Characteristics and corrosion behaviour of the overlapped area in laser surface melted and alloyed aluminum alloys

摘要

Aluminium alloys treated by laser melting and alloying are known to have improved corrosion resistance due to modification of the surface passive film and more uniform dispersion of second phase precipitates in the laser processed region. In large area applications, overlapping of individual tracks corresponding to the width of the laser beam is often applied. This involves the melting and reheating of a portion adjacent to the previous track. This has been found to cause some problems at the overlaps between tracks with coarsening and micro-segregation. When laser alloying is used to form amorphous surfaces, crystalline phases have been found to appear in the heat-affected zone at the border of the neighbouring laser irradiation tracks. Substantial detrimental effects on the corrosion behaviour of the overlapped areas are observed in these cases. It is therefore necessary to study the behaviour of this overlapped area in order todetermine a strategy for large area laser surface treatment.