Observation of exothermic reaction during laser-assisted iron oxide coating on aluminum alloy

Abstract Aluminum and Fe 3 O 4 reacts readily in what is known as thermite reaction to produce large amount of heat. Attempts were made to coat Fe-oxide on A319 cast aluminum alloy employing a high power laser to exploit this reaction. High-speed, high-resolution infrared thermography was employed to study the thermal conditions during the laser treatment. Parallel experiment using a less exothermic oxide (FeO) and the same substrate further emphasized development of higher temperature during highly exothermic reaction. The cooling rate calculated via both steady state and non-steady state relations were one order of magnitude different, which was supported by microstructural observations. Transmission electron microscopy revealed formation of aluminides as a result of reaction between iron oxide and aluminum alloys.