EVOLUTION OF MICROSTRUCTURE IN LASER-SURFACE ALLOYING OF ALUMINUM WITH NICKEL

Surface alloying of a commercially pure aluminium with nickel was carried out using a pulsed Nd-YAG laser. The distribution of the alloying element (nickel) in the alloyed layer was found to be highly non-uniform irrespective of the depth of alloying. The microstructure of the alloyed layer was found to consist mainly of a cellular solid solution phase of nickel in aluminium (alpha-Al), a lamellar eutectic of alpha-Al and Al3Ni phases, and primary Al3Ni dendrites. The microstructure of the alloyed layer is explained in terms of inhomogeneity of the nickel distribution. The effects on the microstructure of inherent rapid solidification under the conditions of laser surface alloying were also examined.