Constitutive model and microstructural evolution of hot deformation of investment-cast Ti-4Al-0.005B alloy

Abstract

Hot compression tests of investment-cast Ti-4Al-0.005B (TA5) alloy were conducted over a wide temperature range of 750 °C–850 °C at strain rates of 0.01–1 s−1. Based on the flow stress curve and dynamic material model, a constitutive equation is established. The thermal deformation behavior and microstructural evolution of investment-cast TA5 alloy at high temperatures is systematically analyzed. The results show that the Zener-Hollomon parameter′s formula calculates the apparent activation energy of TA5 as 469893 J · mol−1, α is 0.0032, and the apparent value of n is 12.34. The peak flow stress decreases with increasing deformation temperature and decreasing strain rate. At high strain rates, the grains appear nonuniform and exhibit microcracks. Thus, high temperature and low-strain rate are beneficial to the occurrence of slip. Under these conditions, grain boundaries can sufficiently migrate, the microstructure remains compact and stable, and dynamic recrystallization grains distribution is more uniform. Therefore, the high-temperature and low-strain zone is most suitable for processing TA5 alloy.