The influence of sintering temperature and pressure on microstructure and mechanical properties of carbonyl iron powder materials fabricated by electric current activated sintering

In this paper, we studied the microstructure and mechanical properties of carbonyl iron powder materials fabricated by electric current activated sintering at temperatures of 650-800 °C under pressures of 20-50 MPa. All sintered samples consist of fine ferrite and spheroidized particles. The average density, average hardness and bending strength increase with an increase in either temperature or pressure. In particular, non-uniform distributions of density and hardness within the sintered samples were discussed, and a three-zone model was also proposed for simulation. Experimental and simulation results reveal that (1) the temperature distribution is homogeneous during sintering. (2) the inhomogeneous axial stress distribution, which is caused by a unidirectional load, is responsible for a poor sintering uniformity. In order to obtain homogenous sintering, more attention should be paid to axial stress distribution rather than to temperature distribution in electric current activated sintering of high thermal conductivity conductive powders like carbonyl iron powders.