Synergistic alloy design concept for new high-strength Al-Mg-Si thick plate alloys

With the aim of fully exploiting the advantageous strength-to-weight ratio evident in Al-Mg-Si alloys, this study presents measures for increasing the yield strength of an EN AW-6082 type plate alloy. In addition to describing the thermodynamic simulation-based adjustment of age-hardenable elements (Si, Mg and Cu) and a modified artificial ageing treatment, it investigates the effects of adding a small amount of Zr. The significant strengthening induced by adding Zr is correlated with sub-grain boundary hardening in a recovered microstructure after solution annealing at 570 degrees C, compared with the almost entirely recrystallized microstructure in an unmodified EN AW-6082 alloy. In combination with a maximum dissolvable number of age-hardenable elements and interrupted quenching, which comprises an improved heat treatment strategy for thick plates, it is seen that the yield strength can be increased by more than 40% to 411 MPa compared to conventional EN AW-6082 base material as verified by tensile testing. In the study scanning electron microscopy and scanning transmission electron microscopy were performed for microstructural characterization with a focus on particle and deformation analysis. All individual contributions which generated the superior strength are calculated and discussed in order to reveal the microstructure-property relationship. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of Acta Materialia Inc. This is an open access article under the CC BY license(http://creativecommons.org/licenses/by/4.0/)