A Spherical Indentation-Based Approach for Non-Destructive Evaluation and Prediction of Pseudoelasticity in Laser Additively Manufactured NiTi Alloys

Abstract NiTi shape memory alloys are widely utilized in biomedical, civil, automotive, aerospace, and consumer applications due to their remarkable pseudoelastic properties. Accurately assessing and predicting this behavior in fabricated components is thus of great practical importance. This study employs spherical indentation to investigate pseudoelasticity by monitoring stress-induced reductions in Young’s modulus. This technique offers flexibility, ease of operation, and the ability to replicate realistic service-condition stress states. As applied stress increases from 415 MPa to 850 MPa, Young’s modulus decreases by 40–65%, indicating a progressive phase transition from austenite (75–83 GPa) to martensite (28–40 GPa). Existing predictive models for pseudoelasticity are largely confined to uniaxial loading and macroscopic descriptions. This work introduces a novel theoretical framework for predicting pseudoelastic response under spherical indentation by correlating it with applied stress, based on the assumption that the martensite volume fraction increases linearly from 0% to 100% within the critical stress window. Experimental results show favorable agreement with the model predictions within the evaluated testing scope, indicating that the proposed framework can effectively capture the load-dependent evolution of pseudoelasticity. This research provides a viable non-destructive and quantitative method for forecasting pseudoelasticity, thereby enhancing the understanding of phase transformation mechanisms in NiTi alloys.