Effect of heat treatment temperature on microstructure and properties of different forming surfaces of TC4 titanium alloy sheet by selective laser melting

By heat treatment test,metallographic examination,scanning electron microscope observation,X-ray diffraction analysis and hardness testing,the effects of heat treatment temperature on phase composition,microstructure and hardness of different forming surfaces of TC4 titanium alloy sheet by selective laser melting were analyzed.The results showed that with the increase of the heat treatment temperature increased from 750℃ to 950℃,the acicular martensite α'phase on the top and side surfaces of selective laser melting TC4 titanium alloy sheet by selective laser melting decreased continuously.When the heat treatment temperature was 850℃,the acicular α'phase was completely transformed into α+β phase.When the heat treatment temperature (950℃) exceeded the α phase transition temperature,the content of β phase increased,the top surface of titanium alloy sheet had basically no columnar β phase,and equiaxed β phase were formed,and there were still columnar β phase on the side.The hardness of the top and side surfaces of titanium alloy sheet first decreased and then increased with the increase of heat treament temperature.