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350℃下,对N36锆合金包壳管环形试样施加周向拉伸载荷,绘制碘浓度分别为102、103、104 Pa下的应力-延伸率曲线,研究包壳材料在碘气体(I2)环境下的碘致应力腐蚀开裂(I-SCC)情况。应力-延伸率曲线能够衡量锆合金包壳管发生I-SCC开裂的敏感性:当I-SCC发生时,在曲线中表现为没有明显的颈缩阶段。在应力-延伸率曲线上可以找出I-SCC裂纹萌生、扩展的相应发生阶段。I-SCC降低材料的延伸率和断裂能量,降低程度均随着碘浓度的升高而增加。I-SCC环形试样在周向拉伸过程中产生平行于断口的裂纹沟槽,裂纹起始阶段均为沿晶扩展形式。
The circumferential tensile load was applied to the ring specimen of N36 zirconium alloy cladding tube at 350 ℃, and the stress-elongation curves of iodine concentration were plotted at 102, 103 and 104 Pa respectively. Environment Iodine stress corrosion cracking (I-SCC) situation. The stress-elongation curve measures the sensitivity of zirconium alloy claddings to I-SCC cracking: when I-SCC occurs, there is no apparent neck-down in the curve. On the stress-strain curve, we can find the corresponding stage of initiation and propagation of I-SCC crack. I-SCC reduces the material elongation and fracture energy, the degree of reduction increases with increasing iodine concentration. The I-SCC ring specimen produced a crack groove parallel to the fracture during the circumferential drawing. The crack initiation phase was in the form of crystal growth.