A thermomechanical process to make iron aluminide (FeAl) sheet

An innovative combination of roll compaction, and thermomechanical processing allowed manufacture of FeAl alloy intermetallic sheets with 24 wt.% Al content. Green sheets of FeAl were obtained by roll compaction of water atomized FeAl powder with a polymeric binder. Roll compacted green sheets were de-bindered and partially sintered prior to cold rolling through tungsten carbide rolls. Cold rolling decreased the thickness, reduced the level of porosity and work-hardened the sheets. Several intermediate annealings at or above 1100°C were found to be necessary to relieve the work hardening stresses prior to rolling the sheets to a final thickness of 0.20 mm. The annealing temperatures were chosen to be at or above 1100°C to allow concurrent sintering of FeAl necessary for the densification of FeAl sheets. Thermomechanical processing of cold rolled sheets allowed commercial manufacture of FeAl intermetallic sheets without the necessity of hot rolling of a cast FeAl ingot. Fully dense sheets possess fine grain microstructure with an average grain size of 20 /xm. The electrical resistivities of FeAl sheets can be varied from 140 to 155 μΩ cm-1, and the high resistivities make them ideally suited for resistive heating applications. Mechanical properties of FeAl sheets are comparable to the properties of hot extruded FeAl alloys.