Preparation And Performance Study Of Al Alloying On AZ31 Mg Alloy

Magnesium as the lightest metal structure of industrial materials, magnesium and its alloys are widely used because of their low densities, high specific strength, strong electromagnetic shielding and antiradiation, easy cutting and recycling. However, the poor anticorrosion performance of magnesium alloys restricts their expanded appli- cations. Therefore, it is great significant to enhance the corrosion resistance and wear of Mg alloys by using the surface modification technology. In this study, AZ31 magnesium alloy was studied with the aluminum alloy surface through the prepulsed tungsten inert gas arc alloying (GTA), laser alloying technology to improve the surface properties of magnesium alloy. In order to improve the quality of alloyed layer, the laser processing on the surface of magnesium alloy were studied with Al+La₂O₃ powders.The formation mechanism of the alloying layer was analyzed. Under the optimi- zed processing parameters(I=80 A,L=15 L/min and P=1.2 KW,v=500 mm/min), the macrosurface of melting layer was uniform and less defects such as porosities, slag and craters. The study of GTA alloying showed that the depth of alloyed layers increase with increasing the welding current or protective gas flow rate; as for the laser alloying, the depth and width decrease with increasing laser translation speed. Within the alloy layer uniform refined grain, and several different microstructure in the alloy layer, such as columnar, equiaxed, snowflake and network structure.Compared with the hardness of AZ31 alloy (approximately 50 HV), the alloyed layer microhardness significantly increased. The hardness of GTA surface melting layer reinforced was approximately 200 HV. Al alloy layer of the laser micro hardness of about 150 HV. Alloyed layer micro hardness increase is mainly fine grains,Al content increases and a mass of Mg₁₇Al₁₂,Mg₂Al₃ phase distribution in melting layer. Al +5wt%La₂O₃ laser alloyed layer micro hardness and wear were slightly lower than without adding rare earth elements.The potentiodynamic polarization results confirm that the corrosion resistance of alloying layer is better than the magnesium alloy AZ31 matrix. The main reason is the grain size in melting layer was obviously refined, and the occurrence of network- intensive second phase, Al elements increasing.