Materials Science and Engineering for the 1990s Maintaining Competitiveness in the Age of Materials (1989) / Chapter Skim
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Appendix B: Processing
Appendix B: Processing
Pages 224-241
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From page 224... ...
· The development of commercial materials processing technology is the special and indispensable province of industry. A strong industrial capability 224
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These technologies include crystal growth, molecular beam epitaxy, and physical and chemical vapor deposition. · Rapid solidification: The continued development of this processing technology should lead to a wide range of applications and products.
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From page 226... ...
The term materials processing refers to an enormously wide range of technologies. A very incomplete list includes refining of metals, rolling of sheet steel, shaping of metals by machining, therrnomechanical processing of alloys, growth of gallium arsenide crystals, zone refining of silicon, pressing and sintering of ceramic powders, ion implantation in silicon, formation of artificially structured materials by molecular beam epitaxy, spinning of high-strength polymeric fibers, gradient doping of glass fibers, sol-gel production of fine ceramic powders, modification of concrete by addition of polymers, and lay-up of composite materials.
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From page 227... ...
Competence in materials processing is also essential to the efficient incorporation into technology of advanced materials such as structural ceramics, composite materials, and high-temperature superconductors. HISTORICAL BACKGROUND Materials processing is probably the oldest of human technological activities, extending back in time to far before the advent of recorded civilization.
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From page 228... ...
An excellent example of application-driven research is the development of the zone refining method for purifying silicon, which followed shortly after the invention of the transistor. This research was application driven in the sense that silicon and germanium semiconductors required impurity levels that were far below those obtainable by existing technologies at that time.
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From page 229... ...
Optical Glass Fibers Just 20 years ago it was realized that glass fiber, as a replacement for copper wire, offers a considerable advantage as a communication medium at optical frequencies. Both improved performance and reduced costs were predicted.
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Rapid solidification is an advanced example of nonequilibrium processing of materials from the liquid state and therefore is the latest in a long line of metallurgical developments that probably started with the accidental melting and casting of native copper many centuries ago. Although there were several experimental and theoretical precursors to the technology of rapid solidification, the critical experiment was probably the demonstration in a university laboratory some 26 years ago that metallic glasses noncrystalline solid solutions of metallic components could be produced by extremely rapid quenching from the melt.
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From page 231... ...
The materials that have responded well to this processing technology include high-strength aluminum and magnesium alloys, tool steels of high toughness, and nickel-based superalloys. Rapid solidification recently played a key role in the remarkable discovery of the so-called quasi-crystalline phases.
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From page 232... ...
In another 40 minutes, the steel is continuously cast into 9-tn.-thick slabs. Such a complex materials processing technology requires a fundamental and detailed understanding of a whole series of complicated materials phenomena, including interactions in gas-metal, metal-slag, and metal-refractory systems.
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From page 233... ...
A steady stream of students went from university graduate programs, usually in metallurgy, to stimulating and technically productive careers in the steel industry. However, career opportunities in the industry for materials scientists with graduate degrees are now sharply diminished, and consequently so are the university graduate programs that relate to steelmaking technology and, indeed, to the metals industry in general.
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From page 234... ...
Processing technologies as different as steelmaking, crystal growth, fabrication of integrated circuits, near-net-shape forming, and rapid solidification might benefit greatly from full use of this capability. To take advantage of this opportunity, major advances will be required in modeling and simulation, characterization of materials behavior during processing, and sensor technology to monitor process inputs and material response.
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From page 235... ...
A sensor development program is under way in the steel industry at present, but a much larger effort and one directed also to other processing technologies is needed. Advanced numerical schemes for optimizing materials processing may ultimately be able to include not just the process parameters themselves but also criteria relating to performance and life prediction.
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From page 236... ...
Major developments in processing technology will be required in order to improve the toughness of ceramic materials. New methods of producing fine, pure, mono-size powders should lead to improved sintering characteristics and lower sintering temperatures.
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From page 237... ...
To date, most interest in the field of artificially structured materials has been focused on semiconductors, but there are many opportunities for new and useful combinations involving metals, insulators, and even polymers. The processing technologies now available are capable of producing both equilibrium and novel nonequilibrium phases, including amorphous structures and extended solid solutions.
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From page 238... ...
This is a potentially important area for collaboration between industry, universities, and national laboratories. Specific processing areas of interest to the steel industry include the following: the roles of fluid dynamics, heat transfer, and diffusion in determining the mechanism of hot dip coating; optimization of batch anneal heating processes through the development of models that incorporate nitrogen pickup, energy input, and productivity; application of computer-based expert systems to process control; three-dimensional fluid flow analyses of gas distribution in batch annealing, steel flow inside a tundish or mold, and gas flow inside a blast furnace or a basic oxygen furnace; and solidification models for simulating near-net-shape casting.
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From page 239... ...
Objects made by solidifying liquid crystals tend to be strong and stiff. It is expected that they will be important structural and optical materials, but optimization of their properties will require a detailed understanding and control of processing technology.
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From page 240... ...
The expanded use of composites in applications such as automobile components is contingent upon major improvements in processing technology. Various processes, including injection molding, are suitable for continuous operation, but the reinforcing materials are restricted to short fibers or particles.
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From page 241... ...
The systems are complicated, usually inhomogeneous, solids, viscous liquids, or suspensions of solids in viscous liquids. These systems seem difficult to analyze quantitatively, but the potential rewards for developing a systematic understanding of polymer processing are great.
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