Auger microscopy of laser induced Fe oxide/Al reaction composite coating

A laser based technique was used to synthesize an Fe₃O ₄/Al composite coating on an Al alloy substrate. The material was analysed using scanning Auger microanalysis. The laser treatment resulted in extensive refinement of the microstructure, and Fe oxide particles were strongly bonded to the matrix owing to reaction induced wetting by liquid Al. The spectroscopy data indicated the formation of several possible stoichiometric compounds as a result of the chemical reaction between Fe₃O ₄ and the alloy. Iron produced as an intermediate product of the aluminothermic reaction between Fe₃O₄ and Al further reacted with Al (and Si) to form Fe and (Fe, Si) aluminides. The composition across the interface region between the reaction product and the matrix was found to vary gradually, resulting in good bonding. Often, the interfacial region was also found to consist of aluminides of varying composition and stoichiometry. Owing to these features, the coating exhibited high toughness, as characterised by dimpled fracture produced in vacuo.