Improved functional stability of Ti-rich TiNi shape memory ribbon prepared by melt-spinning

The great functional stability of Ti-rich Ti50.9Ni48.9Si0.2 ribbon was investigated in this study. The as-spun ribbon underwent a two-stage B2 ⇄ R ⇄ B19′ transformation in both forward and reverse. The grain size of the as-spun ribbon was moderately refined to about 500 nm to 1 μm, which contributed to grain refinement strengthening. The as-spun ribbon was in an early precipitation stage of G.P. zones and was strengthened to a hardness of 5.7 ± 0.2 GPa, which was significantly higher than the 4.7 ± 0.3 GPa of the overaged ribbon. The G.P. zones formed when the ribbon was aged at 500 °C for 15 min. The strengthening effect increased the critical stress for dislocation slip and thus prevented the formation of dislocations during martensitic transformation. During 1500 unconstrained thermal cycles, the R → B19′ and B19’ → R transformation peak temperatures of the as-spun ribbon decreased by only 6.8 °C and 0.6 °C, respectively. In shape memory effect tests for 20 cycles under 139 MPa and 324 MPa, the as-spun ribbon showed excellent stability, with recoverable strains of 4.7% and 5.3%, respectively. The Ti50.9Ni48.9Si0.2 ribbon exhibited a combination of large recoverable strain and high functional stability. These experimental results provide a novel method to improve the functional stability of Ti-rich TiNi shape memory alloys by the melt-spinning process, which results in promising functional properties for engineering applications. [Display omitted] •Ti-rich Ti50.9Ni48.9Si0.2 shape memory ribbon with improved functional stability was prepared by melt-spinning.•The as-spun ribbon shows great transformation stability during 1,500 thermal cycles.•The as-spun ribbon exhibited excellent shape memory effect during 20 cycles under both 139 MPa and 324 MPa.•The as-spun ribbon is at the early precipitation stage, which exhibits a hardness of 5.7 ± 0.2 GPa.•The as-spun Ti50.9Ni48.9Si0.2 ribbon exhibits a combination of large transformation strain and great functional stability.