Microstructure regulation and strength-elongation synergy of the near alpha TZAM alloy via thermomechanical processing

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2024-08, Vol.907, p.146741, Article 146741
• Main Authors: Bai, J.K., Zhang, H., Zhao, Z.B., Yang, R.D., Zhang, S.Z., Zhang, J.S., Zhang, X.Y., Liang, S.X., Liu, R.P.
• Format: Article
• Language: English
• Subjects: Hot-rolled near-α Ti alloy; Mechanical properties; Microstructure evolution; Strength-elongation synergy; Thermomechanical processing
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2024.146741

High strength-elongation synergy and its dependence on microstructure are the eternal themes of metallic materials including Ti alloys. In this study, the relationship between the microstructure evolution and mechanical properties of the Ti-25Zr-4Al-1.5Mn (TZAM, wt. %) near-α Ti alloy was systematically investigated after hot rolling at temperatures ranging in the whole solid solution region. The content of primary α phase decreased gradually with the increasing of rolling temperature. An excellent comprehensive mechanical properties with a yield strength of 1055 ± 10 MPa and a total elongation of 23.6 ± 0.6 % were obtained for the specimen after rolling at 750 °C (single α phase temperature region). This great strength-elongation synergy is mainly due to the synthetic action of substructure strengthening, dislocation strengthening, basal random heterogeneity (BRH) texture, and suitable content of β phase. The α" martensitic phase was formed after rolling at temperatures of 800 and 850 °C (α + β two-phase temperature region), resulting in a significant decrease in yield strength. However, remarkable work hardening with a rate of approximately 10 GPa occurred in both specimens. The whole evolution process of primary α grains, namely dynamic recovery and recrystallization during hot-rolled is deeply discussed. When the rolling temperature increased to 900 °C (single β phase temperature region), the dominated acicular α′ martensitic phase with high dislocation density resulted in an ultra-high strength (1264 ± 12 and 1488 ± 11 MPa for yield and tensile strength respectively) at the expense of plasticity. These findings revealed the microstructure evolution and its relationship to the mechanical properties of a TiZr-based alloy after the thermomechanical processing and helped to understand deeply the theory of metallic strengthening and elongation.