Recrystallization of coherent nanolamellar structures in Ti48Al2Cr2Nb intermetallic alloy

This study is about the recrystallization of a nanolamellar structure in Ti48Al2Cr2Nb intermetallic alloy. This is a specific case of recrystallization, the driving force comes only from the elastic coherency strain and the interfacial energy. Using an estimation of the stored energy, it is shown that the driving force is sufficient for recrystallization to occur without any prior plastic deformation. Two kinds of nucleation sites are identified: at the border between nanolamellar colonies and inside the nanolamellar colonies. For the former, it is proposed that a nucleus preexists. It is formed by local plastic relaxation of strong internal stresses at the tip of the lamellae and by subsequent recovery. For the latter, it is asserted that a nucleus is generated with a new orientation, by formation of a new interface and its migration. These two different mechanisms of nucleation are discussed based on microscopy observations and driving force estimation. In both cases growth proceeds by strain induced grain boundary migration (SIGBM) assisted by successive (111) twinning. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.