(1. 长沙理工大学 材料科学与工程学院，长沙 410076；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用金相显微镜、扫描电镜和能谱分析，研究Sc对Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr合金铸态组织和力学性能的影响。结果表明，添加0.20%~0.60%的Sc，会使合金的铸态组织由粗大的树枝晶变为等轴晶，并使Cu的偏聚减轻，且Sc含量越高，合金铸态组织越细，Sc含量为0.60%的合金铸态组织最细小；随着Sc含量的增加，合金的抗拉强度升高，T6态时，Sc含量为0.60%的合金抗拉强度高达783.9 MPa。从熔体中析出的Al3(Sc，Zr)一次粒子具有与α(Al)基体相同的FCC晶格，晶格常数接近，可有效地细化合金的铸态组织。合金强化机理主要为Al3(Sc，Zr)引起的细晶强化、亚结构强化和沉淀强化。
关键字: Al-Zn-Mg-Cu-Zr合金；Sc；晶粒细化；显微组织；力学性能
（1. School of Materials Science and Engineering, Changsha University of Science and Technology, Changsha 410076, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The as-cast microstructures and mechanical properties of Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr alloys with and without Sc were investigated by optical microscope, scanning electron microscope(SEM) and energy spectrum analysis. The result shows that the addition of 0.20%−0.60%Sc can refine the grain size, change the growth morphology from dendritic to fine equiaxed grain, and reduce the segregation behavior of Cu. The higher the content of Sc of studied alloys, the finer the as-cast grain is. The grain size of the alloy with 0.60%Sc is the finest in the experimental alloys. The tensile strength is enhanced with the increase of Sc. The tensile strength of alloy with 0.60%Sc is 783.9 MPa in T6. The primary Al3(Sc, Zr) particles precipitate from the melt during solidification is the most effective grain refiner for α(Al) matrix, which have the same crystal structure of FCC as α(Al) matrix, whose lattice constant is very close to that of α(Al). The strengthening mechanisms of the alloy are mainly sub-structure strengthening, precipitation strengthening and solution strengthening caused by Al3(Sc, Zr).
Key words: Al-Zn-Mg-Cu-Zr alloy; Sc; grain refine; microstructure; mechanical properties
