Effect of power spinning and heat treatment on microstructure evolution and mechanical properties of duplex low-cost titanium alloy

The microstructural evolution and mechanical properties of low-cost Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy during power spinning and after three types of heat-treatment routines (low-temperature annealing, high-temperature annealing, solution and annealing) were systematically studied. An effective heat-treatment routine to fabricate high-strength and acceptable ductile as-spun Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy tubes was then proposed whereby the relationship between the mechanical performances and microstructures was analyzed. The {0002}_α and {001}_β textures were formed after multi-pass power spinning. The as-spun LC-Ti alloy exhibited a good combination of strength and elongation after heat treatment at 550 °C for 4 h, which was ascribed to the large plastic induced low-temperature spheroidization of deformed α phase and nanoscale α precipitation from deformed β phase. However, the elongation decreased evidently when Zr2Si/TiCr2 participated at the interphase boundaries after heat treatment at 550 °C for 8 h. In high-temperature annealing, the elongation changed nonlinearly owing to the precipitation of Zr2Si particles at triangular grain boundaries treated at 750 °C for 1 h, and the spheroidization of the deformed α_p phase. Under solution and annealing conditions, lenticular α_s would participate from the metastable β grains, which contributed to the greatest strength albeit poor ductility. This study provides an effective guidance for the processing and application of the low-cost titanium alloy.