Selective laser surface melting of a magnesium-aluminium alloy

A High Power Diode Laser (HPDL) has been used to selectively melt one of the phases present in the microstructure of the surface of a magnesium–aluminium alloy (AZ91D). The intermetallic precipitates were molten and they dissolved some of the surrounding Mg. After laser treatment, a new microstructure with modified mechanical properties is obtained on the surface of the Mg-alloy. This methodology can be easily applied to many other systems.

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► For the first time, a laser processing technique is proposed in which only one of the phases present in the microstructure of an alloy is molten.
► After laser treatment of the AZ91D Mg-alloy, the intermetallic precipitates formed were diluted while the Mg-matrix was unaffected.
► Nanoindentation evidences that the brittle phase is diluted and that the Mg-matrix was not softened.
► The new laser process allows modifying the properties of one phase in an alloy without modifying the others.
► Shape and size of the samples are not affected by this laser treatment.