Residual Stresses in High-speed Two-dimensional Ultrasonic Rolling 7050 Aluminum Alloy with Thermal-Mechanical Coupling

Abstract In order to achieve the high-efficiency and high-quality anti fatigue manufacturing of 7050 aluminum alloy, high speed ultrasonic machining was introduced into two-dimensional ultrasonic rolling, the simulation and experiment of high-speed two-dimensional ultrasonic rolling (HTUR) 7050 aluminum alloy were carried out. The evolution of temperature field, stress field and strain field in HTUR process were simulated, and the evolution of the surface flow stress with thermal-mechanical coupling was analyzed. The surface residual stress and microstructure of the cross section of sample after HTUR treatment were characterized by X-ray diffraction and scanning electron microscope (SEM). The results show that HTUR treatment can form a gradient strengthened layer and introduce beneficial residual compressive stress in the surface layer of 7050 aluminum alloy. In HTUR process, the surface temperature field, equivalent stress and equivalent strain field are non-uniformly distributed, and the changes of the temperature, equivalent stress and equivalent strain are not completely synchronous with time. The residual stress with thermal-mechanical coupling is slightly less than that of without thermal-mechanical coupling, and close to the experimental results. The temperature has a little negative effect on the residual stress. The performance of the specimen still mainly depends on the cold plastic deformation in HTUR process, so such technology can realize high-efficiency ultrasonic hardening treatment of 7050 aluminum alloy on the premise of ensuring fatigue strengthening.