Effect of Water Cooling on the Microstructure and Mechanical Properties of 6N01 Aluminum Alloy P-MIG-Welded Joints

In-process water cooling was applied to 8-mm-thick 6N01 aluminum alloy joined using the pulsed metal-inert gas (P-MIG) multi-pass welding method. The influence of the cooling conditions on the microstructure and mechanical properties of the welded joints were mainly discussed. Compared with natural cooling, under water cooling, the peak temperature decreased and the cooling rate increased substantially, leading to a decrease in the partially melted zone of the welded joint. The columnar grain sizes adjacent to the fusion boundary were much more elongated under water cooling than under natural cooling. In addition, when water cooling was performed, the width of the softened zone was approximately 6 mm smaller than that with natural cooling, and the overall microhardness of the welded joint was improved. The tensile and nominal yield strengths of the welded joint were approximately 11 and 7 MPa higher under water cooling than under natural cooling, respectively. The fracture surface morphology of the welded joints exhibited typical ductile fracture. Thus, water cooling can optimize the microstructure and improve the mechanical properties of the 6N01 alloy P-MIG-welded joint.