Effect of forging temperature and subsequent heat treatment on the microstructure, strength anisotropy, and mechanical properties of the Ti-1300 alloy

Metastable β titanium alloys are attractive for demanding structural applications, but achieving a balanced combination of ultra-high strength, toughness, and low anisotropy remains challenging. In this work, the influence of forging temperature and subsequent heat treatment on the microstructure and mechanical response of a Ti-1300 alloy was investigated. Billets were forged at 750 °C (α+β region) and 870 °C (β region), followed by either duplex α+β solution treatment plus aging or β-region solution treatment plus aging. α+β forging produced a bimodal microstructure with fine equiaxed primary α and a recrystallized β phase, resulting in a weak texture and nearly isotropic tensile properties. β forging generated coarse, fibrous β grains suggesting a discontinuous dynamic recrystallization (DDRX)-like restoration behavior, which enhanced impact toughness but introduced pronounced strength anisotropy. Duplex α+β heat treatment increased the tensile strength under both forging conditions, whereas β-region heat treatment produced lamellar α+β microstructures with reduced toughness and increased anisotropy, which may be associated with α-variant selection and the preferential alignment of lamellar α features within coarse prior-β grains. Overall, 750 °C α+β forging followed by duplex α+β heat treatment provided a favorable balance of strength, ductility, toughness, and reduced strength anisotropy in the Ti-1300 alloy.