In-situ analysis of the thermoelastic effect and its relation to the onset of yielding of low carbon steel

Abstract

The thermoelastic effect indicates the dependency of temperature and volume change in the material and, due to the heat released during plastic deformation, a temperature minimum occurs in the region of the onset of yielding. An experimental setup is presented for the microscopic analysis of the thermoelastic effect, which allows high precision measurements of specimen. In-situ diffraction experiments were performed for a single phase low carbon steel HC260Y using synchrotron diffraction at the High Energy Material Science beamline P07 in Petra III, DESY. This allows a direct comparison of the onset of yielding by observing the evolution of lattice strains and dislocations densities with the specimen temperature in a continuous cyclic test having high measuring frequency and accuracy. Therefore, the lattice strains are evaluated based on the peak shift of several lattice planes and the dislocation density is estimated based on the micro strain due to peak broadening. The results prove existing assumptions about the relation between the thermoelastic effect and the onset of yielding and clearly qualify the temperature-based determination method for material characterization on a microstructural basis. The usefulness of the temperature elasticity parameters is shown exemplarily with the determination of loading moduli and compared to existing methods.