## 1 Introduction  
The key material of the main load-bearing components for the airline (such as stringer and reinforced bulkhead) is 7050 aluminum alloy (Al-Zn-Mg-Cu), due to its excellent performances of high strength and fatigue toughness, good formability, corrosion resistance and hardenability [1, 2]. Furthermore, 7050 aluminum alloy is strengthened through the precipitation of strengthening phases into the Al matrix by the aging treatments [3]. The generally accepted precipitation sequence for 7000 series alloys [4] can be expressed as: supersaturated solid solution (SSS) \(\rightarrow\) coherent Guinier Preston zones (G.P zones) \(\rightarrow\) semi-coherent \(\eta^{\prime}\) phase \(\rightarrow\)equilibrium phase \(\eta\) (MgZn\({}_{2}\)). Numerous studies have indicated that \(\eta^{\prime}\) phases and their precursors (G.P zones) were the main strengthening precipitates, while an incoherent \(\eta\) phase cannot contribute to the strength increase. A supersaturated solid solution formed during the solution treatment contributed to the precipitation of strengthening phases during the aging process. However, the solution treatment induced large residual stress of the component, which led to severe distortion and even failure in the subsequent machining stage. The variation and control of residual stress during the preparation processes had been the key factor in the manufacturing of aerospace components with high accuracy and high performances. A thermo-mechanical treatment [5, 6] was adopted to decrease the quenched residual stress by applying cold deformation between the solution and aging process. Meanwhile, the cold deformation also increased the dislocation density of the material, which contributed to the precipitation of strengthening phases and the strength increase in the aging stage [7,8]. The preparation of airline components made from 7050 aluminum alloy consisted of forging, quenching, cold deformation and the followed aging processes. The variation of residual stress was quite complex and many previous studies on the evolution of residual stress have been reported. [PERSON] [9] identified the parameters of the thermo-mechanical model for the quenching process using a limited number of tensile tests achieved after representative interrupted cooling paths in a Gleeble machine. [PERSON] [10] established a 3D finite element model (FEM) to predict the induced distortion and residual stress of a large sized forged block during the water quenching process. The FEM model considered the coupling between the thermal, mechanical and metallurgical fields. [PERSON] [11] investigated the influence of temperature-dependent material properties on the evolution of plastic strain and residual stress in the forged 2A14 aluminum alloy components during the quenching process through the theory analysis, quenching experiments and numerical simulation. The results showed that the thermal expansion coefficients, yield strengths and elastic moduli played key roles in determining the magnitude of plastic strains and residual stresses. [PERSON] [12] employed X-ray diffraction and a layer removal technique to determine the quench-induced residual stress in extruded ZK60 magnesium alloy. By the combination of two test methods, the residual stress on the surface and the center part of the component can be obtained. [PERSON] [13] investigated the correlation between quench-induced residual stresses and the distortion of thin-walled parts during machining. The effects of polymer and uphill quenching methods in comparison with water quenching in the reduction of residual stresses were analyzed and the results indicated that the level of residual stress and distortion can be reduced significantly by adopting the polymer quenching method. [PERSON] [14] studied the influence of a delay between quenching and the cold compression on residual stresses in the heat treatable aluminum alloy 7050.