Effect of Ageing on the Structure and Properties of Continuously-Cast and Rolled Sheet of Aluminum Alloy 6061

The effect of ageing on the structure and mechanical properties of continuously cast and rolled sheet from aluminum alloy 6061 is studied. Atreatment regime involving 2-h water quenching from 550°C and six hours artificial ageing at 200°C is shown to provide the values of σr, δ, and HV equal to 318 MPa, 14%, and 127 HV0.1 respectively. The alloy fractures by a ductile mechanism after quenching and by a mixed mechanism after ageing. The average grain size after ageing is 0.09 nm, and over grain boundaries there is a large amount of Mg2Si nanosize inclusions and heat-resistant α-Fe phase that increase sheet mechanical properties.