Comparative study of R-phase martensitic transformations in TiNi-based shape memory alloys induced by point defects and precipitates. (May 2017)

• Record Type: Journal Article
• Authors: Chang, P.C.; Ko, M.L.; Ramachandran, B.; Kuo, Y.K.; Chien, C.; Wu, S.K.
• Is Part Of: Intermetallics. Volume 84(2017:May)
• Page Start: 130
• Page End: 135
• Publication Date: 2017-05
• Subjects: Shape memory alloys -- Martensitic transformation -- Electrical properties -- Thermal properties -- Point defect; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2017.01.008
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: We studied the influence of point defects (Fe) and precipitates (Ti3 Ni4 ) on the characteristics of R-phase martensitic transformation by comparing the transport and thermal properties of as-quenched Ti50 Ni46 Fe4 and annealed Ti48.7 Ni51.3 shape memory alloys. Both alloys undergo a weak first-order R-phase transformation with a small thermal hysteresis (less than 7 K) and non-zero transformation strain, suggesting the introduction of point defects and precipitates lead to a stable R-phase in these alloys due to the defects induced local lattice deformations. Furthermore, our study revealed that the transition temperature, transformation width, and transformation strain of the investigated R-phase TiNi-based alloys are strongly affected by the induced defects. As a result, the annealed Ti48.7 Ni51.3 has a higher transition temperature than that of Ti50 Ni46 Fe4, as expected. Highlights: As-quenched Ti50 Ni46 Fe4 and annealed Ti48.7 Ni51.3 alloys display metallic behavior. Both shape memory alloys (SMA) show a p -type thermoelectric transport below 350 K. Both SMA systems undergo a weak first-order R-phase martensitic transformation. The induced defects strongly affect the martensitic transformation characteristics.