Achieving outstanding strength-toughness matching in β titanium alloy with coherent α_s/β interface triangular α_s and fine dispersed α_s phases

Achieving strength-toughness trade-off in β titanium is a significant challenge, which are typically incompatible properties. In this study, high-strength toughness synergies can be achieved by adding an appropriate amount of Nb element alloy and conducting appropriate heat treatment to obtain coherent α_s/β interface triangular α_s and fine dispersed α_s phases. The undeformed Ti-4.3Al-6.5Mo–3V–2Sn–2Zr–5Nb sample exhibits a tensile strength of 1298.5 MPa and a toughness of 76.2 MPa m^1/2, surpassing many deformed titanium alloys. The coherent α_s/β interface triangular α_s and fine dispersed α_s phases with good strain compatibility effectively combine the mechanisms of dispersed precipitation strengthening and coherent interface strengthening, resulting in excellent strength toughness matching of titanium alloys. The α_s phases with coherent α_s/β interface activate the pyramidal <c + a> slip systems, which can enhance toughness. These findings provide a crucial theoretical and practical foundations for the development of complex castings with excellent mechanical properties.