GRAIN CONTROL IN MECHANICALLY ALLOYED OXIDE DISPERSION-STRENGTHENED MA-957 STEEL

Mechanically alloyed oxide dispersion strengthened stainless steels tend to recrystallise into columnar grains, a microstructure ideal for certain creep applications. In other circumstances, equiaxed grain structures are desired. In this paper, two methods are described which have been developed to ensure the reproducible development of equiaxed or refined grain microstructures in an alloy, M A957, which has previously not been amenable to control. Grain refinement has been achieved by controlling the stored energy, so that grain boundary velocities are reduced to a level which allows nucleation to develop at many sites, and by inducing a phase transformation from ferrite to austenite. (C) 1993 The Institute of Materials.