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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/13524

Title: FeCoNiCrCux高熵合金之抗蝕性研究
Corrosion Behavior of FeCoNiCrCux High-Entropy Alloys in Various Aqueous Solutions
Authors: Yu-Jui Hsu
許祐睿
Contributors: NTOU:Institute of Materials Engineering
國立臺灣海洋大學:材料工程研究所
Keywords: 高熵合金;電化學;浸漬;鑄造
high-entropy alloy;electrochemical;immersion;casting
Date: 2003
Issue Date: 2011-06-30T07:22:33Z
Abstract: 本研究之目的,主要為了突破傳統合金以特定金屬為主的合金設計觀念,高熵合金強調用五個以上的主元素來製作合金,每個元素含量不超過35%;由於主元素很多,高亂度或高熵成為異於傳統合金的基本特色。而此次研究主要採用鐵、鈷、鎳、銅、鉻五種元素作為原料,以電弧熔煉法熔鑄兩種FeCoNiCrCu、FeCoNiCrCu0.5高熵合金和不含銅之FeCoNiCr四元合金,進一步探討於不同水溶液環境下之抗蝕行為測定、機械性質、微結構觀察,並提出理論解釋。研究方法主要採用電化學動態極化法與實際靜態浸漬重量損失法,來評估高熵合金之抗蝕性。實驗結果顯示出於3.5wt% NaCl水溶液下,FeCoNiCrCu高熵合金比FeCoNiCrCu0.5高熵合金、FeCoNiCr四元合金具有較高之腐蝕速率,亦即為具有較差之抗蝕性,研判為FeCoNiCrCu高熵合金中富含銅元素,而造成偏析的現象產生,反而造成腐蝕速率加快,抗蝕性變差,而與304L不□鋼、316L不□鋼、XM-19不□鋼於1N HCl水溶液之極化數據比較中發現,FeCoNiCrCu高熵合金比FeCoNiCrCu0.5高熵合金、不含銅之FeCoNiCr四元合金和三種不□鋼得到較低的腐蝕速率;於1N NaOH水溶液之極化數據比較中,XM-19不□鋼得到最高之腐蝕速率、FeCoNiCrCu0.5高熵合金具有最低之腐蝕速率;於1N H2SO4水溶液之極化數據比較中,XM-19不□鋼得到最低之腐蝕速率、FeCoNiCr四元合金得到最高之腐蝕速率,且在本研究中亦探討添加三種不同腐蝕抑制劑(NaNO2、Na2MoO4、Na3PO4)對FeCoNiCrCu高熵合金在3.5wt% NaCl水溶液中之腐蝕抑制效果,結果顯示:所有腐蝕抑制劑,都使試片之腐蝕電位(Ecorr)升高,腐蝕電流密度降低且鈍態電位區間增大,其中以Na3PO4腐蝕抑制效果最佳,鈍態電流值(Ipassive)最小,鈍態電位區間也最大,代表產生鈍態保護層的能力最好。且另外合金之硬度值方面發現FeCoNiCrCu高熵合金、FeCoNiCrCu0.5高熵合金和不含銅之FeCoNiCr四元合金三者中,以FeCoNiCrCu高熵合金具有最高之硬度值,後續也針對了不同pH值和不同溫度之3.5wt% NaCl水溶液下作進一步探討。
Abstract The purpose of this study is to break traditional alloys that designed by a specific metal in alloy. We emphasizes that high-entropy alloy used above five major elements metals, and it is not over 35% for one element. Owing to it has many major elements in alloy, so it has special characteristic different from traditional alloys, high entropy. In this study, we use five elements, Fe, Co, Ni, Cr, and Cu to cast three high-entropy multielement alloys including FeCoNiCrCux(x=0), FeCoNiCrCux(x=0.5), and FeCoNiCrCux(x=1). Further, we probe into corrosion properties, mechanical properties, and microstructure. The major methods of this study are immersion test and potentiodynamic polarization. The result shows that Four-major-element alloy FeCoNiCr exhibits excellent corrosion resistance in various test aqueous solutions. FeCoNiCrCu high-entropy five-element alloy shows highest hardness in three high-entropy alloys, but has higher corrosion rate in aqueous solutions due to significant segregation of Cu-riched phase along grain. In other materials that compared with three high-entropy alloys, XM-19ss has highest hardness and it exhibits excellent corrosion resistance in 1N H2SO4 solution. The effects of three corrosion inhibitors (containing NaNO2, Na2MoO4, and Na3PO4) on the corrosion behavior of the Fe-Co-Ni-Cu-Cr high-entropy alloy (HEA) in 3.5% NaCl solution were studied. The results generally showed that the passive potential and corrosion potential increased but the corrosion current density decreased by adding various inhibitors. The addition of Na3PO4 exhibited the best inhibiting-ability among all the inhibitors studied. It showed the lowest passive current (Ipassive) and largest passive region (Epit-Ecorr.). Based on the cyclic polarization curves, the FeCoNiCrCu high-entropy alloy showed a lower Ecorr , but a higher current density (icorr.), as compared to the results of AISI 304 stainless steel, thus resulting in a poor corrosion-resistance. It was also found that FeCoNiCrCu high-entropy alloy is unable to form such a complete protective flim to prevent from pitting corrosion.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M91550012
http://ntour.ntou.edu.tw/ir/handle/987654321/13524
Appears in Collections:[材料工程研究所] 博碩士論文

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