Bending, Nanoindentation and Plasticity Noise in FCC single and poly crystals

TL;DR

This study investigates the effects of in-situ bending on nanoindentation behavior of FCC aluminum and copper at ultra-nano depths, revealing stress-dependent hardness and stress-insensitive plastic noise features.

Contribution

It provides new insights into the relationship between residual stress, hardness, and plastic noise in FCC crystals at ultra-nano scales.

Findings

Hardness inversely depends on in-plane stress below 10nm indentation depth.

Plastic noise features are statistically robust and independent of applied stresses.

A regime exists where ultra-nano hardness is stress-sensitive but plastic noise is not.

Abstract

We present a high-throughput nanoindentation study of in-situ bending effects on incipient plastic deformation behavior of polycrystalline and single-crystalline pure aluminum and pure copper at ultra-nano depths (<200nm). We find that hardness displays a statistically inverse dependence on in-plane stress for indentation depths smaller than 10nm, and the dependence disappears for larger indentation depths. In addition, plastic noise in the nanoindentation force and displacement displays statistically robust noise features, independently of applied stresses. Our experimental results suggest the existence of a regime in FCC crystals where ultra-nano hardness is sensitive to residual applied stresses, but plasticity pop-in noise is insensitive to it.