Heat treatment of metals is a standard process to bring controlled changes in the microstructure and thereby set the desired mechanical properties in the material.
However, currently used methods for microstructure analysis (micrographs, dilatometry, tensile tests, ...) have the disadvantage that they either cannot be used directly in the process or require special sample geometries. By measuring plate resonances on sheet metal specimens using laser ultrasound, Poisson's ratio and, if the thickness is known, also the longitudinal and transverse sound velocity can be determined without contact and with high time resolution during heat treatment (e.g., in a thermal simulator). The temperature variation of these parameters correlates with changes in the microstructure, allowing phase transitions to be monitored using this method.
Further information can be found in our publication: https://doi.org/10.1016/j.actamat.2022.118097