Influences of different heat treatment process on mechanical properties and microstructures of the Ti55531 titanium alloy were investigated by the orthogonal testing with three factors to three level.The results reveal that the influencing orders on microstructure and mechanical properties of the alloy are presented as follows:solid solution temperature

ageing temperature and ageing time.With increasing in solid solution temperature

primary phase is decreased greatly with desirable equaixed feature and uniform distribution

meanwhile

tensile strength is increased with decreasing in elongation.With the increase of ageing temperature

sub-αphase is increased and grown

and microstructure is transformed into dual-phase structure

resulting in the decrease of tensile strength and the increase of elongation.With solid solution treatment at 820℃for 10 hand air cooling

and then aging at 580℃for 10 hand air cooling

the tensile strength and elongation of the Ti alloy reach 1 370 MPa and 8.5%

respectively.