AZ80及LAZ1110鎂合金制振能之研究

Abstract

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.