Effect of cold rolling and solution treatment on β stability and mechanical properties of a metastable β-Ti alloy

This work investigated the influence of cold rolling reduction and solution treatment on β stability and mechanical properties of a metastable β-Ti alloy (Ti–5Mo–2Cr–Fe–3Zr). The microstructure, phase composition and mechanical properties were analyzed by SEM, XRD, EBSD, TEM and tensile test. Deformation mechanism of cold-rolled alloy includes the reversion of athermal α" to β phase, deformation-induced {332}<113>β twinning and ω phase, dislocation slip, and microbands. The phase compositions of samples with different cold rolling reductions after solution treatment are different. Compared with 12.8% cold rolling and solution treatment (CR12.8%ST), the 27.7% and 51.3% cold rolling and solution treatment (CR27.7%ST and CR51.3%ST) have less α" phase and more β and ω phases, indicating that the β stability of CR27.7%ST and CR51.3%ST is higher than that of CR12.8%ST. Furthermore, the tensile strength and elongation of the samples increase simultaneously with the increase of cold rolling reduction. The CR51.3%ST alloy has good mechanical properties including a high ultimate tensile strength of 948 MPa, a uniform elongation of 15.7%, and an ultra-high strain hardening rate of 2000 MPa.