Influence of the Alloying Elements in Al-Si Alloys on the Laser Remelting Process
R. Sturm, J. Grum and S. Bozic
This paper reports on the treatment of different Al-Si alloys after laser surface remelting through analysis of the changes in microstructure and hardness of a modified surface layer. On as cast samples, laser remelting of the thin surface layer was carried out with different energy inputs into the sample surface. The remelting conditions were varied by application of different laser beam power, different degrees of defocusing and different laser beam travel speeds across the sample surface. With the selected remelting conditions for the thin surface layer a sufficiently high energy input into the surface of individual samples was ensured. It varied between 165 and 477 J/mm2. After solidification of the surface remelted layer a fine-grained microstructure was formed. Such a microstructure was found to increase the hardness of the Al-Si alloys by 20 to 50%. The variation and size of the residual stresses greatly depended on the cooling rates determined by the laser travel speeds.
Keywords: Al-Si alloy, alloying elements, laser surface remelting, CO2 laser, residual stresses, micro-hardness