论文部分内容阅读
为了克服单一初晶Si或Mg2Si颗粒增强的铝基复合材料的不足,采用离心铸造的方法制备了一种由初晶Si与Mg2Si两种颗粒互补增强的铝基梯度复合材料。这种复合材料的组织与性能具有明显的梯度分布特征:内层含有高体积分数的初晶Si与Mg2Si颗粒,形成互补增强区域,具有高硬度的特点;外层没有或含有极少量初晶颗粒,形成非增强区域,具有硬度低的特点。对该复合材料的离心成形机制探讨发现,大量细小的初晶Mg2Si颗粒是形成这种梯度复合材料的关键因素。在离心力场中,密度更小的初晶Mg2Si颗粒具有比初晶Si颗粒大得多的向心运动速度,在运动过程中它与初晶Si发生碰撞并推动后者一起快速运动,最终导致二者在内层的剧烈偏聚。此外,为了获得足够的初晶Mg2Si颗粒,在三元Al-Si-Mg合金中,Si的质量分数应不低于19%,Mg的质量分数应不低于4%。
In order to overcome the deficiencies of single primary Si or Mg2Si particles reinforced aluminum matrix composites, an aluminum-based gradient composite reinforced by two kinds of primary Si and Mg2Si particles was prepared by centrifugal casting. The microstructure and properties of the composite material have obvious gradient distribution characteristics: the inner layer contains primary Si and Mg2Si particles with high volume fraction to form a complementary reinforced region with high hardness; the outer layer does not contain or contains a very small amount of primary crystal particles , The formation of non-enhanced area, with low hardness characteristics. The centrifugal forming mechanism of the composite material found that a large number of fine primary crystal Mg2Si particles form a key factor in this gradient composite material. In the centrifugal force field, the primary crystal Mg2Si with smaller density has a much larger centripetal velocity than the primary Si particles. During the motion, it collides with the primary Si and drives the latter to move fast together, finally resulting in two In the inner layer of intense segregation. In addition, in order to obtain sufficient primary crystal Mg2Si particles, in the ternary Al-Si-Mg alloy, the mass fraction of Si should not be less than 19% and the mass fraction of Mg should not be less than 4%.