Effects of heat treatments on AA6061 aluminum alloy deformed by cross-channel extrusion

In this study, the relationship between microstructures and mechanical properties of the cross-channel extrusion (CCE) processed AA6061 alloy caused by different heat treatments were investigated. The ultimate tensile strength of the homogenized AA6061 can be strengthening to 194 MPa after extruded at 448 K for 8 passes. After T6 treatment, the strength was increased from 194 to 323 MPa caused by the formation of fine precipitates; however, the grains were coarsened. The Post-CCE aging treatment was applied on AA6061 alloy that the alloy was processed in supersaturated state at 448 K for 8 passes, and then artificial aged. A higher tensile strength of 364 MPa which is 13% higher when compared with the T6 treated sample was obtained since it consisted of fine-grained matrix with grain structure size of 0.2-0.5 mu m and precipitation hardening effect. It demonstrates that the Post-CCE aging treatment is a suitable method for producing a heat treatable Al alloy with improved strength when applied to CCE process. (C) 2008 Published by Elsevier B.V.