Water-enhanced plasticity of calcium fluoride

Calcium fluoride (CaF2) ionic crystals have been observed to be sensitive to humid environments during ultraprecision machining, but further discussion about detailed mechanisms of the corresponding water-induced mechanical behaviors is still lacking. This work aims to perform a systematic investigation to understand the effect of water on the deformation and correlated plastic enhancement of CaF2 under indentation. Microindentation experiments were employed to observe different mechanical responses including the pop-in behavior and surface pile-up to identify the water-enhanced plasticity of CaF2 preliminarily. Then, atomic simulations were performed to reproduce the indentation process and confirm the close relationship between the indentation behaviors and water. The dislocation activities and crystal slip of both simulations with and without water were captured to analyze the plastic flow induced by hydration. Furthermore, Raman spectroscopy measurement was also adopted in this study to explain the corresponding enhancing mechanisms of plastic behaviors from the perspective of surface effect.

Automated summary

This study systematically investigates the mechanical behaviors of calcium fluoride in humid environments. The effects of water on the deformation and plastic enhancement of CaF2 under indentation are explored through microindentation experiments, atomic simulations, and Raman spectroscopy measurement.