Research on blocky alpha in beta processed TC21 titanium alloy

The microstructural characteristics and formation mechanisum of blocky alpha phase in beta-forged TC21 alloy were investigated by means of optical microscope, SEM, EDS and micro-hardness test. The effects of heating temperature and holding time for forging on blocky alpha phase were also discussed. The results show that blocky alpha is different from normal alpha in morphology and chemical composition. The amount and location of blocky alpha phase in beta processed TC21 alloy depends on the heating temperature and holding time. With the increasing of heating temperature, blocky alpha phases near primary β grain boundaries decrease while those in β inter-grain increase for the forged alloy. On the other hand, with the prolonging of holding time, blocky alpha phases near the grain boundaries increase, those in β inter-grain are almost unchanged.