Microstructure-properties relationshop in two Al-Mg-Si alloys through a combination of extrusion andaging

Aluminum alloys containing magnesium and silicon as the major solutes are strengthened by precipitation of the metastable precursors (beta '') of the equilibrium beta (Mg2Si) phase. In this study, dynamic aging of two Al-Mg-Si alloys-the 6061 (Al-1.34% Mg2Si) and 6069 (Al-2.25% Mg2Si) alloys-was conducted through equal channel angular extrusion (ECAE). Equal channel angular extrusion-assisted dynamic aging provides the potential for improving mechanical properties. The aging time scale is reduced from similar to 1,000 min. for conventional static peak aging to similar to 10 min. by using ECAE-assisted dynamic aging. Compared to the significant strengthening effect in static aging treatment, a notable further increase in ultimate tensile strength is achieved by dynamic aging: over 40 MPa for the 6061 alloy and 100 MPa for the 6069 alloy. Microstructures of both aged alloys were characterized using transmission electron microscopy; dislocation-assisted precipitation was observed to be the primary precipitate nucleation and growth mechanism during the dynamic aging process. It is concluded that ECAE-assisted dynamic aging is controllable and efficient in executing aging treatment that could result in superior mechanical properties of Al-Mg-Si alloys.