AZ63镁合金在氯化钠溶液中的腐蚀及放电行为研究

发布时间：2018-06-12 12:08

本文选题：AZ63镁合金 + 腐蚀　；参考：《中国科学院大学(中国科学院海洋研究所)》2017年博士论文

【摘要】：AZ63镁合金(名义成分Mg-6 wt%Al-3 wt%Zn)由于其优异的力学性能和电化学性能,已作为结构材料和牺牲阳极材料被广泛应用。本论文以3.5 wt%NaCl溶液为电解液,通过材料表征、物相分析、浸泡实验和电化学测试,对AZ63镁合金的腐蚀机理,In元素合金化电化学活化机理以及In、Ga元素对AZ63镁合金腐蚀和放电行为的影响进行了研究。本论文的主要研究工作如下:(1)研究热处理对AZ63镁合金的腐蚀行为的影响。对制备的铸态、固溶态(T4)、时效态(T5)的三种微观组织结构不同的AZ63镁合金进行了腐蚀行为研究,结果表明:T4态镁合金由于表面氧化膜具有较好的保护性,在浸泡初期腐蚀速率为三者中最低。但随着氧化膜消耗殆尽,T4态镁合金表面产物膜对基体保护性最差,使得其腐蚀速率变成三者中最高。铸态和T5态镁合金晶界有析出物的存在,会与晶粒形成微电偶,在浸泡初期表现为高的腐蚀速率,但它们生成的腐蚀产物容易粘附于电极表面,因此对腐蚀的发展起到了一定抑制作用。(2)提出了In元素合金化对AZ63镁合金电化学活化的机理。向AZ63镁合金中添加0.5 wt%的In元素并与镁形成固溶体,可以通过协同作用活化镁合金,协同作用具体包括:促进晶界第二相的析出、生成易脱附的腐蚀/放电产物以及In元素的“溶解-再沉积”作用。(3)In元素合金化提高了镁合金的腐蚀和放电活性。通过向AZ63镁合金中添加不同质量分数(1 wt%,1.5 wt%,2 wt%)的In元素,结果表明:In元素合金化在镁合金自腐蚀和放电情况下均能起到活化作用。主要通过细化合金晶粒、促进Mg17Al12相析出和In元素的“溶解-再沉积”来实现。Mg-6 wt%Al-3 wt%Zn-1.5wt%In合金自腐蚀速率最高,但放电性能却并不理想,说明由Mg17Al12相引起的电流屏蔽作用在阳极极化条件下得到了强化。(4)Ga元素合金化降低了镁合金的腐蚀速率却提高了放电活性。通过向AZ63镁合金中添加2 wt%的Ga元素,结果表明:由于Ga元素促进了第二相Mg17Al12和GaMg2在晶界上的析出,第二相形成了网状结构,该结构能有效屏蔽腐蚀电流,因此含Ga的AZ63镁合金的自腐蚀过程受到抑制。然而,Ga元素的合金化却可以使镁合金的放电电位显著负移,提供高的电流密度,形成有利于电解液渗透的薄而细的产物膜,提高阳极材料的电流效率,提高镁合金作为阳极材料的放电能力。
[Abstract]:AZ63 magnesium alloy (nominal composition Mg-6 wt%Al-3 wtZn3) has been widely used as structural material and sacrificial anode material due to its excellent mechanical and electrochemical properties. In this paper, 3.5 wtNaCl solution was used as electrolyte, which was characterized by material, phase analysis, immersion test and electrochemical test. The corrosion mechanism of AZ63 magnesium alloy and the electrochemical activation mechanism of in alloying and the effect of Ingallium on corrosion and discharge behavior of AZ63 magnesium alloy were studied. The main work of this thesis is as follows: 1) the effect of heat treatment on corrosion behavior of AZ63 magnesium alloy is studied. The corrosion behavior of three kinds of AZ63 magnesium alloys with different microstructure, such as as-cast, solid solution T4N, aged T5), was studied. The results showed that the oxidation film on the surface of the WT4 magnesium alloy had better protection, and the corrosion behavior of the AZ63 magnesium alloy with different microstructure was studied, and the corrosion behavior of the AZ63 magnesium alloy with different microstructure was studied. The corrosion rate was the lowest in the initial soaking stage. However, with the depletion of oxide film, the surface product film of T4 magnesium alloy has the worst protection to the substrate, which makes the corrosion rate of magnesium alloy become the highest of the three. There are precipitates in the grain boundaries of as-cast and T5 magnesium alloys, which will form microelectric couples with the grains and exhibit a high corrosion rate at the beginning of soaking, but the corrosion products produced by them are easy to adhere to the surface of the electrode. The mechanism of in alloying on the electrochemical activation of AZ63 magnesium alloy was proposed. Adding 0.5 wt% in element to AZ63 magnesium alloy and forming solid solution with magnesium can activate magnesium alloy by synergistic action, which includes promoting the precipitation of the second phase in grain boundary. The corrosion and discharge activity of magnesium alloys were improved by the formation of easily desorption corrosion / discharge products and the "dissolution-redeposition" effect of in elements. By adding in elements of different mass fractions of 1 wtand 1.5 wtand 2 wts to AZ63 magnesium alloy, the results show that the in alloying of AZ63 magnesium alloy can be activated under the condition of self-corrosion and discharge. Mg-6 wt%Al-3 wtZn-1.5wtIn alloy has the highest self-corrosion rate, but the discharge performance is not ideal, mainly by refining the alloy grain, promoting the precipitation of Mg17Al12 phase and "solution-redeposition" of in element. The results show that the current shielding effect caused by mg _ (17) Al _ (12) phase increases the corrosion rate of mg _ (17) Al _ (12) alloy and increases its discharge activity. By adding 2 wt% Ga to AZ63 magnesium alloy, the results show that the second phase forms a network structure because Ga can promote the precipitation of Mg17Al12 and GaMg2 on the grain boundary, and the structure can shield corrosion current effectively. Therefore, the self-corrosion process of Ga-containing AZ63 magnesium alloy is restrained. However, the alloying of Ga can significantly shift the discharge potential of magnesium alloy, provide high current density, form thin and thin product film which is favorable to electrolyte permeation, and improve the current efficiency of anode material. The discharge capacity of magnesium alloy as anode material was improved.
【学位授予单位】：中国科学院大学(中国科学院海洋研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG172

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