利用等徑轉角擠型來改善AM60與AM60-1RE鎂合金之高溫成型性研究

Improving the High Temperature Formability of AM60 and AM60-1RE Mg Alloys by Equal Channel Angular Extrusion

江明(Ming Chiang)

指導教授 ： 楊智富

大同大學/工程學院/材料工程學系所/碩士(2004年)

摘要

摘要:
本研究對兩種AM60和AM60-1RE鎂合金進行200 ℃及270 ℃之等徑轉角擠型(ECAE)熱加工，以探討微觀結構變化與機械性質的改變。經由微觀結構的演變與機械性質的量測，探討鎂合金在高溫拉伸時最終之穩定晶粒結構之生成及其對機械性質的影響。
研究結果顯示，在適當測試條件下，AM60與AM60-1RE鎂合金即使未經預應變也很容易發生動態再結晶。而經由等徑轉角擠型AM60與AM60-1RE鎂合金之高溫延伸率可獲得提昇。在較低擠型溫度(200 ℃)可獲致較細晶粒之鎂合金，而較細晶粒者具較佳之高溫延伸率。本研究亦發現，在ECAE及高溫拉伸測試時，再超過一定量之塑性變形後，鎂合金達成一呈現動態穩定之晶粒結構，且在後續恆溫熱加工時其晶粒尺寸維持不變。此穩定之晶粒結構係藉由熱加工過程中「晶粒細化」與「晶粒粗化」達成動態平衡所導致。

關鍵字

鎂合金 ； 等徑轉角擠型

並列摘要

Abstract:
Severe deformation processing is an emerging method for refining the grain structure of conventional alloys to micron and submicron levels. As such, this study aims to explore the microstructural evolution and property change in two Mg alloy, namely the AM60 and AM60-1RE, by ECAE processing at 200 ℃ and 270 ℃. The effects of structure evolution and the formation of a dynamic stable grain structure by hot working on the high temperature tensile ductility of the Mg alloys were also examined in this study.
The results showed that an improvement in the higher elevated temperature ductility in AM60 and AM60-1RE alloys was achieved by applying an ECAE processing to the Mg alloys. Grain refinement in the Mg alloys by ECAE at 200 ℃ was found much more effective than at 270 ℃. The fine-grained Mg alloys obtained by ECAE at 200 ℃ exhibit higher high temperature tensile ductility than Mg alloys with a coarser grain structure. A dynamically stable grain structure with a stable grain size was found in the Mg alloys subjected to hot working by ECAE as well as by tensile deformation. The stable grain structure was reached by a dynamic balance between “grain refining” and “grain coarsening” in the process of hot working.

並列關鍵字

AM60 ； ECAE ； misch metal ； rare metal

參考文獻

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