Microstructure and mechanical property of Zr-4 alloys brazed with Ag-Cu-Ti filler metal

Zr-4 alloys were vacuum brazed using Ag-Cu-Ti filler metal. The effect of brazing temperature on the microstructure evolution, shear strength and corresponding fracture behavior of the brazed joints was investigated. The typical phases at the brazing temperature of 800, 840 and 930 degrees C were inferred to be three different microstructures, i.e., a mixture of (Cu, Ti) phases and Ag-rich phase, Ag-rich phase and brittle intermetallic compound (IMC) AgZr, and a uniformly mixed morphology of CuZr and AgZr. And the width of the whole brazed seam increased from 78.4 mu m to 118.8 mu m. Meanwhile, the shear strength of the brazed joints first increased and then decreased followed by a small increase. The maximum shear strength of 138MPa was obtained at the treatment of 800 degrees C for 10min. The fracture morphology exhibited typical brittle fracture characteristics, and the cracks initiated from the interface of the brazed joints, and propagated into the intermediate zones.