Microstructure and shear strength of SiC/Zr joint brazed with LiAlSiO4/graphene-coated Cu-foam composite interlayer

In the present work, the microstructures and mechanical properties of Cu-foam-(graphene, LiAlSiO₄ and graphene/LiAlSiO₄) and a CoCrNiFeCuSn high-entropy alloy as a composite interlayer for brazing Zr and silicon carbide (SiC) ceramics are explored. Further, the effects of graphene, LiAlSiO₄, and graphene/LiAlSiO₄ on the mechanical properties and microstructure of the SiC/Zr joint are investigated. The results of the data analysis reveal a good connection between SiC and Zr at 1040 °C for 20 min using the different composite interlayers, Cu-foam-graphene, Cu-foam-LiAlSiO₄, or Cu-foam-graphene-LiAlSiO₄, with shear strengths of 122, 147, and 235 MPa, respectively. Particularly, the Cu-foam-graphene-LiAlSiO₄ brazed joint demonstrates the highest shear strength. Furthermore, the dispersion of LiAlSiO₄ in the joint reduces the coefficients of thermal expansion of difference between the brazing materials and ceramics, as well as the residual stress in the joint. Moreover, the synergistic effect of the solid-solution phase, Zr(s, s), with excellent plastic deformation, and enhanced Zr(Cr, Fe)₂ phase further improves the strength and plasticity of the joint.