Optimization of betaear-beta forging process parameters of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si by using processing maps

摘要

The isothermal and constant strain rate compression tests of titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si are conducted by Thermecmaster-Z simulator and the deformation behaviors at the temperature of 990 approx 1080 deg C and strain rate of 0.001 approx 70 s~(-1) are extensively investigated. The processing maps (P-maps) under these deformation conditions are constructed and the forging process parameters are then optimized based on the generated P-maps. The experimental results show that most of the deformation is located at the flow instability zone when the strain rate is high (epsilon > = 0.6 s~(-1)). At the near-beta forging temperature range, the feasible deformation conditions are (990 approx 1008 deg C, 0.001 approx 0.01 s~(-1)) and its deformation mechanism is superplasticity. The optimum process parameters are (990 deg C, 0.001 s~(-1)). At the p forging temperature range, when the deformation strain is smaller (epsilon-bar < = 0.7), the suitable deformation conditions are (1035 approx 1070 deg C, 0.001 approx 0.08 s~(-1)). The optimum deformation parameters, however, are 1055 deg C and 0.001 s~(-1). If the strain is increased (epsilon-bar = 0.8 approx 1.2), there are two feasible deformation zones, viz., (1008 approx 1025 deg C, 0.001 approx 0.02 s~(-1)) and (1025 approx 1050 deg C, 0.008 approx 0.16 s~(-1)), respectively. At the beta forging temperature range, the main deformation mechanism is dynamic recrystallization.