Understanding the microstructure evolution and mechanical behavior of titanium alloy during electrically assisted plastic deformation process

Abstract

Titanium alloys are widely used in aerospace, petrochemical, and automobile industry due to their outstanding mechanical properties. However, the formability/plasticity of most titanium alloys at room temperature is relatively poor, and a large amount of energy is needed to manufacture them. In this study, the electrically assisted plastic deformation (EAPD) process is explored in a titanium alloy – TC11, to investigate how it can be used to enhance its formability/plasticity. A systematic study was conducted on the mechanical behavior and microstructure evolution of the TC11 during the EAPD process under different current densities (5–15 A/mm2) and strain rates (10−3-10−1s−1). The effects of the pulse current on the yield strength and microstructure of the titanium alloy TC11 are investigated. We found that the yield strength of the TC11 titanium alloy decreases with the increment of current density and the decrease of strain rate, suggesting that pulse current can improve the formability/plasticity of TC11 titanium alloy while reducing energy consumption during manufacturing. With the help of EBSD, TEM, and HAADF-STEM, we were able to characterize the phases refinement, dislocation annihilation, and element diffusion in the alloy. This phenomenon was explained by the recrystallization of the β phase during the EAPD process. Furthermore, the constitutive equations for the TC11 titanium alloy during the EAPD process have been formulated. The deformation stress predicted by the constitutive model agrees well with the experimental data. This study provides valuable insight into the mechanical behavior and microstructure evolution of the TC11 titanium alloys during EAPD.