鎂合金相較於一般輕金屬具有質輕、比強度高、制振性佳及電磁波遮蔽效應等優點，廣泛被應用於交通工具結構件及電子產品外殼。鎂鋰合金具有比一般鎂合金更低之密度及延展性優良等特點，因此深具輕量化與溫加工性佳之潛力。本研究針對具有HCP富鎂α相與BCC富鋰β相之雙相Mg-10Li-2Al-1Zn鎂鋰合金擠型板材自-25ºC至250ºC進行拉伸試驗，並改變拉伸應變速率(1.67 × 10 -3 s -1及1.67 × 10 - 4 s -1)，亦分別與擠型方向呈0°、45°及90°進行拉伸試驗，藉以探討此雙相LAZ1021-F合金在改變溫度、應變速率與拉伸方向之拉伸性質變化。
實驗結果發現，降伏強度(YS)、抗拉強度(UTS)均隨溫度上升而下降；總延伸率(TE)則在100ºC後，均提高至35%以上，且在0ºC~100ºC區間內存在延-脆轉換溫度(DBTT)。在改變不同拉伸應變速率情況下，LAZ1021鎂鋰合金仍具有延-脆轉換特性，值得注意的是當拉伸應變速率降低，延-脆轉換溫度亦隨之降低。由XRD與Pole figure顯示LAZ1021具有強烈的擠型織構且α相HCP底面平行擠型方向排列，但在0°、45°及90°拉伸之YS、UTS均約略一致，而UE與TE具有異向性，延性在0°拉伸時最佳且改變拉伸方向後均有延-脆轉換行為。由光學顯微鏡在破斷面觀察到裂縫起始於α相與α/β相界，且隨溫度升高裂縫孔洞化現象越趨顯著。而延-脆轉換行為推論應為α相與β相兩相綜合結果，由β相阻擋裂紋能力所主導，α相扮演提供起始裂紋角色。

Magnesium alloys have attractive properties such as low density, high specific strength and elastic modulus, good damping ability and good absorption of electromagnetic waves. Mg-Li alloys’ unique combination of low density and extraordinary ductility have interested engineers and scientists since the 1940’s, and these alloys are drawing much attention from its lightweight and good formability characteristics in recent years.
Dual-phase as-extruded LAZ1021 alloy (Mg-10.3Li-2.4Al-0.7Zn), which is consist of HCP α-phase and BCC β-phase, was deformed under tensile stress with strain rate 1.67 × 10 -3 s -1 and 1.67 × 10 - 4 s -1 at the temperature range from -25℃ to 250℃. To investigate the tensile anisotropy and dominate deformation mechanism, tensile samples is deformed with the tensile axis forming angles of 0°,45° and 90° to the extrusion direction. The results reveal that ultimate stress (UTS) and yield stress (YS) decrease with increasing temperature, and total elongation (TE) reach 35％ above 100℃. With different strain rates and tensile directions, LAZ1021 has a intrinsic ductile-to-brittle transition characteristic.
While the tensile test was carried out with lower strain rate, the ductility obviously increased at 25℃ and 50℃, and therefore the ductile-to-brittle transition temperature generally decreases by 25℃. The XRD results show that LAZ1021 has a strong texture which the basal planes of α-phase parallel the extrusion direction. The tensile testing with different tensile directions results that YS and UTS have the same tendency, and UE and TE have anisotropic characteristic. The fracture microstructures reveal that initial cracks occurred within the α-phase and α/β-phase interfaces. Ductile-to-brittle transition is dominated by the resistance of β-phase to crack propagation from α-phase.

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