Effect of Scan Amplitude on Microstructure and Properties of CuCrZr Alloy Block/Foil Soft Connection Electron Beam Welded Joint

Welding tests were carried out on 60 mm thick CuCrZr alloy block/CuCrZr foil soft connection for nuclear fusion reactors by the vacuum electron beam welding method. The effects of scan amplitude (1.5, 2.0, 2.5 mm) on the joint morphology, microstructure, hardness and tensile properties were studied. The results show that with increasing scan amplitude , both the weld melting depth and the width increased, and the depth-to-width ratio decreased. The joint consisted of base metal, heat-affected zone on the alloy block side and weld, and the weld was divided into alloy block weld and foil soft connection weld. The weld zone was mainly composed of equiaxed grains and columnar grains, and the grain size of the foil soft connection weld was larger than that of the alloy block weld. The heat-affected zone was composed of equiaxed grains.The amount of elemental Cr in the weld was less than that in the heat-affected zone. With the increase of the scan amplitude, the grain sizes of both the weld and the heat-affected zone increased, and the amount of elemental Cr in the heat-affected zone decreased. The hardness of heat-affected zone on the alloy block side of the joint was the lowest, and the hardness of the weld was between the alloy block base metal and the foil soft connection base metal; the hardness of the alloy block weld was slightly higher than that of the foil soft connection weld. With the increase of scan amplitude, the hardness of the weld and the heat-affected zone and the tensile strength and the percentage elongation after fracture of the joint all decreased. The tensile strength of the joints under different scan amplitudes was lower than that of the base metal, and the fracture occurred at the alloy block weld.