Estimation of kinetic parameters for combustion synthesis of FeAl intermetallic compound by dipping experiment of Fe wire into Al melt

Abstract

The formation reaction rate of Fe-Al intermetallic compounds was examined by dipping experiment of Fe wire into Al melt in the temperature range between 973 K and 1373 K, to determine the kinetic parameters of combustion synthesis of FeAl. A piece of Fe wire and Al powder were put into an alumina crucible, and vacuum-sealed in a quartz tube. The tube was held in an electric furnace to promote the compound formation reaction. A microstructure observation and SEM-EDX analysis of the dipped Fe wire were performed. It was found that the compound formation reaction occurred at the interface between the molten Al and the Fe wire, and a cylindrical Fe2AIs layer was formed in the wire. The thickness of the formed layer depended on the holding time and the dipping temperature. The reaction process has been similar to the combustion synthesis of FeAl intermetallic compound. Therefore, the kinetic parameters could be determined by the dipping experiment. The experimental data have been analyzed using a cylindrical model which took into account the diffusion process of Al in the Fe2AIs compound layer and chemical reaction process on the interface between Fe2Al5 and Fe. The diffusion coefficient, DAl and the reaction rate constant, Jt0 were estimated. The curves were calculated by using the obtained kinetic parameters and were in satisfactory agreement with the experimental values. log10D Al/m2.s-1 = -1887/T-8.369 log 10kc/mol-m-2.s-1 = -3177/T+1.839 ©2010 The Japan Institute of Metals.