低鋁和不同含量的鎂添加對鋅合金微組織及各種性質影響之研究

Investigation into the effects of low Al and various Mg additions on the microstructure, thermal properties and corrosion resistance

陳柏竣(Po-Chun Chen)

指導教授 ： 王惠森

義守大學/理工學院/材料科學與工程學系/碩士(2017年)

摘要

本研究參考Thermal-Calc模擬相圖，針對兩種鋁成分(1.0 wt.%和2.5 wt.%)，並調動其鎂成分(分別為1.0 wt.%-3.0 wt.%及1.5 wt.%-3.5 wt.%)，來設計六組熱浸鍍鋅鋁鎂合金。為了模擬生產製程溫度及冷卻速率，本研究在煉製凝固過程中對澆鑄用的銅合金模具進行預熱，隨後對煉製的鋅鋁鎂合金進行微結構、熱物性質、機械性質、耐腐蝕特性等綜合評估，提供較佳的鋁、鎂添加比例。
從實驗結果顯示，在微組織的方面，無論是鋁成分1.0 wt.%和2.5 wt.%合金系統，在添加低鎂時(例如1.0wt.% or 1.5wt.%)會有高比率的Primary Zn初析相，而在中鎂成分(例如2.0wt.% or 2.5wt.%)添加時，其Primary Zn相的比率會下降，而Ternary結構的比率上升，在添加至高鎂時(例如3.0wt.% or 3.5wt.%)，除了能發現到高比率且細緻的三元組織，還可以觀察到Primary MgZn2相的產生。熱物性質方面，本研究透過高溫示差分析之特徵溫度點與模擬相圖的相變化點進行比對，可以發現本研究所設計的六組合金成分試片的實際液化溫度變化，與相圖的液化溫度有相同的趨勢；而在所有六組試片中，鋅-2.5wt.%鋁-2.5wt.%鎂的合金設計擁有最低的液化溫度。
在腐蝕特性方面，無論是電化學或鹽霧測試的成果顯示，較高的鋁及鎂 (鋅-2.5wt.%鋁-3.5wt.%鎂) 的添加，可擁有最佳的耐蝕性，除此高的鋁及鎂 (鋅-2.5wt.%鋁-3.5wt.%鎂)的添加亦可產生細緻而且體積分率最高的Ternary結構，因此提供最高的硬度值。

關鍵字

熱浸鍍鋅鋁鎂合金 ； 微組織 ； 熱物性質 ； 機械性質 ； 耐蝕性

並列摘要

With the reference to the Thermal-Calc phase diagram, in this study, six hot-dip galvanized aluminum-magnesium (Zn-Al-Mg) alloys were designs by adjusting their aluminum additions (1.0wt.%&2.5wt.%), and magnesium additions(1-3wt.% & 1.5-3.5wt.%). In order to simulate the real processing temperature and the cooling rate of the alloys, a preheated copper alloy mold was used for the casting process. Then, the microstructure, corrosion resistance, thermal and mechanical properties of the cast alloy were evaluated to obtain the better aluminum and magnesium additions for the Zn-Al-Mg alloys .
Experimental results were shown, regarding to microstructure, for both aluminum additions (1.0wt.% and 2.5wt.% of aluminum), low magnesium additions (e.g.1.0wt.% or 1.5wt.%) results in a high volume fraction of primary Zn phase. For the mid-proportion (e.g. 2.0wt.% or 2.5wt.%) of magnesium additions, the volume fraction of primary Zn was decreased, but the volume fraction of ternary phase increased. When the higher magnesium additions (3.0wt.% or 3.5wt.% ) were use, the ternary became finer and denser. Also the primary MgZn2 phase can be observed. For the thermal properties of the alloys, through the comparison the results of Differential Scanning Calorimetry (DSC) tests to the Thermo-Calc phase diagrams, it was found that both approaches has the similar tendency of change in the liquation temperatures. The test results showed that the Zn-2.5wt.%al-2.5wt.%mg alloy design has the lowest liquation temperature.
Regarding to the corrosion resistance, both the electrochemical or salt spray test results were shown, the Zn-2.5wt.% Al-2.5wt.%Mg had best corrosion resistance due to it has higher volume fraction of and finer ternary structure. In additions, the structure of the alloy is also results in a highest hardness.

並列關鍵字

hot-dip galvanized aluminum-magnesium alloys ； microstructure ； thermal properties ； mechanical property ； corrosion resistance

參考文獻

[14] 燁輝企業股份有限公司，熱浸鍍5%鋁鋅(鋁鋅鳳)及5%鋁鋅烤漆(彩色鳳)鋼捲。

[1] T. Prosek, et al., “Corrosion mechanism of model zinc–magnesium alloys in atmospheric conditions”, Corrosion Science, vol.509(8), 2008, pp.2216-2231.

[2] R.P. Edavan, R. Kopinski, “Corrosion resistance of painted zinc alloy coated steels. Corrosion Science”, vol.519(10), 2009, pp.2429-2442.

[3] A.R. Marder, “The metallurgy of zinc-coated steel. Progress in Materials Science”, vol.45(3), 2000, pp.191-271.

[9] S. Li, et al., “The effects of RE and Si on the microstructure and corrosion resistance of Zn–6Al–3Mg hot dip coating”, Applied Surface Science,vol.357, 2015, pp.2004-2012.