The microstructure and mechanical properties of 1Cr17Ni2/QAl7 brazed joints using Cu-Mn-Ni-Ag brazing alloy

A novel Cu-Mn-Ni-Ag brazing alloy was designed to join 1Cr17Ni2 stainless steel and QAl7 Al-bronze at a fixed temperature from the range from 870 to 950 °C for 5 min, and the microstructure and the mechanical properties of the joints were investigated in details. The typical microstructure of the joints was mainly composed of solid solution (s, s) phases and could be expressed as: 1Cr17Ni2/Ni(s, s) layer/Ni3Al+Cu[Ni, Mn](s, s) reaction layer/Cu(s, s)+Ag(s, s) brazing seam zone/Cu(s, s) layer/QAl7. As the brazing temperature increased, the thickness of the brazing seam zone and the thickness of the reaction layer increased. The maximum room temperature shear strength of the joints was about 272 MPa, which was approximately 79% of the QAl7 tensile strength (as-annealed) when the brazing temperature was 950 °C. The shear strength of the joints kept being above 139 MPa at a testing temperature below 500 °C. The fracture mode of the typical joints was characterized by ductile dimple fracture and the joints fractured propagation inside the Cu(s, s) and Ag(s, s) phases in brazing seam zone after shear tests.