Al_2O_(3p)/Al复合材料中颗粒粒径与形态对组织和性能的影响

Effect of particle size and morphology on microstructure and properties of Al_2O_ (3p)/Al composites

选用 5 .0和 0 .15 μm两种粒径的Al2 O3 颗粒 ,制备了Al2 O3 体积分数为 40 %的铝基复合材料。利用透射电镜对两种复合材料拉伸前后的组织进行观察 ,结果表明 :5 μm尖角形Al2 O3 颗粒增强复合材料的铸态组织中存在高密度的位错 ,这主要是由于热错配应力引起的 ;0 .15 μm椭球形Al2 O3 颗粒增强复合材料的铸态组织中几乎观察不到位错 ,这与颗粒细小且为等轴状、分布弥散、界面附近应力分布均匀等因素有关。对拉伸断口附近显微组织的观察表明 ,前者基体中位错进一步增殖 ,后者则存在明显的位错环。室温拉伸结果表明亚微米Al2

Aluminum matrix composites with alumina particles of 40%(volume fraction) were fabricated using 5.0?μm and 0.15?μm Al 2O 3 particles respectively. The microstructure of the two kinds of composites before and after tension was investigated with transmission electron microscope (TEM). It was found that there was a high dislocation density in the as-cast composite reinforced by 5?μm sharp-angle-shaped Al 2O 3 particles, due to the thermal mismatch stress. In contrast, little dislocation was observed in the as-cast composite reinforced by 0.15?μm spherical Al 2O 3 particles, which could be attributed to the following factors, such as the dispersion of the equiaxed fine particles, uniform distribution of the stress near the interfaces, etc. The microstructural observation near the fracture indicated that dislocations increased in the matrix of the former composite, while obvious dislocation loops were found in the latter. The room temperature tensile test confirmed that such microstructure in the sub-micro Al 2O 3p/Al composites was beneficial to an increase in their strength and ductility.