Study On The Ultrasonic Assist Composite Soldering Process Of AZ31B Magnesigum Alloy

Magnesium alloy is deemed as green engineering material in 21 th century,which has important application value and broad prospect.The joining technology is significant for the application of magnesium as structural material.Soldering with ultrasonic vibration is an ecofriendly and efficient method,which can break down the oxide film with ultrasonic cavitation,obtain reliable soldering joint without flux.By adding reinforcement to filler metal,we can obtain stronger,much refining joint,we call such filler material composite filler.In this paper,solder as 49%Mg-47.5%Zn-3.5%Al(wt%)and composite filler which is combined by solder and SiC particle were studied.Through DSC,SEM,EDS analysis,proper soldering experiment were drafted,magnesium soldering in air without flux was studied.Comparing 360? and 375? soldering joint,their main difference is that,in 375? joint,the ?-Mg sosoloid spread all around the joint,but ?-Mg sosoloid in 360? joint only exist in the edge of the joint.With ultrasonic vibration,filler metal can spread over AZ31 B,at 360? holding 1 min,reliable diffusion layer were achieved.With 8 seconds vibration,the thickness of diffusion layer can be 12?m.Mechanical properties and microstructural of soldering joint can be effect by soldering temperature,time of ultrasonic vibration and cooling rate after soldering.Lower soldering temperature and quick cooling is good for mechanical properties.Proper vibration time is also beneficial.Optimal process is soldering at 360?,cooling in the air and with 6s vibration,shear strength of such joint can be 52.28 MPa.Preparing of composite joint by “sandwich structure”,by adding 10wt% or 20wt% SiC particle to Mg-Zn-Al solder.Reinforce the solder by decentralizing SiC particle through ultrasonic vibration.With 4 seconds vibration,SiC particle may not be dispersed well.But with more than 6 seconds,SiC particle can be well dispersed.The hardness of composite joint can be 547 HV and 724 HV as for different amount of SiC particle,comparing to 227.7HV of Mg-Zn-Al solder.The shear strength is enhanced by 12.5% and 18.8% as well.