微觀結構演變對AZ31鎂合金高溫機械性質之影響

The Effects of Microstructural Evolution on the Elevated Temperature Mechanical Properties of an AZ31 Mg Alloy

潘俊宏(J. H. Pan) ； 陳正益(C. Y. Chen) ； 楊智富(C. F. Yang)

《材料科學與工程》 37卷2期 (2005/06) Pp. 57-65

https://doi.org/10.6409/JMSE.200506.0057

摘要

本研究探討動態回復(DRV)與動態再結晶(DRX)對AZ31鎂合金微結構與機械性質的影響，藉由不同預應變量及拉伸溫度、應變速率的改變，分析塑性變形過程中鎂合金微結構變化及其對機械性質之關係。實驗結果顯示，AZ31鎂合金之再結晶溫度約為167℃，將試片進行150℃溫輥軋之預應變，試片蘊藏之應變能隨著預應變的增加而增加。隨著預應變量與拉伸溫度的增加及應變速率的降低，拉伸測試時AZ31鎂合金越容易發生動態再結晶(DRX)，試片隨之呈現強度下降與延性增加。由金相／延伸率綜合分析得知，對AZ31鎂合金而言，DRX本身並未大幅增加延伸率，但一旦試片發生DRX轉變為細晶結構，則後續因細晶減緩微裂縫生成與細晶DRV之效應，卻能大幅提升延伸率。經由定性與定量的解析DRV、DRX及細晶結構對AZ31鎂合金高溫延伸率之貢獻，有關影響鎂合金高溫延伸率之變數：包括試片狀態（預應變、晶粒尺寸）、拉伸測試環境（溫度、應變速率）及動態退火之程度，及其效益均得以了解。

關鍵字

AZ31 ； 鎂合金 ； 動態再結晶 ； 動態回復 ； 微觀組織 ； 機械性質

並列摘要

This study aims to explore the influences of dynamic recovery (DRV) and dynamic recrystallization (DRX) on the microstructures and mechanical properties in an AZ31 Mg alloy. By altering the amount of pre-strain in the Mg alloy the microstructural evolutions occurring upon elevated temperature tensile tests at selected temperatures and strain rates were examined, and their relationships with the mechanical properties were analyzed. According to the DSC analysis the recrystallization temperature of the warm pre-strained AZ31 Mg alloy specimens is near 167℃ and the stored strain energy in the specimens increased with an increase in the amount of pre-strain. A dynamic recrystallization (DRX) was found occurred readily upon elevated tensile testing in the pre-strained AZ31 Mg alloy specimens and the occurrence of DRX was assisted by an increase in the degree of pre-strain and the test temperature and by a decrease in the test strain rate. When the DRX took place, the specimen responded with an increase in the ductility and a decrease in the mechanical strength. It was found from a combined microstructure/elongation analysis that the improvement of tensile ductility during the occurrence of DRX itself was limited. However, after the DRX a fine grain structure was produced, and a significant improvement in the tensile ductility was resulted by the fine grain suppression of microcrack formation and the fine grain enhanced DRV. Through the understanding of the DRV, DRX and fine grain effects on the tensile ductility in the AZ31 Mg alloy, the influences of specimen condition (pre-strain, grain size), tensile test condition (temperature, strain rate) and the degree of dynamic annealing variables on the tensile ductility were comprehended.

並列關鍵字

AZ31 ； Magnesium alloys ； dynamic recrystallization ； dynamic recovery ； Microstructure ； Mechanical properties