A Novel Approach to Estimate the Transition Temperature via Dynamic Nanoindentation

The ductile‐to‐brittle transition temperature (DBTT) is critical for the safe application of structural metals, yet its experimental determination usually requires extensive specimen preparation and material consumption. This work presents a nanoindentation‐based methodology which requires only a single specimen to characterize temperature‐dependent deformation behavior and degree of plasticity using the stiffness ratio obtained from dynamic nanoindentation measurements. Experiments were conducted on cold‐rolled ferritic steel (body‐centered cubic) and austenitic steel (face‐centered cubic) between ‒150 and +75 °C. Young’s modulus, hardness, and the ratio of loading to unloading slope (stiffness ratio) were evaluated as functions of temperature. Ferritic steel exhibits distinct slope changes in stiffness ratio versus temperature curves, yielding transition temperatures of ‒62 ± 9 °C at a strain rate of 0.01 s −1 and ‒43 ± 11 °C at 0.1 s −1 . In comparison, Charpy impact tests yielded a DBTT of roughly ‒20 °C. These differences can be attributed to different strain rates, microstructural states, and testing methods and will be discussed in detail. In contrast, austenitic steel showed monotonic trends without slope changes, consistent with the absence of DBTT in face‐centered cubic materials. Overall, this study provides promising proof of concept for a material‐efficient, complementary method for estimating transition temperatures associated with DBTT.