Post-creep strain of Ni3Al at 380degreeC

Abstract

Post-creep strain tests on single crystal Ni3Al have been conducted at 380degreeC (far below the peak temperature Tp of flow stress) after creep at the same temperature. When specimens were crept at about 225 MPa (just below the conventional yield stress) for 45 h to a plastic strain of about 0.5% and then deformed 2% at a constant strain rate (10-4s-1) at the same temperature, it was found that dislocation structures were different from those observed after constant strain-rate deformation at the same temperature on annealed specimens. Dislocations are mainly on the cube cross-slip plane in the pre-crept specimens instead of on octahedral planes as in conventional annealed specimens. The dislocations exhibit quite a curved morphology although screw and near-screw segments predominate. Although the dislocations are gliding on the cube plane, super or double Lomer-Cottrell locks of the edge segments are not common.