Impact of annealing temperature on martensite transformations and structure of quaternary Ti50Ni47.7Mo0.3V2 alloy

¹Research Institute of Medical Materials, Tomsk State University, ul. 19 Gv. Divizii 17, Tomsk, 634045, Russia

²Material Research Laboratory, Kang & Park Medical Co., 48 Jungsimsangeob-2 ro, Cheongju 28119, South Korea

³School of Material Science and Engineering, University of Ulsan, 93 Daehak-ro, Ulsan, 44610, South Korea

Adv. Mater. Lett., 2017, 8 (2), pp 122-127

DOI: 10.5185/amlett.2017.7023

Publication Date (Web): Dec 27, 2016

Copyright © IAAM-VBRI Press

E-mail: tc77@mail2000.ru

Abstract

Within the wide family of shape memory alloys (SMAs), TiNi-based alloys are characterized by unique characteristics, with good workability in the martensite phase and good resistance to corrosion and fatigue. In the nearest future, TiNi-based SMAs are expected the second birth to begin regarding their practical application, especially in creating a new material generation showing enhanced characteristics for clinical goals. Such a kind of expectations is naturally supposed to make a search among alloying elements for TiNi-based SMAs, as well as studies of adjacent effects in order to improve material properties. The objective of the work is to investigate the effect of heat treatment on the structure and properties of the quaternary Ti₅₀Ni_47.7Mo_0.3V₂ SMA, as potentially promising for medical devices. Specimens were prepared and annealed at 723, 923, 1123 K for 1 h. It was found that the studied alloy was in a multiphase state: TiNi-based intermetallic in three crystallographic modifications (austenite B2-phase and martensitic R- and B19¢structures) and secondary Ti₂Ni(V) phase. The increase of the annealing temperature doesn't affect the martensite transformation (MT) sequence B2«R«B19′, but leads to a growth in lattice parameter of the parent phase. The most remarkable effect on the studied alloy was at 723 K. Volume fraction of Ti₂Ni(V) precipitates in the structure was also maximum. It owes their presence to the shift of the MT points toward the lower temperature range. The temperature vs resistivity r(T) curves show a characteristic shape, which is typical for TiNi-based SMAs with a two-step nature of the B2«R«B19′ MT.

Keywords

TiNi-based alloy, martensite transformation, characteristic temperatures, heat treatment.