充氚不锈钢微观组织及断裂特征

采用力学拉伸实验测定充氚不锈钢的断裂强度值,采用拉伸断口进行SEM观察和正电子湮灭(PAT)分析,采用TEM动态拉伸实验观察和记录材料在微观断裂过程中的行为,通过对比分析氚对不锈钢断裂过程的影响。结果表明,高温充氚后,室温存放2a,样品中氚衰变产生的氦累积已达约30ppm;氚、氦使样品断裂强度降低,内部缺陷增多,正电子寿命变长。TEM观察未发现明显的氦泡组织;动态拉伸实验表明,充氚促进裂纹尖端位错的发射和增殖;HR-1、HR-2不锈钢微观断裂过程相似,可表述为氚致微裂纹的形核-形成微空洞-微空洞长大-空洞连接(断裂)。氚、氦使无位错区减小甚至消失。

Fracture Mechanism of Stainless Steel Charging With Tritium

Based on diffusion equation, the concentration of hydrogen isotopes and helium in the stainless steel film specimen aging at room temperature for two years was calculated and measured by finite diffusion method. The fracture strength was measured by tension test. The SEM and PAT were applied for the investigation of the fracture. The initiation and propagation of cracks were investigated in situ by tension in TEM at room temperature. The effect of tritium on the fracture of stainless steel was evaluated. The results show that the concentration of helium from the decay of tritium in the stainless steel aging at room temperature for two years is up to 30 ppm. The fracture strength decreases by the existence of helium and tritium. The increase of the defects makes the lifetime of positron annihilation longer. There are no helium bubbles by TEM. The tension process in TEM indicates that the tritium provokes the emission, propagation of dislocation in the cracks tip. The micro fracture process of HR-1 SS and HR-2 SS can be described that tritium cracks nucleate, blunt to microvoids and then incorporate into crazing tritium which results in the lessening or vanishing of the dislocation free zone (DFZ) for HR-2 SS.