標題: 利用具超細晶粒胚材進行半固態鍛造加工之研究(III)
Study on the Semi-Solid Forging Process with Ultra-Fine Grain Magnesium Billets (Iii)
作者: 徐瑞坤
HSU RAY-QUEN
國立交通大學機械工程學系(所)
關鍵字: 鎂合金;半固態成形;升溫速率;持溫時間
公開日期: 2011
摘要: 鎂合金具有高強度、電磁遮蔽、散熱性佳、耐衝擊性、耐高溫性、耐腐蝕性等優良的材料特性,但因鎂合金的結晶結構屬六方最密堆積,所以其塑性加工性差,展伸材的製造不易,無法以塑性成形的方式進行材料的加工,所以目前工業界對鎂合金材常使用的方法大多是壓鑄法中的冷室壓鑄法、熱室壓鑄法,以及半溶融加工方式中的觸變射出成型。利用鑄造方式雖具有成本低、生產率高、品質穩定、適合大量且快速生產等優點,但壓鑄法仍然有著捲氣、廢料過多、危險易燃、無法製造太薄的物件、鑄件強度低等缺點。若想利用鎂合金製造車用結構部品,必須採用別種加工方式方可符合強度上的需求。因此本計劃之最主要目的即為開發一種可用於半溶融成形的鎂合金胚材,實際進行車用零件如輪圈等之鍛造加工,希望能夠開創出鎂合金新的應用領域。 為了改善鎂合金室溫下成形性不佳之缺點,本計劃將運用半溶融成形加工技術並結合大量塑性變形法來製作所需胚料。本實驗室過去曾對金屬材料的半溶融加工有過許多探討,根據以往的經驗,如何能夠讓在半溶融溫度區間具有良好球狀晶的鎂合金胚料製備,是此製程目前的關鍵所在。雖然傳統應變導引熔漿活化法製備鎂合金半溶融胚料的製程簡單,但胚材內之應變量分佈不均及無法連續進行的缺點,使其至今仍無法有工業上的實際應用。於是我們打算結合如等徑轉角擠製之大量塑性變形法的製程,來給予鎂合金胚材大量且均勻的應變,使胚料能具有奈米等級的超細晶粒,這樣在將胚材昇溫到半溶融區間時,可得到較以往製程更細微的球狀晶,半溶融鍛造加工後的成品強度也將會提高。最後再利用機械性質測試與非破壞檢測來驗證成品的品質好壞。 本計劃預計分三年來完成: (1) 第一年研究成果如表C012-1內所附成果報告所示,已完成初步設計構想之驗證以及模具本體的設計製作,此外也利用此模具針對擠製溫度、擠製路徑、擠製道次三種不同參數進行實驗,找出細化效果最佳之參數組合 (2) 第二年將藉由設計輔助的油壓系統,改善原有製程之步驟及時間,以期能利用此模具來進行連續自動化的等徑轉角擠製,此外亦藉由退火處理實驗,探討胚料晶粒細化之最佳熱處理參數,然後觀察不同實驗參數下所得胚料的顯微結構,找出可得到均勻分佈超細晶粒的參數。 (3) 第三年將利用第二年所製備之胚料,實際進行車用零件的半溶融鍛造加工,觀察其外觀與充填性,驗證鎂合金之半溶融良好成形性,且透過機械性質測試與非破壞檢測來驗證成品品質。 綜合這三年的研究成果,能開發出一可連續進行之等徑轉角擠製製程,進行半溶融觸變鍛造所需胚料之製備,並且實際探討應用於鎂合金成品的相關製程條件,以期未來能將此製程實際應用於工業生產。
Recently, the growing demand for light-weight products with high strength products in automobile and aircraft industries have push the application of magnesium alloys into a unprecedented high level in these fields. Magnesium has the lowest density among the metals. Its strength-to-weight ratio is the highest of all the structural metals. Because of the ease of recycling, magnesium alloys attract the attention even in the consumer electronic industry. Fabrication of magnesium alloys are often processed by die casting, casting and sometimes thixo-forming since they have limited ductility at room temperature. All of these manufacturing methods have disadvantages especially when a very thin section or better mechanical properties are required. In this study, semi-solid forming technique which has the advantage of lower forming load and suitable for materials that have little ductility will be adopted for the processing of magnesium alloys. In order to improve the homogeneity of the grain size in the microstructure of the magnesium alloys billets, the alloys are intended to subject severe plastic deformation named continuous ECAE, in room temperature. Then with proper heat treatment, the alloys are expected to develop a nano-crystalline structure which in turn will bring better mechanical properties. Finally the magnesium alloys will be applied for forming an automobile part. The study is composed of the following stages: (1) Design and analysis of the continuous ECAE extrusion device. Investigate the influence of processing parameters by experiments. (2) Perform ECAE extrusion, heat treatment of the magnesium alloy billet, investigating the microstructure of the alloy.. (3) Apply the nano-crystalline material for the fabrication of an automobile part. Compare the mechanical properties of the part with the part made of the conventional forming methods.
官方說明文件#: NSC100-2221-E009-031
URI: http://hdl.handle.net/11536/99614
https://www.grb.gov.tw/search/planDetail?id=2342544&docId=369353
顯示於類別:研究計畫