Microstructure and Mechanical Properties of BFe10-1-1 Copper-Nickel Alloy Pipe Automatic TIG Welded Joints at 0° and 180° Positions

In this study, the 2 mm thick BFe10-1-1 copper-nickel alloy pipes were successfully welded using the automatic TIG welding system at 0° and 180° positions. The electron probe microanalyzer (EPMA) and the electron backscatter diffraction (EBSD) techniques were used to analyze the changes in the elements and microstructure of the welded joint at 0° and 180° positions. The experimental results showed that the position of welding would affect the microstructure and mechanical properties of the welded joints. The ductility and toughness of welded joints could be effectively predicted by angle grain boundary and Σ3 coincident lattice (CSL) boundary. The experimental results showed that the grain size had an effect on the microhardness and mechanical properties of the welded joints. When the grain size decreased, the microhardness and tensile strength of welded joints increased. Therefore, these results had certain guiding significance for improving the quality of automatic TIG welded joints in different welding positions.