| Abstract Scope |
Nitinol is recognized for its ability to recover its shape, significantly influenced by its composition and processing history. In this study, hot-rolled, superelastic nitinol sheets were subjected to 1-minute annealing at temperatures ranging from 520 to 600°C to explore the competing mechanisms of recovery, recrystallization, and precipitation. The specimens were characterized using various techniques to establish connections between dislocation density, texture, phase transformation temperatures, and hardness. The grain size reduced from 12 µm to 6–8 µm across all annealing conditions, while the dislocation density sharply decreased after the initial 520°C treatment, enhancing the existing <111>ND texture. Coherent Ni₄Ti₃ precipitates formed between 520 and 560°C, with hardness peaking at 267 HV and stabilizing a two-stage transformation with an Af around 8°C. At elevated temperatures (580–600°C), over-aging took place, resulting in a decline in hardness, weaker R-phase signatures, and the emergence of recrystallization signs, which led to a broader fiber texture. |