Abstract
Rapidly quenched quasibinary TiNi–TiCu system alloys with high copper contents (above 20 at.%) exhibit excellent shape memory effect and have considerably narrower hysteresis as compared with the TiNi binary alloy, this advantage being of special importance for cyclic load applications, e.g. for microelectromechanics (MEMS). The aim of this work is to study the effect of annealing parameters and copper content on the shape memory effect in TiNiCu alloys. Thin amorphous ribbons of TiNi-TiCu alloys with copper contents of 25 to 40 at.% were produced by planar flow casting at a melt cooling rate of about 106 K/s. The alloys were crystallized by isothermal annealing with variable duration and by exposing specimens to a short (10 ms) electric pulse. Increasing the copper content to above 30 at.% considerably reduces the plasticity and shape memory effect of the alloys. However, significant reduction of annealing duration greatly improves the shape memory performance due to prevention of the formation of brittle Ti-Cu phases in the alloys structure.
Highlights
Thanks to their unique properties, shape memory effect (SME) alloys are considered as efficient and promising materials for aeronautic and space industries, biomedicine, robotics and MEMS (Kohl et al 2018; Otsuka and Ren 2005; Mohd Jani et al 2014)
Rapidly quenched quasibinary TiNi–TiCu system alloys with high copper contents exhibit excellent shape memory effect and have considerably narrower hysteresis as compared with the TiNi binary alloy, this advantage being of special importance for cyclic load applications, e.g. for microelectromechanics (MEMS)
Nickel replacement for copper in the binary TiNi alloy leads to a transformation from the cubic austenite phase B2 to the orthorhombic martensite phase B19 having narrow hysteresis whose width decreases with an increase in copper content (Kang et al 2010; Chang, Wu, and Kimura 2007; Nam, Saburi, and Shimizu 1990)
Summary
Thanks to their unique properties, shape memory effect (SME) alloys are considered as efficient and promising materials for aeronautic and space industries, biomedicine, robotics and MEMS (Kohl et al 2018; Otsuka and Ren 2005; Mohd Jani et al 2014). Shape Memory Behavior of Rapidly Quenched High-copper TiNiCu Alloys Alexander Shelyakov, Nikolay Sitnikov, Irina Khabibullina, Kirill Borodako, Oleg Sevryukov of quasibinary TiNi–TiCu system alloys by means of rapid quenching from the melt are an attractive material for the fabrication of microactuators (Nespoli et al 2010) due to their narrow thermal hysteresis, relatively large recoverable strain and insensitivity of MT temperatures to the copper content (Morgiel et al 2002). Structure formation in rapidly quenched planar flow cast TiNiCu alloys with a copper content of above 25 at.% during crystallization in a calorimeter was studied in earlier works (Sitnikov et al 2017; Shelyakov et al 2020a). In this work we dwelt upon the shape memory behavior in these alloys depending on the copper content and the method and duration of crystallization from amorphous state
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