C-276合金晶界结构及性能的优化研究
发布时间：2018-07-21 13:37
【摘要】：Hastelloy C-276合金由于其高温强度高、耐腐蚀性能好,以及优异的耐氧化能力,已经被广泛应用于化工、石油、核工业等领域。近年来Hastelloy C-276合金成为第四代超临界水冷堆(SCWR)燃料包壳候选材料之一。面对严苛的工作环境,Hastelloy C-276合金需要具备更加优良的力学性能和耐腐蚀性能。如何能够经济高效的提高Hastelloy C-276合金的相关性能,是本课题的主要研究目标。材料的晶界分布特征与宏观性能之间有着至关重要的联系,如力学性能、耐腐蚀性能、蠕变性能等。“晶界工程”是Watanabe于1984年提出的晶界设计与控制这一概念发展而来的。材料的属性可以通过提高材料中特殊晶界比例(低ΣCSL晶界)进行优化。大量的科学研究表明,可以通过采用形变与热处理的组合工艺达到提高材料中特殊晶界比例的目的。对一些低层错能面心立方金属(如,镍基合金、奥氏体不锈钢、铜合金等)使用晶界工程加工工艺,都能使材料的性能得到大幅度提高。Hastelloy C-276合金也是一种低层错能面心立方金属,对Hastelloy C-276合金采用晶界工程的加工工艺,也有可能会提高其性能。本论文使用光学显微镜、扫描电子显微镜、电子背散射衍射(EBSD)等检测手段研究了轧制变形和热处理工艺对Hastelloy C-276合金晶界特征分布的影响;观察分析了轧制变形对Hastelloy C-276合金晶粒度的影响规律;通过ASTM G28-A法分析了含有不同比例特殊晶界Hastelloy C-276合金的耐腐蚀性能,并且分析了腐蚀后样品的晶界及基体析出相。同时使用万能拉伸实验机对Hastelloy C-276合金在650℃下进行了高温拉伸实验,分析了不同特殊晶界比例Hastelloy C-276合金的断裂机制。本文研究得出了得出了以下主要结论:1.与未经晶界工程工艺处理的Hastelloy C-276合金相比,晶界工程能够提高该合金的低ΣCSL晶界比例。2.Hastelloy C-276合金中特殊晶界比例的提高主要是基于退火孪晶(∑3)的形成。轧制变形量为10%,再在1120℃退火10min可使Hastelloy C-276的特殊晶界比例最高,达到57.9%。3.晶粒长大阶段并不能使特殊晶界比例提高,过长的退火时间反而会使特殊晶界比例下降。4.低ΣCSL晶界比例为57.9%的样品腐蚀速率最低,主要是因为低ΣCSL晶界比例较高的样品形成了尺寸较大的晶粒团簇,在一定程度上阻止了腐蚀的进行,保护了基体材料。腐蚀严重的样品晶界会有析出相产生,析出相的成分为Ni、Mo和Cr这些Hastelloy C-276的主要组成元素,造成材料成分不均匀,会加速材料的腐蚀。5.不同晶界特征分布的Hastelloy C-276合金的抗拉强度和屈服强度变化不大,随着低ΣCSL晶界比例的增加,抗拉强度和屈服强度有小幅度下降,是细晶强化与孪晶强化共同作用的结果。不同低ΣCSL晶界比例的Hastelloy C-276合金样品在高温下拉伸的断裂机制均为微孔聚集型断裂,断口形貌主要为深浅不一的等轴状的韧窝,有较好的高温延展性。
[Abstract]:Hastelloy C-276 alloy has been widely used in chemical, petroleum and nuclear industry due to its high temperature strength, good corrosion resistance and excellent oxidation resistance. In recent years, Hastelloy C-276 alloy has become one of the candidate materials for the fourth generation supercritical water cooled reactor (SCWR) fuel cladding. Facing the harsh working environment, Hastelloy C-276 alloy needs better mechanical properties and corrosion resistance. How to improve the correlation energy of Hastelloy C-276 alloy economically and efficiently is the main research goal of this paper. The grain boundary distribution is closely related to the macroscopic properties, such as mechanical properties, corrosion resistance, creep properties and so on. Grain boundary engineering was developed by the concept of grain boundary design and control proposed by Watanabe in 1984. The properties of the material can be optimized by increasing the specific grain boundary ratio (low 危 CSL grain boundary). A large number of scientific studies have shown that the proportion of special grain boundaries can be increased by the combination of deformation and heat treatment. The grain boundary engineering process is used for some low stacked error-energy facet cubic metals (such as nickel-based alloys, austenitic stainless steels, copper alloys, etc.). Hastelloy C-276 alloy is also a kind of low layer mission-centered cubic metal. It is possible to improve the properties of Hastelloy C-276 alloy by grain boundary engineering. In this paper, the effects of rolling deformation and heat treatment on the grain boundary characteristic distribution of Hastelloy C-276 alloy were studied by means of optical microscope, scanning electron microscope and electron backscatter diffraction (EBSD). The effect of rolling deformation on the grain size of Hastelloy C-276 alloy was observed and analyzed, and the corrosion resistance of Hastelloy C-276 alloy containing different proportion of special grain boundaries was analyzed by ASTM G28-A method. At the same time, the high temperature tensile test of Hastelloy C-276 alloy at 650 鈩，
本文编号：2135697
[Abstract]:Hastelloy C-276 alloy has been widely used in chemical, petroleum and nuclear industry due to its high temperature strength, good corrosion resistance and excellent oxidation resistance. In recent years, Hastelloy C-276 alloy has become one of the candidate materials for the fourth generation supercritical water cooled reactor (SCWR) fuel cladding. Facing the harsh working environment, Hastelloy C-276 alloy needs better mechanical properties and corrosion resistance. How to improve the correlation energy of Hastelloy C-276 alloy economically and efficiently is the main research goal of this paper. The grain boundary distribution is closely related to the macroscopic properties, such as mechanical properties, corrosion resistance, creep properties and so on. Grain boundary engineering was developed by the concept of grain boundary design and control proposed by Watanabe in 1984. The properties of the material can be optimized by increasing the specific grain boundary ratio (low 危 CSL grain boundary). A large number of scientific studies have shown that the proportion of special grain boundaries can be increased by the combination of deformation and heat treatment. The grain boundary engineering process is used for some low stacked error-energy facet cubic metals (such as nickel-based alloys, austenitic stainless steels, copper alloys, etc.). Hastelloy C-276 alloy is also a kind of low layer mission-centered cubic metal. It is possible to improve the properties of Hastelloy C-276 alloy by grain boundary engineering. In this paper, the effects of rolling deformation and heat treatment on the grain boundary characteristic distribution of Hastelloy C-276 alloy were studied by means of optical microscope, scanning electron microscope and electron backscatter diffraction (EBSD). The effect of rolling deformation on the grain size of Hastelloy C-276 alloy was observed and analyzed, and the corrosion resistance of Hastelloy C-276 alloy containing different proportion of special grain boundaries was analyzed by ASTM G28-A method. At the same time, the high temperature tensile test of Hastelloy C-276 alloy at 650 鈩，
本文编号：2135697
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