Al和C对FCC高熵合金组织和性能的影响

发布时间：2018-09-05 07:12

【摘要】：高熵合金的设计理念相对于传统的多元合金来说是一种创新性的突破,通常主元元素种类不少于五种,每种元素的含量不少于5%且不超过35%,因此拥有与传统合金不同的组织和性能。高熵合金各元素之间起协同作用,故每种元素的种类和含量的变化都会引起高熵合金组织、结构和性能的变化。因此通过调整合金元素的种类和含量得到高性能高熵合金,具有特别重要的理论和实践意义。本文采用真空电弧熔炼炉和铜模浇铸法制备了 AlxFeCrCoNi(Cy)、CoCrFeNiMnCx和CoFeNiMnCx系高熵合金,同时采用真空管式热处理炉进行热处理。然后采用光学显微镜、XRD衍射仪、扫描电镜和透射电镜分析了 A1和C元素对FCC高熵合金的相结构和微观组织的影响。其次采用显微硬度仪和电子万能试验机测试了合金的维氏硬度和拉伸性能。得出了如下结论:在AlxFeCrCoNi(Cy)系高熵合金中,随着A1元素含量的增加,当x≤0.3时合金的晶体结构为面心立方结构;当x=0.4开始出现BCC相,BCC相随A1元素含量的增加而增加。当x≤0.2时金相组织为胞状树枝晶;当x=0.3时金相组织为转变为柱状树枝晶;当x≥0.4时金相组织为等轴树枝晶。在1100℃保温24h热处理后,在AlxFeCrCoNi(x=0.4,0.5)系高熵合金的晶内出现大量针状BCC相。少量A1元素的添加会同时提高合金强度和塑性,当x≥0.3时合金的强度升高但塑性降低。此外,随着C元素的添加,合金产生新相M7C3,提高强度的同时降低塑性。C元素可以提高A1原子在AlxFeCrCoNi(Cy)系高熵合金中的固溶度。综合力学性能最佳的合金为Al0.4CoCrFeNiC0.05,其屈服强度、抗拉强度和延伸率分别为330MPa、621MPa和56%。在CoCrFeNiMnCx系高熵合金中,少量C元素的添加(x≤0.05),合金的晶体结构仍然为FCC,合金的强度和塑性得到改善;当x≥0.1时,产生新相M7C3,合金的强度升高,塑性降低。且随着C元素含量的增加,碳化物由细杆状变为片状,分布于晶界或者晶界旁边。CoCrFeNiMnC0.05合金在高应变下会出现大量纳米级变形孪晶。微量C元素可以使由位错滑移主导的塑性变形过渡为由位错滑移和孪晶组成的混合变形模式。热处理后,合金会出现新相M23C6,合金强度和塑性降低。在CoFeNiMnCx系高熵合金中,随着C元素的添加,点阵常数升高,但合金的晶体结构依然为FCC。强度随C含量的增加而升高,塑性则小幅度的降低。综合力学性能最佳的合金为CoFeNiMnCo.2,其屈服强度、抗拉强度和延伸率分别为521MPa、778MPa和38%。在1200℃保温48h热处理后产生调幅分解,合金的强度和塑性进一步提高。
[Abstract]:The design concept of high entropy alloy is a kind of innovative breakthrough compared with traditional multicomponent alloy, usually there are not less than five kinds of principal element. Each element contains not less than 5% and does not exceed 35%, so it has different microstructure and properties from traditional alloys. There is a synergistic effect among the elements of the high entropy alloy, so the change of the type and content of each element will cause the changes of the structure, structure and properties of the high entropy alloy. Therefore, it is of great theoretical and practical significance to obtain high performance and high entropy alloy by adjusting the kinds and contents of alloying elements. In this paper, AlxFeCrCoNi (Cy) CoCrFeNiMnCx and CoFeNiMnCx system high entropy alloys were prepared by vacuum arc melting furnace and copper mold casting, and the vacuum tube heat treatment furnace was used for heat treatment. The effects of Al and C on the phase structure and microstructure of FCC high entropy alloy were analyzed by means of optical microscope, scanning electron microscope and transmission electron microscope. Secondly, the Vickers hardness and tensile properties of the alloy were tested by microhardness tester and electronic universal tester. The following conclusions are drawn: with the increase of A1 element content, the crystal structure of AlxFeCrCoNi (Cy) system is face-centered cubic structure when x 鈮，

本文编号：2223562