Contact Reactive Brazing Of Mg/Steel Dissiminlar Metals With Zn Base Alloy Interlayer

Magnesium alloy is one of the important light metal materials,used in automobile,and national defense,aerospace and other fields.Steel is the most widely used metal material.Their connection can take advantage of their excellent performance,can achieve the purpose of saving resources and reducing the structure weight.Using the principle of eutectic reaction or other metallurgical reactions for brazing called contact reaction brazing,welding joint is beautiful and dense;contact reaction brazing do not need brazing solder,so it is no pollution;it is also economic and easy to operate,contact reaction brazing is a kind of important welding methods to realize the dissimilar metals welding.In this paper,by the method of contact reaction brazing,through adding different content of copper element in the Zn-xAl(x=3,5,8 wt.%)interlayer,the effect of copper element for the microstructure and mechanical properties of magnesium/steel joint was studied.The research results show that right amount of copper element is added in the Zn-xAl(x=3,5,8 wt.%)interlayer,copper element is dissolved in the interlayer,having the effect of solid solution strengthening,improving the shear performance of joint;excessive amount of copper element is added in the Zn-xAl(x=3,5 wt.%)interlayer,interlayer will generate brittle CuZns intermetallic compound,CuZn5 intermetallic compound is not evenly distributed in the interlayer,the phenomenon increases the brittleness of interlayer and reduces the shear performance of joint;excessive amount of copper element is added in the Zn8Al interlayer,it will reduce the amount of first precipitated phase in the interlayer,the first precipitated phase is easier to be unevenly distributed,the phenomenon is bad for the interlayer organization,when shear performance of joint is tested,the first precipitated phase is easy to cause the stress concentration of joint and reduces the shear performance of joint.When the component of interlayer is Zn3Al2Cu,the shear performance of joint is best,can reach 97.18MPa.In order to further improve the mechanical properties of magnesium/steel joint,by the method of contact reaction brazing,through adding different content of rare earth lanthanum in the Zn3Al2Cu interlayer,the effect of rare earth lanthanum for the microstructure and mechanical properties of magnesium/steel joint was studied.The research results show that right amount of rare earth element is added in the Zn3Al2Cu interlayer,first precipitated phase size will be decreased in the interlayer,having the effect of fine-grain strengthening and improving the interlayer organization,improving the shear performance of joint.When the component of interlayer is(Zn3A12Cu)-0.2La,the shear performance of joint is best,can reach 102.25MPa.The research results have a certain guiding significance and reference value for magnesium/steel dissimilar metals welding.