An examination was made of the deformation behavior, at 77 and 300K, of single crystals which were oriented for single slip. The macroscopic yield strength decreased by a factor of 2 when the deformation temperature was increased from 77 to 300K. At 77K, the work-hardening rate after yielding was very high, and the deformation-induced sub-structures consisted of uniformly-distributed nearly-straight edge dislocations, jogged screw dislocations and prismatic loops. The sub-structure which was observed after deformation at 300K comprised walls which consisted of prismatic loops and zig-zag screw dislocations. These observations were explained in terms of the non-conservative motion of jogged screw dislocations. It was also argued that the observed microstructures could limit the motion of dislocations during additional deformation, thus implying that the limited ductility of NiAl at low temperatures might be 'acquired'.

Evolution of Substructures in Deformed NiAl Single Crystals Oriented for Single Slip. X.Shi, S.Mahajan, T.M.Pollock, V.S.Arunachalam: Philosophical Magazine A, 1999, 79[7], 1555-66