基于EBSD的Z2CND18.12N鋼疲勞損傷研究
發(fā)布時(shí)間：2018-08-13 21:02
【摘要】：Z2CND18.12N奧氏體不銹鋼是壓水堆核電站穩(wěn)壓器波動(dòng)管主要用鋼,長(zhǎng)期服役于高溫、高壓、腐蝕、輻照等惡劣環(huán)境,易在循環(huán)載荷作用下發(fā)生疲勞損傷。理解其疲勞損傷機(jī)理并評(píng)價(jià)其損傷程度對(duì)于預(yù)測(cè)裂紋的起始位置、理解其萌生和擴(kuò)展行為十分關(guān)鍵,同時(shí)也是保證核電構(gòu)件安全運(yùn)行的迫切要求。本文主要利用電子背散射衍射(Electron Back-scatter Diffraction, EBSD)技術(shù)對(duì)Z2CND18.12N奧氏體不銹鋼循環(huán)變形損傷行為進(jìn)行了研究,主要內(nèi)容如下：(1)利用EBSD技術(shù)對(duì)材料晶體取向分布進(jìn)行分析,通過(guò)晶體取向和駐留滑移帶信息推演出激活的滑移系。分析了晶體取向?qū)せ罨葡档挠绊?發(fā)現(xiàn)最大Schmid因子越大的晶粒內(nèi)越容易產(chǎn)生駐留滑移帶,然而激活的滑移系只有80%滿足Schmid定律。不滿足Schmid定律的主要為小尺寸晶粒。同時(shí),在整個(gè)疲勞加載過(guò)程中,尺寸較大的晶粒內(nèi)駐留滑移帶產(chǎn)生的較早,當(dāng)加載至3500周次還未產(chǎn)生明顯駐留滑移帶的也主要為小尺寸晶粒。說(shuō)明Z2CND18.12N鋼疲勞損傷不僅受晶體取向的影響,晶粒尺寸的不均勻也必須得到重視。(2)討論了常用的EBSD損傷評(píng)價(jià)參數(shù)。其中,花樣質(zhì)量能夠反應(yīng)材料力學(xué)損傷過(guò)程內(nèi)部微缺陷的變化,局域取向差和應(yīng)變分布圖可以反應(yīng)損傷過(guò)程中材料微觀塑性應(yīng)變的變化。對(duì)Z2CND18.12N鋼的疲勞損傷行為進(jìn)行了分析。結(jié)果發(fā)現(xiàn),花樣質(zhì)量隨著損傷的增加而降低,局域取向差和最大取向差都呈增大趨勢(shì)。其中,最大取向差對(duì)損傷更為敏感。(3)微區(qū)損傷分析發(fā)現(xiàn),受晶粒間位向關(guān)系和晶粒所處環(huán)境的影響,晶粒內(nèi)塑性應(yīng)變分布并不均勻,傾向于在晶界和小尺寸晶粒附近增加,表現(xiàn)為局域取向差值較大。這與位錯(cuò)滑移是否被阻礙有關(guān),而與表面滑移帶的數(shù)量無(wú)關(guān)。在多晶粒的交點(diǎn)和小尺寸晶粒附近,多個(gè)晶粒內(nèi)的滑移被阻礙,導(dǎo)致局域取向差變化較大。但當(dāng)小尺寸晶粒與小尺寸晶粒相鄰時(shí),尤其是當(dāng)相鄰晶界長(zhǎng)度與晶粒尺寸相近時(shí),晶界長(zhǎng)度的影響減弱,在塑性變形過(guò)程中晶粒間的位向關(guān)系起主導(dǎo)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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TG142.1
本文編號(hào)：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.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TG142.1
【參考文獻(xiàn)】
相關(guān)期刊論文 前2條
1 劉廷光;夏爽;茹祥坤;楊輝輝;李慧;白琴;;利用EBSD技術(shù)分析低應(yīng)變量形變顯微組織[J];電子顯微學(xué)報(bào);2011年Z1期
2 劉慶;;電子背散射衍射技術(shù)及其在材料科學(xué)中的應(yīng)用[J];中國(guó)體視學(xué)與圖像分析;2005年04期
，本文編號(hào)：2182177
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