A two-stage approach of manufacturing FeAl40 iron aluminides by self-propagating synthesis and pressureless sintering

Abstract

A two-stage sintering process was successfully used to sinter FeAl to densification levels of just above 95% at a temperature of 1300°C. In the first stage, mixed iron and aluminium powders were synthesised at 750°C via self-propagating high-temperature synthesis (SHS) to form brittle and porous Fe₂Al₅. Then the pellets were crushed and milled to various sizes and mixed with iron powders in the nominal composition of FeAl40 and pressurelessly sintered at a higher temperature to obtain a higher densification by taking advantage of the less violent exothermic reaction of Fe₂Al₅ and Fe. The intermediate and end products in SHS and sintering were characterised by SEM/EDX and XRD. The porosity level of the final FeAl40 product was controlled by the heating rate and powder size, which was also strongly influenced by the temperature, holding time and the ratio of the two powders.