The Formability, Microstructure, and Mechanical Properties of Powder-Sintered TC4 Alloy Hollow Shafts Formed by Cross-Wedge Rolling

To produce a titanium alloy hollow shaft with low cost and high quality, a powder-sintered TC4 alloy hollow shaft formed by the cross-wedge rolling (CWR) process is innovatively proposed in this paper. The formability, microstructure distribution and mechanical properties of powder-sintered TC4 alloy hollow shafts formed by CWR are experimentally studied to ensure process feasibility. The results show that when the initial deformation temperature (Ti) is 1050-1150 °C, powder-sintered TC4 alloy hollow shafts formed by CWR with a mandrel exhibit obvious cracks and large ellipticity because of the rigid support of the mandrel. However, high-quality powder-sintered TC4 alloy hollow shafts can be formed by CWR without a mandrel at a Ti of 1000-1150 °C. Moreover, Ti and cooling methods have great effects on the microstructural morphology and mechanical properties of the rolled pieces. The microstructure distribution along the radial compression direction of the rolled pieces is different. When Ti is 1150 °C and the workpiece is water-cooled, the ultimate tensile strength can reach 1163.17 MPa. The fracture morphology indicates that the plasticity of the powder-sintered TC4 alloy can also be improved after CWR without a mandrel.