Characteristics of Martensitic Transformation and Shape Memory Properties of Ti-rich TiNi Ribbons
Date Issued
2012
Date
2012
Author(s)
Chen, Chih-Hsuan
Abstract
2000/4000rpm Ti51Ni49 and 4000rpm Ti52Ni48 Ti-rich TiNi ribbons prepared by rapid solidification process were studied to investigate the transformation behavior, microstructure, precipitation hardening effect and mechanical properties. Premartensitic R phase transformation, which has not been occurred in bulk Ti-rich TiNi SMAs, is observed in all of these ribbons after aging at 400℃/500℃using DSC and XRD tests. TEM observations show the R phase transformation is induced by the coherent strain between TiNi matrix and nano-scale Ti2Ni precipitates. Nanoindentation tests indicates that precipitation hardening by nano-scale Ti2Ni precipitates in Ti-rich TiNi SMAs does occur, and an increase of hardness of 1GPa is observed. This feature provides a new way to improve the properties of Ti-rich TiNi SMAs. The shape memory property of these aged ribbons is concluded to be related to two factors: the degree of precipitation hardening effect and the value of transformation latent heat. The reversible strains of SME tests can reach > 5.2% in these ribbons, indicating good shape memory property exhibited in ribbons of aged Ti-rich TiNi SMAs.
Subjects
Ti-rich TiNi SMAs
Ti2Ni precipitate
Ribbon
Precipitation hardening
Nanoindentation
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-101-R99527005-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):0f4d89ea8617ed88d25ea938cce6cd48