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通过进行透射电镜分析和拉伸试验研究了不同时效处理制度对Al-7.2Zn-2.5Mg-1.5Cu-0.08Zr-0.12Sc合金的显微组织及拉伸性能的影响。透射电镜分析结果表明:合金在时效过程中,晶内析出大量弥散分布的Mg Zn2相与Al3(Sc,Zr)相。单级时效状态下,晶内析出相细小,晶界析出断续分布的平衡相,并存在晶界无沉淀区;双级时效状态下,晶内及晶界析出相均长大,晶间无析出带宽化;回归再时效处理状态下,晶内析出相较单级时效略有长大,晶界处组织与双级时效相似。拉伸试验结果表明:单级时效状态下的合金具有较高的强度,但断裂伸长率较小;双级时效状态下的合金强度较单级时效明显降低,但有较大的断裂伸长率;经回归再时效的合金既保证了单级时效的强度,也具有双级时效的伸长率。
The effects of different aging treatments on the microstructure and tensile properties of Al-7.2Zn-2.5Mg-1.5Cu-0.08Zr-0.12Sc alloy were investigated by transmission electron microscopy and tensile tests. Transmission electron microscopy results showed that a large amount of Mg, Zn2 and Al3 (Sc, Zr) phases were precipitated in the grains during the aging process. Under the single-stage aging condition, the precipitation phase in the grain is fine and the equilibrium phase precipitates intermittently in the grain boundary, and there is no sedimentation zone in the grain boundary. In the two-stage aging condition, the precipitates grow both in the grain boundary and in the grain boundary, Precipitation and recrystallization. Under the condition of re-aging treatment, the intragranular precipitation slightly increases compared with the single-stage aging, and the grain boundaries have similar microstructure and two-stage aging. Tensile test results show that the alloy under single-stage aging has high strength, but the elongation at break is small. The strength of alloy under two-stage aging is obviously lower than that of single-stage aging but with larger elongation at break Rate; regrind and re-aging of the alloy not only ensure the strength of single-stage aging, but also has a two-stage aging elongation.