Hot Deformation Mechanism and Process Optimization for Ti-Alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si during α+β Forging Based on Murty Criterion

Abstract

Abstract To investigate the hot deformation and optimize the process configuration for Ti-alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si in α+β forging process, the processing maps (P-maps) are developed for the alloy with α+β microstructure based on Murty instability criterion. The P-maps are constructed by the experimental results obtained through the isothermal and constant strain rate compression test at the temperatures of 780–990 °C and the strain rates of 0.001-70 s−1. The relationship between the deformation mechanism as well as deformation defect and deformation thermomechanical parameter is studied by the generated P-maps. The results show that the superplasticity deformation would occur at the temperature range of 780–990 °C and the strain rate range of 0.001-0.01 s−1. In addition, flow instability including cracks and cavities in β phase, flow localization and adiabatic shear bands would occur at the above mentioned temperature range under the strain rates greater than 0.01 s−1. According to the P-maps, microstructure and flow stress status, the preferred deformation thermomechanical parameters are identified, e.g. the temperature range of 850–940 °C and the strain rate range of 0.001-0.01 s−1. The optimum deformation thermomechanical parameter is around the temperature of 900 °C and the strain rate of 0.001 s−1.