样品尺寸对RAFM钢韧脆转变区内断裂行为的影响研究  

Investigating the Effect of Sample Size on the Fracture Behavior Within the Ductile-Brittle Transition Region of RAFM

作　　者：陈卓辉 施展泽 杨万欢 赵迎超 宁广胜[1] 白冰[1] 杨文[1] CHEN Zhuohui;SHI Zhanze;YANG Wanhuan;ZHAO Yingchao;NING Guangsheng;BAI Bing;YANG Weng(Division of Reactor Engineering Technology Research,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院反应堆工程技术研究部,北京102413

出　　处：《核科学与工程》2024年第6期1427-1436,共10页Nuclear Science and Engineering

基　　金：国家磁约束核聚变能发展研究专项2022YFE03120002;中核集团青年英才项目FY222506000902;中国原子能科学研究院院长基金项目YZ232602000702。

摘　　要：聚变堆包层的候选材料低活化铁素体马氏体不锈钢(RAFM)经辐照后的断裂韧性K_(Jc)和韧脆转变温度T_(0)测试需要用到小尺寸紧凑拉伸(CT)样品。而小样品断裂韧性测值偏大,主曲线方法可以解释部分尺寸效应。然而随着温度的升高,部分小样品测值仍偏大,计算出的主曲线T_(0)也严重不实,表现出尺寸造成的断裂行为差异。研究此差异形成有助于筛选影响T_(0)计算准确性的无效数据。使用国产RAFM钢CLF-1的1/2和1/6CT样品进行断裂韧性试验,同时对断裂面微观特征进行了测量。结果表明两种样品断面上的塑性区宽度随K_(Jc)呈同一指数增长规律,裂纹前沿塑性区大小与K_(Jc)的关系同尺寸和温度无关。K_(Jc)<225 MPa m时裂纹源距离随断裂韧性值线性增长,而更高K_(Jc)下1/6CT样品裂纹源距离偏小,1/2CT裂纹源距离仍增大,表明此时1/6CT样品的裂纹拓展造成了应力卸载,无法反应材料真实韧性。以1/6CT不发生卸载的最大K_(Jc)作为限值用于T_(0)计算,能够改善计算结果。同时塑性区占韧带比例可作为判断断裂行为是否发生改变的指标。Reduced activation ferritic martensitic stainless steel(RAFM)is one of the candidate materials for cladding of fusion reactors due to its excellent radiation resistance.The fracture toughness K_(Jc)and the toughness and brittleness transition temperature T_(0)of irradiated materials can reflect the degree of irradiation embrittlement,while the fracture toughness test under ultra-high dose conditions needs to use small size compact tensile(CT)samples due to the limitation of sample-induced radioactivity.The decrease of the size will result in a larger K_(Jc)measurement,which can be equivalent to the measurement of standard thickness samples based on the Weakest Link theory.However,with the increase of temperature,the K_(Jc)value of some small samples after equivalence is still higher than the actual situation of standard samples,and the calculated Main Curve T_(0)is also seriously untrue.This shows the difference in the fracture behavior caused by the sample size.Studying this difference formation is helpful for screening the invalid data that affect the accuracy of T_(0)calculation.In this paper,1/2 and 1/6CT samples of RAFM steel CLF-1 were used for K_(Jc)tests,and the microscopic characteristics of the fracture surface were measured.The results show that the width of the plastic zone on 1/2 and 1/6CT specimens is the same as the exponential growth law with K_(Jc),and the relationship between plastic zone size and K_(Jc)is independent of size and temperature.When K_(Jc)<225 MPa m,the crack source distance increases linearly with the fracture toughness value,while at higher K_(Jc),the crack source distance of 1/6CT sample is smaller,and the crack source distance of 1/2CT sample still increases,indicating that the crack development of 1/6CT sample causes stress unloading at this situation,which cannot reflect the true toughness of the material.Using the maximum K_(Jc)of 1/6CT without unloading as the limit for T_(0)calculation can improve the calculation result.At the same time,the proportion of the plastic zone i

关 键 词：RAFM钢 断裂韧性 尺寸效应 扫描电镜 

分 类 号：TG142.15[一般工业技术—材料科学与工程]