A microstructural study of phosphorus segregation and intergranular fracture in neutron irradiated submerged-arc welds
A microstructural study of phosphorus segregation and intergranular fracture in neutron irradiated submerged-arc welds
复制标题
中子辐照埋弧焊缝磷偏析和沿晶断裂的显微组织研究
DOI：
10.1520/stp16478s
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
R. Wild
中科院分区：
文献类型：
--
作者：
P. Bischler;R. Wild
对埋弧焊焊缝进行了加速辐照实验，以验证由监测结果建立的趋势曲线。这是通过取出监测样本并在更高通量位置对其进行再辐照来完成的。来自焊缝HS的一批样本在相似剂量下，其夏比冲击转变温度（\(\Delta T_{40J}\)）值的升高明显高于焊缝LS。本文描述了为解释这种差异所做的工作。使用屏蔽扫描电子显微镜对选定的夏比试样进行了检查，以确定存在的断裂模式。在过渡区断裂的HS焊缝试样上发现了混合解理、微孔聚合（MVC）和晶间断裂（IGF）区域。IGF局限于每个焊道内的某些区域。在LS焊缝试样上发现的IGF明显较少。从脆化区域取出亚断裂面火柴棍状试样，并在扫描俄歇显微镜内使其断裂。在这些试样中出现了IGF，并且发现磷是主要的晶界偏析元素。磷的含量随着中子剂量的增加而增加。在任何显著水平上都没有始终发现其他脆化元素，但在某些情况下在晶界表面也发现了碳。确定了每种焊缝在几个中子剂量水平下磷的晶界覆盖度。
Accelerated irradiation experiments have been carried out on submerged-arc welds to obtain validation of trend curves built up from surveillance results. This was done by withdrawing surveillance specimens and re-irradiating them in higher flux positions. One batch, from weld HS, showed a significantly higher increase in the Charpy {Delta}T{sub 40J} value than that for weld LS at a similar dose. Work done to explain this difference is described in this paper. Selected Charpy specimens were examined using a shielded scanning electron microscope to determine the fracture modes present. Regions of mixed cleavage, micro-void coalescence (MVC) and intergranular failure (IGF) were found on HS weld specimens fractured in the transition region. The IFG was confined to certain regions within each weld bead. Significantly less IGF was found on LS weld specimens. Sub-fracture surface matchstick specimens were removed from embrittled regions and fractured within a scanning Auger microscope. IGF occurred in these specimens, and phosphorus was found to be the main grain boundary segregant. The levels of phosphorus increased with increasing neutron dose. No other embrittling element was consistently found at any significant level, but carbon was also found on grain boundary surfaces in some cases. The grain boundary coverage of phosphorusmore » was determined for each weld at several neutron dose levels.« less