Next-Generation Manufacturing of Shape Memory Alloys via Laser-Based Additive Processes: Enabling 4D-Printed Smart Structures

Shape memory alloys (SMAs) are transformative materials renowned for their ability to reversibly change shape in response to thermal and mechanical stimuli. While nitinol (NiTi) remains the most extensively studied SMA, a growing portfolio of alternative systems, particularly copper-based alloys, offer compelling advantages in cost, durability, and functional versatility. These materials are increasingly vital in demanding environments requiring high performance, corrosion resistance, and tailored thermomechanical behavior. Recent breakthroughs in additive manufacturing, especially laser powder bed fusion (LPBF), have revolutionized the fabrication of complex SMA components, enabling unprecedented microstructural control, intricate architectures, and customized properties. This review synthesizes cutting-edge research on LPBF processing of diverse SMA systems, emphasizing how process parameters influence phase transformations, microstructural evolution, defect formation, and functional stability. It explores innovative structural designs, such as lattice and auxetic configurations, that unlock new levels of performance in biomedical devices, aerospace actuators, and energy absorption systems. Despite significant progress, challenges such as residual stresses, material homogeneity, and scalability continue to hinder widespread deployment. This review highlights promising avenues for future research: optimizing alloy compositions, refining processing techniques, and expanding application horizons. By advancing our understanding of microstructure-property relationships, these efforts aim to unlock the full potential of both traditional and emerging SMAs across a broad spectrum of industries.