Heat treatment of Ti–6Al–4V alloy: a study on isothermal hot-compression properties and microstructure evolution law

This study optimizes the solution-aging treatment of Ti–6Al–4V alloy bars fabricated by spark plasma sintering (SPS) and hot extrusion, aiming to address microstructural heterogeneity and high flow stress during thermomechanical processing. Hot-compression tests at 900 °C (strain rate: 0.001 s −1 ) were conducted following solution treatment (950 °C–990 °C/2 h/air cooling) and aging (520 °C/2–4 h/air cooling), characterizing microstructural evolution and flow-stress behavior. The results indicate that increasing the solution temperature enhances grain refinement and homogenization, whereas excessive temperature (990 °C) leads to grain growth and α-cluster formation. Prolonged aging at 980 °C initially coarsens the grains but achieves homogeneity after 3.5 h, forming fine lamellar α and β-transformed structures. Coarse heterogeneous microstructures elevate peak flow stress and promote Al-rich segregation defects. The optimized parameters (980 °C/2 h + 520 °C/3.5 h) effectively homogenize the SPS-processed Ti–6Al–4V microstructure and suppress hot-compression defects, providing a viable approach for aerospace component manufacturing.