鎂鋁合金中Mg17Al12對於磷酸鹽/錳酸鹽化成處理微結構與性質的影響

Effect of Mg17Al12 in Magnesium-Aluminum Alloy on the Microstructure and Properties of Phosphate / Permanganate Conversion Coating

蔡孟熹(Meng-Hsi Tsai)

指導教授 ： 林招松

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00974

摘要

鎂與其合金的標準還原電位低於大部分的結構材料，容易造成腐蝕。潛力與現今應用產生落差，因此各種防蝕的方法因應而生。化成處理的方法之中以鉻酸鹽的防蝕具有最好效果，但六價鉻對於人體具有毒性。磷酸鹽/錳酸鹽的化成處理是具有潛力能夠替代六價鉻化成處理的方法之一。不同鋁含量的鎂鋁合金具有不同的微結構，不同的製程也會造成微結構以及性質的差異。
本研究針對AZ31、AZ80與AZ91鎂鋁合金中Mg17Al12(β相)，對短時間（30、60與120秒）磷酸鹽/錳酸鹽化成皮膜的表面形貌、微結構及性質的差異。以光學顯微鏡、掃瞄式電子顯微鏡、橫截面穿透式電子顯微鏡以及低掠角X-ray晶體繞射，分析皮膜的表面型態和結構，配合極化曲線以及交流阻抗分析皮膜的抗蝕性質，以及百格試驗分析化成皮膜的附著性。結果顯示鎂合金的製程、組成都會影響Mg17Al12(β相)的體積分率、形貌以及分佈，這些因素對化成皮膜的表面形貌、結構、附著性以及抗蝕性質有很大的影響。

關鍵字

Mg17Al12 ； 鎂鋁合金 ； 微結構 ； 磷酸鹽/錳酸鹽化成處理 ； 無鉻化成處理

並列摘要

The standard reduction potential of magnesium and its alloys are lower than the other structural materials. Therefore, magnesium alloys are highly susceptible to corrosion, giving rise to the limitation on their practical application. Many surface modification methods have, thus, been developed to protect magnesium alloys from corrosion. Among the conversion coating methods, chromate conversion caoting exhibits the best corrosion protective properties. Howerver, Cr(VI) is toxic to human body. Phosphate-permanganate conversion treatment is one of the methods that are potentially alternative to the chromate treatments. The microstructures and the properties of magnesium alloy can be controlled by its aluminium contents and the corresponding fabrication processes.
This research focuses on how the Mg17Al12 (β) phase in AZ31,AZ80 and AZ91 magnesium- aluminum alloys influences the surface morphology, microstructures and properties of the phosphate-permanganate coating formed in a short time (30, 60 and 120sec) of immersion. This research utilizes optical microscopy, SEM, TEM and low glancing-angle XRD to analyze the surface morphology and crystal structure of the coating, measures the electrochemical polarization curve and electrochemical impendence spectroscopy to analyze the corrosion properties of the coating, and uses ASTM D3359-97 method to study the adhesion of conversion coating. The results shows that the fabrication process and composition of the alloys markedly influence the shape, volume fraction and distribution of Mg17Al12 (β) phase which in turn, affects the surface morphology, microstructures, adhesion properties and corrosion properties of the coating.

並列關鍵字

Mg17Al12 ； Magnesium-Aluminum alloy ； Microstructure Phosphate/Permanganate Conversion Coating, ； Chromium-free Conversion Coating

參考文獻

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