Microstructure and mechanical properties of Al0·3CoCrFeNi high-entropy alloy joints brazed using a FeCoCrNiCu/Ti composite interlayer

This study introduces a brazing technique for joining Al0.3CoCrFeNi high-entropy alloy (HEA) utilizing a FeCoCrNiCu/Ti composite interlayer. The primary objectives of this investigation encompass an examination of the microstructure of the Al0.3CoCrFeNi joint, as well as an evaluation of the shear strength of the brazed joints under diverse brazing parameters. The characteristic microstructure of the Al0.3CoCrFeNi brazing seam is comprised of Ti (s, s), Cu (s, s) from the FeCoCrNiCu interlayer, and face-centered cubic (FCC) phases containing more than five elements. When the brazing temperature increases from 1100 °C to 1180 °C, there is a gradual augmentation in the diffusion of Ti element and subsequent reactions involving Cu, Ti, and Ni. Furthermore, the impact of holding time on the brazing seam is investigated. The findings suggest that prolonging the holding time has a relatively negligible effect on the reaction layer formed by the Ti foil. However, it does lead to a reduction of the Cu (s, s) content within the FeCoCrNiCu interlayer. Notably, the highest shear strength reaches up to 280 MPa when the joint brazed at 1160 °C for 10 min. In addition, the shear strength did not decrease below 800 °C. During the shear test, ductile fractures are observed in the joint, indicating favorable mechanical properties. Overall, this study successfully demonstrates the potential of the proposed brazing technique employing a FeCoCrNiCu/Ti composite interlayer for the effective joining of Al0.3CoCrFeNi HEA. By optimizing the brazing parameters, it is possible to achieve robust joints with exceptional mechanical characteristics.