Currently, the hot forming of aluminum alloys has garnered significant attention for overcoming poor formability at room temperature (RT). However, the current hot forming technique is facing problems such as time-consuming procedures and high economic cost. To improve forming efficiency, we herein propose a novel forming technique for heat-treatable aluminum alloys, termed pre-aged hardening warm forming (PHF) process. An Al–Zn–Mg–Cu alloy is used to investigate the flow behavior, drawing formability, and post-forming mechanical properties during the aforementioned process. Uniaxial tensile tests and Erichsen tests are conducted to evaluate the plastic flow behavior and drawability, respectively. Stamping tests are performed on a cap beam component to verify the engineering feasibility of the forming technique. Optical microscopy (OM) and transmission electron microscopy (TEM) are performed to characterize the microstructure evolution during the PHF process. The tensile test results show that the pre-aged alloys exhibit true fracture elongation similar to the fracture elongation of the O-temper alloy at RT, and that the Erichsen values of the pre-aged alloys are 5%–16% higher than that of the O-temper alloy at 200 °C. The results of the stamping tests for the cap beam component indicate that the optimal final strength of the stamped component achieves σ/σ_0.2 = 566 MPa/500 MPa, exceeding the strength of the AA7075-T6 alloy. OM observations show that the stamping process does not significantly affect the grain sizes of the pre-aged alloys. TEM results show that numerous thermostable GPⅡ zones exist in the pre-aged alloys, and that the stamping procedure transforms the GPⅡ zones to dispersed η′ phases and results in the entanglement of numerous dislocations. The dual effects of phase transformation and plastic deformation during the PHF process contribute to the desirable mechanical properties of the stamped components.

目前，铝合金的热成型由于克服了室温（RT）下的不良成型性而备受关注。然而，目前的热成型技术面临着工序费时、经济成本高等问题。为了提高成形效率，我们在此提出了一种用于可热处理铝合金的新型成形技术，称为预时效硬化温成形 (PHF) 工艺。Al-Zn-Mg-Cu 合金用于研究上述过程中的流动行为、拉伸成形性和成形后机械性能。进行单轴拉伸试验和 Erichsen 试验以分别评估塑性流动行为和可拉伸性。对顶梁组件进行冲压测试，以验证成型技术的工程可行性。执行光学显微镜 (OM) 和透射电子显微镜 (TEM) 来表征 PHF 过程中的微观结构演变。拉伸试验结果表明，预时效合金的真实断裂伸长率与 O 回火合金在室温下的断裂伸长率相似，并且预时效合金的 Erichsen 值比 O-temper 合金的 Erichsen 值高 5%~16%。 O 回火合金在 200 °C。帽梁构件冲压试验结果表明，冲压构件的最佳最终强度达到σ/σ 并且在 200 °C 时，预时效合金的 Erichsen 值比 O 回火合金的 Erichsen 值高 5%–16%。帽梁构件冲压试验结果表明，冲压构件的最佳最终强度达到σ/σ 并且在 200 °C 时，预时效合金的 Erichsen 值比 O 回火合金的 Erichsen 值高 5%–16%。帽梁构件冲压试验结果表明，冲压构件的最佳最终强度达到σ/σ_0.2  = 566 MPa/500 MPa，超过了AA7075-T6合金的强度。OM 观察表明，冲压过程不会显着影响预时效合金的晶粒尺寸。TEM结果表明，预时效合金中存在大量热稳定GPⅡ区，冲压过程将GPⅡ区转变为分散的η'相，导致大量位错的纠缠。在 PHF 过程中相变和塑性变形的双重效应有助于冲压部件获得理想的机械性能。