旋鍛製程與退火處理對AZ系列鎂合金之機械性質影響

Effects of Rotary Swaging and Annealing on Mechanical Properties of AZ Series Magnesium Alloys

高振洋(Chen-Yang Kao)

指導教授 ： 陳貞光

國立臺北科技大學/工程學院/材料及資源工程系研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00618

摘要

本研究針對AZ系列鎂合金材料，利用旋鍛加工進行31%工程應變量以後，在100至400°C內進行退火，觀察AZ系列鎂合金經退火後的顯微組織變化及常溫機械性質，並研究其100至300°C的高溫拉伸特性；發現在300°C、10-4/s的應變速率下AZ31可以得到30%以上的高溫伸長量，而AZ61的機械性質對於溫度變化的影響相對較小。旋轉鍛造可以在鎂合金材料內產生大量複雜交錯的滑動帶，藉由200°C以上的退火處理，晶粒內累積的高密度差排容易使材料進入再結晶階段，使得晶粒尺寸從原始固溶化組織的150μm在退火及靜態再結晶的熱處理過程大幅縮小到15μm。再結晶過程也伴隨著硬度下降，材料出現軟化現象，當硬度回歸至固溶化狀態時，晶粒仍可維持15μm左右的尺寸。在常溫進行拉伸試驗的破斷面中，劈裂紋分佈隨晶粒細化減少，高溫拉伸試片破斷面的韌窩組織則因為延性提升而越均勻細緻。而經過回爐再鍛造的製程，有助於顯微組織的強化，除了孔隙率再降低以外，晶粒尺寸更可以縮小到10μm，提升鎂合金的機械性能。

關鍵字

鎂合金 ； 旋鍛 ； 晶粒細化 ； 再結晶 ； 機械性質 ； 退火

並列摘要

AZ series magnesium alloys are rotary swaged and annealed at 100-400°C temperatures. The annealed microstructures and mechanical properties are observed. Mechanical properties of these alloys at 100-300°C temperatures are measured as well. The magnesium alloys form a great number of crossing deformation bands by rotary swaging. Due to formation of high dislocation density in the bands, recrystallization occurs easily with annealing treatments. The grain size greatly reduces from 150μm to 15μm, while the hardness of annealed sample returns to that of solutionized material. Among the alloys investigated, mechanical properties of AZ31 are more sensitive to the annealing temperatures. At a strain rate of 10-4 /s, the elongation of AZ31 alloy reaches over 30% at 300°C. The dimple size decreases with increasing temperature indicating ductile failure when tested at high temperatures. It is also observed that the fraction of cleavage fracture decreases with grain refinement. Subsequent reheating and small strain swaging appears to repair microstructures and regain good mechanical properties. Grain size can be reduced further to below 10μm.

並列關鍵字

magnesium alloys ； rotary swaging ； grain refinement ； recrystallization ； mechanical property ； annealing

參考文獻

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