高熵合金异构的强塑性与微观机理研究 | |
英文题名 | Study on strength, ductility and micro-mechanism in hetero-structure high entropy alloy |
刘动 | |
导师 | 武晓雷 |
2021-11-25 | |
学位授予单位 | 中国科学院大学 |
学位授予地点 | 北京 |
学位类别 | 博士 |
学位专业 | 固体力学 |
关键词 | 异构 高熵合金 梯度结构 化学短程有序 |
摘要 | 金属材料的强度和塑性是材料力学中极为重要的两项性能指标,也是关系到材料实际应用的关键因素,良好的强度和塑性的匹配能使得材料在生产生活中获得更为广泛的使用。然而,一直以来材料的强度和塑性都存在着本征的矛盾,即强度和塑性的此消彼长(trade-off),当粗晶态的金属通过晶粒细化得到强度的提升时,通常都伴随着塑性的显著下降。所以如何缓解强度和塑性的此消彼长,提升材料的综合力学性能就成为了关键的问题。高熵合金(high-entropy alloys,HEAs)或多主元合金(multi-principal element alloys,MPEAs)是近年来受到研究者广泛关注的金属材料,这种合金以高构型熵的设计理念使材料获得稳定无序固溶体,避免了元素偏聚和金属化合物的产生,获得了良好的力学性能。但这种合金仍然存在强度和塑性的本征矛盾,且大多数为均匀的微结构,强度都处于比较低的范围。异构(hetero-structure)是一种极为有效的缓解强度和塑性的本征矛盾的微结构设计思路,通过将材料的均匀微结构进行一些处理,得到强度塑性有差异的非均匀微观结构,从而在塑性变形的过程中产生非均匀变形诱导硬化(Hetero deformation induced hardening,HDI hardening),在获得优异的强度和塑性的匹配的同时,缓解了材料的强度和塑性的本征矛盾。此外本文也针对高熵合金的化学短程有序结构进行了研究,尽管中高熵合金的设计理念是最大化材料的构型熵以获得无序的固溶体,但实际的报道表明了,中高熵合金中仍然存在着各组成元素的有序分布,本文通过透射电镜观察与模拟计算相结合的方式对中高熵合金中的化学短程有序结构进行了研究。 |
英文摘要 | Both strength and ductility are crucial properties for metallic materials, and also they are significant factors for application because excellent combination of strength and ductility could make the material more widely used in society. However, a paradox between strength and ductility constantly obsessing researchers, which calls the trade-off. When people refine the soft coarse-grain material to strengthening it, the ductility usually decreased obviously. So it is a pivotal task to alleviate the trade-off and manage to get excellent combination of strength and ductility. High-entropy alloys (HEAs), or multi-principal element alloys (MPEAs), has becoming a scientific hot button in recent years. Getting the maximum entropy of whole system to form ideal random solid solution is the basic concept of HEAs. This concept could restrain the formation of segregation , cluster and intermetallic compound and benefit the mechanical behavior of materials. However, HEAs still suffer from trade-off of strength and ductility. Most of HEAs are homogeneous structure with rather low yield strength. Hetero-structure (HS) is an effective method to alleviate the trade-off between strength and ductility by some deliberate process for homogeneous materials. During the procession, the homogeneous material get both soft and hard area within microstructure and get hetero-deformation-induced (HDI) hardening. Besides, a study on chemical short-range order (CSRO) for HEAs is also been conducted. Although HEAs have a structure of random solid solution nominally, researchers have find a structure of local chemical order in HEAs for some degree. In this article, the CSRO of HEAs is characterized by TEM, EDS-mapping and spatial correlation analysis. |
语种 | 中文 |
文献类型 | 学位论文 |
条目标识符 | http://dspace.imech.ac.cn/handle/311007/87822 |
专题 | 非线性力学国家重点实验室 |
推荐引用方式 GB/T 7714 | 刘动. 高熵合金异构的强塑性与微观机理研究[D]. 北京. 中国科学院大学,2021. |
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