AlFeCoCrNi高熵合金磨损与腐蚀行为研究

发布时间：2018-11-01 10:44

【摘要】：本论文的研究对象为铸态AlFeCoCrNi高熵合金及不同预压量的合金,表征了不同直径及不同预压量高熵合金的微观结构,研究了不同直径AlFeCoCrNi高熵合金在变载荷下在空气中的磨损行为,同时研究了AlFeCoCrNi高熵合金及不同预压量的合金在模拟海水及1mol/L盐酸中的腐蚀行为,探索了高熵合金在两种溶液中的腐蚀机理。借助透射电子显微镜(TEM)观察了AlFeCoCrNi高熵合金及不同预压量的合金的结构,高熵合金的组织内出现了大量的纳米析出相,随冷却速度的增大,析出相尺寸逐渐变得细小,由小块状变为针状;随预变形量的增加,高熵合金未发生相变,但组织由圆状逐渐拉长为长条状。对不同直径AlFeCoCrNi高熵合金的显微维氏硬度进行了测试,高熵合金的硬度随冷却速度的增加而升高,直径为2mm的高熵合金达到最大值。结合磨损面形貌图、质损量和摩擦系数综合评价了AlFeCoCrNi高熵合金在空气中的耐磨损性能。AlFeCoCrNi高熵合金在空气中的表面粗糙程度、质损量及摩擦系数随合金的冷却速度的增加而减小,直径为2mm的高熵合金达到相对最小值,以上结果表明,直径为2mm的高熵合金在空气中的耐磨损性能最好;高熵合金在空气中磨损时,随摩擦过程中载荷的增大,其磨损机制由磨粒磨损逐渐变为氧化磨损和粘着磨损。结合阻抗谱和极化曲线综合评价了铸态及不同预压量AlFeCoCrNi高熵合金在模拟海水和1mol/L盐酸中的腐蚀行为。极化试验表明,在两种腐蚀溶液中,AlFeCoCrNi高熵合金的抗腐蚀性能随预压量的增大先增加后减小,预压量为13%的高熵合金的自腐蚀电流密度最小;阻抗试验表明,13%预压量高熵合金在二种溶液中的电荷转移电阻、阻抗值及容抗弧直径最大,预压量为13%的高熵合金在二种溶液中的耐腐蚀性能最优,并且在模拟海水和1mol/L盐酸中较304不锈钢优异。采用扫描电子显微镜(SEM)观测到预压量为13%的高熵合金在两种溶液中具有最少最浅的点蚀坑,能谱分析结果显示,铸态及不同预压量AlFeCoCrNi高熵合金的腐蚀区域均存在Al、Fe、Cr、Ni元素的溶解以及Co元素的富集。采用X射线光电子能谱测试了高熵合金在模拟海水中腐蚀后的表面电子结构,预压量为13%的高熵合金表面产生富含Al~(3+)、Ni~(2+)、Cr~(3+)的致密氧化膜。
[Abstract]:In this paper, as cast AlFeCoCrNi high entropy alloy and different preloading alloy are studied. The microstructure of AlFeCoCrNi high entropy alloy with different diameters and different preloading amounts is characterized, and the wear behavior of AlFeCoCrNi high entropy alloy with different diameters in air under variable load is studied. At the same time, the corrosion behavior of AlFeCoCrNi high entropy alloy and different preloading alloy in simulated seawater and 1mol/L hydrochloric acid was studied, and the corrosion mechanism of high entropy alloy in two solutions was explored. The structure of AlFeCoCrNi high entropy alloy and the alloy with different preloading amounts were observed by means of transmission electron microscope (TEM). A large number of nanocrystalline precipitates appeared in the microstructure of the high entropy alloy, and the size of the precipitated phase became smaller with the increase of cooling rate. From a small block to a needle; With the increase of predeformation amount, the high entropy alloy does not undergo phase transformation, but the microstructure is gradually elongated from a circular shape to a long strip. The microhardness of AlFeCoCrNi high entropy alloy with different diameters was tested. The hardness of high entropy alloy increased with the increase of cooling rate, and the maximum value of high entropy alloy with diameter of 2mm was obtained. The wear resistance of AlFeCoCrNi high entropy alloy in air was evaluated by means of wear surface topography, mass loss and friction coefficient. The surface roughness of AlFeCoCrNi high entropy alloy in air was evaluated. The mass loss and friction coefficient decrease with the increase of cooling rate of the alloy, and the high entropy alloy with diameter of 2mm reaches the relative minimum. The above results show that the high entropy alloy with diameter 2mm has the best wear resistance in air. With the increase of friction load, the wear mechanism of high entropy alloy changes from abrasive wear to oxidation wear and adhesion wear. The corrosion behavior of as-cast and pre-loaded AlFeCoCrNi high entropy alloys in simulated seawater and 1mol/L hydrochloric acid was evaluated by means of impedance spectroscopy and polarization curves. Polarization test shows that the corrosion resistance of AlFeCoCrNi high entropy alloy increases first and then decreases with the increase of preloading, and the corrosion current density of high entropy alloy with 13% preloading is the smallest. The impedance test shows that the charge transfer resistance, impedance and capacitance arc diameter of 13% prepress high entropy alloy are the largest in both solutions, and the corrosion resistance of high entropy alloy with 13% prepress is the best in both solutions. It is superior to 304 stainless steel in simulated seawater and 1mol/L hydrochloric acid. Using scanning electron microscope (SEM), it was observed that high entropy alloy with preloading amount of 13% had the smallest and shallowest pitting pit in both solutions. The results of energy spectrum analysis showed that there was Al,Fe, in the corrosion zone of AlFeCoCrNi high entropy alloy with as cast and different preloading amounts. Dissolution of Cr,Ni elements and enrichment of Co elements. The surface electronic structure of high entropy alloy after corrosion in simulated seawater was measured by X-ray photoelectron spectroscopy (XPS). A dense oxide film rich in Al~ (3), Ni~ (2) and Cr~ (3) was produced on the surface of high entropy alloy with preloading of 13%.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG172;TG139

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