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 degrees 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. (C) 2009 Elsevier Ltd. All rights reserved.