【摘要】 采用透射电镜和万能材料试验机研究了双级时效处理中终时效对7475铝合金微观组织和力学性能的影响。结果表明：当一级时效工艺为120℃×5 h及终时效工艺为160℃×14 h时，合金基体析出相数量多，且细小弥散，晶界无沉淀析出带较窄，晶界析出相且呈断续分布；此时合金的抗拉强度、屈服强度和伸长率最佳，分别为509 MPa、463 MPa和12.4%,与未处理的合金相比，抗拉强度、屈服强度和伸长率分别提高了4.5%、9.2%和11.7%;终时效温度为160℃时，随着终时效时间的延长，合金的强度先增后减，但变化幅度不大；终时效温度大于等于165℃时，随着终时效时间的延长，合金的强度显著降低，这是由于晶界无沉淀析出带宽度显著变宽，基体析出相尺寸明显粗化所致。更多还原

【Abstract】 Effect of final aging on microstructure and mechanical properties of 7475 aluminum alloy during two-stage aging treatment was studied by means of transmission electron microscopy and universal material testing machine. The results show that when the first aging process is 120 ℃×5 h and final aging process is 160 ℃×14 h, the amount of precipitated phases in the alloy matrix is large, the precipitates are fine and dispersed, the precipitation free zone at the grain boundary is relatively narrow, and the precipitated phases at the grain boundary are discontinuously distributed. At this time, the tensile strength, yield strength and elongation of the alloy are the best, which are 509 MPa, 463 MPa and 12.4%, respectively. Compared with the untreated alloy, the tensile strength, yield strength and elongation increase by 4.5%, 9.2% and 11.7%, respectively. When the final aging temperature is 160 ℃, with the increase of the final aging time, the strength of the alloy first increases and then decreases, but the change is not significant. When the final aging temperature is greater than or equal to 165 ℃, the strength of the alloy decreases significantly with the increase of the final aging time, which is due to the significant broadening of the width of the precipitate free zone at the grain boundary and the significant coarsening of the matrix precipitated phase.更多还原