二元及三元鈦鎳基形狀記憶合金相變態行為及制振能之研究

Abstract

本研究針對二元及三元鈦鎳形狀記憶合金(SMA)之制振能及相變態行為等性質作一系列之探討。由DMA研究結果發現，二元Ti50-xNi50+x (x=0~1.6 at%) SMAs 固溶處理後B2 B19’變態者有較高的tanδ值，而固溶並時效後之B2R相變態者，其制震能則較差，推測可能因Ti3Ni4析出物妨礙R相兄弟晶界面之移動有關。 Ti50-xNi50+x (x>1.0 at%) SMAs 250℃或350℃時效都有鬆弛峰在R相內產生，透過不同頻率與鬆弛峰峰值溫度的變化來求冷卻及加熱下形成鬆弛峰所需的活化能，發現R相內形成者其冷卻過程的ev值均大於加熱過程者;同時也比較後發現B19’者之活化能值最小， R者其次，而B19者其活化能值最大，顯示氫原子牽住B19’,B19 及R相麻田散體之雙晶界面的能力大小不同。 而三元Ti50Ni50-xPdx (x=7,10及13 at%) SMAs的B2 B19變態，發現其tanδ值會隨著Pd含量的增加而下降，且這三種Ti50Ni50-xPdx SMAs其tanδ值、Storage Modulus E0 軟化值以及Strain Variation等皆比Ti50Ni45Pd5 SMA之B2RB19’變態者來得大，顯示擁有B2 B19變態者的制振能較佳，推測其原因為B2 B19相變態時有較大的E0 軟化而使Strain Variation相對較高。此外，Ti50Ni40Pd10 SMA的tanδ曲線中，在低溫下發現有一變態峰的存在，在-130℃的低溫XRD實驗也發現有B19’相之波峰存在，顯示其在低溫下應有B19B19’麻田散體變態的產生。而在持溫條件下作的DMA實驗也顯示Ti50Ni40Pd10 SMA之本質內耗(IFPT+IFI)B2→B19比其他的Ti50Ni50-xPdx SMAs 來得大。

In this study , transformation behaviors and damping capacities of binary and ternary TiNi-based shape memory alloys (SMAs) are investigated. Damping properties of Ti50-xNi50+x (x=0~1.6 at%) and Ti50Ni50-xPdx (x=5~13 at%) SMAs are characterized under temperature and frequency sweep tests by dynamic mechanical analyzer (DMA). According to DMA tested results, solid solution treated binary Ti50-xNi50+x SMAs exhibited B2B19’ one stage transformation have higher magnitude of tan δ value than aged ones exhibited B2R transformation. It is suggested that Ti3Ni4 precipitates might hinder the mobility of R-phase variants‘ interfaces. Besides, relaxation peak appears in R-phase after Ti50-xNi50+x (x>1.0 at%) SMAs have been low-temperature aged. Comparing to other literatures, the activation energy to form the relaxation peak in B19 phase is higher than those in R-phase and B19’ phase. This phenomenon indicates that the abilities of H atoms pinning twin boundaries in B19,B19’ and R-phase are different. For ternary Ti50Ni50-xPdx SMAs, tan δ value magnitude , storage modulus (E0) and strain variation exhibited in B2B19 transformation are all higher than those in B2RB19’ one due to twin boundaries in B19 phase are easier movable and the B2B19 has higher E0 softening and strain variation during transformaiton. For the inherent internal friction under isothermal condition DMA test, it shows the (IFPT+IFI)B2→B19 of Ti50 Ni40Pd10 SMA exhibits higher tanδ value than the other ternary TiNiPd SMAs, and a transformation peak appears at ≈-75℃ in Ti50Ni40Pd10 SMA which has been further confirmed as B19B19’ transformation by the low temperature XRD test.