Effect of Heat Treatment on Microstructure and Mechanical Properties of a New Alpha-Titanium Alloy Ti-6.0Al-3.0Zr-0.5Sn-1.0Mo-1.5Nb-1.0V

A new α-titanium alloy Ti-6.0Al-3.0Zr-0.5Sn-1.0Mo-1.5Nb-1.0 V (Ti603) with high strength was investigated. The ingot was initially hot rolled into sheet. Then the sheet was annealed at 740 °C for 1 h; meanwhile, it was subjected to solution treatment at 900 °C for 0.5 h, followed by aging treatment at 580 °C for 3 h. The microstructure and texture of the alloy were characterized by electron backscatter diffraction (EBSD). The results show that the microstructure of the alloy evolved from lamellar to equiaxed after annealing and solid solution aging treatment. In addition, the grain size of the solid solution aging treated sample was larger compared to the annealed sample. After annealing, low-angle grain boundaries (LAGBs) are transformed into high-angle grain boundaries (HAGBs) due to the occurrence of dynamic recrystallization (DRX). This weakened the dislocations accumulation and entanglement at the grain boundaries, resulting in change in grain orientation, thereby reducing the texture strength of the sample. After solution and aging treatment, the stress concentration at the grain boundary increases, and the preferred orientation of the grains changes, resulting in a slight increase in the texture strength of the sample.