Stoichiometric effect on the strain-rate dependence of flow stress in binary Ni3Al

The strain-rate dependence of the flow stress has been studied by strain-rate change test in binary, stoichiometric and Ni-rich Ni₃Al single crystals at 400 K. In the stoichiometric alloys, the flow stress has been found to be independent of strain rate for all the orientations, though it changes temporarily after the strain-rate change. This stain-rate independence of the flow stress was also confirmed in Ni–24.5 at.% Al and Ni–24 at.% Al. The CRSSs of these Ni-rich alloys were the same as the stoichiometric one. These results indicate that the anti-site defects in the off-stoichiometric alloy have very little effect on the dislocation motion. It is also suggested that the small strain-rate dependence reported in ternary alloys may be due to the ternary elements. In binary Ni₃Al without these elements, the flow stress is considered to be controlled by an athermal process such as dislocation multiplication.