Evolution of aluminum particle-involved phase transformation and pore structure in an elemental Fe-Mn-Al-C powder compact during vacuum sintering

In this work, a quaternary elemental Fe-Mn-Al-C powder compact was sintered at various temperatures (<= 700 degrees C) in vacuum, in order to clarify Al particle-involved pore evolution. This is an essential part of work to thoroughly understand the pore-forming process of the porous high-Mn and high-Al FeMnAl steels. The phase compositions, porosities and microstructure of the sintered samples were comprehensively investigated. It was found that phase transformations started at similar to 550 degrees C, where brand-new FeAl, Fe2Al5, Al8Mn5 and Al11Mn4 phases were generated depending on sintering temperature. Residual elemental Al particles still existed after sintering at 660 degrees C, and it disappeared completely when the temperature reached 700 degrees C. Al particle-involved diffusion/reactions played a key role in the increase of porosities, especially open porosity. No change in porosities occurred if the sintering temperature was <= 500 degrees C. Afterwards, the porosities increased steadily with the increase of the sintering temperature. The total and open porosity of the 700 degrees C-sintered compacts significantly increased by similar to 144% and 235% with respect to the green compacts. It was also found that isothermal holding time had limited impact on phase transitions and pore evolution.