Microscale dynamic testing is vital to the understanding of material behavior at application relevant strain rates. However, despite two decades of intense micromechanics research, the testing of microscale metals has been largely limited to quasi-static strain rates. Here we report the dynamic compression testing of pristine 3D printed copper micropillars at strain rates from ∼0.001 s−1 to ∼500 s−1. It was identified that microcrystalline copper micropillars deform in a single-shear like manner exhibiting a weak strain rate dependence at all strain rates. Ultrafine grained (UFG) copper micropillars, however, deform homogenously via barreling and show strong rate-dependence and small activation volumes at strain rates up to ∼0.1 s−1, suggesting dislocation nucleation as the deformation mechanism. At higher strain rates, yield stress saturates remarkably, resulting in a decrease of strain rate sensitivity by two orders of magnitude and a four-fold increase in activation volume, implying a transition in deformation mechanism to collective dislocation nucleation.
@article{arxiv.2201.01582,
title = {Anomalous High Strain Rate Compressive Behavior of Additively Manufactured Copper Micropillars},
author = {Rajaprakash Ramachandramoorthy and Szilvia Kalácska and Gabriel Poras and Jakob Schwiedrzik and Thomas E. J. Edwards and Xavier Maeder and Thibaut Merle and Giorgio Ercolano and Wabe W. Koelmans and Johann Michler},
journal= {arXiv preprint arXiv:2201.01582},
year = {2022}
}
Comments
Corresponding authors with equal contribution are: Szilvia Kal\'acska and Rajaprakash Ramachandramoorthy. Accepted manuscript: Applied Materials Today