Paper present a thermal analysis of laser heating and remelting of EN AC-48000 (EN AC-AlSi12CuNiMg) cast alloy used mainly for
casting pistons of internal combustion engines. Laser optics were arranged such that the impingement spot size on the material was a
circular with beam radius rb changes from 7 to 1500 m. The laser surface remelting was performed under argon flow. The resulting
temperature distribution, cooling rate distribution, temperature gradients and the depth of remelting are related to the laser power density
and scanning velocity. The formation of microstructure during solidification after laser surface remelting of tested alloy was explained.
Laser treatment of alloy tests were perform by changing the three parameters: the power of the laser beam, radius and crystallization rate.
The laser surface remelting needs the selection such selection of the parameters, which leads to a significant disintegration of the structure.
This method is able to increase surface hardness, for example in layered castings used for pistons in automotive engines.
This article presents a study of the crystallization and microstructure of the AlSi9 alloy (EN AC-AlSi9) used for the alfin processing of iron ring supports in castings of silumin pistons. Alfin processing in brief is based on submerging an iron casting in an Al-Si bath, maintaining it there for a defined time period, placing it in a chill mould casting machine and immersing it in the alloy. This technology is used for iron ring supports in the pistons of internal combustion engines, among others. Thermal analysis shows that when the AlSi9 alloy contains a minimal content of iron, nucleation and increase in the triple (Al)+Fe+(Si) eutectic containing the -Al8Fe2Si phase takes place at the end of the crystallization of the double (Al)+(Si) eutectic. Due to the morphology of the ”Chinese script” the -Al8Fe2Si phase is beneficial and does not reduce the alloy’s brittleness. After approx. 5 hours of alfin processing, the -Al5FeSi phase crystallizes as a component of the +Al5FeSi+(Si) eutectic. Its disadvantageous morphology is ”platelike” with sharp corners, and in a microsection of the surface, ”needles” with pointed corners are visible, with increases the fragility of the AlSi9 alloys.