Nanocrystalline Al-Mg with extreme strength due to grain boundary doping

TL;DR

This study demonstrates that grain boundary doping with Mg in nanocrystalline Al significantly enhances strength, achieving record-high hardness and yield strength for lightweight metals through controlled annealing and doping techniques.

Contribution

It introduces a method of grain boundary doping in nanocrystalline Al-Mg alloys to drastically improve strength without grain growth, a novel approach in lightweight metal development.

Findings

Nanocrystalline Al-7 at.% Mg exhibits a hardness of 4.56 GPa.

The alloy achieves a yield strength of 865 MPa.

It is among the strongest lightweight metals reported.

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 -7 at.% Mg that is annealed for 1 h at 200 {\deg}C is the strongest alloy fabricated, with a hardness of 4.56 GPa or approximately three times that of pure nanocrystalline Al. Micropillar compression experiments indicate a yield strength of 865 MPa and a specific strength of 329 kN m/kg, making this one of the strongest lightweight metals reported to date.