Microstructure and mechanical properties in Al-Mg-Sc alloy induced by hetero-deformation

The hetero-deformation induced (HDI) strengthening of alloys can achieve the superior combinations of strength and ductility. However, there are not enough examples to reveal quantitatively the contributing proportion of HDI strengthening to yield strength, especially the systematic comparisons between classical strengthening mechanisms and HDI mechanism. In this paper, we performed calculations on four microstructures of Al-Mg-Sc alloy that friction stir processing (FSP) and rolled deformation (R80%) were used, including initial material (IM), FSP, IM + R80%, and FSP + R80%. It was found that the FSP + R80% had higher yield strength and elongation than IM + R80%, and strain hardening rate presented two modes in the two materials. Based on the complementation between classical strengthening mechanisms and HDI strengthening, the quantitative calculation implied that the better performance was related to the higher HDI stress (sigma HDI) in FSP + R80%. Precisely, for the contribution ratio of sigma HDI to yield strength, FSP + R80% was 1.39 times that of IM + R80%. Finally, at the small strain, IM + R80% was dominated by dislocation strengthening, while HDI strengthening in FSP + R80% played an important role, thus the mode of strain hardening rates of the two were inconsistent.