Microstructure and mechanical properties of TIG brazing of stainless steel

TIG brazing of stainless steel was carried out with S211 and S201 copper matrix filler metal. The microstructure and mechanical properties of the joint were studied by OM, SEM, EDS, Instron-testing machine, etc. The results show that the joint has a dual characteristic: the up side of the joint and a brazing part in the bottom part. A fusion zone consisting of α and ε phases appears in the upper part and a brazing layer appears in the bottom part, which are joint to the stainless steel soundly. The microstructures of brazed seam are macro-homogeneous supersaturated solid solution of iron in copper matrix and high temperature granules consisting of α and ε distributed unevenly in the brazed seam, which consolidate the tensile strength of the brazed seam. The high temperature granules are distributed more unevenly in upper part than that of in the bottom and the sizes of them are different. Fracture occurs in the brazed seam of the two kinds of joints, S211 joint and S201 joint, in the tensile test. The S211 joint has higher tensile strength than S201 joint, compared 498.33 MPa to 476.67 MPa, whereas the S201 joint has higher extensibility, compared 19.6% to 13.8%.