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 °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.
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Financial support from the Christian Doppler Research Association , the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development is gratefully acknowledged. The authors also wish to express their sincere thanks to AMAG rolling GmbH for the supply of alloy material. Financial support from the Austrian Research Promotion Agency (FFG) in the project 3DnanoAnalytics (FFG-No. 858040 ) is also gratefully acknowledged. MAT and SP are grateful for the European Research Council (ERC) excellent science grant “TRANSDESIGN” through the Horizon 2020 program under contract 757961.
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