高延性鎂合金之特性及成形性研究; Formability and Characteristics of High Ductile Magnesium Alloys

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题名:	高延性鎂合金之特性及成形性研究;Formability and Characteristics of High Ductile Magnesium Alloys
作者:	徐章銓;Chang-chuan Hsu
贡献者:	機械工程研究所
关键词:	熱機處理;超塑性;人工時效;固溶處理;軋延;solid solution treatment;natural aging;rolling;thermo-mechanical treatment;superplasticity
日期:	2008-12-19
上传时间:	2009-09-21 12:05:16 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	鎂質輕(比重1.74)，可供結構件應用。但是鎂合金受限最密堆積六方(hcp)結構因素成形性較差。因此，藉由熱機處理和搭配熱處理製程嘗試獲得微細晶粒的Mg-Zn-Zr合金板材，進而達到高應變速率之超塑性供工業上應用。在這篇論文，主樣研究Mg-Zn-Zr合金經擠製、退火、及軋延的顯微組織及機械性質，及析出物對機械性質之影響。經350℃及80%軋延率軋延後，再265℃x16hrs退火之晶粒尺寸可達3μm之等軸晶，試片在高溫300℃、10-2S-1及10-3S-1拉伸應變速率下超塑性試驗，其伸長率分別可達240%及429%。在論文中亦研究具有低密度及室溫良好成形性的α+β兩相之Mg-Li系合金，但是缺乏機械強度及加工硬化效能。選擇擠製之Mg-Li系合金經由不同製程如擠製+時效、擠製+冷軋、擠製+固溶、擠製+固溶+時效、及擠製+固溶+冷軋，探討顯微組織及機械性質，及析出物強化相之機制。結果發現擠製+固溶+冷軋過程中，以MgLiAlZn擠製板材經400℃x30mins固溶處理後，再經90%軋延率冷軋延，因固溶及加工強化雙重效果可提昇抗拉強度，由擠製時166MPa提昇至276MPa，伸長率仍有20%之高強度、高延性之MgLiAlZn板材。 The magnesium is a very light metal(specific weight 1.74) that can be used for structural application. However, it is commonly recognized that magnesium possessed poor formability because of its hexagonal closed packed structure. Therefore, it is tempting to obtain the refining grain structure of Mg-Zn-Zr alloys plate passing through thermo-mechanical treatment processes and heat treatment, in order to get high strain rate superplasticity of Mg-Zn-Zr alloys for industry application. In this thesis, microstructures and mechanical properties of the Mg-Zn-Zr alloy in as-extruded, as-annealed and subsequent rolled states are studied. The effects of deformation amount, possible precipitates on mechanical properties are examined. The result of grain size is reduced to the of 3μm after 80% rolled and at 265℃x16hrs annealed specimens. High temperature tensile tests indicated that the fine-grained rolling structure exhibited superplasticity，the elongation can reach 240% and 429% at strain rate of 10-2S-1 and 10-3S-1 respectively. I also study two phase(α+β) Mg-Li series alloys，which have better mechanical properties and low density and high formability at room temperature. But Mg-Li series alloys normally have low strength and poor precipitation hardening effect. All those confine its application field. As-extruded of Mg-Li series alloys passed different processes such as extruded/natural aging, extruded/cold rolled, extruded/solid solution treatment, extruded/solid solution treatment/natural aging, and extruded/solid solution treatment/cold rolled . one effective process of improving the mechanical properties is that cold rolled 90% after solution treatment, which tensile strength from as-extruded at 166MPa get up to 276MPa.
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