在室溫下，以10 s 應變率，分別沿著AZ31板材的rolling direction(RD)方向與normal direction(ND)方向進行壓縮測試。因為板材具有強烈的集合組織，試片沿著RD方向壓縮會產生拉伸雙晶，沿著ND方向壓縮會產生壓縮雙晶。
研究發現沿著RD方向進行小應變量的壓縮，變形初期試片內部便會出現雙晶帶，隨著應變量的增加雙晶帶會開始擴展。觀察雙晶帶內部發現不論晶粒大小皆有拉伸雙晶的產生即變形雙晶的生成與晶粒大小無關，其原因為拉伸雙晶在晶界上會造成應力集中而引發鄰近晶粒(不論大小)產生拉伸雙晶。沿著ND方向進行壓縮，則無雙晶帶的產生。由大量金相組織分析的結果得知，壓縮雙晶的生成與晶粒大小有密切的關係，小晶粒中不易生成壓縮雙晶。

Compression tests along the rolling and normal direction of AZ31B plate materials under 10 s strain rate were performed at room temperature to understand the effect of grain size on the formation of deformation twins. When compressed along the rolling direction, tension twins were formed in bands. Within the twin bands, nearly all grains contained tension twins, irrespective of grain size. And outside the bands, no twin was found. Under this deformation condition, grain size has no effect on the formation of tension twins. The reason for this is due to the fact that the formation of a tension twin can trigger the formation of tension twin in the neighboring grain, irrespective of the neighboring grain size.

When compressed along the normal direction, no twin band was formed, and compression twins were formed evenly in the specimens. Under this deformation condition, it was found that the larger the grain size, the higher the fraction of grains which contained compression twins. This result indicates that compression twins are easier to be formed in the large grains.

論文審定書 i
摘要 iii
Abstract iv
表目錄 v
圖目錄 vi
一、前言 1
二、文獻回顧 2
2-1鎂合金的變形 2
2-1-1室溫下之變形機制 2
2-1-1-1 差排滑移 2
2-1-1-2 變形雙晶 3
2-2織構(texture)與相關變形行為 5
2-3晶粒尺寸對變形雙晶生成的影響 6
三、研究目的 13
四、實驗方法 14
4-1 實驗材料 14
4-2 壓縮試驗 14
4-3 光學顯微鏡與掃描式電子顯微鏡的試片製備 14
4-4 OM與SEM儀器 15
4-5 晶粒尺寸的量測 15
4-6 EBSD(electron backscatter diffraction)的試片製備 16
4-7 XRD繞射分析 16
五、實驗結果 18
5-1 退火材料之組織 18
5-2 RC試片之結果 19
5-2-1 RC試片之應力-應變曲線 19
5-2-2 RC試片之OM與SEM觀察 19
5-3 NC試片之結果 21
5-3-1 NC試片之應力-應變曲線 21
5-3-2 NC試片之OM觀察 21
5-3-3 NC試片之雙晶統計結果 22
六、討論 23
6-1 初始材料的金相組織與集合組織 23
6-2 RC試片結果之討論 23
6-3 NC試片結果之討論 26
七、結論 27
八、參考文獻 28
表 30
圖 34

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