Effects of Si Content on the Tensile Strength and Machinability of Al-Mg-Si-Cu-Mn-Cr Alloys

This study investigated the effects of the Si content on the tensile properties and machinability of 6xxx−series aluminum alloys for application in hydrogen container valve housing. Four types of extruded Al−Mg−Si−Cu−Mn−Cr alloy specimens with different Si contents of 0.6−3.0 mass% were prepared. The effects of the Si content on characteristics such as microstructural features, tensile strength, and drill machinability were examined and compared with those of a commercial A6061 alloy. These specimens were found to exhibit different microstructures, tensile strengths, and chip segmentation behaviors after T6 heat treatment. These results were attributed to the interaction of the amount of second phase particles and solid-solute Mn and Cr with changes in the Si content.