Effects of heat treatment on microstructure and tensile properties of Alloy 28

To explore the heat treatment process of Alloy 28, the effects of different heat treatment temperatures and holding times on its microstructure and tensile properties were studied. The results show that Alloy 28 underwent complete recrystallization after heat treatment, forming equiaxed grains. With the increase in heat treatment temperature, the growth rate of the average grain size exhibited a trend of initially slow and then fast, with the apparent activation energy for grain boundary migration being 248.75 kJ/mol at a holding time of 10 min. As the holding time continued to increase, the average grain size of the alloy gradually increases, following a parabolic growth pattern. Meanwhile, the kinetic time exponent η showed a trend of initially remaining stable, then increasing, and finally stabilizing again with the rise in temperature. The tensile strength of Alloy 28 displayed a trend of initially slow and then rapid decline with increasing temperature, while the reduction in tensile strength with prolonged holding time exhibited a trend of initially fast and then slow. The yield strength of Alloy 28 showed a trend of initially slow and then rapid decline with temperature, and its relationship with the average grain size conformed to the Hall-Petch equation.