Origin of shear induced beta to omega transition in Ti-Nb-based alloys

TitleOrigin of shear induced beta to omega transition in Ti-Nb-based alloys
Publication TypeJournal Article
Year of Publication2015
AuthorsLai, MJ, Tasan, CC, Zhang, J, Grabowski, B, Huang, LF, Raabe, D
JournalActa Materialia
Volume92
Pagination55 - 63
Date Published2015/06/15/
Abstract

Ti-Nb-based alloys are essential materials for biomedical implant and aerospace applications. They reveal complex phase transformation behavior. Here, a {211}(beta)< 111 >(beta) twinning induced beta (body-centered cubic phase) to omega (hexagonal phase) transition in Ti-Nb-based alloys is demonstrated by transmission electron microscopy and analyzed employing ab initio calculations and the linear elastic inclusion theory. Our theoretical results reveal a distinct energy barrier for the beta to omega transition, where the contribution from lattice rearrangement, rather than the elastic contribution associated with lattice parameter mismatch, plays the major role. It is shown that this energy barrier can be overcome by {211}(beta)< 111 >(beta) shear, explaining why {211}(beta)< 111 >(beta) twinning or, alternatively, the beta to alpha" (orthorhombic phase) transition promotes local formation of the omega phase. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.