Strengthening strain-transformable β Ti-alloy via multi-phase nanostructuration

Multi-phase nanostructurations, using short-time thermal treatment (STT) at ω and α precipitation ranges (573 K–973 K), were applied on the strain-transformable β Ti-12Mo alloy with TRIP and TWIP effects (TRIP: Transformation induced Plasticity, TWIP: Twinning induced Plasticity). The aim is to study the evolution of the tensile properties and deformation mechanisms as a function of STT-induced nanostructurations. A series of multi-phase precipitations, i.e. athermal ω (ω_ath), isothermal ω (ω_iso), nanoparticle-like α (α_nano) and plate-like α (α_eq), were obtained in metastable β matrix with strong strengthening effects. The nanostructurations via the multi-phase precipitations brought about important improvements of yielding stresses of tensile deformation. Microstructural investigations were performed before and after the deformations using transmission electron microscopy (TEM). The {112}〈111〉 twinning, {332}〈113〉 twinning and stress-induced martensitic (SIM) transformation were identified in the deformed samples. The evolution of the deformation mechanisms revealed the key roles of the multi-phase nanostructurations on the strengthening of strain-transformable Ti alloys. Two interesting nanostructurations at ω_ath/ω_iso nanostructuration range and α_nano/α_eq range were highlighted for the promising potentials to preserve TRIP/TWIP effects in the strengthened alloys.