An Experimental Study of Elasticity in Polycrystalline Iron

The velocity of longitudinal elastic waves is measured between room temperatures and 880 °C in polycrystalline iron and compared with predictions of several theoretical models utilizing single‐crystal elastic constants from the literature. Wave velocities are measured from successive reflected peaks in laser‐ultrasonic signals with very high precision and accuracy. Iron is chosen as the test material because its inherent crystal anisotropy varies widely over this temperature range. Great care is taken in processing the material to ensure a suitable microstructure and random texture. Wave velocity varies considerably with temperature in a nonlinear manner. The consistently best fit for the experimental data is found for the Hill model with arithmetic averaging of the Voigt and Reuss bounds of the shear modulus. Kröner's self‐consistent model predicts values very close to the Hill arithmetic average though slightly more deviant from the measured values.