铸锭预析出处理对Al-4.3Zn-1.7Mg合金组织与性能的影响

Effects of Ingot Casting Pre-Precipitation Treatment on the Microstructure and Properties of Al-4.3Zn-1.7Mg Alloy

采用OM、SEM、TEM和TS等测试方法对比研究有无预析出处理的均匀化工艺对Al-4.3Zn-1.7Mg合金显微组织和力学性能的影响。结果表明:半连续铸造急冷条件下合金中复合添加的Mn、Cr和Zr等微量元素以固溶体的形式保留在基体中,均匀化处理过程中分解析出Al_6Mn、Al_7Cr及Al_3Zr等预析出相粒子。通过低温预析出处理能显著改善预析出相在均匀化过程中的析出行为,获得尺寸细小分布弥散的预析出相,且具有很好的热稳定性,在热轧及后续固溶时效等热处理过程中不发生明显粗化,因而能显著抑制晶界迁移和位错运动,提高合金板材性能。

The effects of the single-stage homogenization process without pre-precipitation treatment and the two-stage homogenization process with pre-precipitation treatment on the microstructure and mechanical properties of Al-4.3Zn-1.7Mg alloy were investigated contrastively by optical microscopy（OM）, scanning electron microcopy（SEM）, transmission electron microcopy（TEM） and uniaxial tension（TS） test. The results show that the trace elements Mn, Cr and Zr in the alloy after semicontinuous casting quenching are retained in the form of solid solution in the matrix, and the pre-precipitated phase particle Al6Mn, Al7Cr and Al3Zr are precipitated in the process of homogenization treatment for supersaturation solid solution. The precipitation behavior of the precipitated phase can be improved significantly in the process of homogenization by the low temperature pre-precipitation treatment. The fine pre-precipitated phase with dispersion distribution is obtained. The precipitated phase particles have good thermal stability, and they cannot be markedly coarsened in the process of hot rolling and subsequent solid solution aging heat treatment. So the migration of grain boundary and dislocation movement are inhibited significantly, and the performance of alloy plate is improved.