Study On Microstructure And Property Of Infiltration Layer In Magnesium Alloy Surface

Magnesium is the lightest metal structural material, has a"green metal"reputation. It is a new material and widely used in the aerospace, military equipment, vehicles and communications. The development and application of magnesium alloys has become the world competition focus in technology and industry. However their commercial application has been limited because of poor corrosion resistance.In this thesis, a technique has been studied by infiltrating on casting process to AZ91D magnesium alloy respectively, which is the most widely used magnesium alloy. A melting layer was formed on the surface of alloys in casting process by infiltration, and that improved the corrosion resistance. This technique can fundamentally change the physical and chemical properties of magnesium alloys, and the existing surface modification process are simplified, importantly, it is low-cost, green and environmental protection.The macro morphology, thickness, microstructure and properties of infiltration layer were analyzed by digital, scanning electron microscopy, spectroscopy and erosion etc and so on. The results show an uniform and dense infiltration layer on magnesium alloy surface was obtained in sync with the die-casting process by using surface infiltration technology, and the infiltration layer is bonding withα-Mg matrix. The continuity and thickness of infiltration layer increases gradually, with increasing the thickness of coat. However, the effect of coat thickness on micro-area composition is small. The element content in infiltration layer decreases gradually from alloy surface to interior. All infiltration layers protect the base alloy, and improve the corrosion resistance of matrix. The infiltration layer is more dense, continuous and thicker in die-casting than other.Furthermore, this article also discussed the composition of modified power melt layer on the microstructure morphology and corrosion resistance. A rule was found that Al element is easier in infiltration process into the matrix than Zn. However, Zn element plays an important role to improve the corrosion resistance. This technology will obtain a good prospect for industrial application because the process is simple, low labor costs and green.