Production and characterization of porous iron aluminide materials by combustion synthesis

In this study, the production of iron aluminide parts containing controlled amounts and sizes of pores through combustion synthesis starting from Fe and Al elemental powders using powder metallurgy techniques has been investigated. In this context, two different approaches have been studied for pore formation. In the first method, the effect of cold pressing pressure was examined in the production of the raw part consisting of Fe and Al powders. For this purpose, cold pressing pressures of 25, 50, 100, 200, 300, and 400 MPa were applied. With this application, it was ensured that the porosity of the raw part was controlled, and consequently, the porosity of the FeAl part to be formed after combustion synthesis was controlled. In the second method, the space holder method was applied using urea particles with different size ranges to create microspaces inside the material. Urea particles with sizes ranging from 150-300, 300-500, and 500-800 microns were used with Fe and Al powders in ratios of 20%, 40%, and 60%. In both methods, the combustion synthesis of the samples took place at two different temperatures, namely 750°C and 1050°C. As a result of the experiments, it was observed that porosity decreased with increasing pressure. It was observed that the strength values decreased with increasing urea size in samples produced using the template method. Samples produced with the VCS (volume combustion synthesis) process applied at 1050°C exhibited higher strength values compared to those produced at 750°C. Numerical relationships between pore size and ratio and strength were investigated; for this purpose, Gibson-Ashby, Bal'shin, Hall Petch, and Bhattacharjee equations were used.