Combined Strengthened Layer of Al/TiB₂ on Magnesium Alloy Surface by Laser Cladding and Its Properties

A pulsed Nd: YAG laser was employed to strengthen the surface of Mg-Gd magnesium alloy with raw material of Al-TiB2 composite micro powders (Al powders as the binders) by cladding. The effects of TiB2 content on the microstructure and abrasive resistance of the strengthened layer, the compatibility between the strengthened layer and substrate were investigated. The results show that the in situ reaction generated between Al from the strengthened layer and elements of Gd, Y in Mg alloy substrate, and the intermetallic compounds such as Al2Gd and Al2Y were in-situ generated. Meanwhile, it was not found the decomposition of the strengthening phase TiB2. The compatibility among matrix, intermetallic compounds by in-situ synthesis and introduced strengthening phase TiB2 was fairly excellent. However, their characteristics of distribution and structures were different significantly. The strengthened layer had fine and uniform microstructure when the TiB2 content in composite powders was less than 70wt%. The overall microhardness of the strengthened layer increased with increasing of TiB2 content and improved up to 4-6 times compared with the substrate. Furthermore, the wear resistance improved dramatically.