Effect of thermal exposure on the compressive strength and microstructure of Al-6061 alloy

Al 6061 is a commercial-grade aluminium alloy highly utilized in aerospace, automotive, high-pressure gas cylinders, and many other construction purposes. Al 6061 is a heat-treatable grade. Heat treatment can enhance the alloy's mechanical and microstructural qualities by controlling grain size and precipitate distribution. Three heat treatment steps are followed for any non-ferrous alloy to achieve the desired mechanical properties. In this work, only two heat treatment steps have been followed- solution annealing followed by quenching in three different media, i.e., water, oil, and air. The heat-treated samples' compression, hardness and microstructural properties were assessed and compared with those of untreated samples. A significant drop in the yield stress was noticed in the solutionized+quenched samples due to dissolved secondary and ternary phases in the primary α matrix. However, the improved precipitation of the secondary (Mg2Si) phase has greatly increased the hardness of the quenched sample. Optical microscopic images have observed high fine ternary Al-Mg-Si and secondary Mg2Si precipitated.