Microstructure and mechanical properties of transient liquid-phase diffusion bonding GH5188 and AlCoCrFeNi_2.1 high entropy alloy

In this study, transient liquid phase (TLP) diffusion bonding was conducted between GH5188 co-based superalloy and AlCoCrFeNi_2.1 high-entropy alloy (HEA) using a BNi-2 interlayer. The effects of bonding temperature on the microstructure and mechanical properties of the joints were systematically investigated. The results indicate that, during the heating process, in the diffusion affected zone on the HEA side (DAZ I), while the formation of precipitates on the HEA side was suppressed due to the high entropy effect. The amount of Cr[sbnd]W boride precipitates in the diffusion affected zone on the GH5188 side (DAZ II) significantly increased with temperature, the morphology of the precipitates exhibited a notable transformation. The volume fraction of needle-like precipitates increased from 0.21 % at 1160 °C to 20.6 % at 1220 °C, accompanied by a corresponding reduction in granular precipitates. The joint achieved the highest shear strength of 774 MPa at 1190 °C. With increasing temperature, the fracture mode of the joint evolved significantly from brittle fracture at 1160 °C to a mixed fracture mode at 1190 °C, characterized by the coexistence of dimples and cleavage steps.