本文用带有拉伸装置的扫描电镜和金相显微镜,研究了纯Nb在室温电解充氢后形变和断裂的动态微观行为。结果表明,Nb的氢化物都在{100}晶面析出,较多的正交针状氢化物能构成魏氏组织。固溶氢的α基体在拉伸变形时,有明显的滑移线和晶界凸起,裂纹萌生在形变带或晶界处。含氢化物的基体在拉伸时表现出完全的脆性,呈穿晶解理断裂。解理面上有各种脆性断裂特征的花样和两种氢化物,裂纹多从氢化物处萌生。
SEM and optical microscope in situ examinations under tensile loading were performed on the effect of hydrogen upon the microprocess of deformation and fracture behaviour in cathodic charged pure Nb. The Nb hydrides are found to precipitate on the {100} plane of matrix. Most dendritic hydrides in orthorhombic needleshape are of the Widmanstatten structure. The slip lines and grain boundary hunches are obviously observed in the α-solid solution matrix with hydrogen dissolved under tensile deformation. The microcracks initiated themself along the slip lines predominately and the deformation bands as well as the grain boundary oriented normal to the stress axis. The main crack propagation is the coalescence of micro-craks in the vicinity of the crack tip and through the transgranular path. The α-solid solution matrix with β-hydride is extremely brittle and of transgranular cleavage fracture under tension. The micro-patterns featuring all brittle fractures and two β-hydrides are appeared on the cleavage facets. The mierocrack growth are presented at the hydride/matrix interface. The crystal orientation of hydrogen embrittlement cleavage facets in pure Nb, the stress induced β-hydride and two typical hydrogen embrittlement mechanisms of pure Nb have been also discussed.
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