Abstract
This paper reports the comprehensive study of the characteristics of the R-phase transformations observed in low temperature aged (@ 1500C) Ti-49.85 atomic percent Ni shape memory alloys (SMAs). The stabilizations of the R-phase transformations occurred with two separate transformation peaks were observed in DSC study in prolonged aged conditions. In conventional ageing temperature ageing at 3000C, R-phase transformations exhibit an increase in Af temperature; but in low temperature aged NiTi shows that measured Af temperature is lower than the solutionized sample and R-phase appeared well below the original B2→B19’ transformation temperature initially; this result is very peculiar for this ageing treatment. The energy required for the nucleation of this phase ∆HB19’→R on heating cycle was 2.24 J/g, which was much lower than the reverse transformation (on cooling) ∆HB19’→R = –12.6 J/g. This loss of about –8.55 J/g, is believed to be covered by the transformations between the two peaks of B19’→R and R→B2 in heating. The occurrence of the R-phase transformation is attributed to precipitation-induced inhomogeneity of the matrix, both in terms of composition and internal stress fields.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
