Effect of high-density pulsed electric current on residual stress relief and microstructural modification of cold-bent commercially pure titanium

Abstract

The effect of high-density pulsed electric current (HDPEC) on removing residual stress of the cold-bent commercially pure titanium TP270 was investigated. After HDPEC treatment, the tensile residual stress on the external surface decreased from 287.75 MPa to 77.33 MPa, and the internal compressive residual stress recovered from −166.56–1.28 MPa. In addition, the hardness on the external and internal surfaces showed the same tendency and almost recovered to the initial state. The microstructural characterization showed that the cold-bending process introduced plenty of dislocations and twins into samples, which were evidently removed by HDPEC due to the coupling effects of electron wind force and Joule heating, thereby resulting in the recovery of residual stress and hardness. Furthermore, through comparison with rapid heat treatment experiments, we have found that both electron wind force and Joule heating effects play equally significant roles in eliminating dislocations and deformed twins. More importantly, the HDPEC treatment maintains the original microstructure, such as grain size, grain boundary characteristics, crystalline orientation, etc. Hence, this method provides a promising way to relieve the residual stress of processed components without affecting the microstructure.