High-strength Fe-2OMn-Al-C-based alloys with low density

Mechanical properties of Fe-2OMn-(10-14)Al-(0-1.8)C (mass%) quaternary and Fe-2OMn-(10-14)Al- (0.75-1.8)C-5Cr (mass%) quinary alloys were investigated by hardness, cold-workability and tensile tests at room temperature. The γ(fcc) alloys in both quaternary and quinary systems with a low density of less than 7.Og/cm³ showed an excellent ductility and their hardness and tensile strength increased with increasing Al and C contents. The γ+α(bcc) duplex alloys also exhibited a high tensile strength by controlling the α volume fraction. TEM observation confirmed that high hardness and tensile strength of the alloys with high Al and C contents are caused by the precipitation of nano-size κ-carbide with perovskite structure during cooling from the annealing temperature. Fe-2OMn-11AI-1.8C-5Cr alloy with a density of 6.51 g/cm³ showed a high specific strength of more than 180 MPa cm³/g with a good tensile elongation of 40%. The present Fe- 2OMn-Al-C(-5Cr) alloys showed a higher specific strength than conventional steels.