Ultrasonic study on the change in elastic properties of cementite with temperature and Mn content using nearly full density polycrystalline bulk samples

Abstract

The elastic properties of cementite were studied using a laser-ultrasonic technique. The temperature dependence and effect of Mn alloying were investigated using nearly full density polycrystalline bulk cementite samples. The Young’s modulus (E), shear modulus (G), bulk modulus (B), and Poisson’s ratio (ν) were obtained from the measured longitudinal and shear velocities (VL and VS, respectively). The elastic properties of cementite changed substantially with the temperature, especially around its Curie temperature (TC). The change in longitudinal velocity around Curie temperature was larger than the change in shear velocity. Around Curie temperature, a small decrease was observed in Young’s modulus and shear modulus and sharp minima were observed in bulk modulus and Poisson’s ratio. Mn addition to cementite increased the sound velocity and elastic stiffness and decreased Curie temperature. The present study revealed the temperature dependence of the elastic constants of cementite across Curie temperature for the first time.