15 vol.% SiC/Al-6.5Zn-2.8 Mg-1.7Cu (wt%) composites with varying particle sizes (3.5, 7.0, 14 and 20 μm), i.e., C-3.5, C-7.0, C-14, and C-20, respectively, were fabricated by powder metallurgy (PM) method and subjected to microstructural examination. The effect of particle size on mechanical properties and fracture behaviors of the T6-treated composites was revealed and analyzed in detail. Element distribution and precipitates variations in the composites with varying particle sizes were emphatically considered. Results indicated that both tensile strength and plasticity of the T6-treated composites increased first and then decreased with particle size decreasing. The C-7.0 composite simultaneously exhibited the highest ultimate tensile strength (UTS) of 686 MPa and best elongation (El.) of 3.1%. The smaller-sized SiC particle would introduce more oxide impurities, which would react with the alloying element in the matrix to cause Mg segregation and depletion. According to strengthening mechanism analysis, the weakening of precipitation strengthening in the T6-treated C-3.5 composite was the main cause of the lower tensile strength. Additionally, the larger SiC particle, the more likely to fracture, especially in the composites with high yield strength. For the T6-treated C-20 composites, more than 75% SiC particles were broken up, resulting in the lowest plasticity. As decreasing particle size, the fracture behaviors of the T6-treated composites would change from particle fracture to matrix alloy fracture gradually.

15 vol.% SiC/Al-6.5Zn-2.8 Mg-1.7Cu (wt%) 具有不同粒径（3.5、7.0、14 和 20 μm）的复合材料，即.、C-3.5、C-7.0、C-14 和 C-20 分别通过粉末冶金 (PM) 方法制造并进行显微组织检查。详细揭示和分析了粒径对 T6 处理复合材料力学性能和断裂行为的影响。着重考虑了具有不同粒径的复合材料中的元素分布和析出物变化。结果表明，随着粒径的减小，T6处理的复合材料的拉伸强度和塑性均先增加后减小。C-7.0 复合材料同时表现出 686 MPa 的最高极限拉伸强度 (UTS) 和 3.1% 的最佳伸长率 (El.)。较小尺寸的 SiC 颗粒会引入更多的氧化物杂质，它会与基体中的合金元素发生反应，导致 Mg 偏析和耗尽。根据强化机理分析，T6处理的C-3.5复合材料的析出强化减弱是拉伸强度降低的主要原因。此外，SiC 颗粒越大，越容易断裂，特别是在具有高屈服强度的复合材料中。对于经 T6 处理的 C-20 复合材料，超过 75% 的 SiC 颗粒被破碎，导致塑性最低。随着粒径的减小，T6处理的复合材料的断裂行为会逐渐从颗粒断裂转变为基体合金断裂。SiC 颗粒越大，越容易断裂，尤其是在高屈服强度的复合材料中。对于经 T6 处理的 C-20 复合材料，超过 75% 的 SiC 颗粒被破碎，导致塑性最低。随着粒径的减小，T6处理的复合材料的断裂行为会逐渐从颗粒断裂转变为基体合金断裂。SiC 颗粒越大，越容易断裂，尤其是在高屈服强度的复合材料中。对于经 T6 处理的 C-20 复合材料，超过 75% 的 SiC 颗粒被破碎，导致塑性最低。随着粒径的减小，T6处理的复合材料的断裂行为会逐渐从颗粒断裂转变为基体合金断裂。