THE SURFACE CHARACTER AND SUBSTRUCTURE OF ALUMINUM-ALLOYS BY LASER-MELTING TREATMENT

A series of laser melted samples of Al-Si alloys with various Si conte nts were produced using a 2 kW CO2 laser. The surface characteristics of these laser-treated samples, their microstructures and their substr uctures were investigated. Experimental results showed that hardened z ones 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-li ke; and that the proportion of silicon in the cc-Al was much more than the saturation content of silicon in the aluminium alloys. After soli dification, 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 redu ced after laser melting. (C) 1997 Elsevier Science S.A.