离心铸造Al-18Si-8Ni复合材料的微观组织分布与性能研究

Study on Microstructures and Properties of Al-18Si-8Ni Composites Fabricated by Centrifugal Casting

采用离心铸造方法制备了Al-18Si-8Ni复合材料筒状铸件,使用XRD、SEM及OM观察分析了复合材料的微观组织,并检测了材料的硬度及耐磨性能。结果表明:Al-18Si-8Ni筒状铸件形成了具有大量初晶Al3Ni和Si颗粒的外层、中间基体层以及含有较多初晶Si和少量Al3Ni颗粒的内层的三层组织。铸件外层具有最高的硬度及最大的初晶颗粒体积分数。沿筒状铸件半径方向、轴向方向,初晶Al3Ni分别呈现颗粒状及片状两种形貌,且在半径方向上铸件具有更高的硬度。沿铸件半径方向,随着初晶颗粒体积分数的减少,复合材料的耐磨性能逐渐降低。初晶Al3Ni的离心运动与初晶Si的向心运动是形成Al-18Si-8Ni复合材料三层组织的主要原因。

The microstructures of the AI-18Si-8Ni composites tubes fabricated by centrifugal casting were observed and analyzed by using ofXRD, SEM and OM. The hardness and wear resistance of the casting were measured. The results show that the tubes consist of an outer layer containing many primary A13Ni and Si particles, the middle layer of the A1 matrix and the inner layer having some primary Si and a few A13Ni. The outer layer of the tube has the largest particle volume fraction and the highest hardness. Along the radial and longitudinal directions of the tube, the primary A13Ni appears granular and flake morphologies, respectively. Moreover, a higher hardness was measured on the radial direction of the casting. Along the radial direction, the wear resistance of the composites gradually decreased as the reducing particle volume fractions. The centrifugal migration of A13Ni and centripetal movement of Si play an important role in the formation of the A1-18Si-8Ni composites with three layers.