喷射态7075合金欠时效低温回归处理

摘要

The effects of low-temperature retrogression in RRA on the microstructure, mechanical and conductivity properties of spray formed 7075 aluminum alloy with different pre-aging treatments were investigated by transmission electron microscopy, extension and conductivity tests. The results show that, pre-aging treatment (at 120℃for 16 h) is more beneficial for the re-dissolution of precipitates in matrix than peak aging (T6, at 120℃ for 24 h) at low-temperature (160℃) retrogression, and the grain boundary precipitates are interrupted after RRA treatment. After pre-aging at 120℃ for 16 h and RRA treatment, the tensile strength, yield strength, elongation and conductivity of the alloy are 773 MPa, 724 MPa, 8.8% and 37.2%(IACS), respectively. The mechanical properties are higher than those after T6 or conventional RRA treatment (neither low-temperature or high-temperature) and the conductivity is close to the small sample after conventional high-temperature RRA treatment. This process is fitted for large workpiece in industrial heat treatment.%采用欠时效代替传统峰值时效处理，再结合低温回归处理，可获得良好的综合性能指标，采用透射电镜观察、拉伸及电导率测试等方法，研究RRA处理中预时效处理对低温回归和再时效后喷射成形7075合金组织与性能的影响。结果表明：采用120℃、16 h的欠时效预处理比120℃、24 h峰值时效预处理更有利于合金在160℃低温回归过程中晶内析出相的回溶，并且晶界相粗化、断开，合金抗腐蚀性能改善。欠时效预处理的合金经低温RRA处理后，其抗拉强度、屈服强度、伸长率和电导率分别为773 MPa、724 MPa、8.8%和37.2%(IACS)，力学性能均高于T6峰值时效和传统低温与高温RRA的水平，且耐蚀性能也接近传统高温RRA制备小尺寸试样的，此工艺更适用于大型件的工业化热处理。