Diffraction Plane Dependence of Elastic Constants in Ferritic Steel in Neutron Diffraction Stress Measurement

Neutron diffraction measurement have been made to investigate the diffraction plane dependence of elastic constants in ferritic steel. The measured diffraction planes were 110, 220, 112, 222 and 200. In the measurement a small tensile specimen was loaded in the tensile test rig specially degsined for a neutron diffractometer. The strains obtained for five diffraction planes increased almost in proportion to the applied stress up to 230MPa nearly equivalent to the yield stress. The mean elastic constants obtained were E=243GPa and ν=0.28 for 110, 220 and 112, 182GPa and 0.31 for softest 200, and 268GPa and 0.30 for stiffest 222, respectively. The bulk elastic constants, E=222GPa and ν=0.29, measured by the strain gauges almost agreed with the mean values for 110, 220 and 112. The Kroner elastic model is found to account for the diffraction plane dependence of Young's modulus and Poisson's ratio of the ferritic steel.