Effect of Cooling Rate on Phase Transformation and Microstructure of TC21 Titanium Alloy

摘要

Effect of cooling rate from β phase region on phase transformation and microstructure of TC21 titanium alloy were investigated. Martensites,α and β phases are formed under different cooling conditions. Water quenching and air cooling result in the formations of α' and α" martensitic microstructures,characterized by parallel or orthogonal acicular martensitic plates. The phase transformation process is gradually dominated by diffusion mechanism with decrease of cooling rate. At furnace cooling rate, colony microstructure, characterized by parallel a laths separated by β phase,is formed. As the increase of cooling rate, the colony microstructure changes into mixed microstructure,characterized by the combination of colony microstructure and basketweave microstructure.