Research on Residual Stresses and Microstructures of Selective Laser Melted Ti6Al4V Treated by Thermal Vibration Stress Relief

Abstract

The efficient and cost-effective residual stress control method is of great significance for the application of additive manufacturing (AM) technology. In this work, thermal-vibration stress relief (TVSR) with different temperatures and dynamic stresses was performed on Ti6Al4V samples prepared by selective laser melting (SLM), the stress relief effects of TVSR and its influence on phase and microstructure were investigated and compared with thermal stress relief (TSR) and vibration stress relief (VSR), and the stress relief mechanisms of these methods are discussed. It was found that the residual stress relief rate can reach 86.76% after TVSR treatment at a temperature of 380 °C and a dynamic stress of 400 MPa, which increased by 63.63% compared with VSR under the same dynamic stress. The efficiency is increased by 76% compared with TSR at 580 °C and the residual stress relief rate is almost the same. After TVSR, VSR and TSR treatments, the grain morphology, size and phase content of samples were basically unchanged, and low-angle grain boundaries (LAGBs) were increased after TVSR and VSR treatments and decreased after TSR treatment. The results confirm that the TVSR method has the ability to control the residual stress of selective laser melted Ti6Al4V with low time and cost consumption, and are helpful for engineering applications of TVSR.

Effect of Electrolytic Plasma Polishing on Surface Properties of Titanium Alloy

“…The surface temperature of the sample is continuously increased and decreased alternately to form an annealing effect, which causes the residual stress on the surface to be released quickly. Its essence can be seen as the microstructure evolution and stress relaxation behavior of the material at a certain temperature [51]. According to the analysis of microstructural changes in Section 3.2, after EPPo, the increase in crystallinity and grain size on the sample surface can reduce the number of grain boundaries and reduce the local dislocation barrier and stress concentration phenomenon, which are thus conducive to the reduction in residual stress.…”