(1. 長沙理工大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410076；
2. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用金相顯微鏡、掃描電鏡和能譜分析，研究Sc對Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr合金鑄態(tài)組織和力學(xué)性能的影響。結(jié)果表明，添加0.20%~0.60%的Sc，會使合金的鑄態(tài)組織由粗大的樹枝晶變?yōu)榈容S晶，并使Cu的偏聚減輕，且Sc含量越高，合金鑄態(tài)組織越細，Sc含量為0.60%的合金鑄態(tài)組織最細小；隨著Sc含量的增加，合金的抗拉強度升高，T6態(tài)時，Sc含量為0.60%的合金抗拉強度高達783.9 MPa。從熔體中析出的Al3(Sc，Zr)一次粒子具有與α(Al)基體相同的FCC晶格，晶格常數(shù)接近，可有效地細化合金的鑄態(tài)組織。合金強化機理主要為Al3(Sc，Zr)引起的細晶強化、亞結(jié)構(gòu)強化和沉淀強化。
關(guān)鍵字: Al-Zn-Mg-Cu-Zr合金；Sc；晶粒細化；顯微組織；力學(xué)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
