Strong and plastic metastable β-T13V alloy by double hierarchical nanostructured introduction

Abstract

Hot deformation exhibits limited strengthening effects in titanium alloys, typically yielding strengths below 1300 MPa. This strength barrier can be overcome through aging treatments of metastable β titanium alloys, which enable precipitation of nanoscale secondary α phase (α_S). However, the heterogeneous distribution of α_S near grain boundaries and in grain interiors often leads to severe deterioration in plasticity. In this work, the pre-solution treatment of Ti-13V-5Zr-3Al-2Cr (wt. %) alloy precipitated the pyramid and slatted primary α phase (α_P). The pyramidal α_P significantly enhanced strength. During subsequent aging, the formation of twinning within slatted α_P enhanced plasticity. Uniform α_P distribution prevented elemental segregation, enabling α_S precipitation with consistent widths near grain boundaries and in grain interiors. This homogeneity mitigated localized strain concentration during deformation, suppressing intergranular fracture. Compared to directly aged specimens, the specimens with pre-solution treatment precipitated finer α_S after aging. This refinement was attributed to spinodal decomposition in the β-matrix after solution treatment, accelerating α_S nucleation. The α_S also exhibited pyramidal and slatted morphologies, forming a double hierarchical nanostructured with α_P. By optimizing the aging temperature, the width of α_S was precisely controlled. After aging at 440 ℃, the average α_S width reached 31.7 nm, facilitating well stress transfer between α_S precipitates. Consequently, the alloy achieved remarkable mechanical properties, including a yield strength of 1454 MPa, ultimate tensile strength of 1548 MPa, and plasticity of 5.4%.