Decomposition of a〈111〉 and a〈101〉 dislocations in hard-oriented NiAl single crystals

Abstract

The B2 intermetallic compound NiAl and its alloys have been subjects of extensive study for potential use as high temperature structural materials, particularly in the aerospace industry. The factors that make them attractive candidates are their low density (5.85 g/cm{sup 3}), excellent oxidation and corrosion resistance and high melting points. But they suffer from lack of ductility at low temperatures and poor strength at higher temperatures. There are still several issues regarding deformation behavior in NiAl and other B2 alloys (e.g., FeAl) that merit further research. Study of the deformation behavior in NiAl should provide further insight into some of the outstanding issues in B2 alloys: chiefly, the nature of slip transition and the effect of various parameters such as temperature, strain rate and stoichiometry on the deformation behavior. The preferred slip system in NiAl involves a slip. But on stressing along the cube axes, also known as the hard orientation, single crystals of NiAl deform at much higher stresses through the motion of a dislocations at lower temperatures. Non-a slip dominates at higher temperatures, with an associated increase in ductility and dramatic decrease in strength. There is also some confusion regarding the mode of deformation beyond the slipmore » transition temperature. The exact process of this slip transition needs to be addressed in its entirety to completely understand the mechanical response of NiAl.« less