臺灣博碩士論文加值系統

本實驗使用-200mesh大小、平均粉末粒徑約為74μm的鎂粉，並選擇銅棒作為鎂粉容器來進行ECAE製程，在200℃、250℃、300℃的溫度下以路徑BC擠型一次、二次、四次。將得到的鎂粉塊材以SEM觀察其顯微組織並使用阿基米德法量測密度，接著做微硬度與壓縮試驗測試，最後進行腐蝕浸泡實驗。
結果顯示，鎂粉理想密度為1.88 g/cm3，而經過不同溫度與擠型道次ECAE製程的鎂粉塊材在溫度300℃且擠型道次為N=4時，密度可達到最高值1.85 g/cm3，為理想密度的98.4%。
微硬度方面，當溫度300℃且擠型道次為N=4時，微硬度可達到最高值49Hv，在300℃, N=4時孔洞率僅有1.6%；在200℃、250℃、300℃, N=4時，氧化物聚集大小的平均粒徑分別為29.14、21.16、14.95μm，因此當溫度從200℃增加至300℃時氧化物分散較均勻，可得到最高微硬度值。
壓縮試驗方面，200℃、250℃、300℃, N=4的最大抗壓應力分別為155MPa、175MPa、190MPa，壓縮降伏應力分別為75MPa、85MPa、100MPa，在300℃, N=4強度最大，
腐蝕浸泡實驗方面，200℃、250℃, N=4以及300℃, N=1, 2, 4的氧化程度(面積比例)分別為42%、39%、38%、34%、31%，且可觀察到腐蝕會先從顆粒邊界及顆粒與氧化物接觸介面開始發生，而300℃, N=4氧化程度最低，因此粉末間鍵結強度(Bonding)最高。

In this research, microstructure and mechanical behaviors of bulk magnesium consolidated from magnesium powder by equal channel angular extrusion (ECAE) were investigated. Particle size of magnesium powder was about 74μm in diameter. Magnesium powder was filled into copper cans then ECAEd for 1, 2 and 4 passes via Bc route at 200℃, 250℃ and 300℃, respectively. Microstructure of as ECAEed samples was observed by SEM. Density of each sample was carried out by Archimedes law. Microhardness, compression test and immersion corrosion test were conducted to investigate the properties of each ECAEed sample.
Maximum density of bulk magnesium is 1.85 g/cm3 achieved after 4 passes of ECAE at 300℃. Magnesium powder is softer and more ductile at higher temperature; therefore, it is more easily to be deformed and filled into pores between partilces. ECAE process deforms and fines magnesium powder to fill residual pores, hence pores are eliminated by filling of magnesium powder.
Maximum hardness value of bulk magnesium is 49 Hv achieved after 4 passes of ECAE at 300℃. It is due to the elimination of pores and the more uniform dispersion of oxides of samples at higher temperature.
After 4th pass of ECAE at 200℃, 250℃ and 300℃, ultra compressive stress (UCS) of consolidated bulk magnesium achieved 155MPa, 175MPa and 190MPa. Compressive yield stress (CYS) of consolidated bulk magnesium achieved 75MPa, 85MPa and 100MPa, respectively. It is due to the more uniform dispersion of oxides of samples at higher temperature.
After immersion corrosion for bulk magnesium of 4 passes at 200℃ and 250℃ and 1, 2 and 4 passes of ECAE at 300℃, degree of corrosion are 42%, 39%, 38%, 34% and 31%. Corrosion will take place initially between Mg and MgO interface. Best bonding strength between powders is achieved after 4 passes of ECAE at 300℃.

第一章 前言 1

第二章 文獻回顧 3
2.1 鎂的簡介 3
2.1.1 鎂的來源與冶煉 3
2.1.2 鎂與鎂合金的基本性質與應用 3
2.2 晶粒細化的方法 4
2.2.1 等通道轉角擠型(Equal Channel Angular Extrusion, ECAE)4
2.2.2 ECAE的原理 5
2.2.3 ECAE的擠型路徑 5
2.3 以ECAE製備粉末塊材 6
2.3.1 ECAE製備粉末塊材的發展 6
2.3.2 利用ECAE製程時溫度的影響 7
2.3.3 利用ECAE製程時擠型道次的影響 7

第三章 實驗方法 11
3.1 實驗流程 11
3.2 試棒製備 12
3.3 ECAE所用設備 12
3.4 測試與分析 13
3.4.1 掃描式電子顯微鏡分析(SEM) 13
3.4.2 密度量測 13
3.4.3 微硬度測試 13
3.4.4 材料壓縮測試(Compression test) 13
3.4.5 腐蝕浸泡分析 14

第四章 實驗結果與討論 19
4.1 加工前鎂粉粒徑大小與EDX分析 19
4.2 鎂粉經等通道轉角擠型後的顯微組織 19
4.2.1 顯微組織分析 19
4.2.2 溫度對鎂粉塊材密度的影響 20
4.2.3 擠型道次對鎂粉塊材密度的影響 21
4.3 機械性質探討 21
4.3.1 微硬度分析 21
4.3.2 Compression test 22
4.4 腐蝕浸泡實驗 23

第五章 結論 49
參考文獻 50

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