| In this paper, the surface diffusion permeated aluminum of AZ91D magnesium alloy is realized by means of the solid thermal diffusion treatment at different diffusion time and diffusion temperature. The microstructure morphology and the phase composition of the aluminized coatings are analyzed by using OM, EPMA and XRD.The micro-hardness and the corrosion resistance of diffusion aluminizing sample are analyzed combining with optimal parameters, the main conclusions are the followings:1. AZ91D magnesium alloy is treated by aluminizing diffusion for 8 ~ 12h at 430℃~ 440℃. The aluminized coating is formed on its surface. the optimal parameters of diffusion aluminizing process of permanent mold casting and semi-solid formed AZ91D magnesium alloy and the AZ91D magnesium alloy after surface mechanical attrition treatment are at 430℃for 12h,430℃for 8h or 440℃for 8h.2. At appropriate diffusion temperature conditions, the appropriately prolongation of diffusion time befit the increase in the thickness of diffusion coating.3. The aluminized coating is mainly composed of Mg17Al12, Al3Mg2 and a small amount ofα-Mg.4. Surface mechanical attrition treatment has little effect on process parameters of the AZ91D magnesium alloy surface diffusion permeated aluminum.5. After diffusion aluminizing, the micro-hardness of the surface coating of AZ91D magnesium alloy is up to HV120-180 compared with which the micro-hardness of the substrate is HV60-80. Because the surface hardness of the material is increased, it is helpful to improve the wear resistance of the materials, thereby improving the applications of magnesium alloys range.6. In 3.5 wt % NaCl aqueous solution, permanent mold casting and semi-solid forming AZ91D magnesium alloy are treated by diffusion aluminizing, the corrosion potential of them is improved approximately 100mV, the corrosion current of them is decreased about an order of magnitude, thus improving the corrosion resistance of magnesium alloys. |
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