Acoustic energy enabled dynamic recovery in aluminium and its effects on stress evolution and post-deformation microstructure

It is now well established that simultaneous application of acoustic energy during deformation results in lowering of stresses required for plastic deformation. This phenomenon of acoustic softening has been used in several manufacturing processes, but there is no consensus on the exact physics governing the phenomenon. To further the understanding of the process physics, in this manuscript, after-deformation microstructure of aluminium samples deformed with simultaneous application of kilohertz range acoustic energy was studied using Electron-Backscatter Diffraction analysis. The microstructure shows evidence of acoustic energy enabled dynamic recovery. It is found that the subgrain sizes increase with an increase in acoustic energy density applied during deformation. A modified Kocks-Mecking (KM) model for crystal plasticity has been used to account for the observed acoustic energy enabled dynamic recovery. Using the modified KM model, predicted stress versus strain curves were plotted and compared with experimental results. Good agreements were found between predictions and experimental results. The manuscript identifies an analogy between microstructure evolution in hot deformation and that in acoustic energy assisted deformation.