Coexistence of multi-deformation modes in beta Ti alloys with improved yielding strength and ductility

^a School of Material Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221008, China
^b PSL Research University, Chimie ParisTech-CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, France
^c Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

^* Corresponding author: J.Y. Zhang and F. SUN jyzhang@cumt.edu.cn and sun.fan@chimieparistech.psl.eu

Abstract

By suppressing SIM (stress induced martensitic) phase transformations, a strong and ductile beta TWIP (twinning induced plasticity) Ti-Mo based alloy was achieved, thanking to the coexistence of mechanical twinning ({112}<111> mode and {332} <113> mode) and dislocation glide. The alloy displayed extra high yielding stress, stable strain-hardening rate and adequate ductility. In-situ traction/EBSD technique and TEM characterizations were employed to investigate the plastic deformation mechanism. The dislocation slipping was mediated by bimodal twinning mechanism, composed by high density nano-scale {112} twinning in micro {332} twinning grid. The study aims to exploit novel design strategy for strengthening ductile TWIP Ti alloys, attributed to multimodal twinning effects.