The role of nano-scaled structural non-uniformities on deformation twinning and stress-induced transformation in a cold rolled multifunctional β-titanium alloy

The microstructure in a multifunctional beta-titanium alloy, Ti-24Nb-4Zr-8Sn (wt%), before and after cold rolling was investigated using conventional and aberration-corrected scanning/transmission electron microscopy. With the presence of nano-scaled orthorhombic phase (O') and hexagonal phase (omega), primary (332)<113>(beta) deformation twins were activated during cold rolling with a thin layer of orthorhombic martensite (alpha '') occupying every twin boundary. In the interior of primary twins, nano-scaled alpha '' particles were observed, together with secondary {112}<111>(beta) twins. Our work may indicate that the preformed nano-scaled 0' phase assists in activating the {332)<113>(beta) deformation twining and O' phase transforms to nano-scaled stress-induced alpha '' during cold rolling. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.