中文摘要：

采用激光熔覆Al-Si/Al_2O_3粉体来对Mg-Nd-Zn-Zr镁稀土合金进行表面改性,并对熔覆层的形貌、组织、相组成及性能进行了表征。X射线衍射（XRD）分析和扫描电镜（SEM）观察显示,熔覆层主要由α-Mg、Mg_2Si、Mg_（12）Nd以及Al_（3.21）Si_（0.47）或Mg_（17）Al_（12）几种相组成,而Al_2O_3则大部分聚集在熔覆层和基体之间的界面处。截面硬度测试显示,熔覆层的显微硬度最高值在3090至4750 MPa之间,是基体硬度（550 MPa）的5~8倍以上,这主要归结为熔覆层内晶粒细化、固溶强化、增强相的形成以及氧化物颗粒的弥散强化作用。在3.5%（质量分数）NaCl水溶液中的电化学测试显示,激光熔覆后的镁合金腐蚀电位上升,腐蚀电流密度可由基体的1.683×10~（-4）A/cm~2下降至激光熔覆后的0.843×10~（-5）A/cm~2,表明激光熔覆后样品表面的腐蚀性能也得到显著提高。

英文摘要：

Laser cladding of Al-Si/Al_2O_3 powders were applied on Mg-Nd-Zn-Zr magnesium rare earth alloy,and the microstructure,phase components and properties of the clad layers were characterized. X-ray diffraction（XRD） analyses and scanning electron microscope（SEM） observations show that the clad layer is mainly consisted of α-Mg,Mg2 Si,Mg12 Nd and Al_（3.21）Si_（0.47） or Mg_（17）Al_（12） phases. However,Al_2O_3 particles agglomerate at the bottom of the clad layer close to the melt-substrate interface. The cross section microhardness tests reveal that the maximum hardness of the clad layer ranges from 3090 to 4750 MPa,about 5 to 8 times higher than that of the Mg-Nd-Zn-Zr alloy（550 MPa） substrate. Such an increased hardness is attributed to the grain refinement,the solution strengthening,the formation of hardening phases and the dispersion strengthening from oxide particles. According to the potentiodynamic polarization measurements carried out in the 3.5 wt% Na Cl water solution,the corrosion potential of the alloy increases after laser cladding,while the corrosion current density decreases from1.683×10~（-4）（A/cm~2） for the Mg alloy substrate to 0.843×10~（-5）（A/cm~2） for the laser clad alloy. Therefore,the corrosion resistance of Mg-Nd-Zn-Zr alloy can be also significantly improved by laser cladding with Al-Si/Al_2O_3 powders.