High-temperature nanoindentation size effect in fluorite material

Abstract Micromechanical loading events such as pop-in and indentation size effect (ISE) are well understood at room temperature and have been widely accepted as fundamental factors in the study of material mechanics at the microscale. Experimentally it has been observed that such phenomena can be greatly affected by temperature, but quantitative studies of temperature effects are rarely conducted. This paper presents the effects of high-temperature on the pop-in load and ISE of calcium fluoride (CaF 2 ) single crystal material through in-situ high-temperature nanoindentation experiments and explains the localized dislocation events at the atomic level with molecular dynamic (MD) calculations. Our experimental results show that an increase in temperature leads to a reduction of the pop-in load, the hardness of the material, and the material dependent length scale during plasticity (defined in the Nix-Gao relation). Our computed results show that the differences in dislocation nucleation characteristics of CaF 2 at various temperatures are the main reasons for the changes in its material properties. Such an experimental-computational study provides a comprehensive analysis of the relationships between temperature and dislocation mechanisms during nanoindentation.