本研究主要利用動態機械分析儀(DMA)之測試,探討商業用AZ80合金和LAZ1110鎂鋰合金在各溫度下之制振能,並藉由硬度量測、顯微組織觀察與XRD分析等,協助瞭解冷軋延或時效處理對鎂合金制振能的影響,以及各個制振峰及200-300℃區間高溫制振背景值(HTDB)之機制。經測試結果顯示,AZ80合金在HTDB的溫度區間內,不論有無後續的100℃時效處理,經過20%冷軋延後其HTDB制振能皆可獲得明顯的提升。然而,形成HTDB的活化能卻在冷軋延後由1.69eV降至1.37eV,表示冷軋過程會加速合金內部之擴散作用,並同時促進潛變的發生。因此,當AZ80合金的應用拓展到HTDB之溫度區間時,冷軋延對其制振能以及抗潛變能力的正反兩面影響,是需要被審慎考量的。對LAZ1110合金而言,無論是剛取得之擠製板材或者不同程度之冷軋薄板,其制振能於升溫過程依序均有P1、P2與P3三個制振峰出現。而冷軋程度愈大者,不僅於室溫下tanδ值愈高,其P3峰頂的溫度也會愈往低溫平移,且均在鎂金屬的再結晶溫度200℃附近。經研究結果推斷,鎂鋰合金有P3峰的出現與基材上β(200)優選晶位極為相關,且在大量冷軋延後還涉及再結晶作用。另外,以0.1Hz之低頻率對80%冷軋延之LAZ1110合金薄板進行DMA測試,可於室溫下有效達到高制振能材料之標準(即tanδ≧0.03)。
Damping capacities (DCs) of AZ80 and LAZ1110 magnesium alloys are investigated by Dynamic Mechanical Analyzer (DMA) at the temperature range of 0-300℃. DC of the high-temperature damping background (HTDB) at 200-300℃ for AZ80 alloy increases significantly after 20% cold-rolling with or without aging. However, the activation energy of HTDB decreases from 1.69eV to 1.37eV, which indicates cold-rolling can accelerate alloy’s diffusion process and promote its creep development simultaneously. Consequently, the contrary cold-rolling effect on DC and creep resistance of AZ80 alloy should be taken into account carefully for its high-temperature applications. Three damping peaks P1, P2 and P3 are observed for LAZ1110 Mg-Li alloy. Severe cold-rolling can effectively improve the DC of LAZ1110 alloy at room temperature. The P3 peak located at about 200℃ shifts to lower temperature if the extent of cold-rolling increases. Experimental results show that, after severe cold-rolling, the formation of P3 peak is well-related to β(200) preferred orientation and caused by recrystallization process. Besides, high damping criterion (tanδ≧0.03) can be met at room temperature for 80% cold-rolled LAZ1110 sheet tested at 0.1Hz low frequency or at 30-35μm operating amplitude.
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