Ultrasonic attenuation due to grain boundary scattering in copper and copper-aluminum

Abstract

Ultrasonic attenuation in copper and copper-aluminum samples is measured as a function of frequency and average grain size. At low frequencies the attenuation scales quadratically with the frequency and linearly with average grain size. In addition, there is a large difference in attenuation between powder metallurgy samples and cast-and-wrought samples, although their qualitative behaviors are similar both in terms of frequency dependence and grain size dependence. Such difference and the discrepancy with the existing theory may point to mechanisms of scattering by grain boundaries that are not included in the current theoretical model.

Finite element modelling of elastic wave scattering within a polycrystalline material in two and three dimensions

“…. This also confirms 27 Wave scattering in a polycrystalline material 14 /38 that the grains behave as Rayleigh scatterers and shows that, in this specific case, other scatterers, such 1 as voids or material imperfections were not required to explain the dominance of Rayleigh scattering at 2 low frequencies 22 . 3…”

“…The chosen material is a relatively strong scattering 23 medium, Inconel 600, of cubic symmetry. 24 As an example of the utility of modelling such as this, recent research [22][23][24] has raised interesting queries 25 regarding our current understanding of grain scattering, including the role of grains as Rayleigh 26 Wave scattering in a polycrystalline material 5 /38 scatterers 22 and whether it is not the material imperfections such as voids and inclusions which are 1 contributing to that effect. FE can be useful in this matter by modelling a perfect polycrystalline 2 microstructure, clear of flaws, and identifying the dominant scattering behaviour of the grains.…”

Ultrasonic attenuation in polycrystals using a self-consistent approach

“…Furthermore, a specimen exhibiting a high level of crystalline anisotropy is needed to ensure that the total attenuation is primarily governed by scattering. With these considerations, the samples investigated in the articles by Zhang et al [37] and Haldipur et al [34] were selected for comparison to the theoretical longitudinal attenuation derived from the SC averaging scheme. The copper-aluminum samples used in Zhang, et al, were created through the powder metallurgy (PM) method.…”

“…(26) was employed because of its simplicity and [37]) and (b) Cu-Al sample with d = 26.9 µm (PM5 Sample [37]). The experimental data were generated using the curve fits given by Zhang [37].…”

Influence of spatial correlation function on attenuation of ultrasonic waves in two-phase materials

“…The general formulation here can be directly related to sintered metals, concrete, and polycrystals with decorated grain boundaries for which previous models had difficulty explaining the experimental results. 31,32 These results should be very useful for nondestructive testing and materials characterization research despite the simplicity of the assumptions made.…”