Joining of oxygen-free high-conductivity Cu to CuCrZr by direct diffusion bonding without using an interlayer at Low temperature

摘要

This study describes direct diffusion bonding of OFHC to CuCrZr without using an interlayer at a temperature lower than the optimal aging temperature of CuCrZr, namely 475 degrees C. Firstly, the effects of bonding parameters on the strengths of Cu/CuCrZr joints have been studied. The most appropriate bonding parameters are a bonding pressure of 100 MPa, a bonding temperature of 450 degrees C and a bonding time of 180 min. The average shear and tensile strengths of the Cu/CuCrZr joints are similar to 128 MPa and similar to 180 MPa, respectively. The average Brinell hardness of CuCrZr after bonding is 142 HB, which meets the hardness requirement of HB >= 120 in ITER program. Secondly, thermal cycling (300 degrees C-450 degrees C) test was conducted for the Cu/CuCrZr joint. The Cu/CuCrZr joint still has good strength and toughness after thermal cycling. Thirdly, the microstructure of Cu/CuCrZr interface has been investigated. The metallurgical bonding interface between Cu and CuCrZr has been con- structed and the thickness of the diffusion layer is about 15 mu m The phases at the Cu/CuCrZr interface consist of Cu and Cr crystals and Cu5Zr compounds. Lastly, the results of ultrasonic C-scanning show that the effective bonding areas between Cu and CuCrZr can exceed 97%.