Effect of heat treatment on the microstructure of an Fe-40Al-0.7C-0.5B alloy

The effect of heat treatment on the microstructure of an extruded Fe-40Al-0.7C-0.5B (at.%) alloy was investigated. Four types of precipitates were found to be present in the B2 matrix in the as-extruded condition. These were Fe3AlC05 with the perovskite structure, Fe2B, a tetragonal boride with the CuAl2 structure, graphite (free carbon), and a new tetragonal phase (v) that is likely coherent with the matrix. In addition, fringe contrast was observed, both in the matrix and within the precipitates and is thought to arise from the presence of stacking faults. The stability of these precipitates and the faults following various heat treatments was determined.