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磁控溅射AlCrTiVZr高熵合金薄膜及高温性能研究
Alternative TitleStudy on AlCrTiVZr High-entropy films and high temperature properties by DC Magnetron sputtering
文偲嘉
Thesis Advisor夏原
2019-05-29
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype硕士
Degree Discipline工程力学
Keyword高熵合金 耐高温性能 磁控溅射 微观结构 硬度
Abstract

高熵合金是指以五种或五种以上金属元素通过近等摩尔比的方式混合构成的合金,由于其特殊的微观结构和特性,被认为具有高强度、高韧性、良好的耐磨性、耐高温性、抗扩散性等许多优秀性能,作为一种全新的材料概念受到了广泛的关注。

本文通过直流磁控溅射的方法,在不同的制备工艺下,通过拼靶制备了AlCrTiVZr高熵合金薄膜,并对不同参数下的薄膜的形貌成分以及性能进行了检测和研究,结果如下:

通过拼靶成功制备了近等摩尔比的AlCrTiVZr高熵合金薄膜,在不同的溅射电流(溅射功率)下,薄膜均主要呈现非晶的特征,在不附加偏压的情况下薄膜出现了FCC相的结构,FCC相结构对应的峰在一定的溅射电流下也有所出现。薄膜表面形貌致密均匀,截面则是致密的无定型截面。在无附加偏压的情况下,薄膜表面出现了较多的缺陷,截面有微弱的柱状晶特征。AlCrTiVZr高熵合金薄膜的硬度约在12GPa,随电流变化影响不大。薄膜的耐腐蚀性良好,腐蚀电位约在-0.505V,腐蚀电流约在10-11A/cm2,在耐腐蚀材料中属于较高水平。在中性盐雾实验中,薄膜由于自身的缺陷在48h的中性盐雾试验后出现了点蚀,但在96h盐雾实验后点蚀无扩大痕迹,也无新的点蚀出现,表明薄膜致密与低腐蚀电流可有效地阻止点蚀的扩散,适合作为耐腐蚀涂层中的阻挡层。

为了研究AlCrTiVZr高熵合金薄膜的高温性能,首先通过差热分析的方法检测了AlCrTiVZr高熵合金薄膜的吸放热特性,从其DSC曲线可以得知AlCrTiVZr高熵合金薄膜的吸放热特性具有典型的非晶材料的特征,其玻璃化转变温度约在500℃,相变温度约在650℃。基于DSC曲线的结果,对AlCrTiVZr高熵合金薄膜进行了高温原位XRD测试,测试结果表明,在650℃时,AlCrTiVZr高熵合金薄膜的晶体结构依然与室温下相同,而在700℃及以上时,薄膜内产生了全新的相,微观结构发生了变化。同时,对退火后的AlCrTiVZr高熵合金薄膜的形貌也进行了观测,结果表明,在650℃退火后,高熵合金薄膜的表面与截面形貌均无明显变化,而在700℃以及以上时,薄膜先后发生了皱缩、膨胀,产生蜂窝状缺陷,剥落,表面产生裂纹等变化,可以认定薄膜失效。最后对650℃退火后的AlCrTiVZr高熵合金薄膜进行了力学性能检测,结果表明薄膜的硬度与弹性模量均未下降。因此可以认定AlCrTiVZr高熵合金薄膜具有良好的耐高温性能,能够在650℃的环境下保持其结构、形貌与性能的稳定,具有良好的应用前景。

通过反应溅射法制备了AlCrTiVZr高熵合金氮化物薄膜,薄膜呈现典型的FCC结构,并且择优取向随着通入氮气的增加逐渐由(1 1 1)转换为(2 0 0)。薄膜的表面呈现密排的颗粒状,截面则是底层的致密无定型结构与上层的柱状晶结构构成。随着通入氮气流量的增多,薄膜的厚度逐渐减小,致密无定型层厚度逐渐增加,柱状晶组织逐渐细化。AlCrTiVZr高熵合金氮化物薄膜的硬度均在20GPa以上,硬度最高的制备参数为通入氮气30sccm,占比气体总流量的27.2%时,此时薄膜的硬度可以达到28.71Gpa

Other Abstract

High entropy alloy is a new kind of alloy formed by five elements or more in an equimolar or near-equimolar way. Due to its special microstructure and features, high entropy alloy is more likely to form a simple single-phased microstructure, which is very different from what was expected by Gibbs phase rule. High entropy alloy is considered to have a high strength, a strong toughness, a great wear resistance, a great performance against high temperature and a stand out performance of being diffusion barrier. The possibility of having these abilities has attracted high entropy alloy of researchers’ eyes.

In this paper, different AlCrTiVZr high entropy alloy films were made by using DC magnetron sputtering and a mosaic target. The composition and properties of AlCrTiVZr high entropy films were studied, the results are listed below:

Near-equimolar AlCrTiVZr high entropy films were successfully made by using mosaic target. The films mainly show typical amorphous morphology even under different sputtering parameters, except sample without bias voltage, which slightly shows a FCC structure mixing with amorphous structure. The film surface is filled with particles, and the cross section of the film is condensed and smooth, except sample without bias voltage, which slightly shows the signature of columnar crystal. AlCrTiVZr high entropy films’ hardness is about 12GPa, and varied a little from sputtering parameters. The AlCrTiVZr high entropy film shows a standout corrosion behavior, it has a polarization potential of -0.505V, a polarization current of about 10-11A. During the neutral salt spray test, only 2 pitting corrosive point appears after 48 hours of NSS test, and no pitting corrosive point spread on the film after 96 hours of NSS test. The NSS test results prove this AlCrTiVZr high entropy films has a condensed structure and a very low corrosion current, which can effectively prevent the film from corrosion. AlCrTiVZr high entropy film is suitable to be the corrosion barrier layer.

To study the high temperature properties of AlCrTiVZr high entropy film, firstly using differential thermal analysis to study the heat absorption ability of AlCrTiVZr high entropy films. From the DSC curve it can be seen that the Tg temperature of AlCrTiVZr high entropy film is about 500℃, and 650℃ is where the film phase starts to transfer. In-situ high temperature XRD test results show that the microstructure of AlCrTiVZr high entropy films at 650℃ doesn’t change, however, new phase showed in the film at 700℃. The morphology of AlCrTiVZr high entropy films was also observed. The results prove that the surface and cross section morphology of AlCrTiVZr film after 650℃ annealing are no difference to room temperature. After 700℃ or higher temperature annealing, the film starts to wrinkle, expand, crack and fall off. The mechanic properties of annealed film was also tested, and the hardness and modulus of the AlCrTiVZr film after 650℃ annealing didn’t fall comparing to its room temperature mechanic properties. Based on the experiment result it can be seen that the AlCrTiVZr film has a high temperature resistance of 650℃.

AlCrTiVZr high entropy nitride films were made by reactive magnetron sputtering, the films state a typical FCC microsturcure, and the prefer orientation varied from (1 1 1) to (2 0 0) with the increasing nitrogen flow. The surface of the nitride film is fulfilled with small particles, and the cross section of the film is formed with a condensed amorphous root and a columnar crystal top. The thickness of the film decreased by increasing nitrogen flow, however, the condensed amorphous root gets thicker and the columnar crystal top gets thinner with the increasing nitrogen flow, and the size of the columnar crystal top gets smaller. The hardness of the nitrogen film is over 20GPa, the hardest sample is made with 30 sccm nitrogen flow, reaching 28.71GPa.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/79081
Collection先进制造工艺力学重点实验室
Recommended Citation
GB/T 7714
文偲嘉. 磁控溅射AlCrTiVZr高熵合金薄膜及高温性能研究[D]. 北京. 中国科学院大学,2019.
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