Effect of trace additions of cadmium,silver and zirconium on the precipitation hardening behavior of aluminum 6061 alloy

Age hardening response was investigated in Aluminum 6061 alloy to determine the influence of trace additions of 0.01 and 0.1 % of cadmium, 0.01, 0.1 and 0.5% of silver, 0.05 and 0.1% of zirconium, as well as 0.1% each of Cd + Zr and Ag + Zr. Thermo-mechanical stabilization treatment followed by artificial aging of these alloys were carried out at 313 K, 353 K, 393 K and 453 K. Vickers hardness was used to monitor the progress of age hardening. The Precipitate morphology, distribution and size were studied by Scanning Electron Microscopy. Tensile tests on selected alloys after selected treatment conditions assisted in determining the UTS, YS and % elongation. Fractography of the tensile fractures by scanning electron microscopy was used to delineate the effect of trace element addition on the fracture type. The trace addition effects observed seem to be caused by the precipitate size refinement and distribution. The observed effects seem to corroborate results obtained by several other techniques. The present work strengthens, both qualitatively and quantitatively, the viewpoint that it is possible to choose an age hardenable aluminum base alloy and improve it significantly by making judicious additions of trace elements.