经激光表面熔凝处理的Mg-11Y-2.5Zn合金的显微组织和摩擦学性能

用X-ray衍射和激光共聚焦扫描显微镜对经激光表面熔凝处理的Mg-11Y-2.5Zn合金进行显微组织和相组成分析,并测量改性层硬度变化。研究结果表明,经激光表面熔凝处理后,改性层由熔化区和热影响区组成,熔化区的显微组织明显细化,硬度有所改善。研究了经激光表面处理和铸态Mg-11Y-2.5Zn合金的摩擦学性能,滑移速率为0.785m/s,载荷范围为20～320N。两者的摩擦因子无显著差异,但经激光表面处理的Mg-11Y-2.5Zn合金表现出较低的磨损率,归结于熔凝区的组织细化和硬度增加。SEM磨损表面形貌分析表明,激光表面熔凝处理的合金与未处理合金的磨损机制基本相同,轻微磨损阶段为磨粒磨损和剥层磨损,严重磨损阶段为表面热软化和熔化磨损。

Microstructure and tribological properties of Mg-11Y-2.5Zn alloy modified by laser surface melting-solidification

The microstructure and phase constitution of alloy Mg-11Y-2.5Zn surface modified by melting and resodification by a 6.0 kW continuous wave CO2 laser were analyzed by X-ray diffractometer and laser cofocused SEM, and its hardness change was measured by Vickers. The results revealed that the modified surface layer consists of a melted zone and a heat affected zone, the microstructure in the melted zone is considerably finer with correspondingly higher hardness. The tribological properties of the alloy were investigated in as-cast state and after laser treatment under a load range of 20~320 N and a sliding velocity of 0.785 m/s on a tester with a pin-on-disc configuration. The results show that there was no obvious difference in their friction factors, but the laser surface treated alloy exhibited better wear resistance due to finer microstructure and higher hardness. The morphology analysis of the worn surfaces by SEM showed that their wear mechanism is basically the same, in the light wear stage the dominant are the abrasive and peeling wear, and in the serious wear stage are wear due to heat softening and melting of the surface.