Effects of Hot Dipping Velocity on Microstructure and Mechanical Properties of Pb40Sn60 Alloy Coating on Copper Wire

Pb40Sn60 alloy coatings were prepared on copper wires by hot dipping to improve the weldability and corrosion resistance. The microstructure and phase composition of Pb40Sn60 alloy coating at different hot dipping velocities were examined by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). And the mechanical properties of Cu wires with Pb40Sn60 alloy coating at different hot dipping velocities were investigated by tensile tests. The results show that the Pb40Sn60 alloy coatings are all composed of a phase and beta phase, and a phase is more than beta phase in relative amount. With the increase of hot dipping velocity, the thickness of Pb40Sn60 alloy coating on copper wire is increased, and the crystal morphology changes from lamellar or equiaxial to dendritic. The work hardening of copper wires can be eliminated during the hot dipping process. With the decrease of hot dipping velocity, the strength of copper wires with Pb40Sn60 alloy coating decreases significantly, the elongation has not obvious change, and the hardness of copper wires substrate as well as the hardness of coating shows a slight decreasing trend. Increase in the hot dipping velocity is beneficial to the crystallization and growth of the coating; on the contrary, decrease in the hot dipping velocity is beneficial to removing the work hardening of copper wire substrate.