Bi对原位自生Mg_2Si/Al复合材料组织和干滑动摩擦磨损行为的影响

Influence of Bi Addition on Microstructure and Dry Sliding Wear Behaviors of In-situ Mg_2Si/Al Composite

考察了Bi变质对原位自生Mg2Si/Al复合材料显微组织和干滑动摩擦磨损行为的影响。结果表明:在Mg2Si增强的Al基复合材料中添加适量的金属Bi对初生Mg2Si和共晶Mg2Si能够同时起到良好的变质作用,初生Mg2Si的形貌由粗大的树枝状或多角形块状转变为细小的块状,而共晶Mg2Si则由粗大的片状转变为细小的片状、纤维状或点状。并且初生和共晶Mg2Si尺寸大大减小。添加Bi复合材料的磨损率和摩擦系数均比未添加Bi复合材料的低;4%Bi的添加使复合材料的磨损机理由磨粒、粘着及疲劳的综合磨损转变为单一的轻微磨粒磨损。Bi改善复合材料耐磨性是其变质细化初生和共晶Mg2Si相及其自身具有的自润滑性能的综合反映。

The influence of additions of Bi on the microstructure and dry sliding wear behaviors of cast Al-15 wt.%Mg2Si in situ metal matrix composites was investigated.The results expatiate that the addition of proper amount of Bi has significant modification effect on both primary and eutectic Mg2Si in the Al-15 wt.%Mg2Si composites.The morphology of primary Mg2Si is changed from dendritic to polyhedral shape and the eutectic Mg2Si from flake-like to very short fibrous or dot-like,and their average particle sizes are significantly decreased.The wear rates and friction factors of the composites with Bi are lower than those without Bi,and the addition of 4%Bi changes the wear mechanism of the composite from the combination of abrasive,adhesive and delamination wear without Bi into single mild abrasion wear.The improvement of wear properties of the composites with Bi originate from a combination of Bi modification on Mg2Si and self-lubrication function of Bi particles in the friction process.