Microstructural Analysis and Defect Characterization of WAAM-Fabricated Nitinol Shape Memory Alloy

Wire Arc Additive Manufacturing (WAAM) has emerged as a promising metal additive manufacturing technique for fabricating large-scale components with high deposition rates and reduced material waste. However, processing shape memory alloys such as Nitinol using WAAM presents significant challenges due to their sensitivity to thermal cycling, composition variation, and defect formation. In this study, a detailed experimental investigation is carried out to analyze the microstructural characteristics and defect mechanisms in WAAM-fabricated Nitinol components. The influence of process parameters on porosity, cracking, and grain morphology is examined using stereo microscopy, optical microscopy, and scanning electron microscopy. Phase analysis is conducted using X-ray diffraction, while mechanical behavior is evaluated through hardness and tensile testing before and after heat treatment. The results reveal a strong correlation between heat input, microstructural evolution, and defect distribution. The findings provide valuable insights into process stability and quality challenges in WAAM of Nitinol and contribute toward establishing a reliable processing window for advanced aerospace and actuator applications.