Transformation Behaviors and Damping Capacities of Binary and Ternary TiNi-Based Shape Memory Alloys
Date Issued
2016
Date
2016
Author(s)
Lee, Yu-Ning
Abstract
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 B2B19’ one stage transformation have higher magnitude of tan δ value than aged ones exhibited B2R 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 B2B19 transformation are all higher than those in B2RB19’ one due to twin boundaries in B19 phase are easier movable and the B2B19 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 B19B19’ transformation by the low temperature XRD test.
Subjects
Binary and ternary TiNi SMAs
Damping capacities
Relaxation peak
Transformation behaviors
Inherent internal friction
Type
thesis
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