Nanomechanical investigation on FCC metals surface patterning: shaping by stacking fault energy and strain rate

In order to develop an understanding of how strain rate and stacking fault energy modulate indentation-induced surface patterns on small length scales, the formation mechanism on face-centered cubic single crystals was investigated. Different patterns have been successfully obtained on Cu (100) and Ni (100) with distinct stacking fault energy under quasi-static nanoindentation ($\dot{\epsilon }$$\dot{\epsilon }$<10¹ s⁻¹) and high strain rate nano-impact ($\dot{\epsilon }$$\dot{\epsilon }$ >10³ s⁻¹) conditions. Along the imprint, the Ni (100) imprint exhibited sink-in deformation and gradual pile-up with four-fold symmetry, while the Cu (100) displayed sharp pile-up with three-fold symmetry. At the high-impact strain rate, the overall profiles remain unchanged, but the height and range were reduced, particularly pronounced for Ni (100). A dislocation-driven mechanism for surface patterns has been unveiled based on analysis of stress field features as well as distinct deformation microstructures. Furthermore, the strategy of modulating surface patterns by altering stacking fault energy and strain rate was proposed. This study not only deepens the understanding of small-scale deformation behavior but also paves the way for developing effective methods to control micro/nano-sized textures for various applications.