原位TiB2/Al−xSi−0.3Mg复合材料的显微组织与力学性能

Microstructures and mechanical properties of in-situ TiB2/Al−xSi−0.3Mg composites

采用盐−金属反应制备原位2%TiB2(体积分数)颗粒增强Al−xSi−0.3Mg(x=7%,9%,12%,15%,质量分数)复合材料,并对其显微组织和力学性能进行研究。结果表明,TiB2/Al−xSi−0.3Mg复合材料中的主要强化相是直径为20~80 nm的TiB2颗粒和长度为1~10μm的共晶硅相。TiB2颗粒能促进晶粒细化,使共晶硅由针状变为短棒状。但是,当Si含量超过共晶成分时,TiB2颗粒的强化作用减弱,这可能是由于形成了大且不规则的初生Si相。轴向拉伸试验和断裂观察结果表明,复合材料比相同成分的基体合金具有更多的脆性断裂特征。

In-situ 2 vol.%TiB2 particle reinforced Al−xSi−0.3Mg(x=7,9,12,15 wt.%)composites were prepared by the salt−metal reaction,and the microstructures and mechanical properties were investigated.The results show that the TiB2 particles with a diameter of 20−80 nm and the eutectic Si with a length of 1−10μm are the main strengthening phases in the TiB2/Al−xSi−0.3Mg composites.The TiB2 particles promote grain refinement and modify the eutectic Si from needle-like to short-rod shape.However,the strengthening effect of TiB2 particles is weakened as the Si content exceeds the eutectic composition,which can be attributed to the formation of large and irregular primary Si.The axial tensile test results and fractography observations indicate that these composites show more brittle fracture characteristics than the corresponding alloy matrixes.