Phase transition, microstructure and mechanical properties of TC4 titanium alloy prepared by plasma activated sintering

Highlights: • High strength TC4 titanium alloy material is rapidly prepared by Plasma Activated Sintering. • The dense TC4 titanium alloy material is obtained in PAS at 20 MPa and 900 °C for 3 min. • The yield strength of TC4 titanium alloy material is exceeded 1034.09 MPa. In this paper, plasma activated sintering was used to prepare powder metallurgy TC4 titanium alloys, and the effects of the sintering process on the densification, microstructure, phase transition and mechanical properties were investigated. The densities were evaluated by a drainage method. The microstructures and mechanical properties were characterized by OM, SEM, XRD, EBSD, and TEM methods, a universal testing machine and a Vickers hardness tester. The results showed that the PAS method could significantly shorten the sintering time and reduce the sintering temperature. With an increase in the sintering temperature, the sample changed from an equiaxed microstructure with short plate-like mixed-shaped grains to a double lamellar transitional structure. This structural change led to a decrease in the plastic deformation ability and an increase in the microhardness and compression strength of the sample. A coherent relation among the secondary α grains was observed, which had both a beneficial and detrimental effect on the material properties. A relative density of 98.11% and enhanced mechanical properties including an offset yield strength of 1034.09 MPa, a tensile strength of 1028.14 MPa, a Vickers hardness of 389.7 HV, and a sectional shrinkage of 28.4% were achieved and attributed to different microstructures controlled by the PAS sintering system.