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Author Radi, A.; Khalil-Allafi, J.; Etminanfar, M.R.; Pourbabak, S.; Schryvers, D.; Amin-Ahmadi, B.
Title Influence of stress aging process on variants of nano-N4Ti3precipitates and martensitic transformation temperatures in NiTi shape memory alloy Type A1 Journal article
Year 2018 Publication Materials & design Abbreviated Journal Mater Design
Volume 262 Issue 262 Pages 74-81
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract In this study, the effect of a stress aging process on the microstructure and martensitic phase transformation of NiTi shape memory alloy has been investigated. NiTi samples were aged at 450 degrees C for 1 h and 5 h under different levels of external tensile stress of 15, 60 and 150 MPa. Transmission electron microscopy (TEM) was used to characterize different variants and morphology of precipitates. The results show that application of all stress levels restricts the formation of precipitates variants in the microstructure after I h stress aging process. However, all variants can be detected by prolonging aging time to 5 h at 15 MPa stress level and the variants formation is again restricted by increasing the stress level. Moreover, the stress aging process resulted in changing the shape of precipitates in comparison with that of the stress-free aged samples. Coffee-bean shaped morphologies were detected for precipitates in all stress levels. According to the Differential Scanning Calorimetry (DSC) results, the martensite start temperature (M-s) on cooling shifts to higher temperatures with increasing the tensile stress during the aging process. This can be related to the change ofaustenite to martensite interface energy due to the different volume fractions and variants of precipitates. (c) 2018 Elsevier Ltd. All rights reserved.
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Publisher Place of Publication Editor
Language Wos Publication Date 2018-01-04
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition (up)
ISSN 0264-1275 ISBN Additional Links UA library record; ; WoS full record; WoS citing articles
Impact Factor 4.364 Times cited Open Access OpenAccess
Notes Approved Most recent IF: 4.364
Call Number UA @ lucian @ c:irua:149854 Serial 4938
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