具有超高强度和良好塑性匹配的Al-Zn-Mg-Cu合金设计与研究

Design and Research on Al-Zn-Mg-Cu Alloy with Ultra-high Strength and Good Plasticity Matching

摘要:

根据Zn、Mg和Cu元素在Al中的固溶度设计了一种Al-8Zn-3Mg-1.05Cu合金。对热轧后的板材进行固溶处理。SEM和XRD结果表明，经过固溶处理后获得了仅有少量化合物残留的固溶体组织。进一步对合金冷轧以及轧后固溶和时效处理，冷轧固溶后的EBSD结果表明，此时合金获得了未完全再结晶的组织，局部取向差（KAM）图表明未完全再结晶区域的位错密度较高。经过固溶后的合金拉伸性能良好，屈服强度和延伸率分别为458.61 MPa和15.6%。TEM结果表明，经过时效处理后的合金组织中析出了大量细小的MgZn₂相，平均尺寸约为6.40 nm，该尺寸小于报道的该类合金中MgZn₂析出相的尺寸。时效后合金获得了超高的强度和良好的塑性，屈服强度和延伸率分别为729 MPa和10.37%。对合金的强度组成进行了计算，其中细小MgZn₂相的析出强化贡献值为348.48 MPa，计算屈服强度值与实验值匹配良好。

Abstract:

An Al-8Zn-3Mg-1.05Cu alloy was designed according to the solid solubility of Zn, Mg and Cu elements in Al matrix. Then, the hot-rolled plate was subjected to solid solution treatment. The results of SEM and XRD show that the solid-solution microstructure with only a small amount of compound residue is obtained after solid solution treatment. Subsequent cold rolling, solid solution and aging treatment of the alloy were carried out. The EBSD results indicate that the alloy obtains incompletely recrystallized structure after cold rolling and solid solution treatment. The KAM diagram shows that the dislocation density in the incompletely recrystallized zone is high. The alloy after solid solution treatment exhibits favorable tensile properties, with the yield strength of 458.61 MPa and elongation of 15.6%. The TEM results after aging treatment show that a large number of fine MgZn₂ phases are precipitated in the microstructure. The average size of MgZn₂ phase is about 6.40 nm, which is notably smaller than that in the reported alloys. After aging treatment, the alloy obtains ultra-high strength and good plasticity with the yield strength and elongation of 729 MPa and 10.37%, respectively. The strength composition of the alloy was calculated, and the precipitation strengthening contribution value of fine MgZn₂ phase is 348.48 MPa. The calculated yield strength value matches well with the experimental value.