Temperature dependence of strain-rate sensitivity, work hardening and dislocation structure in Ni₃Al single crystals

Abstract

Ni₃Al single crystals have been deformed at 77, 292 and 500 K and at different strain rates. Dislocation structures in the deformed specimens have been examined by high-voltage electron microscopy. It is found that the structures depend strongly on test temperatures even at small strains such as 1%. The anomalous strengthening in the present alloy is thus attributed to be of a structural origin, particularly at high temperatures. It is also shown that flow stress is independent of strain rate both at 77 K and at 500 K while a weak strain-rate dependence appears at room temperature. On the basis of these observations, a possible mechanism of thermal and athermal strengthening is proposed by taking account of the work hardening and the structural change.