预时效处理对 Al-Zn-Mg-Cu 合金硬化响应及微观组织的影响

研究了预时效处理对Al-Zn-Mg-Cu铝合金薄板力学性能和微观组织的影响,测试了显微硬度和力学性能,表征了TEM微观精细组织。结果表明:固溶处理后在180 ℃立即进行人工时效处理,可获得Al-Zn-Mg-Cu合金的显著时效硬化效果,且在8 h后达到峰值硬度195 HV0.5,与基体呈共格关系的η′相为主要强化相;120 ℃×10 min为最佳的预时效处理制度,经14天的室温停滞后,相比于固溶+自然时效态,硬度降低了13 HV0.5,降幅达到10.7%,具有明显的抑制自然时效作用;预时效+自然时效态试样,经烘烤硬化处理后,屈服强度和抗拉强度分别达到了465和545 MPa,强度增量分别达到170和95 MPa,同时伸长率达到12.5%。

Effect of pre-aging treatment on hardening response and microstructure of Al-Zn-Mg-Cu alloy

Effect of pre-aging treatment on mechanical properties and microstructure of Al-Zn-Mg-Cu aluminum alloy was investigated. The micro-hardness and mechanical properties were tested. The microstructure was characterized. The results indicate that the best pre-aging hardening effect of the experimental Al-Zn-Mg-Cu aluminum alloy is achieved while aging at 180 ℃ immediately after solution treatment, during which the peak value reaches 195 HV0.5 and the main hardening phase is η′ phase. The optimal pre-aging treatment is under 120 ℃×10 min. Thus, after 14 days natural aging, the hardness of the alloy is decreased by 13 HV0.5 or 10.7% compared to the solution+natural aging treatment. Finally after bake hardening process, the yield strength and tensile strength of the pre-aged alloy reach 465 MPa and 545 MPa, showing a hardening increase of 170 MPa and 95 MPa,respectively, and the elongation reaches 12.5%.