共查询到18条相似文献,搜索用时 46 毫秒
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利用扫描电镜和EDXA对新锆合金碘致应力腐蚀的断口进行了形貌观察和成分分析。在断口表面发现腐蚀产物、二次裂纹、沿晶开裂和穿晶准解理开裂等应力腐蚀断裂特征,并观察到锆合金碘致应力腐蚀的“沟槽”特征。起裂区为沿晶开裂,在裂纹扩展阶段,开裂以穿晶为主。断口上腐蚀产物的成分主要是氧和锆,局部准解理开裂区域可检测到碘。去应力退火试样上发现了平行轧面的深沟,且沿晶开裂不明显。试验温度升高,断口上的腐蚀产物增多,而且沿晶开裂更容易。碘分压不仅影响腐蚀产物层的厚度,而且碘分压较高时沿晶开裂容易发生。 相似文献
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发展了两种新型锆合金(N18,N36)作为PWR燃料元件包壳材料。研究了N18,N36两种锆合金的堆外性能。研究表明,具有均匀弥散分布的细小β-Nb或Zr(Fe,Cr)2第二相粒子的新合金表现出最好的抗腐蚀性能,N18和N36合金都有优良的耐腐蚀性能。合金的吸氢行为与其腐蚀行为成对应关系,而两种新型锆合金的吸氢比Zr-4合金的低。两种新锆合金的拉伸强度、爆破和蠕变性能也优于Zr-4合金。此外,两种新锆合金的热物理性能、织构和应力腐蚀行为相当或优于Zr-4合金。 相似文献
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锆合金耐腐蚀性能研究综述 总被引:8,自引:0,他引:8
锆合金主要用作核反应堆燃料元件的包壳材料及其他堆内构件。回顾了有关锆合金水侧腐蚀的主要研究结果及存在的问题,概括了现有的理论及面临的挑战。80年代,关于锆合金化学成分、微观结构及辐照对耐腐蚀性能影响的研究取得了很大进展。近几年来的研究工作主要集中在探索腐蚀机理、选择最佳合金成分及控制微观结构方面,以满足提高燃耗、降低核电成本后对锆合金提出的更高要求。 相似文献
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核反应堆用锆合金构件在服役过程中会发生氢致延迟开裂(HIDC)而失效,构件表面的微缺陷是否会引起HIDC是值得研究的问题。本文采用真空电子束焊接方法制备表面有微缝隙缺陷的样品,以研究这类微缝隙缺陷在400℃过热蒸汽中腐蚀以及在350℃高压水中热循环处理过程中的行为。由于这类缺陷处会形成尖劈状的氧化膜并镶嵌在金属中,在氧化膜前端将形成应力集中和应力梯度区,引起氢的扩散、富集和氢化物析出,即使样品中原先没有残余应力,也没有受到外加应力的作用,也会发生HIDC导致裂纹扩展而开裂。因此,在设计和加工制造核反应堆堆芯中锆合金的各种结构件时,需要重视如何避免锆合金构件表面可能生成这种缺陷的问题。 相似文献
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固溶态控氮不锈钢在高温水中的应力腐蚀破裂 总被引:1,自引:0,他引:1
采用高温电化学测控和慢应变拉伸实验方法,研究了304NG超低碳控氮不锈钢(固溶态)在250℃高温水中的应力腐蚀破裂(SCC)与电极电位和水中Cl^-浓度的关系,并与316LN控氮不锈钢对比:结果表明,在不同环境下两种不锈钢的SCC敏感性随电极电位的升高而升高,并且存在一个临界电位Ec,当电位高于该Ec时,才发生SCC。该临界电位Ec随水中Cl^-浓度升高而下降,即发生SCC的环境范围扩大。304NG钢在含5mg/L Cl^-的250℃高温水中的Ec处于0~+200mV标准氢电极(SHE)之间,更高时发生穿晶型SCC,表明该Cl^-浓度下只有在高氧(高电位)环境中才能发生SCC。当Cl^-浓度升高到50mg/L时,Ec降到-700mV(SHE)以下,表明该浓度下即使完好除氧(低电位)也可能发生SCC。316LN的SCC抗力高于304NG,其在含5mg/L Cl^-的高温水中的Ec位于+300~+400mV(SHE)之间,主要是穿晶型SCC。 相似文献
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采用紧凑拉伸(CT)试样.研究了不同氢含量的Zr-4及Zr-Sn-Nb合金在室温下疲劳加载裂纹扩展(dα/dN)行为.用扫描电镜观察了断口形貌。结果表明,氢含量对疲劳裂纹扩展速率影响微弱,疲劳断裂受通常的裂纹萌生、稳态扩展和瞬间断裂机制控制。根据疲劳裂纹扩展机理.导出了裂纹扩展门槛值△Kth的关系式.得出了一个描述疲劳裂纹扩展速率油(dα/dN)与材料性能常数之间的关系式,该关系式可用于预测材料的疲劳裂纹扩展速率。用锆合金实验数据对(dα/dN)预测表达式进行验证.结果表明,预测值与实验值吻合较好。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(6):443-451
Iodine stress corrosion cracking of Zircaloy-2 cladding under static tensile stress has been studied over the temperature range of 250~450°C. The lowest iodine concentration required to cause cracking was 0.15 mg iodine per cm3 free volume in test ampoule at 300°C, and 1.1 mg/cm' at 350°C. The minimum circumferential plastic strain to cause failure was about 0.4% for specimen tubes possessing high cracking susceptibility. Softer tubes tolerate more circumferential deformation before they failed. This is attributed to greater margin retained for work hardening, rather than to smaller residual tensile hoop stress. Cracking was also inhibited by the presence of oxygen in the iodine atmosphere, the threshold partial pressures being 28 torr at 300°C and 9 torr at 350°C. Scanning electron micrographs of the fractured surfaces revealed brittle transgranular fracture carrying river patterns on part of the cleavage facets. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(9):654-661
The role of β-particles for the localized in-pile corrosion of components made of zirconium alloys, such as fuel channels closely facing stainless steel components, has been discussed and the distribution of β-particles near fuel channels has been evaluated using a multi-layer calculation method. It is shown that electric charges which come from β-particles produced mainly by the Compton effect, but not by β-emitting radionuclides, make electric fields in and on the zirconium oxide surfaces in the reactor by a model analogous to an electric circuit, and that these electric fields induced by β-particles could be essential for the understanding of localized in-pile corrosion of zirconium alloys. The mechanism of the localized in-pile corrosion of zirconium alloys adjacent to other welded alloys is also discussed as an enhanced corrosion by electric potentials using the proposed electric circuit model in detail. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):930-939
Ring tension testing methods were applied for studying the iodine stress corrosion cracking (SCC) behavior of unirradiated cold-worked (CW) and recrystallized (RX) Zircaloy-2 tubing at 300°C. Two kinds of tests—constant load and constant cross-head speed—were conducted on the grooved ring tension specimen simulating a plane-strain stress state under uniaxial loading, as well as on the simple ring tension specimen. The results showed that SCC failure threshold stresses were approximately 450 and 300 MPa, respectively, for the grooved CW and RX specimens. The ratio between the threshold stress of the grooved specimen and the yield stress derived from the simple specimen is equal to 1.4 for both CW and RX materials. The threshold value of the grooved RX specimen is 1.3 times larger than found on the same material of simple shape, which corresponds to the yield stress ratio between the grooved and simple specimens. Inside surface observations of specimens stressed in iodine environment suggested that corrosion lines, presumably corresponding to corrosion pits, and chemical attacks on grain boundaries would be incipient phases of SCC for CW and RX materials, respectively. They may appear at stresses lower than those for SCC failure. 相似文献