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標題: | CoCrFeMnNi等莫耳高熵合金與Fe5Mn3CoCr中熵合金
腐蝕行為之比較 Electrochemical properties of CoCrFeMnNi high entropy alloy - a comparison with Fe5Mn3CoCr medium entropy alloy |
作者: | Che-Wei Lu 呂哲維 |
指導教授: | 溫政彥(Cheng-Yen Wen) |
關鍵字: | 高熵合金,抗蝕性,循環極化, High entropy alloy,Corrosion resistance,Cyclic polarization curve, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | Fe5Mn3CoCr中熵合金為近年來所被提出之新穎合金,此合金在產生形變時可表現出相變誘導塑性效應(Transformation induced plasticity)而發揮卓越的強度及延性,其良好之機械性質甚至優於傳統CoCrFeMnNi等莫耳高熵合金,但在腐蝕環境中之抗蝕性質依舊未知。因此本篇將CoCrFeMnNi高熵合金及Fe5Mn3CoCr中熵合金在不同環境中所呈現的腐蝕電化學特性進行分析,並探討兩者的極化破壞過程。在循環極化測試中,採用的腐蝕環境為不同pH值(3, 6, 9, 12)和溫度(10oC, 40oC, 70oC)的3.5wt%氯化鈉水溶液以及0.1M硫酸水溶液。實驗結果顯示,在3.5wt%氯化鈉水溶液中,CoCrFeMnNi高熵合金的鈍化區間明顯大於Fe5Mn3CoCr中熵合金,但二者之腐蝕電流密度並無顯著差異。在0.1M硫酸水溶液中,Fe5Mn3CoCr中熵合金的腐蝕電流密度較CoCrFeMnNi高熵合金高。在3.5wt%氯化鈉水溶液進行循環極化試驗後,可觀察到CoCrFeMnNi高熵合金所留下的蝕孔形貌,其是由介在物的崩解並擴展而產生;Fe5Mn3CoCr中熵合金則是呈現條線狀的腐蝕形貌,此形貌是由蝕孔相接形成。在0.1M硫酸水溶液進行循環極化試驗後,CoCrFeMnNi高熵合金之腐蝕型態為晶界腐蝕與加凡尼腐蝕;而Fe5Mn3CoCr中熵合金呈現分支狀組織,此一腐蝕形貌主要來自於ε麻田散相的溶解。 In recent years, Fe5Mn3CoCr medium entropy alloy (MEA) has been reported as an alloy system which shows transformation-induced plasticity effect during deformation. The excellent strength and ductility combination of this alloy is even better than CoCrFeMnNi high entropy alloy (HEA), but the corrosion behavior is still unknown. In this study, the corrosion behavior of CoCrFeMnNi HEA and Fe5Mn3CoCr MEA were investigated. The environments chose for the cyclic polarization measurement were 3.5wt% NaCl solution with different pH values (pH=3, 6, 9, 12) and temperatures (10oC, 40oC, 70oC) and 0.1M H2SO4 solution. The results show that, compared with CoCrFeMnNi HEA, Fe5Mn3CoCr MEA the had smaller passivation region in every test environment, but the two substrate had almost the same corrosion current density value in 3.5wt% NaCl solution without any adjustment. In 0.1M H2SO4 solution, the corrosion current density of Fe5Mn3CoCr MEA is higher than CoCrFeMnNi HEA. The surface morphologies of CoCrFeMnNi HEA after polarization measurement in 3.5wt% NaCl solution exhibited a pitting appearance, which was resulted from the disintegration of inclusions on surface; Fe5Mn3CoCr MEA showed “lath-shaped” corrosion morphologies which were caused by the connection of pits. After cyclic polarization in 0.1M H2SO4 solution, CoCrFeMnNi HEA showed intergranular corrosion and galvanic corrosion morphologies; Fe5Mn3CoCr MEA showed “branch-like” corrosion morphologies which is attributed to the dissolution of ε martensite. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71956 |
DOI: | 10.6342/NTU201804092 |
全文授權: | 有償授權 |
顯示於系所單位: | 材料科學與工程學系 |
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