The grain size dependence of yield stress has been investigated for nanocrystalline (nc) bulk aluminum produced by hot extrusion of ballmilled powders. The Hall-Petch slope is positively deviated as the grain size is reduced below 60 nm. For the specific grain size range from 60 nm down to 48 nm, structural analyses and estimation of deformation mechanism exhibit that perfect dislocation emission critically governs deformation of nc aluminum, since the inherent aluminum properties of high stacking fault energy and low twinability can not afford any other deformation modes.
Supersaturated Cu-Sn alloy sheets were successfully fabricated by hot-rolling mechanically alloyed (MAed) nanocrystalline powders within a range of up to 22 wt.% of Sn, and their antibacterial and ionization properties were investigated. While the pure Cu and hot-rolled Cu-Sn sheets using MAed powders show excellent antibacterial properties, the corrosion potential of the hot-rolled Cu-Sn using MAed powders is much less than that of the as-cast Cu-Sn and decreases as the Sn content increases, implying that the hot-rolled Cu-Sn alloy sheets using MAed powders have a more effective antibacterial property, mainly due to supersaturation.
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