Abstract
The deformation behaviour of polycrystalline NiAl of various compositions, and of stoichiometric single crystals with different orientations, has been studied in compression in the temperature range 77–1300° K. All alloys except the aluminium-rich composition (53 at.-% aluminium) were deformable down to 77°K. Plastic deformation of single crystals was strongly anisotropic. All polycrystals and single crystals exhibited the three-stage temperature-dependence of the yield stress typical of b.c.c. alloys. The main effect of non-stoichiometry was to increase the athermal contribution to the yield stress; the strengthening produced by vacancies (aluminium-rich alloys) was greater than that produced by substitutional atoms (nickel-rich alloys).
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