A 5 KW CO 2 laser has been used to modify the surface microstructure of Al-Mg-Si aluminum alloy with pure Ni and Ni-Cr-B-Si powders. The experimental results indicate that a porosity-free zone can be generated after laser surface alloying (LSA). The Al 3 Ni particles were only observed in the LSA Ni sample. In the LSA Ni-Cr-B-Si sample, there are three regions indicated as surface region in the melt zone (region A), bottom region in the melt zone (region B), and amorphous phase in bottom region (region C) from the top to the bottom. In the region A, the Al 3 Ni particles are present and the Al 3 Ni 2 particles distributed in the region B. The partial Al-Ni-Cr amorphous structures are dispersed in the region C. And, the AlNi and Al 8 Cr 5 structures were observed in the interface of region B and C. The hardness of the LSA NiCr-B-Si sample is sharply increased than Al-matrix and Ni specimen, specifically the amorphous structure in region C is about 18 times higher than the Al-matrix.

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The microstructure and wear resistance of a laser surface alloyed Al-Mg-Si with Co alloy powder were investigated. The experimental results indicate that a porosity-free zone can be generated but some cracks appear after laser surface alloying (LSA). In this investigation, two regions, A (surface region) and B (bottom region), are observed in the pool. Al 9 Co 2 particles with a network structure are present in region A and block-like Al 13 Co 4 particles are distributed in region B. The hardness of the LSA specimens is three to nine times higher than that of the Almatrix. The high hardness of LSA specimens cause them to exhibit excellent sliding wear performance so they have a lower friction coefficient and wear rate. Notably, the critical temperature of the sliding wear resistance of the LSA specimen exceeds that of the Al-matrix by approximately 50 K.