Effects of heat treatment conditions on microstructure and mechanical properties of TC11 titanium alloy

The effects of heat treatment temperature and cooling rate on microstructure and mechanical properties of TC11 alloy with equiaxed primary microstructure were investigated. The results show that with increase of temperature at air cooling condition, α phase volume fraction of TC11 titanium alloy decreases; when temperature exceeds 980°C, micro-structure morphology of the alloy is transformed from equiaxed pattern to bimodal and further to widmanstatten and lamellar microstructure. With increase of cooling rate above 980°C, the transformed lamellar microstructure decreases and changes to martensite when cooling rate is high enough (water cooling). The best mechanical properties of TC11 alloy are achieved after heat treating at 980-1020°C by air cooling or oil cooling, and optimized mechanical property from bimodal microstructure with more than 50% equiaxed α phase can be got with heat treatment temperature between 980°C and 1000°C.