中文摘要：

通过设计准正交实验,利用极差分析法和期望方差分析法分别对Al-7Si-Mg铝合金的尺寸/因子（合金晶粒或共晶硅的尺寸与形状因子或折算因子的比值）和硬度进行分析,正交探究混合稀土添加量和固溶时效工艺的较佳工艺组合,并探讨固溶时效处理对Pr/Ce铝合金组织和性能的影响。研究的结果表明,对于合金的尺寸/因子的影响,固溶温度较大,固溶时间与时效时间其次,Pr/Ce添加量最弱。对于合金的硬度的影响,固溶温度较大,固溶时间和Pr/Ce添加量其次,时效时间最弱。综合分析得到的较佳工艺组合为：添加0.6%Pr/Ce混合稀土,在510℃固溶6 h,在180℃时效4 h。经过较佳工艺组合处理后的合金中,共晶硅相细小,平均尺寸约为10.8μm,呈雨点状分布,形状因子达到0.81,且合金硬度达到92.1 HB。

英文摘要：

Based on the design of the quasi- orthogonal test,the ratio of size to factor（ the size of alloy grain or eutectic silicon divided by the shape or the conversion factor） and the hardness of Al-7Si-Mg alloy were analyzed by range analysis method and expectation variance analysis respectively. The quasi- orthogonal test investigated the effects of rare earth additions,solution and aging treatment process on microstructure and properties of Pr / Ce aluminum alloy. The results show that solution temperature has the greatest effect on the ratio of size to factor of alloy,the solution and aging time secondly,and the Pr / Ce additions weakest. Solution temperature has the greatest effect on the hardness of alloy,solution time and Pr / Ce additions the secondly,and aging time the weakest. According to the comprehensive analysis,the best combination process of the alloy is that the addition of Pr / Ce 0. 6%,solution treated at 510 ℃ for 6 h and artificial aging treated at 180 ℃ for 4 h. After the optimum combination process,eutectic silicon phase is tiny,the size is about 10. 8 μm with distribution likes rain,the shape factor of the alloy reached 0. 81 and the hardness reached 92. 1 HB.