Thermally stable nanostructured Al-Mg alloy with relaxed grain boundaries

Grain refinement into the nanoscale greatly hardens metals and alloys but reduces the stability. By means of cryogenic plastic deformation at very high strain rates, a high proportion of relaxed grain boundaries (GBs) were generated in an Al-5Mg alloy through emitting partial dislocations from GBs when grain sizes are below a critical value. The nanostructured Al-5Mg alloy with an average grain size of 31 nm exhibited a high hardness of 2.67 GPa and a grain coarsening temperature of about 95 K higher than that of submicro-grains. In addition, Mg depletion rather than segregation at some relaxed GBs was observed, that is in account with considerable compressive strains in the vicinity of the relaxed sigma 9 GB. The re-laxed GBs with Mg depletion are effective in stabilizing the nanostructured Al-Mg alloys. It offers a novel approach to developing stable nanostructured alloys. (C) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

By means of cryogenic plastic deformation, a high proportion of relaxed grain boundaries can be generated in the Al-5Mg alloy, which is essential for stabilizing nanostructured alloys.