This paper presents some of the results obtained in an on-going study of NiAl alloys for potential high temperature applications. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some promising ternary alloying additions (Hf, Ta and Nb) have been identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. Interesting effects of grain size and stoichiometry in binary alloys are also presented.

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Continuous silver-clad Y-123 wire has been fabricated from cofired green fibers produced by melt-spinning polymers loaded with Y-123 powders. Metal claddings are provided by coating with silver-alloy powder slurries. The sintered polycrystalline Y-123 wires have 77 K self-field critical current density (Jc) values up to 2900 A/cmZ, with typical ranges in long lengths of about 1000 A/crnZ, but are weak linked. High-J, wire is made by continuous melt texturing of the presintered wires. Values of Jc above 10000 A/cm2 at 77 K have been achieved. I. -IntroductionE IIAVE developed a unique process for fabricating multi-vv filament, high-temperature superconducting (HTSC) wire from metal-clad ceramic fibers. The process has been applied to YBaZCu3O7-, (Y-123) and Bi-Sr-Ca-Cu-0 systems. This papcr describes the processing and electrical properties of Y-123-based wire. To fabricate the wire, we have developed a novel "green-fiber" process. Green fibers are melt-spun thermoplastic fibers loaded with 50 to 60 vol% HTSC powder. We use fully prcreacted HTSC powder, either phase-pure Y-123 or a two-phase mixture, such as 123 plus 211 or 123 plus silver. This separates the HTSC phase formation from fiber forming, so that the synthesis step and the spinning can be separately optimized. The green fibers are produced and handled with conventional textile equipment. Monofilament wire is made from single green fibers, and multifilament wire with transposed superconducting filaments IS made by braiding green fibers.Simple HTSC filaments themselves are not practical for use as wire. At a minimum, they must be clad with a suitable metal to provide mechanical strength, hermetic isolation from the environment, and a normal metal current path for electrical stabilization and contact. To produce metal-clad wire, the green fibers are "green clad" by coating them with a silveralloy powder formulated as a paintlike slurry. The green-clad fiber is sintered to burn off the polymer and cofire the metal W. Hammetter~contributing editor Manuscript No. 196657.