- 學位論文
多元合金電渣重熔製程問題之研究
A Study on the Electro-Slag Remelting of Multi-component Alloys
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摘要
多元高性能合金比傳統合金更具耐蝕性、更耐高溫、硬度更高且更不易氧化，所以吸引了國內外許多研究上的投入。但發現即使是用氣氛保護電弧爐ARM或真空電弧爐熔煉鑄造多元合金的鑄錠，也經常會有成份偏析、晶粒形狀大小不一、縮孔和特定含量的異常析出物等巨觀或是微觀的缺陷，而造成性質再現性不佳。如何熔煉製造缺陷少與清淨度高之多元合金，為成功發展新合金精煉的關鍵，亦是本研究的主軸。 本研究選取Al-Cr-Fe-Mn-Ni及Al-Co-Cr-Mn-Fe-Ni兩多元合金系統，來進行電渣重熔製程上的分析與比較。從一系列的實驗分析結果可以得知，經過電渣重熔後的合金鑄錠，在部份實驗參數的設計之下，確實可以達到清淨度高的效果。除此之外，兩合金系統的微結構觀察，皆出現樹枝狀晶與樹枝間晶的分布狀態，並在二次精煉過後，都呈現出FCC相的晶體結構，而合金本身的晶粒也變得較為細小，同時還減少了偏析現象與析出物的產生。 自加工應用的角度來看，熱輥軋壓延實驗過後的合金試片，晶粒因為拉長甚至打斷的關係，進而達到細化的效果並提升了合金本身的性質。在高溫氧化的實驗數據中顯示，電渣重熔之後的合金鑄錠，由於鋁含量下降的緣故，並沒有足夠的來源可以形成緻密的氧化鋁保護層，所以在抗氧化能力與效果的表現上不如預期。因此，若要兼顧偏析、縮孔與清淨度的改善，又要發揮抗高溫氧化的能力，必須在電渣重熔二次精煉的製程上作改善，才有辦法達到這個目標。
並列摘要
Multi-component alloys show good corrosion resistance, high erature mechanical properties, great oxidation resistance, and excellent high temperature phase stability, comparing to traditional alloys. However, it has been found that the ingots, prepared by using a normal arc melter with protection gas of argon, contain both macro and micro defects such as pores, cavity, segregations, large dendrite grains and inclusions. In the present research, electro-slag remelting was employed to attain purer multi-component alloys with less microstructure defects. This research aims at analyzing the manufacturing process of electro-slag remelting for Al-Cr-Fe-Mn-Ni and Al-Co-Cr-Mn-Fe-Ni multi-component alloys. From the results of a series of experiments, it was found that, under some specific conditions, the electro-slag remelting did improve the purity of the multi-component alloys. In addition, we observed that, after the electro-slag remelting, dendrite and inter-dendrite structures distributed in these two kinds of alloys, and both alloys possessed FCC crystal structure. The crystalline grains of the alloys became finer. And less segregations and precipitates were observed. It was also found that a hot-rolling process could further make the crystalline grains of alloys elongated and even broken up, which resulted in finer grain and stronger mechanical properties. However, high temperature oxidation experiment showed that, after electro-slag remelting, the alloys did not have enough alumina to form fine and dense surface layers because alumina were lost during the remelting. As a result, the oxidation resistance did not reach the expectation. Therefore, further improvement on the electro-slag remelting process is still needed to obtain multi-component alloys with both good mechanical properties and high oxidation resistance.
參考文獻
【43】H. H. Hsieh, C.C. Lee, W. Kai, “The Oxidation Behavior of Cu60Zr30Ti10 Bulk Metallic Glass at 300-500℃”，防蝕工程，第十九卷第三期，第405~414頁（2005）
【46】蔡宗晏，“鐵-鋁-釹合金高溫氧化與微結構組織的研究”，國立台灣大學材料科學與工程學研究所碩士論文（2004）
【47】吳正德，“高熵合金相圖模擬之研究”，國立台灣大學材料科學與工程學研究所碩士論文（2005）
【1】W. L. Johnson, “Fundamental aspects of bulk metallic glass formation in multi-component alloys”, Mater SCI Forum, Vol.35, p.225-2（1996）
【2】A. Inoue, “High strength bulk amorphous alloys with low critical cooling rates”, Mater Trans JIM, Vol.36, p.7-866（1995）