Numerical simulation and experimental investigation of microstructure and mechanical properties of flexible skew rolling TC11 alloy based on finite element model coupled with microscopic parameters

In this study, the finite element model coupling with multiple internal-state-variable parameters was used to numerically investigate the forming and microstructure evolution of TC11 titanium alloy shafts formed by flexible skew rolling. Combined with the rolling experiments, the effects of process parameters on the microstructure and mechanical properties of TC11 alloy were investigated. The results show that increasing the deformation temperature, area reduction, and rolling speed lead to an increase in the globularization fraction of strip primary α and β volume fraction of the workpiece. In addition, increasing the deformation temperature coarsens the secondary α phase, which improves the plasticity of the workpiece. The workpiece exhibits outstanding mechanical properties at 910 °C, with a yield strength of 1119 MPa and a plasticity of 21.4 %. Under large area reduction, the primary α in the workpiece center is significantly refined yet grows larger near the outer surface of the workpiece. This results in differences of 61 MPa in strength and 3.2 % in elongation between the interior and exterior of the workpiece, indicating nonuniform mechanical properties. A very low rolling speed increases the temperature loss in the workpiece, increasing the deformation resistance, while a very high rolling speed exacerbates differences in the mechanical properties inside and outside the workpiece. To achieve optimal workpiece microstructure and performance, rolling temperature of 910 °C should be used, the area reduction should be less than 67 %, and the rolling speed should be 30–35 r/min within the studied parameters.