Quantitative analysis of dendrite evolution and property enhancement in 2A12 aluminum alloy welded joints: Role of MIG welding and post-weld heat treatment

Abstract

For demanding applications such as lightweight pipelines and structures, this study investigates the effects of MIG welding and post-weld heat treatment (PWHT; specifically solution treatment at 510 °C for 65 min followed by water quenching and ageing at 180 °C for 2 h) on the dendrite structure and properties of 2A12 aluminum alloy joints using ER2319 and ER5356 fillers. After PWHT, significant dendrite fragmentation and spheroidisation occur, reducing columnar dendrite fraction to 5% (ER2319) and 15% (ER5356). The uniform θ'-Al₂Cu precipitates enhance tensile strength by 52% and 43%, respectively, with the ER2319-PWHT joint reaching 378 MPa, 11.5% higher than the base metal. While PWHT promotes <100> equiaxed grain recrystallisation and increases low-angle grain boundaries to 35%, corrosion resistance in 3.5% NaCl solution remains primarily governed by filler composition (ER2319 > ER5356). These findings provide critical insights for microstructure control in aluminum weldments.