Analysis and discussion of mechanical properties and microstructure developments for Ti40 alloy thermal exposed at 550°C

Microstructures and mechanical properties of Ti40 alloy after hot-rolled, heat treatment and thermal exposure at 550°C for different times were studied. The results show that there is only a little precipitation during thermal exposure, which mostly distributes on grain boundaries. The main reason of deterioration of mechanical properties is due to the precipitated phases distributing on grain boundary. By simulating and analyzing for the microstructures, the thermal exposure process of Ti40 alloy at 550°C can be divided into three stages, and every stage is defined by the shapes of precipitated phases. In the last stage, the main reason of non-matched mechanical properties between strength and hardness is due to the formation of continuous precipitated zone along the grain boundary. Lastly, it is pointed out that the adjustments of heat treatment and composition are feasible methods to use for Ti40 at higher temperatures.