Effects of non-isothermal aging and microalloying on precipitation strengthening for Al-Mg-Si alloys

The impacts of non-isothermal aging (NIA) and microalloying (Ag and/or Cu) on precipitation strengthening and mechanical properties in Al-Mg-Si alloys are investigated using advanced microscopic analysis techniques combined with tensile testing. The NIA treatment exhibits different age hardening for this alloy with different compositions. The Ag-Cu-added A3 alloy exhibits the most significant enhancement in peak hardness under NIA treatment than that of the isothermal aging (IA), while only marginal increases are observed for the other alloys (the base A1 alloy and the Cu/Ag-added alloys). The optimal NIA treatment for the Ag-Cu-added A3 alloy is identified as follows: 200 degrees C x 1 h + cooling down to 180 degrees C at 20 degrees C/h. This specific treatment leads to a peak hardness of 139.0 HV and an ultimate tensile strength of 384.0 MPa for this alloy, which is 16.0 HV higher than that of the base Al-Mg-Si alloy when subjected to IA at 180 degrees C. These findings provide valuable insights for the advancement of novel aluminum alloys and heat treatment methodologies.