Effect of carbon on the density, microstructure and hardness of alloys formed by mechanical alloying

• We report steel alloys with several C contents obtained by mechanical alloying.
• Increasing C content affected alloy compressibility and decreased green density.
• Increasing C content increased hardness but decreased ductility of the alloys.
• The maximum theoretical densification was obtained at 500 MPa and 0.5% C.

This work aimed to produce iron-based alloys containing resistant microstructures to improve the mechanical properties of the resulting alloy. The effects of both carbon content and compaction pressure on the microstructure, density and hardness of the alloys were examined. Iron-based alloys with initial carbon contents of 0.5%, 1%, 2% and 3% were produced by powder metallurgy following a process that involved ball milling elemental powders, cold pressing and sintering. The composition, density, microstructure, porosity, hardness and ductility of the alloys depended on both compaction pressure and carbon content. As the carbon content increased, the amount of the resistant microstructure bainite in the alloys also increased, as did their hardness. In contrast, the density and ductility of the alloys decreased with increasing carbon content. This study shows that formation of the resistant microstructure bainite in alloys fabricated by powder metallurgy is influenced by both the initial carbon content of the alloy and compaction pressure during cold pressing.