Constitutive Equation and Heat Distortion Behavior of TA4 Titanium Alloy

In this study, the high-temperature thermal deformation behavior of the TA4 alloy was investigated by thermal compression experiments. The effects of deformation temperature and strain rate on the rheological stress are described by analyzing the variation of stress–strain curves with different parameters and establishing the constitutive equation based on the dynamic material theory model. Thermal processing diagrams were established and plotted to analyze the optimal processing zone and the destabilization zone under different strains. From the thermal machining diagram, it can be concluded that the optimum machining zone at a strain of 0.9 is 1040~1133 K/0.01~0.7 s−1. The optimum machining zone at a strain of 0.6 is 940~1000 K/0.01~0.04 s−1. The optimum machining zone at a strain of 0.3 is 940~1000 K/0.01~0.08 s−1. The effects of different deformation conditions on the thermal deformation mechanism were analyzed in conjunction with EBSD characterization. The results showed that dynamic recrystallization (DRX) was the main deformation softening mechanism when at low strain rate (≤0.1 s−1). At higher strain rates (>0.1 s−1) and lower temperatures (<1083 K and ≥933 K), the main deformation softening mechanism was DRV; at higher temperatures (≥1083 K and ≤1133 K), the main deformation softening mechanism was DRX.