Effect of age hardening to reclaim mechanical properties at different levels of temperature with prolong holding time on GTAW weldments

Abstract

It is evident for heat treatable aluminum alloys, that a great reduction in mechanical properties was reported against the fusion arc welding process. This is considered an utmost industrial issue and direct usage of critical components in the automobile and aerospace industries are not acceptable without performing any post process that reclaims the properties up to a certain limit. The AA6061 aluminum alloy was considered as a base material and ER4047 as filler utilized in the GTAW process at constant parameters. After welding, all the specimens were solution treated at 500°C for 2 hours, age hardening cycle was performed at different temperatures ranging from 135-195°C at an interval of 30°C difference with considering prolong aging time of 7, 10 and 13 hours. A microstructure based comparison has been presented in the welded zone (WZ) at each combination of aging temperature and time. A change in mechanical properties has been observed due to dissolution and aging of precipitates in the WZ and heat affected zone (HAZ). A stage-wise comparison of hardness in the WZ and HAZ represented the gradual recovery in mechanical properties. Higher values of hardness and recovery were concluded in HAZ which is actually a heat treatable sensitive (AA6061) region and, up to 80.2% in contrast to BM was recorded. A significant improvement in WZ against the age hardening is also reported, up to 71% of hardness recorded but still less than HAZ. Therefore, it is considered to be an effective strategy to regain the acceptable range of mechanical properties in the affected zones.