Research On Preparing Metallurgy Diffusion Layer On Magnesium Alloy Surface By Electric Arc Spraying Pure Aluminium

As one of the lightest structure materials, magnesium alloy have a wide application prospect in many important areas because of their high specific intensity, high specific rigidity and easy recovering. But the corrosion resistance, wear resistance, strength and hardness of magnesium alloy are all relatively low. So its surface modification research is urgently needed. Prepg preparing metallurgy diffusion layer on magnesium alloy surface is an important surface modification method. It can effectively improve the corrosion resistance and wear resistance, and significantly improve the hardness of magnesium alloy surface.This article uses the arc spraying technology to spray pure Al coating on the surface of die-cast and as-cast AZ91D magnesium alloy. For die-cast AZ91D magnesium alloy, after electric arc spraying pure Al, heat diffusion treated for1h,5h and10h at250℃、300℃、350℃、400℃and437℃, respectively, and then cool to room temperature in the air. For as-cast magnesium alloy, heat diffusion treated for1h at300℃,350℃,400℃and437℃, then cool to room temperature in the furnace. The microstructure and property of diffusion layer were tested by X-ray diffractometry (XRD), scanning electron microscope (SEM), energy diffraction system (EDS), micro hardness tester, electrochemical analyzer and high speed reciprocating friction and wear tester. The following conclusions were obtained:1. The diffusion between AZ91D die-cast magnesium alloy substrate and Al coating did not happen at250℃. But at300℃-350℃, the diffusion layer was β-Mg]7Al12phase. And the thickness of diffusion layer increased with the extension of heat preservation time. The diffusion layer was P-Mg17Al12phase when for1h and5h at400℃, The diffusion layers were β-Mg17Al12phase layer near Al coating and (a-Mg+β-Mg17Al12) composite layer near AZ91D magnesium alloy substrate when for10h at400℃. When the temperature of heat treatment was437℃according to the eutectic temperature of Mg-Al alloy system, for1h, the diffusion layers were γ-Mg2Al3phase layer near Al coating and β-Mg17Al12phase layer near AZ91D die-cast magnesium alloy substrate.2. The hardness, corrosion resistance and wear resistance of Mg-Al metallurgy diffusion layer were greatly improved than AZ91D die-cast magnesium alloy.3. For as-cast magnesium alloy, at300℃-437℃for1h, along with the furnace cooling, the diffusion layers are γ-Mg2Al3phase layer and β-Mg17Al12phase layer. The y-Mg2Al3phase layer was near the Al coating, and β-Mg17Al12 phase layer was near the as-cast magnesium alloy substrate. And the thickness of diffusion layer increased with the increase of heat treatment temperature.4. The fine grain made more interfaces and Mg and Al atoms’transition paths, then the transition speed would increased, so the spread effect was better.