Study on rolling of a new near-α titanium alloy: Microstructure refinement and dual-scale silicides evolution

In this study, a novel near-α titanium alloy sheet with dual-scale silicides was successfully fabricated by rolling in α+β two phase field. The microstructure refinement, dual-scale silicides evolution and their influence on the tensile properties were systematically investigated. The results indicate that the preheating before rolling and the reheating between rolling passes play vital roles in the process of microstructure refinement. Thus, a new microstructure refinement mechanism was proposed considering the heat treatment besides the rolling deformation. The dual-scale silicides exhibit obvious differences in size, shape and distribution. The mean size of large-scale silicides is about 1.58 μm while the one of small-scale silicides is only 152 nm. The sheet with dual-scale silicides shows an outstanding room temperature tensile strength (1370 MPa) but an ordinary 650 °C tensile strength (513 MPa). This is because the strengthening mechanisms can be attributed to the microstructure refinement, dual-scale silicides and the residual substructures at room temperature. At 650 °C, however, the matrix softening is dominant due to the directionally arranged α/β microstructure has a low flow resistance at high temperature.