The thermal deformation behavior and processing map of TC9 titanium alloy

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This investigation delves into the thermal deformation behavior of TC9 titanium alloy. Compression tests at isothermal conditions were performed on a Gleeble thermal simulator under conditions spanning 700–1200 °C and strain rates of 0.001–1 s−1. The true stress-true strain curves indicated that stress increases with rising strain rate and decreasing temperatures. The softening mechanisms in the biphasic and monophasic regions were discussed. By correcting errors caused by friction, the strain-compensated Arrhenius-type constitutive equation, which accurately describes the flow behavior of TC9 titanium alloy, has been established. A processing map at a strain of 0.7 was constructed based on the power dissipation factor, revealing an unstable region at 700–800 °C/0.01–1 s−1 and 800–900 °C/0.1–1 s−1, where microcrack defects were observed, suggesting that processing should be avoided in this region. Efficiency values as high as 60–70 % indicate superplasticity deformation, with corresponding m values within this efficiency range of approximately 0.4–0.5, reaching the strain rate sensitivity index range of superplasticity titanium alloys. Tensile tests conducted at 900 °C and a deformation rate of 0.001 s−1 showed elongation exceeding 100 %. The sample compressed at 900 °C and 0.001 s−1 exhibits small grain size, uniform orientation, the lowest dislocation density, and a uniform two-phase mixture. These microstructural features indicate the material's good machinability.