AZ91D镁合金渗铝层的耐蚀性研究

摘要本次研究是选用最佳参数在真空条件下，以铝粉作为渗剂对 AZ91D 镁合金进行金属粉末热扩渗来改善其耐蚀性能。利用蔡司显微镜观察渗层的微观结构，通过 XRD 测试渗铝层的相组成，在不同浓度的 NaCl 溶液中分别做均匀腐蚀和电化学腐蚀试验来测试耐蚀性能，利用扫描电镜观察渗铝层腐蚀后的形貌。79379

结果表明：400℃保温 90min 的条件下获得致密连续的渗铝层，渗铝层中没有出现任何开裂或者孔洞等缺陷不好的现象；最佳工艺参数制备出的镁合金扩渗铝后的试样，主要由α-Mg、α-Al、β-Mg17Al12、Al3Mg2 组成；进行均匀腐蚀时，在浓度为 2。5% 的 NaCl 溶液中，镁合金渗铝层的耐蚀性最好，在浓度为 3。5%的 NaCl 溶液中的耐蚀性次之，在浓度为 5%的 NaCl 溶液中腐蚀最为严重，电解质溶液浓度变化得到的结果与均匀腐蚀一致，其自腐蚀电位比较为：Ecorr3。5%>Ecorr5%，在浓度为 3。5%的 NaCl 溶液中的耐腐蚀性能优于在浓度为 5%的 NaCl 溶液的耐蚀性。

毕业论文关键词：AZ91D 镁合金；渗铝层；腐蚀；电化学；耐蚀性能

Abstract In this paper, the metal powder thermal expansion method is adopted on AZ91D magnesium alloy under vacuum using the optimum parameters to improve the poor corrosion resistance of Mg alloy。Aluminum powder is used as diffusion material。 Micro-structure of the infiltration layer is observed by the Cai Si microscope。 Phase composition of the diffusion coating is analyzed by XRD test。 the corrosion resistance can tested by uniform corrosion and electrochemical corrosion in different consistence NaCl solution。 The morphology of the diffused aluminum coating after the corrosion is observed by SEM。

This research indicates that: The dense continuous Al layer of the magnesium alloy was obtained at 400 degrees for 90 minutes。 The crack or the void in the whole aluminum infiltration layer doesn’t appear。 the specimen using the optimized parameters prepared by magnesium alloy after the expansion of aluminum。 Diffusion coating layer is mainly composed of α-Mg, α-Al, β-Mg17Al12 and Al3Mg2。 During uniform corrosion, the corrosion resistance of diffusion coating is the best in the consistence=2。5% NaCl solution。The corrosion resistance of diffusion coating in the consistence=3。5% NaCl take second place,and the corrosion in the consistence=5% NaCl is the most serious。The result of the change of PH in electrolyte solution is consistent with the uniform corrosion。 Comparing the corrosion potential during this experiment, we can conclude: Ecorr3。5%> Ecorr5%。 In the solution of consistence=3。5% better than in the corrosion of consistence=5% NaCl solution。

Keywords: AZ91D magnesium alloy; diffusion coating; corrosion; electrochemistry, corrosion resistance

第一章绪论 1

1。1 前言 1

1。2 镁及镁合金概述 1

1。2。1 镁及镁合金的历史与现状 1

1。2。2 镁及镁合金的性质 2

1。2。3 镁合金使用的制约因素 3

1。3 镁合金的应用 4

1。3。1 在汽车行业中的应用 4

1。3。2 在航空航天行业中的应用 5

1。3。3 在电子通讯业中的应用 5

1。4 镁合金的腐蚀与防护 6

1。4。1 镁合金腐蚀类型 7 AZ91D镁合金渗铝层的耐蚀性研究:http://www.youerw.com/cailiao/lunwen_91725.html