Abstract: Electron beam-physical vapor deposition, scanning electron microscopy, X-ray diffraction and finite element simulation were used to study the effect of crack in micrometer scale on the failure of water-cooled oxygen-free copper crucible. The temperature distribution of the water-cooled copper crucible ranged from 33 to 183 ℃, and the highest temperature region was referred to the interference fit at the water channel near the water outlet. The cross section of the upper part of the inner wall had a large temperature gradient, which induced large thermal stress. The reason of the failure of the water-cooled copper crucible was the macrocrack induced by the thermal stress, rather than the corrosion of molten metal cerium and the formation of harmful impurity phase. The macrocrack was rooted in the microcrack in tens of micron induced by the interference fit at the water channel during the manufacturing processes of copper crucible. Under the effect of thermal stress, the microcrack grew into the approximately straight crack band. The crack band was composed of cracks with approximately parallel extension direction. Then the growing crack penetrated through the inner wall of the water-cooled copper crucible, which made the copper crucible failure. The frontal area of the inner wall varied a little in the crack growth. No obvious change happened at the regions other than the inner wall of copper crucible.

Key words: microcrack in micrometer scale, water-cooled oxygen-free copper crucible, electron beam-physical vapor deposition, material failure