Strength-toughness optimisation scenarios through interrupted ageing in AA6061 and AA2024

Aimed at the maximisation of strength-toughness relationships in aluminium alloys, interrupted ageing has been proposed as a means to combine these properties. Such processing schedule initiates with a T6 short underageing (177 °C for up to 1 hour), followed by a dwell period at a lower temperature for periods of up to two weeks, and further re-ageing to the T6 temperature. By combining DSC with hardness, tensile and Kahn-tear testing, the present work studies several heat treatment scenarios and their impact in the strengthtoughness improvements in AA6061 and AA2024. The dwell temperature of 65 °C results in a hardness increase whereas interruption at room temperature decreases it in comparison to the standard T6. In AA2024, interruption at room temperature leads to the formation of GPB2 zones. The strength-toughness behaviour for the different heat treatment scenarios is presented.