Deformation mechanism of metastable titanium alloy showing stress-induced α′-Martensitic transformation

In this study, the deformation mechanism of a metastable Ti-4Al-4Fe-0.25Si-0.1O alloy was investigated via ex-situ electron backscattering diffraction (EBSD) and field-emission transmission electron microscopy (FE-TEM). A stress-induced alpha'-martensitic transformation occurred from the retained beta phase. New variants of alpha'-martensite were nucleated and grew in the transformed alpha'-martensite under increasing levels of applied stress. Microstructural observations revealed that the orthorhombic nanodomains were sheared in the prior alpha'-martensite; these sheared nanodomains contributed to the formation of different variants of alpha'-martensite. This additional martensitic transformation resulted in an excellent combination of strength (ultimate tensile strength; UTS: 1340 MPa) and ductility (30%). (C) 2018 Elsevier B.V. All rights reserved.