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ZrB 2 -SiC ceramic and Nb were brazed by using a novel high entropy alloy CoFeNiCrCu filler. Interfacial microstructure, mechanical properties and brazing mechanism of the joint were systematically investigated. It was found that the activity of Cr could be maintained during the brazing process due to the high-entropy mixing effect of CoFeNiCrCu. The newly generated Cr 2 B had a tooth shape and it improved interfacial bonding between ZrB 2 -SiC and Nb. A composite microstructure containing a soft FCC and hard Laves phase was formed in the joint due to the presence of Nb and this microstructure significantly enhanced the joint strength. Influences of brazing temperature on the interfacial reaction and shear strength of joint were also investigated. After being brazed at 1160 °C for 60 min, the maximum shear strengths of the joint were 216 and 94 MPa at room temperature and at 650 °C, respectively, indicating the successful use of the filler. [ABSTRACT FROM AUTHOR]

In order to reduce intermetallic compound formations in brazed joints, a CoFeCrNiCu high entropy alloy was invented and employed to braze SiC ceramics. Results show that SiC ceramics were tightly and strongly brazed with the CoFeCrNiCu filler. Microstructure, phase and shear strength were systematically studied for joints brazed at different temperature. Main compositions were identified as high-entropy FCC, Cu(s, s), Si(s, s), and Cr 23 C 6 phases, regardless the brazing temperature differences. After being brazed at 1453 K, the joint reached a maximum shear strength of 60 MPa, much higher than those brazed with conventional AgCuTi filler. Thanks to high entropy effect of CoFeCrNiCu filler, random solid solution turned out in the seam and benefitted joint quality. The successful use of CoFeCrNiCu high entropy alloy as fillers can expand the application range of high entropy alloys and provide a new filler system to braze ceramics. [ABSTRACT FROM AUTHOR]

In order to relieve high residual stresses between ceramics and metals during brazing processes, an AgCuTi/graphene-reinforced Cu foam composite filler was developed and used to braze the ZrB 2 -SiC ceramic and Inconel 600 alloy. Microstructures and shear strengths of the joints were systematically studied. The joints are composed of TiFe 2 , TiCu, TiC, Cu(s, s), Ag(s, s), and Ti 5 Si 3 phases. It is found the addition of graphene on the Cu foam surface can effectively retard diffusions of metal atoms and avoid the collapse of the foam matrix. After being brazed at 900 °C, the joint can get a maximum shear strength of 157 MPa, much higher than those brazed without graphene addition. The high shear strength was investigated in detail and attributed to the integrity of the Cu foam, formation of the TiC and thickness of the reaction layer at the ceramic side. [ABSTRACT FROM AUTHOR]