Grain size softening effect in AI_(62.5)Cu_(25)Fe_(12.5) nanoquasicrystals

摘要

Inverse Hall-Petch (IHP) behavior in nano-quasicrystalline AI_(62.5)Cu_(25)Fe_(12.5) is reported. Powders with varying grain sizes were produced by mechanical milling of spray-formed quasicrystals. The hardness of the milled powders increased with decreasing grain size down to about 40 nm and decreased with further refinement, demonstrating the IHP behavior. This critical grain size was found to be larger compared to other metallic nanocrystalline alloys. This IHP behaviour has been attributed to the structural complexity in quasicrystals and to thermally activated shearing events of atoms at the grain boundaries.