鎂合金具有低密度、高比強度、制振性佳及電磁波遮蔽效應等優點，廣泛運用於交通及電子產業。於鎂合金添加鋰元素所形成的鎂鋰合金，密度較一般鎂合金更低，對交通工業及電子產品的輕量化有正面的助益。本研究針對具有HCP富鎂a相及BCC富鋰b相之雙相Mg-10Li-2Al-1Zn合金擠型材，於248K~523K(−25℃~250℃)溫區間進行拉伸試驗，探討其拉伸性質及延性脆性轉換特性。
實驗結果顯示，抗拉強度及降伏強度隨拉伸溫度增加而降低。均勻延伸率在50℃以下會隨溫度增加而增加，50℃以上則隨溫度升高而遞減。總延伸率由−25℃及室溫時的5~7%，於50℃大幅增加至35%左右，當溫度上升至100℃，總延伸率繼續增加至55%左右，可知在室溫過渡至50℃的溫區間，存在延脆轉換行為。
由破斷次表面可觀察到拉伸過程中裂縫起始於a相以及a/b相界，在低溫時裂縫生成後快速傳播並相互連結，最後導致材料的破壞；在高溫時裂縫生成後則受拉應力的作用被撐開形成孔洞，最後孔洞與孔洞互相連結導致材料的破壞。由破斷面的觀察可發現低溫時存在延性及脆性混合式破壞特徵，其中代表脆性破壞行為的劈裂特徵存在於a相中，而b相則屬於延性破壞行為。當溫度上升，脆性破壞所佔面積率減少，於100℃以上已無劈裂特徵，此時材料整體皆屬延性破壞行為。

Magnesium alloys have many advantages such as low density, high specific strength, good mechanic damping properties and good radiation absorption of electromagnetic waves. They are commonly applied in traffic and electronic industries. Magnesium alloys with adding lithium element could make the density lower than the pure magnesium. This study focuses on tensile properties and ductile to brittle transition characteristics of the two-phase Mg-10Li-2Al-1Zn alloy, which is consist of HCP a-phase and BCC b-phase, at the temperature range of 248K ~ 523K (−25℃~250℃).
Tensile testing results show that the ultimate tensile stress and the yield stress decreased with increasing temperatures. The uniform elongation has a maximum value at 50℃. The total elongation is significantly increased at the temperature range of RT~50℃, and it further increases to 55% at 100℃. The ductile to brittle transition behavior is occurred at the temperature range of RT~50℃. Fracture sub-surfaces reveal that initial cracks occurred within a-phase and a/b-phase interfaces. At low temperatures, failures are resulted from cracks propagation and inter-connection rapidly. When the temperature raising upon 50℃, cracks grow into pores by tensile stress and inter-connection result in failures. Fracture surfaces coexist ductile and brittle features at lower temperatures, the cleavage failures are observed in a-phase and a lot of ductile fracture features are represented in b-phase. There is no cleavage fracture feature and materials show almost ductile fracture features when the temperature raising upon 100℃.

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