Effect of Temperature and Cooling Rates on the α+β Morphology of Ti-6Al-4V Alloy

Abstract

Ti-6Al-4V is a dual phase (α+β) titanium alloy widely used in aerospace industry. Mechanical properties of a component strongly depend upon its microstructure and morphology. Desired mechanical properties can be achieved by the development of appropriate microstructure with the help of different heat treatments and deformation. In the present work, different microstructures obtained through different heat treatment processes are studied and presented. A variety of morphologies of α+β microstructure are obtained by heating above and below β transus temperature and cooling at different rates i.e. water quench, air cool and furnace cool. Heating above β transus and cooling with different rates results into lamellar structure whereas a duplex microstructure is obtained after heating below β transus and cooling with different rates. A lamellar structure with blocky acicular α is obtained after heating above β transus followed by furnace cool up to temperature below β transus and cooling with different rates. It is observed that cooling rate has a significant effect on hardness of heat treated sample. Faster cooling results in higher hardness.