by the authors, but they have been successfully tested in a number of testbeds.
Abstract: Over the past 20 years, a significant number of processes have been developed to recover lead from scrap batteries. These processes recover lead via hydrometallurgical processing of the paste component of the battery followed by electrowinning. A number of pilot plant operations have been conducted, but thus far none of the processes have become operational.
68 citations
TL;DR: In this paper, it appears that this technology responds well to many of the challenges facing sheet metal forming today: formability is enhanced, springback is minimized and die tryout time should be minimized.
Abstract: High-velocity metal forming was the focus of much research approximately 30 years ago. It appears that this technology responds well to many of the challenges facing sheet metal forming today: formability is enhanced, springback is minimized, and die tryout time should be minimized.
62 citations
TL;DR: In this paper, the mechanical and physical properties of aluminum-matrix composites reinforced with high-performance continuous alumina fibers are reviewed and compared with those of other structural materials.
Abstract: The mechanical and physical properties of aluminum-matrix composites reinforced with high-performance continuous alumina fibers are reviewed and compared with those of other structural materials. Continuous-fiber reinforced aluminum-matrix compositesoffer outstanding improvements in specific strength and specific stiffness over conventional alloys and particulate composites. Thelongitudinal tensile strength of an aluminum matrix reinforced with 55–65 vol.% alumina fibers is in the range ofl.4-1.9 GPa, the longitudinal Young's modulus is 220–240 GPa, and the density is 3.2-3.4 g/cm3. The mechanisms of strengthening and fracture under longitudinal, transverse, and shear loading are reviewed. Examples of applications are presented that are representative of the range of product forms being developed.
54 citations
TL;DR: In this article, the authors present the range of thermal-spray processes and the materials systems that are able to be produced, leading from a coating to a forming technology, and describe the attributes of the materials sprayed by such processes.
Abstract: Thermal spray is a microsolidification consolidation process for metals, intermetallics, ceramics, polymers, and composites. Thermal-spray processing has become an important powder-consolidation technique, and innovations are now yielding novel ways of manufacturing new materials and material combinations. This article, the first of two parts, reviews thermal-spray processes, describes their characteristics, and describes the attributes of the materials sprayed by such processes. Part I presents the range of thermal-spray processes and the materials systems that are able to be produced, leading from a coating to a forming technology.
TL;DR: In this paper, the authors reviewed the theory and the mechanism of the electromagnetic separation of inclusions from molten metal and described the induced-current electromagnetic separator developed at the University of Alabama.
Abstract: The production of clean metal, free from oxides and other types of nonmetallic inclusions, is central to product quality and performance. Toward this end, electromagnetic filtration is an emerging technology for the purification of molten metals. This paper reviews the theory and the mechanism of the electromagnetic separation of inclusions from molten metal and describes the induced-current electromagnetic separator developed at the University of Alabama. The results of laboratory and large-scale experiments on the purification of molten aluminum demonstrate the capability of the system for producing super clean metals.
TL;DR: The gamma flotation process, which operates on the basis of solution surface tension control to facilitate the separation of inherently hydrophobic solids, combined with the alkali-treatment of a mixed polyvinal chloride-polyethylene terephthalate feedstock generates clean polymer concentrates at high recoveries as discussed by the authors.
Abstract: Patents and other literature on recycling post-consumer plastics from various sources (e.g., municipal solid waste) indicate that unit operations common to minerals processing have been seriously considered at various times. A review of the available literature and statistics on recoverable plastics reveals that only 2.4 percent is recycled. This article presents a flowsheet that we developed and tested in a bench-scale pilot plant. It shows that a combination of mineral processing techniques, including comminution, heavy media separation, and flotation, can be successfully adapted to the recycling of post-consumer plastics. The gamma flotation process, which operates on the basis of solution surface tension control to facilitate the separation of inherently hydrophobic solids, combined with the alkali-treatment of a mixed polyvinal chloride-polyethylene terephthalate feedstock generates clean polymer concentrates at high recoveries.
TL;DR: In this article, the authors discuss recent advances in research and development for the direct production of coilable thin strips by twin-roll casting in both the aluminum and steel industries, and the latter is striving to put pilot casters into commercial operation.
Abstract: This two-part paper discusses recent advances in research and development for the direct production of coilable thin strips by twin-roll casting in both the aluminum and steel industries. While the former is empowering the casters to approach the theoretical productivity limit, the latter is striving to put pilot casters into commercial operation. These intensive R&D efforts are derived from the advantages, both economic and metallurgical, offered by the process. As twin-roll casting combines solidification and hot rolling into a single operation, the process requires low capital investment and low operational cost. Also, because of the high solidification rate attained in the process, the thin strips produced have a refined metallurgical structure, characterized by columnar and equiaxed zones with fine intermetallic particles. The enthusiasm about twin-roll casting is now being spread worldwide. This paper focuses on the process aspects and quality control of twin-roll casting. Part II, which will appear in the August issue, will review process modeling and pilot-plant development activities.
TL;DR: A review of diamond and diamond-like carbon coatings, the properties and performance of the materials, and their applications can be found in this paper, with a focus on the applications of wear and corrosion resistance or high-thermal conductivity.
Abstract: Diamond is an attractive material for use in many applications where wear and corrosion resistance or high-thermal conductivity are important. Recent developments in the deposition of poly crystalline diamond (and amorphous diamond-like carbon) coatings have opened up a range of new applications. This paper reviews the deposition of diamond and diamond-like carbon coatings, the properties and performance of the materials, and their applications.
TL;DR: Methods to improve the overall accuracy of the vision-based strau]n measurement system are outlined and the possible ultimate accuracy that can be attau]ned by the use of such a measurement method is discussed.
Abstract: The vision-based measurement method is capable of determining three-dimensional (3-D) coordinates of all the intersecting points of a square grid pattern located on the surfaceof a deformed sheet-metal part. These 3-D coordinates are used to determine the surface strau]n over the area. To measure the coordinates of such a surface, multiple video photographs are usually taken over the measurement area. Methods to improve the overall accuracy of the vision-based strau]n measurement system are outlined and the possible ultimate accuracy that can be attau]ned by the use of such a measurement method is discussed.
TL;DR: In this paper, the essential characteristics of crevice corrosion established during the last four decades as well as some recent results that provide a fresh approach to understand the process were presented, including the current and resistance between the anodic reaction in the crevice and the cathodic reaction at the outer surface.
Abstract: Crevice corrosion is a poorly understood and very damaging form of corrosion. This paper presents the essential characteristics of crevice corrosion established during the last four decades as well as some recent results that provide a fresh approach to understanding the process. A simple criterion has been developed that involves two factors. First is the current and resistance between the anodic reaction in the crevice and the cathodic reaction at the outer surface; second is the polarization curve. Practices for preventing crevice corrosion are also discussed. The size of the active peak in the polarization curve and, in particular, whether it increases or decreases can be used to determine whether or not a change in a system parameter (e.g., a solute addition to the alloy) will promote or inhibit crevice corrosion. A second indicator is whether the solution resistivity increases or decreases.
TL;DR: In this article, the authors present a methodology for comparing the costs and benefits associated with the use of alternative materials in automotive applications by focusing on steel and aluminum in the unibody body-in-white.
Abstract: In order to make informed material choice decisions and to derive the maximum benefit from the use of alternative materials, the automobile producer must understand the full range of costs and benefits for each material. It is becoming clear that the conventional cost-benefit analysis structure currently used by the automotive industry must be broadened to include nontraditional costs such as the environmental externalities associated with the use of existing and potential automotive technologies. This article develops a methodology for comparing the costs and benefits associated with the use of alternative materials in automotive applications by focusing on steel and aluminum in the unibody body-in-white. Authors' Note: This is the first of two articles documenting a methodology for evaluating the lifetime monetary and environmental costs of alternative materials in automotive applications. This article addresses the traditional money costs while a subsequent paper, which is planned for the August issue, will address the environmental externalities.
TL;DR: The Modified Zincex Process (MZP) as discussed by the authors combines an electrowinning stage, a solvent-extraction unit and a leaching procedure to extract zinc secondary materials.
Abstract: A basic technology coping with a wide range of secondary zinc sources has been developed. The process combines an electrowinning stage, a solvent-extraction unit and a leaching procedure. The acidity generated in zinc electrowinning, transferred by the organic solvent to the aqueous raffinate, is reused to leach the zinc secondary materials. The basic process recovering zinc is described in detail. The route recovering other valuable metals such as copper, cadmium and lead associated with zinc is also described. This nonferrous metals recovery route is advisable for either ecological and/or economical reasons. Main results of an experimental program aiming at the demonstration of the suitability of the process for several feed materials are summarized. Waelz oxides, galvanizing ashes and EAFD coming from different sources were tested in laboratory and continuous pilot plant campaigns. High zinc recovery, low reagents and utilities consumption, and effluents meeting environmental regulation were confirmed. The paper also includes the main results of a feasibility study of an industrial ``base case``. A mixed raw material and Spanish EAFD and 20,000 ta of zinc ingots production were chosen. The SGH zinc recovery from secondary raw material by means of the clean, safe and profitable Modified Zincex Process has beenmore » demonstrated. This reliable technology is ready for industrial application.« less
TL;DR: In this paper, a cost-effective processing technique for manufacturing ceramic-matrix composites (CMCs) containing two-dimensional woven-fiber reinforcement has been developed, which relies on the electrophoretic deposition (EPD) of ceramic sols on/into the fiber preforms to achieve the required impregnation.
Abstract: A novel, cost-effective processing technique for manufacturing ceramic-matrix composites (CMCs) containing two-dimensional woven-fiber reinforcement has been developed. The technique relies on the electrophoretic deposition (EPD) of ceramic sols on/into the fiber preforms to achieve the required impregnation. The laboratory-scale results achieved thus far indicate that the processing approach offers great potential for the manufacture of high-quality, composite products with dual-component oxide matrices for high-temperature structural applications.
TL;DR: In this article, the authors describe the process development and properties of these materials and describe the transfer of this technology from its early success in cost-effective defense applications to commercialization in highly competitive applications.
Abstract: Advanced powder-metallurgy (P/M) technology provides the key to a new class of low-cost, high-performance titanium-matrix composites known as CermeTi. Titanium carbide, the most successful particulate addition to date, imparts both strengthening effects and enhancement of the bulk modulus of elasticity when added to a titanium-alloy matrix, this article describes the process development and properties of these materials and describes the transfer of this technology from its early success in cost-effective defense applications to commercialization in highly competitive applications.
TL;DR: In this paper, the results of the processing, microstructure, and properties of free-forms produced from ceramics in the alumina, zirconia, and alumina-zirconica system are reported.
Abstract: In a program at the Thermal Spray Laboratory at the State University of New York at Stony Brook, both conventional gas-stabilized plasma and high-throughput water-stabilized plasma spray torches are being used to produce thick free-standing structures of oxide ceramics, metal-reinforced ceramic laminates, and multilayered or functionally graded ceramic materials. The results of the processing, microstructure, and properties of freeforms produced from ceramics in the alumina, zirconia, and alumina-zirconia system are reported.
TL;DR: In this paper, the key transport phenomena associated with electromagnetic levitation, the fundamental relationships associated with thermophysical property measurement that can be made using this technique, reasons for working in microgravity, and some of the results obtained from the microgravity experiments.
Abstract: Electromagnetic levitation is one area of the electromagnetic processing of materials that has uses for both fundamental research and practical applications. This technique was successfully used on the Space Shuttle Columbia during the Spacelab IML-2 mission in July 1994 as a platform for accurately measuring the surface tensions of liquid metals and alloys. In this article, we discuss the key transport phenomena associated with electromagnetic levitation, the fundamental relationships associated with thermophysical property measurement that can be made using this technique, reasons for working in microgravity, and some of the results obtained from the microgravity experiments.
TL;DR: In this paper, the effect of ion implantation on the surface properties of the alloys of the fan blade and disk was evaluated using microstructural characterization and analyses of elemental and phase distributions within the implanted region.
Abstract: Severe fretting damage has been observed on the pressure surfaces of fan and compressor blade dovetails/disks in an aerospace gas turbine engine. A study has been carried out to evaluate the effect of an ion implantation technique in combination with the presently used surface treatments, such as shot peening and coating, on the fretting fatigue life of titanium alloy gas turbine engine components. The results from fretting fatigue tests, residual stress measurements, and nanoindentation tests were used to quantitatively evaluate the effect of various surface treatments on the fretting fatigue life of the fan blade and disk materials. Results from microstructural characterization and analyses of elemental and phase distributions within the implanted region are used to understand the effect of ion implantation on the surface properties of the alloys. Finally, an attempt has been made to evaluate the potential for improving the fretting fatigue life of the engine components using various surface modification techniques.
TL;DR: In this paper, the fundamental phenomena governing the operation of the caster and the structure of the ingots cast are examined and a review of the development of the technology and its fundamental properties are presented.
Abstract: Electromagnetic casting is used within the aluminum industry to cast approximately
two million ton per year of metal. It is a semicontinuous casting operation where the metal is solidified without contacting a mold. Consequently, the surface of the ingot does not have the imperfections that mar the surface of ingots cast using other technologies. This paper reviews the development of the technology and examines the fundamental phenomena governing the operation of the caster and the structure of the ingots cast.
TL;DR: The processing of aluminum scrap has been practiced for as long as aluminum has been produced due to the inherent value of the metal and the amount of energy required to produce primary aluminum from bauxite ore as mentioned in this paper.
Abstract: The processing of aluminum scrap has been practiced for as long as aluminum has been produced due to the inherent value of the metal and the amount of energy required to produce primary aluminum from bauxite ore. Scrap can be remelted at a fraction of the expense. With the large-scale introduction of aluminum beverage containers in the 1970s, increases in energy costs, and the need to reduce solid waste, aluminum recycling has grown at an increasing rate. This article provides a overview of the technologies and issues that surround the melting and reclamation of aluminum scrap.
TL;DR: In this article, the best results were obtained by combining pyrometallurgical and hydrometric treatments, which enabled the efficient recovery of manganese, nickel, copper, and cobalt.
Abstract: Many studies have investigated methods of recovering valuable metals from sea nodules. Recently, a research group in Japan developed a smelting and chlorine process after investigating a variety of existing processes and comparing their respective efficiencies with the same nodules. The best results were obtained by combining pyrometallurgical and hydrometallurgical treatments, which enabled the efficient recovery of manganese, nickel, copper, and cobalt. High-purity nickel can be also produced through further solvent extraction.
TL;DR: In this article, the constitutive response and deformation mechanisms in refractory metals with a hexagonal close packed (hcp) crystal structure are reviewed, focusing on the high-strain-rate stressstrain response under uniaxial compressive loading and the associated microstructural deformation mechanism.
Abstract: The constitutive response and deformation mechanisms in refractory metals with a hexagonal close packed (hcp) crystal structure are reviewed. The research focuses on the high-strain-rate stress-strain response under uniaxial compressive loading and the associated microstructural deformation mechanisms. Some aspects relating to dynamic failure such as adiabatic shear banding in refractory metals and subsequent failure processes are also discussed.
TL;DR: In this article, the magnetic field distributions above the surface of in-situ active corroding 2024-T3 and 7075-T6 aircraft aluminum alloy plates have been measured using a high-resolution superconducting quantum interference device (SQUID) magnetometer.
Abstract: The magnetic field distributions above the surface of in-situ active corroding 2024-T3 and 7075-T6 aircraft aluminum alloy plates have been measured using a high-resolution superconducting quantum interference device (SQUID) magnetometer. The magnetic field distributions and their variation with time are clearly different for the two aluminum alloys in an identical solution and for 2024-T3 in two different solutions. It is believed that these results demonstrate theability of SQUID to noninvasively detect in-situ active corrosion in aircraft aluminum alloys in a way that present corrosion-detection methods do not allow.