Developing extreme hardness (> 15 GPa) in iron based nanocomposites

Through a unique methodology, novel nanocomposite microstructures were created in a bulk iron based alloy by first processing into a glass condition followed by devitrifying the glass through heat treating above the crystallization temperature. The as-crystallized microstructure was made up of three nanoscale phases; alpha-Fe, FP23C6, and Fe3B phases. Vickers hardness testing revealed a maximum hardness of 16.2 GPa which is significantly harder than existing commercial steel alloys and hardmetals. Detailed structural studies uncovered two important factors which contribute to the development of this extreme hardness; reductions in microstructure scale to the nanometer regime and supersaturation of transition metal alloying elements significantly above their equilibrium solubility limits. (C) 2002 Published by Elsevier Science Ltd.