Effect of forging steps on microstructure evolution and mechanical properties of Ti-6Al-4V alloy during multidirectional isothermal forging

In this study, the multidirectional isothermal forging (MDIF) was used to modify the ß transformed microstructure into an equiaxed a+ß structure in Ti-6Al-4V alloy. After two steps forging, the initial ß grains were nearly disappeared. a colonies with different orientations became kinked and globularized due to the change of loading direction. The microhardness of the sample was 323 HV. The yield strength and ultimate tensile strength were 859 MPa and 907 MPa, respectively. After three steps forging, the lamellar a structures were globularized completely, a homogeneous microstructure was formed. The microhardness of the sample increased to 335 HV. The yield strength and ultimate tensile strength increased up to 900 MPa and 921 MPa, respectively. The homogeneity of microstructure and mechanical properties were improved with the isothermal forging steps increasing.