| The status quo of the shortage of copper resource in China becomes more and more serious, copper prices continue to rise, aluminum instead of copper technology has become an important way to alleviate the current situation of the shortage of copper resources. Data shows the application of aluminum and copper fittings will account for 5.8% in dissimilar metal joints in the 21 st century. Copper and aluminum brazing method has the advantages and characteristics of welding deformation small,stable and reliable welding quality, simple brazing equipment and low cost,it has become one of the better advantageous method for connecting copper and aluminum. In order to achieve and optimize the copper and aluminum brazing, further promote the technology application of aluminum instead of copper, This paper selects Zn9.3Al7 Cu solder which has better comprehensive properties to be the matrix, trace mixed rare earth La Nd were added in Zn9.3Al7 Cu solder formed multiple solder alloy, the effects of adding elements La Nd on physical properties(melting temperature, density, resistivity, brinell hardness, microhardness), mechanical properties(tensile strength, elongation), brazing properties(spreading area on Cu, Al) and corrosion properties(corrosion potential, corrosion current density, corrosion rate) of Zn9.3Al7 Cu solder alloys were studied, optimized alloy composition and got a good comprehensive properties’ alloy formula. The results showed that:Zn9.3Al7 Cux La Nd solder’s melting temperature increased gradually with the increase of rare earth element La Nd’s content,but the increment was a litter, Zn9.3Al7Cu0.1La Nd solder’s melting range of solid-liquid phase decreased 7℃compared with Zn9.3Al7 Cu solder, which has a role in promoting for solder wetting properties.density and resistivity of Zn9.3Al7 Cu solder added with the increase of rare earth element La Nd’s content, solder resistivity changes greatly during these changes,the resistivity of Zn9.3Al7Cu0.5La Nd solder is 0.2×10-6?m increased 11% than the substrate solder(0.17×10-6?m). brinell hardness and microhardness of Zn9.3Al7 Cu solder added with the increase of rare earth element La Nd’s content, the brinell hardness of Zn9.3Al7Cu0.5La Nd solder is 88.7HB which increased 4.1% than the substrate solder(85.2HB), the microhardness of Zn9.3Al7Cu0.5La Nd solder is 113.5HV which increased 6.2% than the substrate solder(97.5HV).The content of La Nd in Zn9.3Al7 Cu solder had a greater impact on solder’s spreadability on Cu and Al board, the spreading areas of Zn9.3Al7 Cu solder on Cu and Al are 50.1mm2 and253.2mm2,When content of La Nd was 0.3%, Zn9.3Al7Cu0.3La Nd solder has the largest spreading area on Cu and Al board and they are 60.3mm2 and 371.2mm2, which are 20.4% and 46.6% more than the base solder. Adding the appropriate content of La Nd could improve tensile strength and elongation of the solder,the tensile strength and elongation of Zn9.3Al7 Cu solder are 287 MPa and 8.6%,the Zn9.3Al7Cu0.3La Nd solder has the maximum tensile strength and elongation, they are 307 MPa and 11.6%,which increased 7% and 11.6%.compared with the substrate solder respectively. The corrosion potential of Zn9.3Al7 Cux La Nd increased at the first and then decreased with the increase of La Nd content in solder, but only slightly, after the corrosion current to decrease with the increase of the added amount increased La Nd,the corrosion current density of Zn9.3Al7Cu0.3La Nd solder reduced nearly an order of magnitude than the substrate solde’s, whose corrosion resistance was the best.The corrosion rate of Zn9.3Al7 Cux La Nd in 3.5% Na Cl solution increased with the increase of La Nd content in solder at first and then reduced, Zn9.3Al7Cu0.3La Nd solder had the lowest corrosion rate which decreased 76.8% compared to the substrate solder’s.The appropriate content of La Nd in solder can improve solder’s corrosion property greatly. |
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