Microstructure and hardness characterization of mechanically alloyed Fe–C elemental powder mixture

Mechanical alloying of iron–carbon (Fe–C) mixture powders was performed at various milling duration (2, 4, 6 and 8 h) and with different carbon content (1, 2, 3 and 4 wt.%). The milled powders were consolidated by cold pressing at 400 MPa and sintering at 1150 °C. The sintered samples were examined under an optical microscope and a scanning electron microscope for microstructure evolution, and measured for density, Rockwell F and Vickers hardness. This technique has produced Fe–C alloy with pearlite structure at lower temperature compared to conventional technique. With increasing milling time, more pearlite was formed which improved the hardness. Milling beyond 6 h, however, decreased the hardness due to the presence of higher porosity because hardened powder hindered densification. Similarly, the hardness value reached the maximum at 2% carbon before decreasing at 3% and 4% carbon levels due to the residual graphite.