本研究進行Mg-xAl-Zn (x=3, 6, 9 wt %)合金擠形材之振動破壞特性探討。研究內容包括(1)探討Al含量對振動破壞特性，包括制振性及裂縫傳播。(2)利用退火處理，探討擠形態跟經退火材間性質的差異。
實驗結果顯示，在固定振動出力值時，試片起始偏移量與對數衰減率成反比趨勢，也就是當對數衰減率愈大時起始偏移量愈低，擠形態以AZ61-F制振性最好，經退火後則是AZ91-O最佳。共振壽命方面，擠形態之共振壽命隨鋁含量的添加而逐步減少，以AZ31-F為最佳；另一方面，退火材之共振壽命則是隨鋁含量的添加成上升趨勢，以AZ91-O壽命最好。此外，固定退火材之起始偏移量振動實驗結果顯示，在屏除制振性影響下，共振壽命趨勢與固定振動出力值一樣，亦以AZ91-O為最佳。
試片經振動變形後表面主要之變形組織為形變雙晶的生成，其生成量在各成份與處理狀態下有很大差異。擠形態中各組成形變雙晶生成量差異不大，表示振動雙晶的生成受制於原先存在之形變雙晶與介在物，另一方面，雙晶的生成量於退火材中隨鋁含量上升而增加。本研究證實，基地鋁含量的提高有助於振動雙晶的形成，以及共振性質的提升。

Effects of Al content (3~9wt%) on the resonant vibration fracture properties of extruded Mg-Al-Zn alloys were examined in this study. The study items were to investigate (a) the influences of Al content on the resonant vibration behaviors, including damping capacity and crack growth, and (b) differences in the properties between the as-extruded (F samples) and fully-annealed (O samples) materials.
Experimental results indicate that under constant force conditions a greater damping capacity leads to a smaller initial deflection. The AZ61-F specimens exhibit the highest damping capacity among as-extruded materials, but AZ91-O specimens become the one with greater damping capacity after full annealing.
Furthermore, low Al (AZ31-F) as-extruded samples show a greater vibration life under constant force conditions while high Al fully-annealed samples (AZ91-O) possess greater vibration fracture resistance under both constant force and initial-deflection conditions.
The main deformation mechanism of Mg-Zn-Al alloys suffering vibration can be considered as twining. It can be also found that twining during vibration is stunted by pre-existed deformation twins and precipitates. Also, the formation of the twins can be enhanced by an increase in the Al content of the matrix, and thus the vibtation fracture properties, including damping capacity and vibration life can also be improved.

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