Abstract:The isothermal transformation process of TC17 alloy was investigated by microstructure analysis and numerical simulation. The experimental results show that TC17 alloy firstly precipitates α phase at or near grain boundaries. And with the increase in aging time, a large number of needle-like α phases precipitated inside the grains, and the precipitated α phase gradually becomes fine with the decrease in aging temperature. With the decrease in the aging temperature, the rate of precipitated α phase shows a tendency of increasing and then decreasing, and both the phase transition driving force and solute atom diffusion rate reach the maximum matching degree at aging temperatures of 600?650 °C. The maximum rate of precipitated α phase is reached currently. At the aging temperature of 600?650 °C, the phase transition driving force and the diffusion speed of solute atoms reach the maximum matching degree, and the rate of precipitating α phase reaches the maximum currently. Numerical simulation results show that the precipitation rate of α phase is the fastest at an isothermal temperature of 650 °C, and the results are in good agreement with the experimental results.