臺灣博碩士論文加值系統

本研究以鑄造態之ZK60合金分別進行熱滾軋(Hot Rolling) 10% 與50%及等徑轉角擠型(Equal Channel Angular Pressing，ECAP) Route BA之1與4道次後，將合金置於380oC做 1小時固溶處理後，以水淬後自然時效與爐冷兩種方式冷卻，再進行熱機處理對合金顯微組織、硬度與拉伸性質及儲氫性質影響之探討。
ZK60合金鑄錠在冷卻過程中，除了形成以Mg為主要成份之dendrite基地相之外，因其冷卻速率較快，使其產生熱力學上之非平衡組織，即為interdendrite之共晶/共析複合組織。合金於鑄造態、或經機械加工、或再經固溶處理後，於FESEM 100kx之下均可觀察到由介金屬相所形成的三維網狀組織，顯示經過機械加工即使合金發生動態再結晶、或再經高溫之固溶處理後，其高倍下之顯微組織仍然不變。EPMA之分析顯示含Zr第二相(可能為Mg3Zn5Zr)不會單獨存在於合金之基地相中，而是混雜在共晶/共析組織中，且其體積分率遠低於共晶/共析組織。
合金經機械加工及固溶處理後水淬進行自然時效，其硬度值隨時效時間而遞增，當時效達32小時，Hot Rolling合金之硬度達最大值，隨後產生過時效使硬度值下降，而ECAP合金的硬度值仍呈現單調遞增並趨近一個上限值，且ECAP合金之硬度值明顯高於Hot Rolling之合金。合金經Hot Rolling與ECAP之機械加工及固溶處理後，以水淬自然時效與爐冷將其冷卻，在相同條件下比較其拉伸性質時，ECAP之σUTS略高於Hot Rolling，但εf則明顯高出很多，顯示ECAP之合金所呈現的拉伸性質較Hot Rolling 之合金明顯為優。
合金經不同機械加工後，直接於400oC活化10小時，再於不同溫度吸放氫之前五次平均吸氫量，隨著吸放氫溫度與加工量提高時，吸氫量皆有增加的趨勢，其中以ECAP BA 4Passes最為明顯，吸氫量在400oC時可達2.29 wt%，但吸氫性質均不盡理想。合金經機械加工、或再經固溶處理後再添加5 wt%活性碳，並經球磨20小時及400oC活化10小時後，於280oC以上吸放氫時，吸氫量均可大幅提升，於360oC時達到最大值(約為6.43 wt%)，而於400oC時因吸氫平衡壓之升高使得吸氫量均明顯下降，顯示熱機處理後再添加5 wt%活性碳及球磨20小時之效應已遠遠超過合金是否經380oC 1小時之固溶處理所產生之差異。

In this study the cast ZK60 alloy was strained by Hot Rolling 10%, 50% and Equal Channel Angular Pressing (ECAP) Route BA 1Pass, 4Passes, respectively. After 380oC/1 hr solid solution treatment followed by water quenching then aging or furnace cooling, the effects of various thermo-mechanical treatments on the microstructures and mechanical / hydrogen storage properties of the ZK60 alloy were investigated.
The microstructures of the alloy ingots are composed of the dendrite of α phase and the interdendrite of eutectic / eutectoid mixtures. By FESEM observation under 100kX for various thermo-mechanical treatments, it shows a nanostructure with a three-dimensional network of intermetallic phases in the matrix of α phase. EPMA analysis shows that the second phase which contains Zr and is indentified possibly as Mg3Zn5Zr does not exist in the matrix of α phase but is mixed in the eutectic / eutectoid mixtures, and its volume fraction is far less than that of the eutectic / eutectoid mixtures.
After 380oC/1 hr solid solution treatment followed by water quenching then aging at room temperature, the hardness of the alloys increases with increasing aging time, and it reaches a maximum at 32 hrs for Hot Rolling then decreases with aging time due to over aging. However, the hardness of the alloys for ECAP after 32 hrs still increases monotonically and approaches an upper value with increasing aging time, and is obviously higher than that for Hot Rolling. Under the same conditions, the tensile stress σUTS of the alloys for ECAP is slightly higher than that for Hot Rolling. However, the fracture strain εf for ECAP is obviously higher than that for Hot Rolling. It means that the tensile properties of the alloys for ECAP is superior to that for Hot Rolling.
By various mechanical processes followed by 400oC/10 hrs activation treatment, the hydrogen capacity of the alloys increases with increasing hydrogenation temperature and / or plastic strain. The hydrogen capacity can reach 2.29wt% for the alloy by ECAP BA 4Passes at 400oC. However, the hydrogenation properties of the alloys is still not so good. After improvement by adding 5wt% activated carbon and 20 hrs ball-milling, the hydrogen capacity of the alloys increases obviously at hydrogenation temperature higher than 280oC, and it can reach the maximum 6.43wt% at 360oC, then decreases with hydrogenation temperature due to the increasing of the hydrogen absorption pressure. It shows the fact that the hydrogenation properties of the alloys can be improved significantly by the addtion of 5wt% activated carbon and the treatment of 20 hrs ball-milling rather than various thermo-mechanical treatments.

中文摘要 i
Abstract iii
總目錄 v
圖目錄 viii
表目錄 xi
第一章 前言 1
第二章 理論與文獻回顧 3
2.1 鎂合金的基本介紹 3
2.2鎂合金之熱機處理 7
2.2.1鎂合金晶粒細化 7
2.2.2鎂合金晶粒細化之熱機處理 8
2.2.2.1軋延法(Rolling) 8
2.2.2.2等徑轉角擠形(Equal Channel Angular Pressing, ECAP) 8
2.2.2.2.1等徑轉角擠型之應變 10
2.2.2.2.2等徑轉角擠型之路徑 11
2.2.2.3機械冶金法(Mechanical Alloying, MA) 15
2.2.2.3.1 機械冶金法之原理 16
2.2.2.3.2 球磨機類型 18
2.2.2.3.3 球磨速度與時間 18
2.2.2.3.4 鋼球與粉體之重量比 18
2.2.2.3.5 球磨氣氛 19
2.2.2.3.6 球磨溫度 19
2.2.3鎂合金晶粒細化之機制 19
2.3 氫能源的儲存技術 24
2.3.1高壓氣態儲氫 25
2.3.2金屬氫化物儲氫 25
2.3.3低溫液態儲氫 26
2.4儲氫合金 28
2.4.1儲氫合金簡介 28
第三章 實驗步驟與方法 39
3.1實驗流程圖 40
3.2熱滾軋 41
3.3 等徑轉角擠型擠製 42
3.4 硬度測試 44
3.5 拉伸試驗 44
3.6 球磨製備合金粉末 45
3.7 儲氫合金儲氫特性檢測 46
3.7.1 活化 47
3.7.2 動力學曲線 48
3.8 冷場發射掃描式電子顯微鏡 49
3.9電子微探分析儀 50
第四章 結果與討論 51
4.1合金基本性質 51
4.2合金顯微組織 55
4.2.1機械加工後之顯微組織 55
4.2.1.1熱滾軋 55
4.2.1.2 ECAP 59
4.2.2機械加工後再經固溶熱處理之顯微組織 63
4.2.2.1機械加工再經380oC 1小時後水淬與自然時效 63
4.2.2.2機械加工再經380oC 1小時後爐冷 67
4.2.2.3機械加工再經380oC 4小時後水淬與自然時效 68
4.2.3 EPMA分析 69
4.3合金機械性質 72
4.3.1時效硬度曲線 72
4.3.2拉伸相關性質 74
4.4合金儲氫特性 80
4.4.1不同機械加工之儲氫性質 80
4.4.2機械加工後再添加5wt%活性碳與球磨之儲氫性質 82
4.4.3熱機處理後再添加5wt%活性碳與球磨之儲氫性質 89
第五章 結論 90
參考文獻 92