Process And Mechanical Research On Semisolid Stirring Brazing Of2024Aluminum And AZ31B Magnesium

The2024alloy and AZ31B alloy were brazed with stirring assist in air, without flux.For the welding dissimilar Al alloy and Mg alloy, the technology provides a feasiblemethod. The corrosion of base metal can be avoided due to flux-free. It is more flexible forspecimens due to experiment in air. Mg-Al IMCs can be avoided by filler metal, whichrestrain the direct contact between Al base metal and Mg base metal. Oxide film andMg-Sn IMCs can be interrupted by mechanical stirring, which can enhance the flow offiller metal fluid.Sn-Zn-Al system filler metal was made, which was applied to stirring brazing2024Alalloy and AZ31B Mg alloy. The relation ship between solid fraction of filler metal fluid,viscosity of filler metal fluid and temperature was investigated.The relation ship between microstructure, mechanical properties of interfaces andbrazing temperature, rotation speed of stirring, diameter of stirring, welding speed wasresearched. With the increase of brazing temperature, the shear strength of Al base metalinterface was up to77.7Mpa and the shear strength of Mg base metal down to28.5Mpa.With the increase of stirring rotation speed, the shear strength of Al and Mg base metal wasup to76.7Mpa and47.2Mpa. The shear strength of Al base metal interface can beenhanced by increase stirring diameter. The maximum shear strength value of Mg basemetal interface can be obtained when stirring diameter was1.8mm. The shear strength ofAl and Mg base metal interfaces increases to55.5Mpa and41.9Mpa when welding speedslower at0.25mm/s.The relation ship between mentioned parameters and total pressure of interfaces wasstudied by FLUENT software. The increase of total pressure of interfaces with declining ofbrazing temperature, rising of stirring rotation speed, rising of diameter of stirring,declining of welding speed.Optimization brazing parameters were brazing temperature at300℃, stirring rotationspeed at5440rpm, stirring diameter at1.8mm(filler metal thickness at2.0mm),weldingspeed at0.25mm/s,which obtained by experiments results and experiments processes.Formation of joints was researched by regular disrupting test. The oxide film on theAl substrates was removed gradually and solid solution was expanded to a solid solutiondiffusion layer on the whole interface. Continuous IMCs layer was formed on the interface near Mg substrates. The continuous IMCs layer was broken to a blocky one. The blockyshape IMCs dispersed into filler metal following the stirring. At this time, the continuousIMCs layer changed a thin one.