Microstructure and mechanical properties of TC21 titanium alloy by near-isothermal forging
(1. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China;
2. School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China)
2. School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: Microstructure and tensile properties of TC21 titanium alloy after near-isothermal forging with different parameters plus solution treatment and aging were investigated. It is found that the residual β matrix, which was strengthened by fine secondary α platelets forming during aging, exists in all the samples; while primary equiaxed α phase, bent lamellar α phase and α plates are simultaneously or individually present in one sample. The strength of alloy increases proportionally with increasing the content of residual β matrix, which is the result of increasing α/β interphase boundary. The plasticity of alloy has a downward trend as the content of residual β matrix increases. This attributes to the increase of fine secondary α platelets, which are cut by dislocations during the deformation. Additionally, coarse α plates with long axis parallel to the maximum resolved shear stress (MRSS) also reduce the plasticity of TC21 alloy.
Key words: TC21 titanium alloy; near-isothermal forging; microstructure; α phase morphology; residual β matrix; tensile properties