Study On Preparation And Brazing Property Of Ag-Cu-Ga Alloy

Ag-Cu eutectic alloy(Ag-28Cu)is a medium-temperature brazing material widely used in silver-copper alloys.It is widely used for vacuum brazing of Kovar alloy.Ag is expensive and has limited reserves on the earth.Thus it is significant to develop a new type of solder with comparable brazing properties of Ag-28 Cu alloy.Here,based on Ag-28 Cu alloy,Ag-28Cu-5Ga,Ag-34Cu-5Ga,Ag-39Cu-5Ga,Ag-49Cu-5Ga and Ag-55Cu-5Ga were prepared by adding 5 % Ga element and adjusting the content of Ag and Cu.The cold working deformation performance and intermediate annealing process of these five alloys were compared and studied,0.2mm thick alloy sheets were prepared,and the optimized Ag-Cu-Ga alloy processing technology was determined.Differential thermal analysis(DSC)was used to determine the solid-liquid line and complete melting temperature(Tendset)of the alloy to determine the appropriate brazing temperature of the alloy.The brazing experiment of Ag-Cu-Ga alloy and Kovar alloy(4J29)was carried out.The brazing strength and brazing structure of Ag-Cu-Ga alloys with different compositions were studied,and finally the Ag-Cu-Ga alloy brazing filler metals with excellent properties were screened out.The main results are as follows:(1)After introducing 5 % of Ga element into Ag-Cu alloy,its as-cast structure and the eutectic lamellar structure of Ag-28 Cu alloy have undergone significant changes.On the basis of lamellar structure Obviously irregular Ag-rich phase and Cu-rich phase regions appear on the surface;and with the increase of Cu content,the distribution of the as-cast structure also changes.(2)The hardness of the Ag-Cu-Ga alloy increases with the increase in the amount of cold working deformation,from about 100 HV in the as-cast state to about200 HV under the 90 % deformation amount;secondly,as the annealing temperature increases,the alloy in the annealed state the hardness is reduced.The research has obtained the annealing softening curve of Ag-Cu-Ga alloy.When the annealing temperature is ?500 ?,the hardness of the alloy tends to 120 HV.(3)With the increase of Cu content,the solidus temperature of Ag-Cu-Ga alloy increases from 733.02 ? to 762.13 ?,which is lower than the eutectic temperature of Ag-28 Cu alloy of 778.5 ?;768.51 °C increased to 874.58 °C.The difference between the melting temperature of Ag-28Cu-5Ga,Ag-34Cu-5Ga,Ag-39Cu-5Ga,Ag-49Cu-5Ga,and Ag-55Cu-5Ga alloy Tendset and the solidus temperature is35.49 ?,54.53 °C,56.45 °C,88.36 °C,112.45 °C;it is concluded that the ?T of Ag-28Cu-5Ga,Ag-34Cu-5Ga and Ag-39Cu-5Ga alloys are more suitable for brazing materials.(4)Select the appropriate brazing temperature(Ag-Cu-Ga alloy Tendset + 40 ?)and brazing time(10 min),and compare and study Ag-28Cu-5Ga,Ag-34Cu-5Ga,Ag-39Cu-5Ga The brazing strength of Ag-49Cu-5Ga and Ag-55Cu-5Ga alloy to Kovar alloy is 366,390,445,299 and 200 MPa,respectively.It can be seen that Ag-28Cu-5Ga,Ag-34Cu-5Ga The brazing shear strength of Ag-39Cu-5Ga alloy to Kovar alloy is 68.7 %,79.7 % and 105 % higher than the brazing shear strength of Ag-28 Cu to Kovar alloy 217 MPa,respectively,and the shear strength is improved significantly.In Summary,the Ag-34Cu-5Ga alloy and Ag-39Cu-5Ga alloy studied in this paper not only have good processing properties in the preparation of alloy sheet,but also have much better welding strength in the vacuum brazing of Kvar alloy than Ag-28 Cu alloy.Compared with Ag-28 Cu alloy,the proportion of silver content also decreased by 21.79 % and 28.21 %.It has the advantage of replacing Ag-28 Cu alloy as a new alloy in welding.