基于EBSD的Z2CND18.12N钢疲劳损伤研究
发布时间：2018-08-13 21:02
【摘要】：Z2CND18.12N奥氏体不锈钢是压水堆核电站稳压器波动管主要用钢,长期服役于高温、高压、腐蚀、辐照等恶劣环境,易在循环载荷作用下发生疲劳损伤。理解其疲劳损伤机理并评价其损伤程度对于预测裂纹的起始位置、理解其萌生和扩展行为十分关键,同时也是保证核电构件安全运行的迫切要求。本文主要利用电子背散射衍射(Electron Back-scatter Diffraction, EBSD)技术对Z2CND18.12N奥氏体不锈钢循环变形损伤行为进行了研究,主要内容如下：(1)利用EBSD技术对材料晶体取向分布进行分析,通过晶体取向和驻留滑移带信息推演出激活的滑移系。分析了晶体取向对激活滑移系的影响,发现最大Schmid因子越大的晶粒内越容易产生驻留滑移带,然而激活的滑移系只有80%满足Schmid定律。不满足Schmid定律的主要为小尺寸晶粒。同时,在整个疲劳加载过程中,尺寸较大的晶粒内驻留滑移带产生的较早,当加载至3500周次还未产生明显驻留滑移带的也主要为小尺寸晶粒。说明Z2CND18.12N钢疲劳损伤不仅受晶体取向的影响,晶粒尺寸的不均匀也必须得到重视。(2)讨论了常用的EBSD损伤评价参数。其中,花样质量能够反应材料力学损伤过程内部微缺陷的变化,局域取向差和应变分布图可以反应损伤过程中材料微观塑性应变的变化。对Z2CND18.12N钢的疲劳损伤行为进行了分析。结果发现,花样质量随着损伤的增加而降低,局域取向差和最大取向差都呈增大趋势。其中,最大取向差对损伤更为敏感。(3)微区损伤分析发现,受晶粒间位向关系和晶粒所处环境的影响,晶粒内塑性应变分布并不均匀,倾向于在晶界和小尺寸晶粒附近增加,表现为局域取向差值较大。这与位错滑移是否被阻碍有关,而与表面滑移带的数量无关。在多晶粒的交点和小尺寸晶粒附近,多个晶粒内的滑移被阻碍,导致局域取向差变化较大。但当小尺寸晶粒与小尺寸晶粒相邻时,尤其是当相邻晶界长度与晶粒尺寸相近时,晶界长度的影响减弱,在塑性变形过程中晶粒间的位向关系起主导作用。
[Abstract]:Z2CND18.12N austenitic stainless steel is the main steel used in pressurizer fluctuation tube of PWR nuclear power station. It is used in high temperature, high pressure, corrosion and radiation environment for a long time, and it is easy to cause fatigue damage under cyclic load. It is very important to understand the fatigue damage mechanism and evaluate the damage degree to predict the starting position of crack and to understand its initiation and propagation behavior. It is also an urgent requirement to ensure the safe operation of nuclear power components. In this paper, the cyclic deformation damage behavior of Z2CND18.12N austenitic stainless steel is studied by electron backscattering diffraction (Electron Back-scatter Diffraction, EBSD). The main contents are as follows: (1) the orientation distribution of Z2CND18.12N austenitic stainless steel is analyzed by EBSD technique. The active slip system is derived from the crystal orientation and the information of the resident slip band. The effect of crystal orientation on the active slip system is analyzed. It is found that the larger the maximum Schmid factor is, the easier is the resident slip band in the grain. However, only 80% of the active slip system satisfies the Schmid law. Small grain size is the main one that does not satisfy Schmid's law. At the same time, during the whole fatigue loading process, the resident slip bands in the larger grains occur earlier, and when the loading times to 3500 weeks, the obvious resident slip bands are mainly small grains. The results show that the fatigue damage of Z2CND18.12N steel is not only affected by the crystal orientation, but also the inhomogeneity of grain size must be paid attention to. (2) the commonly used parameters of EBSD damage evaluation are discussed. The pattern mass can reflect the change of internal microdefects in the process of material mechanical damage, and the local orientation difference and strain distribution map can reflect the change of microplastic strain of the material during the damage process. The fatigue damage behavior of Z2CND18.12N steel was analyzed. The results show that the pattern mass decreases with the increase of damage, and the local orientation difference and the maximum orientation difference increase. Among them, the maximum orientation difference is more sensitive to the damage. (3) the microzone damage analysis shows that the plastic strain distribution in the grain is not uniform due to the influence of the grain orientation relationship and the grain environment, and tends to increase near the grain boundary and small grain size. The local orientation difference is larger. This is related to whether dislocation slip is blocked, but not to the number of surface slip bands. Near the intersection point of multi-grain and small grain, the slip in multiple grains is blocked, which leads to a large variation of local orientation difference. However, when the grain size is adjacent to the grain size, especially when the grain boundary length is close to the grain size, the influence of grain boundary length is weakened, and the orientation relationship between the grains plays a leading role in the plastic deformation process.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1
本文编号：2182177
[Abstract]:Z2CND18.12N austenitic stainless steel is the main steel used in pressurizer fluctuation tube of PWR nuclear power station. It is used in high temperature, high pressure, corrosion and radiation environment for a long time, and it is easy to cause fatigue damage under cyclic load. It is very important to understand the fatigue damage mechanism and evaluate the damage degree to predict the starting position of crack and to understand its initiation and propagation behavior. It is also an urgent requirement to ensure the safe operation of nuclear power components. In this paper, the cyclic deformation damage behavior of Z2CND18.12N austenitic stainless steel is studied by electron backscattering diffraction (Electron Back-scatter Diffraction, EBSD). The main contents are as follows: (1) the orientation distribution of Z2CND18.12N austenitic stainless steel is analyzed by EBSD technique. The active slip system is derived from the crystal orientation and the information of the resident slip band. The effect of crystal orientation on the active slip system is analyzed. It is found that the larger the maximum Schmid factor is, the easier is the resident slip band in the grain. However, only 80% of the active slip system satisfies the Schmid law. Small grain size is the main one that does not satisfy Schmid's law. At the same time, during the whole fatigue loading process, the resident slip bands in the larger grains occur earlier, and when the loading times to 3500 weeks, the obvious resident slip bands are mainly small grains. The results show that the fatigue damage of Z2CND18.12N steel is not only affected by the crystal orientation, but also the inhomogeneity of grain size must be paid attention to. (2) the commonly used parameters of EBSD damage evaluation are discussed. The pattern mass can reflect the change of internal microdefects in the process of material mechanical damage, and the local orientation difference and strain distribution map can reflect the change of microplastic strain of the material during the damage process. The fatigue damage behavior of Z2CND18.12N steel was analyzed. The results show that the pattern mass decreases with the increase of damage, and the local orientation difference and the maximum orientation difference increase. Among them, the maximum orientation difference is more sensitive to the damage. (3) the microzone damage analysis shows that the plastic strain distribution in the grain is not uniform due to the influence of the grain orientation relationship and the grain environment, and tends to increase near the grain boundary and small grain size. The local orientation difference is larger. This is related to whether dislocation slip is blocked, but not to the number of surface slip bands. Near the intersection point of multi-grain and small grain, the slip in multiple grains is blocked, which leads to a large variation of local orientation difference. However, when the grain size is adjacent to the grain size, especially when the grain boundary length is close to the grain size, the influence of grain boundary length is weakened, and the orientation relationship between the grains plays a leading role in the plastic deformation process.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1
【参考文献】
相关期刊论文 前2条
1 刘廷光;夏爽;茹祥坤;杨辉辉;李慧;白琴;;利用EBSD技术分析低应变量形变显微组织[J];电子显微学报;2011年Z1期
2 刘庆;;电子背散射衍射技术及其在材料科学中的应用[J];中国体视学与图像分析;2005年04期
，本文编号：2182177
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