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

Abstract In this work, a quaternary elemental Fe–Mn–Al–C powder compact was sintered at various temperatures (≤700 °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 ~550 °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 °C, and it disappeared completely when the temperature reached 700 °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 °C. Afterwards, the porosities increased steadily with the increase of the sintering temperature. The total and open porosity of the 700 °C-sintered compacts significantly increased by ~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.