Effect of matrix recrystallization on morphology, crystallography and coarsening behavior of vanadium carbide in austenite

The effect of matrix recrystallization on the morphology and crystallography of B1-type vanadium carbide (VC) formed in austenite (gamma) was studied in ail Fe-12Mn-0.3V-0.8C (mass%) alloy by transmission electron microscopy. With direct aging at 1173 K after solutionizing, without cold rolling, VC precipitates display a cube-cube orientation relationship with respect to gamma. In the early stage of aging, the morphology of VC is octahedral with {111}(gamma) facets, but with prolonged aging, {011}(gamma) facets with lower boundary energy replace the preexisting {111}(gamma) facets, resulting in a change in VC morphology from octahedral to tetra-kai-decahedral. After the gamma matrix containing these VC precipitates is recrystallized, the morphology and crystallography of the VC change significantly, exhibiting no specific My orientation relationship as well as no specific morphology. Coarsening of VC is significantly accelerated after gamma recrystallization, presumably due to an increase in VC/gamma boundary energy and short-circuit diffusion during passage of the gamma grain boundary over the VC particles during grain growth. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.