Abstract
Deformation and fracture behaviors of metastable β-Ti alloys (Ti–15Mo–5Zr and Ti–15Mo–5Zr–3Al) have been investigated. Large elongation in as-quenched Ti–15Mo–5Zr results from an appropriate combination of {332}⟨113⟩ twinning and ⟨111⟩ slip. Although mechanical twinning is suppressed by initial aging, considerable ductility is attained in Ti–15Mo–5Zr hardened by such aging at 573 K for 1.2 ks that ω-phase is precipitated. The reduction in macroscopic ductility on further aging could be related to an inhomogeneous slip. Embrittled Ti–15Mo–5Zr exhibits a ductile, dimple type fracture surface. On the other hand, mechanical twinning is not induced in as-quenched Ti–15Mo–5Zr–3Al, although large elongation is obtained. Ti–15Mo–5Zr–3Al is remarkably embrittled by precipitation of α-phase on aging at 623 K. As-quenched or embrittled Ti–15Mo–5Zr–3Al shows a mixture of an intergranular fracture surface and a dimple type fracture surface. The ductility of the present metastable β-Ti alloys is discussed in comparison with other metastable β-Ti alloys.
