AgCuTi/graphene-reinforced Cu foam: A novel filler to braze ZrB2-SiC ceramic to Inconel 600 alloy

Abstract

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 ZrB2-SiC ceramic and Inconel 600 alloy.Microstructures and shear strengths of the joints were systematically studied. The joints are composed of TiFe2, TiCu, TiC, Cu(s, s), Ag(s, s), and Ti5Si3 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 o 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.

Effect of metallization temperature on brazing joints of SiC ceramics and 2219 aluminum alloy

“…The fracture path of the joint was marked by an arrow. The more severe interfacial reaction, possible existence of oxidation of Ag‐Cu‐Ti or the possible outflow of Ag‐Cu‐Ti liquid alloy away the surface of SiC ceramics could contribute to the low shear strength of the brazed joint 9 …”

“…The metallized layer, formed by the reaction of Ag‐Cu‐Ti and SiC, has an important effect on the properties of the joint 27 . The following equation occurs between Ti and SiC: 9,18,21,23,28,34,35 …”

“…However, the mismatch in the coefficient of thermal expansion (CTE) and Young's modulus between the ceramic and metals leads to high residual stress concentrate on the brazed joint. Stress corrosion cracking, low bearing capacity, and low fatigue strength are related to the presence of residual stress (performance of SiC ceramics used in this work is shown in Table 1, and the linear expansion coefficient of aluminum alloy is 23 × 10 −6 /°C) 7–10 . Besides, the aluminum alloy is easily oxidized and forms an oxide layer during brazing.…”

Effect of the B4C particles on the brazed joints of SiC ceramics and 2219 aluminum alloy

“…When the content of B 4 C was too high, it tended to form small blocks (the aggregated B 4 C as shown in Figure 10), which affected the fluidity of the alloy, split the solid solution with good plasticity, resulted in the more complex stress situation in the joint. At the same time, the B 4 C particle also consumed too much active Ti element, the reaction between Ti and SiC base material to form a reaction diffusion layer was hindered 6,31,32 . The shear strength of brazed joints with different B 4 C additions confirmed this analysis, as shown in Figure 11.…”

“…They usually need to be connected for performing certain properties and broadening their application in industry. And brazing is a relative promising way to connect dissimilar materials with incompatible properties, although the mismatch in the coefficient of thermal expansion (CTE) and Young's modulus between the ceramic and metals will lead to high residual stress concentration on the brazed joint, so as to make the mechanical properties of the brazed joint deteriorated 5,6,7 . (Performance of SiC ceramics used in this work is shown in Table 1, and the CTE of aluminum alloy is 23 × 10 −6 /K) 5,8–10 .…”