Adaptive nickel–titanium shape memory alloy for smart systems: Mechanisms, manufacturing, and applications across biomedical, aerospace, civil, and energy

Nickel–titanium (NiTi) shape memory alloys (SMAs), commonly known as Nitinol, are widely employed in smart systems due to their thermoelastic martensitic transformation, superelasticity, corrosion resistance, and biocompatibility. Although NiTi SMAs have been extensively reviewed, many existing reviews emphasize applications while providing limited treatment of the manufacturing and processing routes that govern functional reliability, particularly for commercially dominant semi-finished forms such as wires and tubes. This review presents a process-oriented assessment of NiTi SMAs, integrating fundamental transformation behavior with fabrication, forming, thermomechanical conditioning, and surface engineering. Plastic deformation routes including hot working, cold drawing, rolling, pilgering, and severe plastic deformation are examined in relation to microstructure evolution, texture development, transformation temperatures, and fatigue performance. Shape-setting and thermomechanical treatments are discussed as essential steps for fixing functional properties and ensuring transformation stability in practical devices. Secondary manufacturing processes such as laser cutting, micro-EDM, polishing, chemical etching, and electropolishing are reviewed as performance-critical operations governing surface integrity, fatigue life, and corrosion behavior. Electrochemical surface engineering, including electroplating and electroforming, is addressed with emphasis on recent advances in NiTi biomaterials, alongside advanced coatings deposited by physical and pulsed laser deposition. Tribology and corrosion are treated as coupled engineering phenomena, highlighting the role of surface condition and transformation-mediated deformation in wear, nickel release, and long-term durability. Overall, this review establishes a unified processing–structure–performance framework to support the design and deployment of NiTi-based smart systems across biomedical, aerospace, and structural applications.