Transient liquid phase bonding of cast Al0.3CoCrFeNi high-entropy alloy using Ni/Zr/Ni laminated foils

Abstract Cast Al0.3CoCrFeNi high-entropy alloy was successfully bonded by Ni/Zr/Ni laminated foils using a transient liquid phase bonding method. When the bonding temperature exceeded 1140 °C, the active Zr atoms from Zr-Ni liquid alloy diffused into the grain boundaries and interdendritic region of the Al0.3CoCrFeNi base material and triggered a eutectic reaction with Al0.3CoCrFeNi in this region, which acted as a pseudo element. The formed liquid phase accelerated the dissolution of cast Al0.3CoCrFeNi base metal and a composite microstructure with the soft FCC Al0.3CoCrFeNi phase embedded into the brittle Ni7Zr2 intermetallic compound formed in the seam upon cooling. The mechanical performance of the joint was significantly affected by the bonding parameters. When the bonding was carried out at 1160 °C for 30 min, a joint with balanced ductility (face-centered cubic phase) and strength (Ni7Zr2) was obtained. The maximum shear strength of approximately 247 MPa was obtained. This value was approximately six times higher than that of the joint bonded at 1120 °C. The joints fractured in ductile interlamellar fracture mode.