In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, the relationship between microstructure and residual stress is investigated. The results show that there is no phase transition during annealing, but atom distortion occurs with the change of temperature, and the average grain size slightly increases after annealing. There are some atom clusters in the grains, with a few point defects, and the point defect concentration increases with the rise in temperature, and vice versa; the higher the annealing temperature, the fewer the point defects in the grain after annealing. Due to the grain boundary volume shrinkage and and an increase in the plastic deformation of the grain boundaries during cooling, stress is released, and the average residual stress along Y and Z directions after annealing is less than the average residual stress after prepressing.

The deformation problem caused by the excessive residual stress has brought great challenges to the high-precision machining and geometrical stability of thin-walled components. Aiming to ensure the verticality within 0.012 mm after the processing and forming of a certain type of outer ring components, this paper firstly employs the ultrasonic critical refraction longitudinal wave (LCR wave) detection method to test the residual stress distribution in the key process. Additionally, the stress elimination effect of cryogenic stress relief treatment and the effect of residual stress on vertical deformation are analyzed. After that, combined with the self-developed ultrasonic stress relief (USR) equipment, the ultrasonic regulation treatment was used to replace the heat treatment stress relief process for the processing. The results show that after wire cutting and milling, excessive residual stress induces deformation of components, and USR method can eliminate machining residual stress more efficiently and quickly. As the whole component has torsional deformation along the cross section, the hole position at the upper and lower end faces is changed, which leads to the change in verticality. Finally, based on the results of X-ray diffraction (XRD), the potential microscopic mechanism of stress relief by ultrasonic treatment is analyzed. This study provides guidance for ultrasonic residual stress regulation to achieve the high-precision outer ring thin-walled components.

In this paper, molecular dynamics (MD) simulations are performed to study the influence of residual stress on fracture behavior in γ-TiAl alloy with ∑3(111) twin boundaries. The tensile processes are simulated at 1, 300, 1050 K after the residual stress is introduced by prepressing. The evolution of microdefects during tensile fracture is observed, and the distribution of residual stress in three direction is characterized. Results show that the introduced residual stress is symmetrically distributed on both sides of ∑3(111) twin boundaries. The residual compressive stress can prevent the nucleation of micro-cracks and increase the yield strength. The fracture mode of the γ-TiAl alloy with ∑3(111) twin boundaries during tensile load at 1 K is the nucleation of microcracks at grain boundaries followed by intergranular fracture. The ∑3(111) twin boundaries have good thermal stability. The residual compressive stress is completely released and the amplitude of residual tensile stress increases at 1050 K, and the γ-TiAl alloy with ∑3(111) twin boundaries exhibits good ductility.

The residual stress fields of the initial billet and subsequent machining in the material bring great challenges to the precision machining and geometrical stability of aluminum alloy thin-walled components. To ensure that a certain type of large-sized aluminum alloy thin-walled antenna has a small flatness deformation during forming, this paper firstly employed the ultrasonic critical refraction longitudinal wave (LCR wave) detection method to measure the different depth ranges’ residual stress distribution of 5A06/6061/7075 aluminum alloy plate, both as blanks and after multiple milling. Additionally, the effects of inherent residual stress (IRS) and machining-induced residual stress (MIRS) on the subsequent milling deformation were analyzed. After that, combined with the self-developed ultrasonic stress relief (USR) system, the deformation control effect of a thin-walled plate after eliminating residual stress in each stage was tested. The results show that the ultrasonic stress relief treatment can quickly and efficiently eliminate the IRS and MIRS with small flatness deformation. By introducing the URS treatment in the blank, rough machining, and semi-finishing stages, the components before each subsequent machining are in a low-stress state, and the component deformation can be gradually controlled so that the final thin-walled antenna has a smaller flatness.

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