The origin of the indentation size effect has been extensively researched over the last three
decades, following the establishment of nanoindentation as a broadly used small-scale
mechanical testing technique that enables hardness measurements at submicrometer
scales. However, a mechanistic understanding of the indentation size effect based on direct
experimental observations at the dislocation level remains limited due to difficulties in
observing and quantifying the dislocation structures that form underneath indents using …