Effect of Mn element on microstructure and mechanical properties of bulk nanocrystalline Fe3Al based materials prepared by aluminothermic reaction

Bulk nanocrystalline Fe3Al based materials containing 5, 10 and 15 wt.% Mn element were prepared by aluminothermic reaction. The materials were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM) and electron probe microanalyzer (EPMA). Compressive behavior and hardness of the materials were investigated. It shows that all of the three materials consist of nanocrystalline matrix and a little contamination phases. The nanocrystalline matrix phases are solid solutions composed of Fe, Al and Mn elements. The nanocrystalline matrix phases of the materials containing 5 and 10 wt.% Mn have disordered solid solution of bcc crystal structure and that of the material containing 15 wt.% Mn has ordered DO3 crystal structure. Average grain size of the nanocrystalline matrix phases dramatically decreases at first and then increases a little with content of Mn and that of the material containing 10 wt.% Mn is the smallest. The material containing 10 wt.% Mn does not fracture in the compression and exhibits good plasticity, the yield strength and hardness increases at first and then decreases with content of Mn and those of the material containing 10 wt.% Mn are the highest.