BS in Materials Engineering
Materials Engineering Department
This investigation is focused on the effect paint-bake cycles have on the tensile strength and microhardness of GMAW welded RX82 aluminum extrusions in T4 and T6 base conditions. To simulate the paint-bake cycle, T4 and T6 RX82 aluminum samples were GMAW welded and heat treated at 350°F, 390°F, and 425°F for durations of 30 minutes, 1.0 hour, and 2.0 hours, with five replicates for each treatment. Microhardness profiles of T4 samples treated at 350°F for 30 minutes and 1.0 hour display weld/HAZ HV values of 86.04 and 82.51 respectively, followed by maximums of 123.21 and 121.10. Average ultimate tensile strength (UTS) of T4 samples treated at 350°F started at 38.26 ksi, dropped to 34.91 ksi, and increased to 38.24 ksi for 30 minutes, 1.0 hour, and 2.0 hour treatments. T4 samples treated at 390°F showed an increase in UTS with increasing exposure duration; however 425°F treatments displayed a decrease in UTS. T6 samples treated at 350°F and 390°F increased in average UTS, while T6 samples treated at 425°F increased then decreased in strength. A general linear model of the T4 tensile samples shows no statistically significant difference in UTS between treatments or treatment levels, while T6 tensile data shows statistically significant differences between the 350°F and 390°F/425°F treatment temperature, with another significant difference between the 30 minute and 1.0 hour/2.0 hour treatment durations.