Application of laser-based resonant ultrasound spectroscopy to study texture in copper

Two copper specimens with distinct grain microstructures are investigated using laser resonant ultrasound spectroscopy (LRUS). One consists of randomly oriented crystallites and exhibits isotropic elastic behavior (two elastic constants), and the other has been highly textured by rolling and exhibits anisotropic elastic behavior (three elastic constants). The elastic constants are measured using electron backscatter diffraction, LRUS, and time domain laser ultrasound (LU). The elastic constants of the isotropic sample obtained via electron backscatter diffraction (EBSD), LU, and LRUS agree closely. However, for the anisotropic sample, there is considerable disagreement between results obtained using LRUS and results obtained using LU and EBSD. Analysis reveals that increasing the dimensionality of the modulus space leads to a questions of whether the LRUS results are unique to within experimental error. The consequence is that for anisotropic materials, small measurement uncertainties can lead to large uncertainties in the measured elastic constants. This observation has important implications for the use of LRUS to measure the elastic constants of thin texture samples. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3692386]