Effect of high temperature deformation and different cooling rates on microstructure and mechanical properties of Fe-Al alloys

Although iron and aluminum alloy forms several intermetallic phases, the iron-rich iron aluminide compositions appear to have the most potential for structural applications. A 100 kg of steel containing 0.88 wt.% C, 1.88 wt.% Mn, 0.44 wt.% Si, 0.081 wt.% Cu, 6.9 wt.% Al and 2.00 wt.% Cr was prepared using vacuum induction furnace. The dilatation was carried out to determine the critical phase transformation. Hot forging process was carried out after heating at 1200 °C with a high reduction ratio in cross-section 85%. The transformation temperatures Ac1 and Ac3 are 897.7 and 964.2 °C respectively. The density of Fe-Al after hot forging was measured using Archimedes method and it is approximately 6.804 gm/cm3. The as-cast grain size is more than 3000 μm. Hot forging process refines the grain size down to 423 μm. The non-metallic inclusions (after severe hot forging) are very fine and well distributed. The material is so sensitive to the final cooling rate after hot forging. After introducing different cooling rates, the material exhibits different tensile characteristics, of sand cooling (slow cooling) the tensile strength is 729.5 MPa and elongation is 3.4%. After air cooling (moderate cooling rate), the strength is 62.1 MPa and elongation is 2.9% while of water quenching (drastic cooling), the strength is 559.3 MPa and the elongation is 1.4%.