中文摘要：

在快速水冷的条件下采用CO2连续激光器对ZM61镁合金表面进行了激光熔凝处理。利用光学显微镜、扫描电子显微镜（SEM）、X射线衍射仪（XRD）分析熔凝层的微观组织及其物相成分信息，采用显微维氏硬度计、摩擦磨损试验机、电化学工作站分别测试了熔凝层的显微硬度、耐磨性能和耐蚀性能。研究结果表明：在水冷条件下，经激光快速扫描得到的熔凝层组织主要呈规则分布的柱状树枝晶，有明显的细晶强化效果；基材的物相主要由α-Mg和枝晶间网状的及枝晶内颗粒状的金属间化合物Mg7Zn3二元相组成，激光熔凝处理后，Mg7Zn3发生部分分解生成Mg7Zn3；熔凝层的显微硬度相对于基材有了明显的提高，硬度峰值达120．4HV，接近于基材的两倍；激光熔凝试样的磨损量是基材的59．8％，耐磨性得到改善；熔凝层的腐蚀电位（-1．4455V）低于基材的腐蚀电位（-1．4262v），耐蚀性能略有降低。

英文摘要：

Laser surface melting on ZM61 magnesium alloy is carried out by a continuous CO2 laser under a rapid water-cooling condition. The microstructure and phase constitution of the melted layer are analyzed by optical microscopy, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The microhardness, and wear resistance and corrosion resistance of the melted layer are tested by Vickers microhardness tester, scratch testing machine and electrochemical workstation, respectively. The results show that the melted layer consists mainly of regular columnar dendrites with a significant fine-grain strengthening effect in the water-cooling condition. The phase constitution is altered by the laser melting process, that is, the substrate is mainly consisted of α-Mg and the interdendritic network intermetallic compound Mg7 Zn3 while Mg7 Zna phase partially decomposed into Mg2 Zn3 phase during the laser melting process. In comparison to the substrate, the microhardness of the melted layer is enhanced obviously. The peak hardness of the melted layer is 120.4 HV, which is about twice of that of the substrate. The tribilogical property of the melted specimen is improved with a 59.8 % wear mass loss of the substrate. The corrosion resistance of the alloy is slightly decreased with the corrosion potential of the melted layer （- 1. 4455 V） in comparison to that of the as-received alloy （-1. 4262 V）.