热处理工艺提高Al-17Si-5Cu合金的干滑动耐磨性

摘要

To improve the wear resistance of cast Al-17Si-5Cu alloy (AR alloy),isothermal heat treatment is employed to modify the morphology of Si particles (particularly eutectic Si particles).Furthermore,wear behaviour of heat-treated alloy (HT alloy) along with AR alloy is studied using a pin-on-disc tribometer.Worn surfaces are then characterised using scanning electron microscope.The result reveals considerable microstructural modifications after the heat treatment.Accordingly,higher hardness value in HT alloy is obtained compared with AR alloy.The overall wear rate for HT alloy is found to be significantly lower compared with AR alloy at all the applied loads,indicating remarkable improvement in wear resistance.Eutectic Si particles become from acicular/rod-like to spherical/equiaxed morphology (aspect ratio close to 1) on heat treatment,resulting in good bonding with the matrix.Thus,they remain intact during wear and being harder,providing resistance to wear.Moreover,the increased hardness on heat treatment causes further resistance to wear.Therefore,the combined effect of intact harder Si particles on the wearing surface and higher hardness results in superior wear behavior in HT alloy at all loads compared with AR alloy.%通过等温热处理调整铸态Al-17Si-5Cu (AR)合金中Si(尤其是共晶Si)颗粒的形貌以提高合金的耐磨性能.通过销-盘式摩擦机对比研究热处理后的合金(HT合金)和AR合金的磨损行为,并采用扫描电镜观察磨损表面.结果表明,HT合金的显微组织发生显著变化,相应地,HT合金较AR合金的硬度值增大.与AR合金相比,HF合金在所有载荷下总磨损率明显降低,耐磨性能明显改善.热处理后,共晶Si颗粒由针/棒状变为球形/等轴状(长径比接近1),与基体形成良好结合,在磨损过程中保持完整且更加坚硬,为材料提供良好的耐磨性.另外,HT合金硬度的增加进一步提高合金的耐磨性.因此,完整且较硬的Si颗粒对磨损表面的作用以及材料整体硬度的提高导致HT合金在所有载荷下的磨损行为均优于AR合金.