Laser (Nd:YAG) cladding of AZ91D magnesium alloys with Al + Si + Al2O3

The laser surface cladding of AZ91D magnesium alloy with Al + Si + Al2O3 powders (in the wt.% ratio of 7:1:2) was investigated. Laser processing was carried out with a 5 kW Nd:YAG laser. The microstructure and phase analyses of the surface cladding layer were carried out; furthermore, the morphology of the cladding zone, volume fraction and distribution of the Si and Al2O3 particles in the laser surface cladding layer were also investigated. The average microhardness of the surface layer was measured in detail as a function of laser parameters. Microhardness of the surface layer was significantly improved to as high as 210 HV0.05 as compared to 60–70 HV0.05 of the AZ91D substrate, and the average microhardness of the cladding layer of the composite surfaced specimen decreases with increasing of laser power. However, the rate of decrease is faster at lower power. Though the average microhardness of the surface cladding layer remains constant, there is a little fluctuation in the reading in some regions possibly, because of the random distribution of hard particles in the cladding layer. Finally, the proper processing parameter ranges for formation of a homogeneous microstructure and enhancement of microhardness for laser surface cladding of AZ91D with Al + Si + Al2O3 were established.