鋁含量對AlxCrFe1.5MnNi0.5高熵合金在0.5M硫酸中腐蝕性質之影響

The Effect of Aluminum on the Corrosion Behavior of the High Entropy Alloys AlxCrFe1.5MnNi0.5 in 0.5 M Sulfuric Acid

高熵合金為數種常用的合金元素如鋁、鈷、鉻、銅、鐵、矽以及鎳等所組成的新型多元合金。其打破傳統合金以單一元素為主要成份的觀念，藉由5種以上的主要元素相混合，各種元素之原子含量均大於5atom%，小於35atom%。高熵合金具有許多優秀的機械、磁性與電化學性質。為了進一步瞭解高熵合金的腐蝕行為，故有必要拿它與一般常用的抗蝕合金如304不銹鋼做比較，利用陽極極化與電化學阻抗頻譜分析（EIS）來研究高熵合金在0.5 M硫酸溶液中的腐蝕行為。並探討在AlxCrFe1.5MnNi0.5高熵合金中鋁成分的多寡對其腐蝕與電化學性質之影響。由陽極極化曲線中可以明確得知：AlxCrFe1.5MnNi0.5在0.5 M的硫酸溶液中隨著Al成分的增加其腐蝕電流會有明顯的上升且鈍態區域也會變窄。而由電化學阻抗頻譜分析清楚顯示：當Al之含量為0.3、0.5莫耳時，其Nyquist圖為兩個半圓所構成。其中第一個半圓之出現乃為鈍態層之存在，而第二個半圓為溶液中之離子於試片表面產生另一吸附層之結構。SEM圖可證實：隨著高熵合金中Al成分的增加，會有較嚴重的蝕孔產生。

High entropy alloys are a newly developed family of multi-component alloys composed of several major alloying elements, such as copper, nickel, aluminum, cobalt, chromium, iron, etc. Each element in the alloy system is between 5 atom% and 35 atom%. High entropy alloy has a lot of advantages regarding its mechanical, magnetic and electrochemical properties. In order to further realize the corrosive behaviors of high entropy alloys, it is necessary to compare it with other alloy such as type 304 stainless steels. The anodic polarization curves and electrochemical impedance spectra were studied the corrosive behaviors of high entropy alloy in 0.5 M sulfuric acid. This study discusses the effect of aluminum on the electrochemical properties of AlxCrFe1.5MnNi0.5 alloys. The anodic polarization curves of AlxCrFe1.5MnNi0.5 in 0.5 M sulfuric acid clearly indicated that the corrosion current increases and the passive region decreases as the amounts of aluminum increases. On the other hand, the electrochemical impedance spectra indicated that the Nyquist plot presents two semicircles when the content of aluminum is 0.3 and 0.5 mole. The first semicircle represented the passive layer and the second semicircle represented the adsorptive layer. By SEM micrograph, it is confirmed that high entropy alloy was corroded more seriously with increasing content of aluminum.