The surface character and substructure of aluminium alloys by laser-melting treatment

A series of laser melted samples of Al-Si alloys with various Si contents were produced using a 2 kW CO2laser. The surface characteristics of these laser-treated samples, their microstructures and their substructures were investigated. Experimental results showed that hardened zones of specific area and penetration depth on the sample surface can be obtained with a particular laser power. It was found that the laser treatment refined the aluminium alloy grains; that silicon crystal in eutectic was altered morphologically from lath-like into coralline-like; and that the proportion of silicon in the α-Al was much more than the saturation content of silicon in the aluminium alloys. After solidification, the super-saturated silicon precipitated out in the 〈110〉 direction and in very small rod-like form. X-ray diffraction analysis of the samples illustrated that the lattice parameters of Al were reduced after laser melting.