鎂合金具有低密度、高比強度、回收性佳等優點，因而普遍使用在交通工業、3C產業上。鎂合金於室溫下成形性不佳的原因歸因於其HCP結構於室溫下滑移系統不足，需要在高溫環境中加工成形，導致成本提高，故本實驗使用摩擦攪拌製程(Friction Stir Process, FSP)進行改質，可以獲得再結晶之細小晶粒，以得到較好加工性。首先將AZ61鎂合金材料進行退火處理後施以FSP，進行顯微組織觀察，以及在不同溫度(200℃至250℃)和應變速率(8.33×10-3sec-1、1.67×10-3sec-1 及 8.33×10-4sec-1)下進行拉伸試驗以了解織構及洋蔥環效應對機械性質之影響。
　　在顯微組織方面，AZ61-O鎂合金在經過FSP後SZ區有明顯晶粒細化效果；由XRD結果顯示，銲道上織構為HCP的基面沿著攪拌棒的凸梢圓周排列。拉伸試驗結果顯示，O材及FSP材在200℃以上的應力-應變曲線可以觀察到有抖動現象產生，根據觀察結果可知這是由於材料在拉伸過程中產生動態再結晶所致。各試料的降伏強度、抗拉強度及均勻延伸率皆隨拉伸溫度上升及應變速率下降而下降，總延伸率隨拉伸溫度上升及應變速率下降而有增大傾向。值得注意的是FSP材於200℃拉伸之總延伸率雖小於O材，但是升溫至225℃及250℃後之總延伸率卻大於O材，根據實驗結果可確認是由於FSP後之織構特徵導致拉伸時較易產生形變雙晶。
　　FSP後材料抗拉強度及降伏強度下降，延性提升之原因，推測因大量產生動態再結晶使材料軟化，因此促進擴散頸縮行為發生，並降低材料的均勻延伸率；根據n值量測，材料於高溫低應變速率下產生晶界滑移，並導致應變硬化效果，降低動態再結晶對於材料的軟化作用，進而提升延性。

　Magnesium alloys have several advantages including low density, high specific strength and well recyclability. There are common applications in traffic and 3C industry. The inherently poor workability exists in Magnesium alloys at room temperature due to the limited slip systems associated with the HCP crystal structure. Since high temperature forming is applied in general, it would cause more cost. Therefore, mechanical properties are improved by Friction Stir Process (FSP), and the grains would be well recrystallized to increase the workability.
　Full-annealed magnesium alloys of AZ61, called AZ61-O, are processed by FSP. In order to study the effects of microstructure, texture, and onion rings by FSP. AZ61-O and FSP AZ61 are both studied by tensile test with different temperatures(200℃ to 250℃) and strain rates(8.33×10-3sec-1,1.67×10-3sec-1 and 8.33×10-4sec-1). The relationship between texture distribution and mechanical properties of a FSP AZ61 alloy is discussed. In the microstructure of FSP AZ61 Mg alloys, Stir Zoon (SZ) has fine recrystallized grains. An intense basal plane texture detected by X-ray diffraction (XRD) roughly surrounded the rotation pin column after FSP. On tensile test, both of the AZ61-O and FSP AZ61 experimental results indicate that the serrations of stress-strain curve observed above 200℃ owing to the dynamic recrystallization (DRX). The ultimate stress, yield stress and uniform elongation of the specimens decreased with the increasing tensile temperature and decreasing strain rate. Total elongation increased as the tensile temperature increased and/or the strain rate decreased. According to the experiment results, all FSP AZ61 samples have better elongation than AZ61-O ones above 225℃. The reason why the elongation of FSP AZ61 alloys is less than AZ61-O at 200℃ is attributed to the deformation twins growing out of the tensile test more easily in FSP AZ61. This phenomenon is associated with the texture of FSP.
　DRX softened the structure and induced the diffused necking that is the domain reason to cause the decreasing of flow stress and increasing of elongation; thus the uniform elongation was reduced. The grain boundary sliding (GBS) which can be presented by the stress exponent(n) suppressed the DRX softening and local necking so that the total elongation tended to increase under the high temperatures and low strain rates.

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