Abstract
Nanocrystalline Al-Mg alloys are used to isolate the effect of grain boundary doping on the strength of nanostructured metals. Mg is added during mechanical milling, followed by low homologous temperature annealing treatments to induce segregation without grain growth. Nanocrystalline Al -7at% Mg that is annealed for 1h at 200°C is the strongest alloy fabricated, with a hardness of 4.56GPa or approximately three times that of pure nanocrystalline Al. Micropillar compression experiments indicate a yield strength of 865MPa and a specific strength of 329kNm/kg, making this one of the strongest lightweight metals reported to date.
Highlights
Nanocrystalline Al and Al-Mg alloys with an average grain size of 24 nm were used to isolate the effect of grain boundary doping on strength
Our results showed that nanocrystalline Al -7 at. % Mg had a maximum hardness of 4.56 GPa, approximately three times the hardness of pure nanocrystalline Al with the same grain size
We find that boundary segregation has a much stronger effect on strength than solid solution effect, while observing that alloys that are roughly three times as strong as pure nanocrystalline Al can be created through such methods
Summary
Nanocrystalline Al and Al-Mg alloys with an average grain size of 24 nm were used to isolate the effect of grain boundary doping on strength. This was followed by annealing treatments to induce segregation of solute (Mg) to the grain boundary, changing the overall energy state that affects material properties.
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