Structural and magnetic properties of Fe-Al-C and Fe-Mn-Al-C alloys

The remanence and coercivity of Fe-Al-C and Fe-Mn-Al-C alloys have been measured and studied as a function of ageing at 623 K. The resulting formation and growth of carbide precipitates of Fe sub(3)AlC and Mn sub(3)AlC in the same samples have been investigated by transmission and scanning electron microscope techniques. The addition of Manganese to the Fe-Al-C alloy is shown to be severely deleterious to the magnetic properties of the resulting quaternary alloy; however, simultaneously, the electron diffraction and microscopic studies demonstrate that the structural order of the carbide precipitates is considerably improved. It is concluded that this observed decline in the magnetic properties of this alloy system is related to the formation of Mn sub(3)AlC in preference to Fe sub(3)AlC carbide precipitates.