Deformation texture of hydrostatically extruded polycrystalline NiAl

Abstract

NiAl is currently a candidate for high temperature structural applications because of its high melting temperature, low density, and excellent oxidation resistance. Polycrystalline NiAl possesses low ductility at ambient temperatures, but it has a brittle-to-ductile transition temperature (BDTT) of approximately 573 K (1,2). Its high melting temperature, however, puts limits on its formability, usually requiring it to be processed at high temperatures. High temperature processing can lead to diffusive effects which may nullify the benefits of deformation processing. Processing of NiAl at lower temperatures, yet above its BDTT, might yield the conditions necessary for large amounts of strain to be attained from processing but might also limit the amount of diffusion related phenomena that would occur either during or following high temperature deformation. Deformation textures give insight into the modes of deformation that result from processing. When extruded below approximately 1,173 K, NiAl typically develops a (110) fiber texture. When extruded at higher temperatures or subsequently annealed, a (111) recrystallization temperature develops. The first successful low temperature hydrostatic extrusion of NiAl has been reported recently. It is the purpose of this paper to give the details of the resulting deformation texture and relate it to the potential benefits of processingmore » of NiAl with the use of hydrostatic pressure.« less