Effects of In and Ni on the microstructure and properties of silver-based brazing alloys

The study involves replacing the Ag element in Ag20CuZn solder with In and Ni to improve the Ag20CuZn solder while reducing its cost. It also investigates the impact of the modified solder on the welding performance and microstructure of stainless steel capillaries and red copper capillaries in refrigerator refrigeration systems.The differential scanning calorimetry (DSC) technique is used to analyze the solidus and liquidus temperatures of the solder. A 3D laser measuring instrument is employed to test the wettability of the solder on 304 stainless steel. Analytical methods such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) are utilized to observe the influence law of In and Ni replacing Ag in Ag20CuZn solder on the microstructure of the alloy. Additionally, a universal testing machine is used to test and analyze the shear strength of the stainless steel/Cu joints welded with the solder. The partial replacement of Ag in Ag20CuZn with In and Ni effectively reduced the solidus and liquidus temperatures of the filler metal while enhancing the wettability of the silver-based filler metal on 304 stainless steel. When the In and Ni contents were 1.2 wt% and 1.8 wt%, respectively, the most significant refinement of the microstructure was observed. Additionally, tThe welded joint exhibits the highest shear strength. The brazing of stainless steel capillary tubes and copper tubes using Ag17CuZn-1.8Ni-1.2In filler metal meets the welding requirements for capillary tubes in refrigerator refrigeration systems.