Difference in recrystallization between electropulsing-treated and furnace-treated NiTi alloy

• Published in: Journal of alloys and compounds 2016-02, Vol.658, p.548-554
• Main Authors: Zhu, Rufei, Jiang, Yanbin, Guan, Lei, Li, Huailin, Tang, Guoyi
• Format: Article
• Language: English
• Subjects: Atom diffusion; Electropulsing; Hardness; Intermetallics; Nickel base alloys; Nickel compounds; Nickel titanides; Recrystallization; Resistivity; Shape memory alloys; Titanium compounds
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2015.10.239

The cold-rolled NiTi alloy was treated by electropulsing and muffle furnace at the same temperature for minutes, respectively. In order to find the difference between two methods for the recrystallization of the NiTi alloy, the hardness, electrical resistivity and microstructure of the NiTi alloy were investigated. The hardness and microstructure evolution of NiTi alloy indicates that electropulsing can reduce the recrystallization temperature of NiTi alloy by 200 °C owing to the enhancement of atom diffusion. Compared with the traditional heat treatment, electropulsing can easily refines grain of the NiTi alloy with an average size of about 41 nm, due to increases of the nucleation rate and limited grain growth. In addition, electropulsing can decrease resistivity of NiTi alloy to the minimum value at the low frequency of electropulsing for 2.5 min. For NiTi alloy treated by furnace annealing at 300 and 350 °C, the phase transition from martensite to austenite induces the hardness increase with increasing temperature and prolonging time. [Display omitted] •Electropulsing decreases the recrystallization temperature of NiTi alloy.•Electropulsing easily refines grain size to 41 nm.•Electropulsing enhances the atom diffusion and increases the nucleation rate.