CYCLIC DEFORMATION-BEHAVIOR OF NI3GE SINGLE-CRYSTALS AT ROOM-TEMPERATURE

Fully reversed strain-controlled tension-compression tests have been performed at room temperature to study cyclic deformation properties of Ni//3Ge single crystals. The cyclic deformation was performed with the stress axis parallel to the left bracket 245 right bracket direction. Cyclic strain-hardening occurred to saturation over the range of the employed strain amplitudes. The cyclic stress amplitude was found to be higher in compression than in tension at a plastic strain amplitude larger than 1 multiplied by 10** minus **5, where screw dislocations are operative. This stress asymmetry became more prominent as the plastic strain amplitude became larger. At a plastic strain amplitude less than 1 multiplied by 10** minus **5, where edge dislocations are operative, the stress amplitude was found to be symmetric. A similar stress asymmetry was also observed for monotonic flow stress. The cyclic hardening is explained by considering an interaction between the screw dislocations.