DISLOCATION MECHANISMS IN CREEP OF NI3AL AT INTERMEDIATE TEMPERATURE

The creep behaviour and dislocation structure of polycrystalline Ni, A l have been investigated at intermediate temperatures. At a temperatur e just below the peak strength temperature T-p different creep respons es occurred with relatively low and high stress levels respectively. U nder high stress, creep exhibited a normal primary creep regime and th en an inverse creep regime. At low stress, however, no visible inverse creep was displayed. With variation in temperature, an anomalous temp erature-dependence of creep strength was confirmed. Microstructural ob servation indicates that superdislocations slip on the cube cross-slip plane more easily at lower temperatures in the temperature regime inv estigated in the present study, which is considered to be one of the r easons for the creep strength varying anomalously with temperature. Mo reover, although inverse creep is produced by the operation of cube cr oss-slip, the operation of cube cross-slip does not necessarily lead t o inverse creep.