DISLOCATION MECHANISMS IN CREEP OF NI3AL AT INTERMEDIATE TEMPERATURE

The creep behaviour and dislocation structure of polycrystalline Ni, Al have been investigated at intermediate temperatures. At a temperature just below the peak strength temperature T-p different creep responses occurred with relatively low and high stress levels respectively. Under high stress, creep exhibited a normal primary creep regime and then an inverse creep regime. At low stress, however, no visible inverse creep was displayed. With variation in temperature, an anomalous temperature-dependence of creep strength was confirmed. Microstructural observation indicates that superdislocations slip on the cube cross-slip plane more easily at lower temperatures in the temperature regime investigated in the present study, which is considered to be one of the reasons for the creep strength varying anomalously with temperature. Moreover, although inverse creep is produced by the operation of cube cross-slip, the operation of cube cross-slip does not necessarily lead to inverse creep.