Effect of Cold Work on the Precipitation Process in Aluminum Alloy 6063

Abstract

Aluminum alloys can be strengthened by cold or hot working due to interaction between precipitates and dislocations. The alloy 6063 was deformed (2, 5, 10, 15 and 20) % after water quenching, and artificially aged at different aging temperatures (1605 180 and 200) oc for various periods of time (0.5, 5, 10, 50 and 100) hours. The results showed a considerable improvement in yield and tensile strength with an increasing level of prestrain. Generally aging temperature of 160 oc gave the best increase of yield and tensile strength, but these were decreased with increasing aging temperature i.e. (180 and 200) oc at a given level of prestrain.The peak aging time that improves the mechanical properties decreased with an increasing aging temperature. The alloy of 20 % deformation and aged at 160 oc for 10 hours developed maximum (yield, tensile strength and hardness) values compared with all other conditions involved, because the density of dislocation tangles which improved (yield and tensile) strength increased with increasing degree of prestrain.The 6xxx aluminum alloys are readily welded by most types of welding processes, but with severe local softening in the heat-affected zone (HAZ) where the hardness reduces to about half that of the parent metal.