Simultaneous determination of elastic constants and crystallographic orientation in coarse-grained nickel by acoustic spectro-microscopy

The inverse analysis method is newly developed to determine the elastic stiffness tensor and the crystallographic orientation simultaneously for cubic crystal nickel from the measured angular distribution of surface wave velocity by acoustic spectro-microscopy. In the experiment, the angular dispersion of Rayleigh surface wave velocity was measured for six grains. For each grain, the inverse analysis was iteratively performed to deduce both the elastic constants and the crystallographic orientation, which finally provided the best-fitted theoretical dispersion curve to the original measured one. The obtained average elastic stiffness constants for nickel are: C₁₁=245 GPa, C₁₂=152 GPa and C₄₄=124 GPa. The maximum relative error of C_ij's was less than 5% among six grains. The crystallographic orientations {α, β, γ} were obtained with the maximum absolute error less than 1°. Sensitivity evaluation of the present inverse analysis to disturbance in C_ij and {α, β, γ} was also made to demonstrate robustness of our developed procedure for practical use.