Study On Microstructure And Properties Of Contact Reaction Brazing Joint Between Magnesium Alloy And Steel

Nowadays with the rapid development of science and technology in the society,new materials and new processes are more and more widely used in industrial production.People's requirements for the comprehensive properties of materials are also increasingly urgent.However,the performance of single metal materials is often difficult to meet various engineering requirements,and the welding structure of dissimilar metals is an important way to realize the composite properties of materials.Among them,magnesium alloy/steel welding structure has the advantages of lightweight structure and high mechanical properties,which has a wide application prospect.However,the direct welding of magnesium alloy/steel is difficult to achieve metallurgical bonding.The use of intermediate transition materials is an important way to realize the reliable connection between magnesium alloy and steel.In this paper,Zn-15 Al and Zn-22 Al filler metals were used as interlayer transition materials to carry out contact reactive brazing between AZ31 B magnesium alloy and DC01 steel.Then rare earth La was added into the interlayer.The microstructure of interlayer and joint with different composition were compared.The shear strength of the joint was measured,and the phase composition on both sides of the fracture was analyzed.The results show that the microstructure of the interlayer can be refined by adding proper amount of Rare Earth La into the interlayer.However,when the content of La is too high,the La in the front of the solid-liquid interface will form Zn-Al-La ternary compound with Zn and Al,which will weaken the refining effect of La on the microstructure.When the content of La is 0.05 wt.%,the shear strength of Mg alloy/steel joint with Zn-22 Al interlayer is 93 MPa.When the Zn-22Al-x La(x=0,0.05,0.1,0.2wt.%)filler metal is used as interlayer transition materials for welding AZ31 B magnesium alloy and DC01 steel,Fe Al3 in the joint prevents Mg in the magnesium matrix from reacting with Zn in the interlayer,thus avoiding the formation of a large number of Mg Zn2 intermetallic compounds in the joint.Because the performance of Fe Al3 intermetallic compounds is better than Mg Zn2,the shear strength of AZ31B/Zn-22Al-x La(x=0,0.05,0.1,0.2wt.%)/DC01 joint is greater than that of AZ31B/ Zn-15Al-x La(x=0,0.05,0.1,0.2wt.%)/DC01 joint.