Microstructural evolution of a ductile metastable β titanium alloy with combined TRIP/TWIP effects

Herein, we investigated the microstructural evolution of a metastable beta Ti-12(wt%)Mo alloy under tension, exhibiting combined phase transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effects. The deformed samples were analyzed by X-ray diffraction (XRD), optical microscopy (OM) and transmission electron microscopy (TEM) until fracture. Lamella-like {112}< 111 > nano twinning was observed at the onset of plastic deformation. Upon straining, {332}< 113 > twinning and stress induced martensitic (SIM) beta->alpha '' transformation were both identified locally in the deformed beta matrix as primary mechanisms. Secondary mechanisms such as 2nd twinning and 2nd SIM, were then observed in the primary 13 twins. At the end of the uniform plastic deformation, a complex deformation microstructure was observed, showing highly disturbed matrix induced by a high volume fraction of twins and occurrence of multiples secondary mechanisms. Resultant macroscopic mechanical properties of the material display a combination of very high ductility (45%), high strength and superior strain hardening behavior. (C) 2016 Elsevier B.V. All rights reserved.