Effect of Solution Aging Treatment on Microstructure Properties of TC21 Titanium Alloy After Quasi-β Forging
The quasi-β forging of TC21 titanium alloy was conducted,and then the alloy was treated by the solution aging heat treatment experiment.The effects of different solution aging heat treatment systems on the microstructure and mechanical properties of the alloy were investigated.The results show that after TC21 titanium alloy was forged by quasi-β and treated by solution aging heat treatment process,the microstructure of the alloy presents a typical basket-weave structure.With increasing the solution temperatures,the content and length of the lamellar a phase are decreased significantly,the strength of the alloy is increased,the tensile strength can reach 1269 MPa,whereas while the plasticity change shows the opposite trend,and the maximum fracture toughness can reach 71.7 MPa·m1/2.With increasing the aging temperature,the effect on the lamellar a phase is slightly smaller,but the thickness of the secondary a phase is increased significantly.The strength of the alloy decreases,the tensile strength is 1218 MPa,and the plasticity increases.The fracture morphology of the alloy becomes flatter with increasing the solution temperature,and the crack growth path also becomes flatter.The fracture toughness value presents a downward trend,but it is increases with increasing the aging temperature.Considering the good match among the strength,plasticity,and fracture toughness of the alloy,after comprehensive analysis,it can be obtained that the best heat treatment system of TC21 titanium alloy after quasi-β fracture is:870 ℃/2 h,AC+590 ℃/4 h,AC.The tensile strength,elongation,and fracture toughness are 1250 MPa,6.61%,and 64.6 MPa·m1/2,respectively.