Fabrication of the Cu/AgCuTi/Nb composite for superconducting radio-frequency material under extreme service conditions based on electroplating additive manufacturing

The primary objective of this study is the development of Cu/Nb composite materials for Superconducting Radio-Frequency (SRF) applications under extreme service conditions characterized by a strong RF electromagnetic field, extremely low temperatures, and relatively low heat loss. A novel integrated manufacturing approach is proposed, which combines cold-sprayed AgCuTi alloy as an intermediate coating on the Nb surface and an electroplated Cu layer with a subsequent heat treatment brazing effect. This strategy aims to address the significant challenge of non-intermelting Cu and Nb while also considering effective lateral heat transfer. Mechanical property tests showed that the bond strength of Nb/AgCuTi/Cu composites exceeded 150 MPa. Low-temperature thermal transport tests indicate that the Residual Resistance Ratio (RRR) of the Cu layer surpasses 150, with a thermal conductivity at 4.2 K exceeding 1600 W/(m·K). Moreover, both the composite interface and mechanical properties of the specimens remain stable even after undergoing cyclic cold shock experiments. These findings suggest that the Nb/AgCuTi/Cu composite material developed in this study meets the technical requirements for long-term stable and high-performance operation in high-current and high-power superconducting accelerators.