Effect of Heat Treatment on the Microstructure and Micro-mechanical Behavior of Quenched Ti-6Al-4V Alloy

To determine the influence of the solution treatment temperature and holding time on the microstructure and micro-mechanical behavior of Ti-6Al-4V alloys, micro-indentation experiments were conducted at maximum loads of 3000, 3500, 4500, 4600, 4700, 4800, and 4900 mN. A microstructure examination was also performed with an optical microscope. Based on the test data, the micro-hardness H, Young’s modulus E, yield strength σ_y, ultimate tensile strength σ_b, and strain-hardening exponent n were obtained by the Oliver-Pharr method. It was found that the solution treatment temperature and holding time had a significant influence on the morphology, size, and volume fraction of the α and β phases. The equiaxed microstructure (obtained at 950 °C) exhibits a higher H, E, and σ_b. In contrast, σ_y shows a downward trend over the entire range of solution treatment temperatures. The influences of holding time on H, E, σ_b, and σ_y were also significant.