Effect of Post-Weld Heat Treatment Parameters on Microstructure, Mechanical Properties, and Fatigue Life of TIG-Welded AA2024-T3 Aluminium Alloy Joints: A Response Surface Methodology Study

Abstract

Welding of AA2024- T3 aluminium alloy results in substantial reduction of fatigue life in the weld heat- affected zone due to dissolution of strengthening precipitates and microstructural coarsening during the thermal cycle, making post- weld heat treatment (PWHT) essential for structural fatigue- critical aerospace applications. This study investigates the influence of three PWHT parameters: solution treatment temperature (480 to 530 degrees C), quench medium (air, polymer solution, water), and artificial ageing temperature (160 to 190 degrees C), on microstructure, hardness, tensile properties, and fatigue life of TIG- welded AA2024- T3 joints using a Box- Behnken response surface design (15 experimental runs). A quadratic regression model for fatigue life achieved R- squared of 0.9621 and adjusted R- squared of 0.9108, confirming adequate model fitness. The optimal PWHT condition (510 degrees C/1h solution treatment, water quench, 175 degrees C/8h ageing) increased mean fatigue life from 42,600 cycles (as- welded) to 186,400 cycles, a 337.6% improvement and recovery of 78.2% of parent metal fatigue life. ANOVA identified solution temperature (F=28.74, p < 0.001) and ageing temperature (F=23.18, p < 0.001) as the most statistically significant parameters.