• High-pressure torsion (HPT) effectively refines NiTi alloy microstructure to nanocrystalline scale, enhancing hardness and tensile strength.
• The optimized HPT processing parameters (e.g., 5 turns at 6 GPa) yield a good balance between strength and ductility, overcoming the typical trade-off.
• Phase transformation temperatures can be tuned via HPT, enabling customization of superelastic and shape memory behavior.
• The proposed SPD method offers a scalable pathway for producing high-performance NiTi components for aerospace and biomedical applications.