DEFORMATION MECHANICS IN A MECHANICALLY ALLOYED FE-40AL ALLOY AND THEINFLUENCE OF RECRYSTALLIZING AND AGING HEAT-TREATMENTS

The deformation behaviour of a mechanically-alloyed Fe-40Al material c hanges significantly as high temperature hear treatments are given to coarsen grains and reinforcing particles, and as low temperature agein g treatments are given to annihilate quenched-in vacancies and cluster s. Deformation at low temperatures starts with a significant yield dro p in all materials of fine grain size, indicating that there are insuf ficient numbers of dislocation sources. The flow stress retains some s ensitivity to vacancies and their clusters up to high temperatures, th is depending on the grain size of the material. Dislocations of variou s Burgers vectors, <100> , <110> and <111> materials and it is the num bers and types of these that determine the initial flow behaviour. A w eak flow stress anomaly is seen for most material states and this has been related to reactions and decompositions of <111> dislocations. (C ) 1997 Acta Metallurgica Inc.