Effects of Mn contents on the microstructure and mechanical properties of the Fe-10Al-xMn-1.0C alloy

The microstructures and mechanical properties of the Fe-10 mass%Al-(5-40)mass%Mn-1.0 mass%C alloys sheet castings have been investigated by using optical microscope (OM), transmission electron microscope (TEM), scanning electron microscope (SEM), experimental model analysis, tensile test and hardness test. Based on the present studies, the macroscopic microstructure of the present alloys are a mixture of austenite (gamma) and ferrite (alpha) duplex phases, and the a phase would decrease with the Mn content increased. In the meantime, according to the examination of TEM, the macroscopic gamma phase is a mixture of the gamma + fine(Fe, Mn)(3)AlCx (kappa) + (Fe, Mn)(3)AlCx (kappa') phases and the macroscopic a phase is a mixture of the D0(3) + coarse(Fe, Mn)(3)AlCx (kappa") phases. The mechanical properties such as the ultimate tensile strength (UTS), yield strength (Y.S.), elongation of these alloys were in the range of 646-887 MPa, 575-824 MPa, and 16.3-29.2%, respectively. The hardness of these alloys were in the range of HRC 31-44. Moreover, the relationship between hardness and ultimate strength is UTS (.)=(.) 20.93HR(C). In addition, the damping ratios and Young's modulus of the present alloys were in the range of 0.0603-0.0417, and 139-165 GPa, respectively. It is noted here that the results have never observed by other research workers in the Fe-Al-Mn-C alloy system.