Strength-Toughness Synergy of the Heterogeneous Timo Alloy Via Optimizing the Microstructure and Texture Through Thermomechanical Treatment

Abstract

Strength-toughness synergy for metallic materials is always a direction of committed development as the requirement becomes higher and higher. In this work, a simple and feasible approach involving spark plasma sintering combined with hot diffusion and hot rolling treatments is used to design and prepare a TiMo alloy with a gradient coupling grain (GCG) heterostructure to achieve strength-toughness synergy. After rolling at 500 °C, the specimen with the optimized GCG heterostructure exhibits excellent mechanical properties with yield strength of 1192 ± 13 MPa, ultimate tensile strength of 1307 ± 8 MPa, and elongation of 10 ± 0.9%. As the rolling temperature increases, the strength decreases but elongation increases before 700 °C. The main strengthening mechanism includes dislocation strengthening, grain refinement strengthening, and texture strengthening. After processing at 800 °C, a significant reversal in mechanical properties occurred. There was an unexpected increase in yield strength but a decrease in elongation. That abrupt reversal mainly results from the precipitation of hard ω phase and texture variation. This work not only provides a GCG heterostructural TiMo alloy with excellent strength-toughness synergy but also proposes a simple yet effective strategy to push the new upper limits of the strength-toughness trade-off, and contributes to a deeper understanding of relevant theories regarding heterostructure formation and its strengthening-toughness mechanisms.

Keywords: titanium alloy, Heterogeneous microstructure, Microstructure evolution, Strength-toughness synergy, Strengthening mechanism