Intermetallic compound formation during laser alloying of aluminum alloys with metals

This article studies the process of laser alloying of aluminum and alloy AL25 with metals: nickel, chromium, niobium, in a melting regime. Choice of metals for the study is made according to the criterion of efficiency of melt zone filling under laser treatment. Theoretical analysis of possible intermetallic phases within Al-Ni, Al-Cr, Al-Nb systems is performed, including physical parameters and crystallographic characteristics. Experimental studies by methods of metallography and X-ray diffraction analysis allows establishment of the spectrum of phases formed during alloying of aluminum from powders of these elements. They include both aluminum-rich intermetallics, and chemical compounds enriched with alloying metal. Alloying with niobium disilicide is also investigated to reveal differences in mechanisms of introducing chemical compounds into a laser-affected zone. On alloying with NbSi2 particles get into the melt zone directly from the powder (a mechanism of particle "flight"), and when alloying with pure metal intermetallic formation of occurs in situ during crystallization. On the basis of calculating the change in lattice spacing of aluminum the concentration of alloying metals within supersaturated solid solution is estimated. The increase in microhardness of alloying zones due to solid solution hardening and dispersion strengthening by intermetallic particles is established.