50% Si/Al复合材料微区不均匀性表征及其对力学性能的影响

Measurement of Micro-Nonuniformity of 50% Si/Al Composites and Its Influence on Mechanical Properties

采用粉末冶金法制备50%Si/Al(质量分数,下同)复合材料,利用金相显微镜(OM)、万能试验机和扫描电镜(SEM)对材料的组织不均匀性及性能稳定性进行了研究。结果表明:在不同混料条件下,50%Si/Al复合材料能够轻易达到宏观均匀,组织之间的区别在于微区不均匀性。对于50%Si/Al复合材料而言,微区域大小为75μm×70μm所反映的组织微区不均匀性规律与断裂韧性稳定性的变化趋势相吻合。而断裂韧性的稳定性与组织的微区不均匀性相关,因此选取大小为75μm×70μm的微区域能够较好地反映材料的微区不均匀性。相比较而言,4种不同混料工艺中,最佳混料工艺为混料24 h,球料比1∶1。组织微区不均匀性对于断裂韧性稳定性影响最为突出,对抗弯及抗拉强度稳定性的影响并不明显。

The micro-nonuniformity and property stabilities of 50% Si/A1 （mass fraction） composites, fabricated by powder metallurgy （ PM ） method under four different mixing processes, were studied by optical microscope （ OM）, mechanical test and scanning electron microscope （SEM）. The results indicated that under different mixing processes, the macro-homogeneity could be reached easily, and the difference between the structures was micro-nonuniformity. For 50% Si/Al composites, the rule of micro-nonuniformity was identical with the stability law of fracture toughness. The stability law of fracture toughness was related with the discipline of micro-non- uniformity, therefore the micro-district with size of 75 μm × 70 μm was suitable for quantitative analysis of Si particle distribution in the aluminum matrix. The composite with ball-to-powder weight ratio （BPWR） of 1： 1, homogenized for 24 h had the lowest value of nonuniformity index （M）. The distribution of particles influenced fracture toughness greatly, compared to tensile strength and bending strength.