Research On Sintering Process Impacting The Weldability Of Ag-Cu-Zn-Sn Filler Metal Formed By Electromagnetic Compaction

As the increased for environmental welding technology,the research and preparation of “a new type of Lead-free and Cadmium-free solder” have become the hot topic of global attention of academic circles and enterprises.And now,the silver filler metal has become the best choice for welding stressed materials with its excellent welding performance and low cost.The traditional process of preparing silver filler metal produces a large number of brittle phases during the process of smelting and solidification.And it is inevitable that all the elements would burn and lost.Both of the above facts make a bad influences on the welding performance.Not only that,the traditional process is complex and cost much time and money.As a consequence,the preparation of solder foils by the combination of electromagnetic compaction and powder metallurgy becomes a new research direction.The parameters of WG-III low voltage electromagnetic pulse powder molding machine which we used in the experiment are 1300 V for discharge voltage?8200uF for energy-storage capacitor.We use this machine to suppress miled metal powder.We used multigroup silver filler metals of BAg44Cu28Zn25Sn3 which were prepared in different conditions of liquid phase sintering as researched objects.Then,conducted the brazing copper plates in protective atmosphere in the vertical tubular furnace SG-GL 1200 L.After that,we carried out micro-hardness testing and T peeling strength test on the welded butt joint with control variable method.And we analyzed the microscopic structure and mechanical property of welded joint by a series of methods such as metallographic observation?scanning electron microscope(SEM)observation and X-ray diffraction analysis.And we discussed the properties of these silver filler metals of BAg44Cu28Zn25Sn3 that were magnetic pulse suppressed first,and then sintering in different temperatures and thermal insulation.Finally,we obtained the best technological parameter of preparation of a new type of Lead-free and Cadmium-free solder with excellent comprehensive properties.That would provide certain theory and engineering practice guidance for the research on Cadmium-free solder.The results showed that,when the holding time after liquid phase sintering was constant,with the increment of sintering temperature,both of the hardness and peel strength of joints increased;When the sintering temperature was constant,with the extended holding time,the hardness of joints decreased.And when the sintering temperature was constant,the peel strength of joints prepared in short holding time was stronger than those in longer holding time.During the brazing,there was metallurgic reaction between liquid solder and base metal,and the liquid solder diffused to the base metal,which made the micro-hardness appear gradient distribution from the center of soldering seam to interface region.The coarse grain was formed easily because of the great thermal cycle temperature gradient in HAZ,which was result of the decrease in micro-hardness.As a result,the micro-hardness of joints show a rising trend from base metal to soldering seam.Sn can dissolve in copper-rich phases of solder alloy to form solid solution.As the conditions changed,the content of Sn that dissolved in the copper-rich phases changed,forming new intermetallic compounds with Cu,tin bronze phase(Cu5.6Sn)?intermediate phase(Cu13.7Sn)and hard brittle phase(Cu10Sn3)formed.The content and distribution of different phases is the reasons for changes of mechanical properties of micro-hardness and peel strength.In conclusion,sintering temperature mainly affects the proportion of phase in brazing joints.Sintering time mainly affects the joints micro-structure.And the solders with excellent properties could be obtained in condition of higher temperature and shorter holding time within limits.