Effect Of Ni?Ti Alloy Elements On Properties Of W/Fe Brazed Joints

In this paper,the influence of the addition of Ni,Ti and mixed elements on the microstructure and properties of the solder was investigated by using AgCu30 alloy as the matrix material.With the increase of Ni content,the solid solution(Cu,Ni)of the solder alloy was increased,and the structure of Silver-copper eutectic organization was decreased;With the increase of Ti content,the ?-Ag and brittle intermetallic compounds was increased,and the Silver-copper eutectic organization was decreased;When the content of Ni is 2%,the silver-rich phase was decreased and the eutectic organization was increased with the increase of Ti content.The influences of Ni,Ti and the its mixed addition of the microstructure and mechanical properties for the joint of tungsten alloy and steel.The results showed that,the width of the brazing seam was firstly decreased and then increased,and the diffusion degree of the elements at interfaces near tungsten alloy was first enhanced and then weakened,and the solid boundary layer of the steel was increased with the increase of Ni content.The shear strength of joint increases first and then decreases,and the maximum shear strength reached 151.3MPa at the addition of 2% Ni.With the increase of Ti content,the width of the brazing seam was firstly decreased and then increased,the diffusion degree of the elements in the interface near tungsten was enhanced,while the diffusion of the elements on the interface near steel was increased first and then remained unchanged.When the content of Ti was 5%,Cu NiTi brittle intermetallic compound were formed at the interface near tungsten.The shear strength of brazed joints increases first and then decreases,and the maximum shear strength reached 173.5MPa at the addition of 2% Ti.When the content of Ni was 2%,the diffusion degree of on the tungsten alloy and steel side was first increased and then decreased,the shear strength decreased with the increase of Ti content.On the basis of research,the vacuum brazing process was studied,brazing temperature and brazing time,which influenced microstructure,interface element diffusion and mechanical properties of the joints.The results showed that,With the increase of brazing temperature,the degree of interdiffusion of elements between tungsten and steel side interface was increased,the shear strength was increased first and then decreased.With the increasing of holding time,the interdiffusion of elements at the interface near tungsten was improved,but the degree of mutual diffusion of elements in the steel side interface was increased first and then remains unchanged,the shear strength of brazed joints were increased first and then decreased.The optimum process parameters were 880?of brazing temperature and 30 min of time.which were obtained by experiment.The joint shear strength could reach 173.5MPa under the process parameters.