Correlation Between Hardness and Loading Transformation Stress of Superelastic NiTi

The relationship between the microhardness and the loading transformation stress of superelastic NiTi is investigated at room temperature. Superelastic NiTi shows a loading stress plateau under mechanical loading due to austenite-to-martensite microstructural phase transformation. The stress level at which the transformation from austenite to martensite occurs is a key mechanical property that dominates the design of several mechanical and biomedical components. Experiments in this study indicate a direct relationship between the loading transformation stress of superelastic NiTi and the value of Vickers hardness for this material. Regression analysis was conducted to investigate the correlation between the microhardness values and loading transformation stress of superelastic NiTi and determine the appropriate form of relation between these two mechanical properties. Based on the analyses, a linear relation was found to appropriately represent the relationship between the microhardness and loading transformation stress.