Surface roughness effects on the displacement bursts observed in nanoindentation

The distinctive finding of unstable displacement bursts of indent depth observed in nanoindentation is thought to be linked to the dislocation emission phenomenon. However, because of a lack of understanding of the surface physics of the contact area, the explanation of the instability mechanism remains vague. In this paper, an effect of the surface roughness on the displacement bursts was experimentally investigated using single-crystalline aluminum. The surface properties of samples with several degrees of roughness of less than 10 nm were measured using atomic force microscopy. The discussion focuses on the relations between critical values of the load at the displacement bursts and the burst width.