碳对不同晶体结构高熵合金组织和性能的影响

发布时间：2018-07-31 12:34

【摘要】：高熵合金是由五种或五种以上元素按等摩尔比或近等摩尔比的形式组成的一种新型合金。多主元特性使得高熵合金具有优于传统合金的性能。由于元素间的相互作用,元素含量及种类的变化对合金的组织和性能都有较大的影响。通过研究元素对合金组织及性能产生的影响,获得性能优异的高熵合金,对以后的科学研究具有很好的理论指导和借鉴意义。本文采用传统的真空电弧熔炼技术制备了AlFeCoNiCx、(Fe40Mn40Co10Cr10)100-xCx和(Fe40Mn40Co10Ni10)100-xCx、(Fe50Mn30Co10Cr10)100-xCx三种不同晶体结构高熵合金系列,采用X射线衍射仪(XRD)、光学金相显微镜(OM)、扫描电子显微镜(SEM)及能谱仪(EDS)等分析测试方法,分别研究了合金元素碳对不同晶体结构高熵合金的组织和力学性能的影响。取得主要研究结果有:(1)将碳元素加入AlFeCoNi多元合金中,合金由单一体心立方(BCC)相转变为BCC+面心立方(FCC)两相。碳含量增加到一定程度时,有片状石墨在FCC相中析出。合金的强度和塑性随碳含量的增加而提高,抗压强度由1291MPa最大提高到了2875MPa,塑性由5%最多增加到了27%。合金由解理断裂转变为准解理断裂。(2)碳元素的加入没有改变Fe40Mn40Co10Cr10和Fe40Mn40Co10Ni10两种合金的晶体结构,但增大了合金的晶格常数。在(Fe40Mn40Co10Cr10)100-xCx系合金中,合金的强度随碳含量的增加而提高,塑性降低;当碳含量增加到一定程度时,合金中有少量Cr7C3化合物产生。在(Fe40Mn40Co10Ni10)100-xCx系合金中,碳能显著改善合金的强度和塑性。(3)Fe50Mn30Co10Cr10高熵合金为FCC+密排六方(HCP)两相高熵合金。碳的加入促进了HCP相转变为FCC相,随碳含量的增加HCP相的体积分数减小,FCC相体积分数增加。碳元素的加入使合金的衍射峰向右偏移,晶格常数减小。该体系合金的硬度随碳含量的增加而降低,但抗压强度随碳含量的增加而提高。
[Abstract]:High entropy alloy is a new alloy composed of five or more elements in the form of equal molar ratio or near equal molar ratio. The properties of high entropy alloys are superior to those of traditional alloys due to their multi-principal component properties. Because of the interaction between elements, the change of element content and type has a great influence on the microstructure and properties of the alloy. By studying the effect of elements on the microstructure and properties of the alloy, a high-entropy alloy with excellent properties is obtained, which has a good theoretical guidance and reference significance for future scientific research. In this paper, AlFeCoNiCx, (Fe40Mn40Co10Cr10) 100-xCx and (Fe40Mn40Co10Ni10) 100-xCx, (Fe50Mn30Co10Cr10) 100-xCx series of high entropy alloys with different crystal structures have been prepared by traditional vacuum arc melting technique. The methods of analysis and measurement are (XRD), optical microscope, (OM), scanning electron microscope, (SEM) and (EDS). The effects of alloying elemental carbon on the microstructure and mechanical properties of high entropy alloys with different crystal structures were studied. The main results are as follows: (1) when the carbon element is added to the AlFeCoNi multicomponent alloy, the alloy changes from a single body-centered cubic (BCC) phase to a BCC face-centered (FCC) two-phase. When carbon content increased to a certain extent, flake graphite precipitated in FCC phase. The strength and plasticity of the alloy increase with the increase of carbon content. The compressive strength of the alloy increases from 1291MPa to 2875 MPa, and the plasticity increases from 5% to 2775 MPA. (2) the addition of carbon element does not change the crystal structure of Fe40Mn40Co10Cr10 and Fe40Mn40Co10Ni10 alloys, but increases the lattice constant of the alloy. In the (Fe40Mn40Co10Cr10) 100-xCx alloy, the strength of the alloy increases with the increase of carbon content, and the plasticity decreases, and a small amount of Cr7C3 compounds are produced when the carbon content is increased to a certain extent. In (Fe40Mn40Co10Ni10) 100-xCx system, carbon can significantly improve the strength and plasticity of the alloy. (3) Fe50Mn30Co10Cr10 high entropy alloy is a FCC dense hexagonal (HCP) two-phase high-entropy alloy. The addition of carbon promoted the transformation of HCP phase into FCC phase, and the volume fraction of HCP phase decreased with the increase of carbon content. With the addition of carbon element, the diffraction peak of the alloy shifts to the right and the lattice constant decreases. The hardness of the alloy decreases with the increase of carbon content, but the compressive strength increases with the increase of carbon content.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139

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