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This proceedings volume is a record of the third Materials Research Society symposium on High-Temperature Ordered Intermetallic Alloys. This volume also includes the paper 'Effect of Strain Rate on the Plastic Behavior of L(1,2) Compounds Based on Ni3AL. These proceedings demonstrate recent advances in understanding the physical metallurgy and mechanical properties of aluminides, silicides, and other intermetallics, with special emphasis on the beneficial effects boron additions on grain-boundary ductility of Li(1,2) compounds. Significant progress has also been made on processing and alloying of titanium aluminides with TiAL3, TiAL, and Ti3AL compositions. One session was devoted to alloy design and material processing, which aimed at improving mechanical and metallurgical properties of ordered intermetallic alloys. Because of recent growth of interest in multiphase intermetallic alloys, one session was also devoted to this area. Contents of this volume are broken down into the following eight parts: Alloy Theory and Phase Stability; Defects and Microstructures; Mechanical Behavior; Alloy Design and Material Processing; Multiphase and Composite Materials; Nickel Aluminides; Titanium Aluminides; and Other Ordered Intermetallics.

For several decades the special properties of ordered intermetallic alloys have intrigued alloy designers. In particular, the aluminides offered the potential for high temperature structural applications due to good strength combined with oxidation resistance. Attainment of this potential has been hampered by the brittle behavior and low fracture toughness of these materials. However, in recent years significant improvement in the ductility and toughness of, at first, titanium aluminides, then iron and nickel aluminides, has been achieved by metallurgical techniques such as processing control, grain refinement, and microalloying. These successes have stimulated new interest in ordered intermetallics - in particular the aluminides. The Materials Research Society symposium on High-Temperature Ordered Intermetallic Alloys provided a forum to discuss the alloy chemistry, physical metallurgy, and mechanical behavior of ordered intermetallic alloys which have potential to be used as new structural materials. The symposium contained presentations in the areas of theory of alloy ordering, microstructural features and phase transformation, mechanical behavior, alloy design, and physical properties., See also Volume 40, AD-A157 197. Supported in part by Office of Naval Research.

The goal of this research is to elucidate the mechanism(s) controlling Mechanical Alloying (MA) and the alloy structures so formed. The experimental approach is to systematically study process variables such as temperature, energy input, environment, and starting material and relate such variables to the structure produced by MA. Microanalytical and structure determinations emphasize electron microscopy and x-ray diffraction methods. Quantification of the mechanism(s) is sought.

A hydrogenated f.c.c. alloy, 66Ni-30Cu-3Al, was subject under the conditions examined to brittle delayed failure. The static fatigue curve together with discontinuous crack propagation was an almost perfect image of that observed in high strength steel. Fracture behavior in alpha brass was studied under conditions where strain-aging type phenomena are operative. Alpha brass, under the proper conditions, exhibited both spontaneous strain-aging embrittlement and embrittlement produced by separately straining and aging. The alpha brass also exhibited delayed failure which has all the main characteristics of interstitial induced brittle delayed failure. The phenomenon of delayed failure has been correlated with microstructure in two alloy steels at three moderate strength levels. Delayed failure may occur over a relatively significant range of applied stress at these strength levels. The sensitivity to delayed failure may persist even though conventional tensile results indicate full ductility. The observed reductions in ductility are a function of microstructure at given strength level. (Author)