Regulating the interfacial reaction of Sc₂W₃O₁₂/AgCuTi composite filler by introducing a carbon barrier layer

Negative thermal expansion (NTE) materials can offset the high expansion of metal brazing alloys, and play a key role in alleviating the residual stress and improving the mechanical properties of the joint. However, in Sc₂W₃O₁₂ reinforced AgCuTi composite filler, the strong interfacial reaction between active Ti and Sc₂W₃O₁₂ has become a bottleneck restricting the NTE behavior of Sc₂W₃O₁₂. Herein, a novel strategy is proposed by designing a carbon barrier layer between active filler and Sc₂W₃O₁₂ materials. Under the guidance of experimental results and theoretical analysis, the interface evolution mechanism is proposed. The results show that the carbon barrier layer increases the diffusion path of Ti atoms and weakens the interfacial reaction. With the help of carbon barrier layer, Sc₂W₃O₁₂ gives full play to its NTE behavior during brazing, and the retention rate increases from 65.8% to 97.6%. Consequently, a highest shear strength of ∼77 MPa is achieved in the C/SiC-GH3536 joints by the designed composites filler, which is 1.3 times higher than that without carbon barrier layer and 3.2 times higher than that of AgCuTi filler. Our work opens the way for expanding the application of NTE materials in brazing process, and also provides new insights for the development of low-CTE composites.