Study On Laser Cladding Technology And Microstructure Properties Of Magnesium Alloys

As a new surface modification technology,laser cladding technology cansignificantly improve the surface properties of the substrate.In this paper,the laser cladding technology is applied to the surface modification of magnesium alloys,and the laser cladding is carried out by presetting Al-Si and rare earth oxide powders,to explore the influence of laser scanning power,laser scanning speed and rare earth oxide on the structure and properties of the modified layer.The modified layer without defects can be successfully prepared by laser melting of magnesium alloy.The bonding area between the modified layer and the matrix is consisted of columnar crystal structure,and the internal area is consisted of isometric crystal structure.Fine Al₁₂Mg₁₇ phases is observed to distribute at the long?-Mg grain boundary or in the grain.The hardness,wear resistance and corrosion resistance of the modified layer are improved lightly.The optimal parameters of magnesium alloys by presetting silicon powder for laser cladding process as follows:preset cladding layer thickness is 250?m,laser scanning power is 145 W,laser scanning speed is 200 mm/min,modified layer thickness is 200?m.Large amounts of diffuse distribution of new phases Mg₂Si and solid solution aging precipitates tiny Al₁₂Mg₁₇ phases are observed in the modified layer,which elaborated the organization,improved the performance.The hardness,wear resistance and corrosion resistance of the modified layer has been increased significantly:the hardness is increased by 3.3 times,the volume wear is only 2/3 of the matrix's,and the self-corrosion current density reduces by an order of magnitude.The laser cladding treatment of magnesium alloy by presetting Al-Si powder is carried out successfully.The optimal process parameters are as follows:the presetting cladding layer thickness is 250?m,the laser power is 165 W,the scanning speed is 200mm/min,and the thickness of modified layer is up to 1000?m.The modified layer structure is mainly consisted of a large number of dispersed fine acicular Mg₂Si phases,fine Al₁₂Mg₁₇ phases,dendritic?-Mg phases and(?-Mg+Al₁₂Mg₁₇)eutectic structure.The hardness,wear resistance and corrosion resistance of the modified layer is significantly improved compared with the matrix:the maximum hardness is increased by 2.2 times,the volume wear is 2/3 of the matrix's,and the self-corrosion current density is reduced by 186.94?A/cm²,reduced by an order of magnitude.When Y₂O₃content is 2 wt.%,the rare earth oxide has the best effect on the improvement of the modified layer,and the modified layer organization is obviously refined and homogenized,the regional differences in hardness decreases,the wear resistance is improved further,and volume loss is only 1/2 of matrix,and the corrosion resistance is also significantly improved,compared with the matrix,the corrosion potential is 72 m V,the corrosion current density decreases by 197.29?A/cm²,reduces by two orders of magnitude.