Nanoindentation characterised plastic deformation of a Al_0.5CoCrFeNi high entropy alloy

Abstract

The plastic deformation of a high entropy alloy Al_0.5CoCrFeNi was investigated by instrumented nanoindentation over a broad range of strain rates at room temperature. Results show that the creep behaviour depends on the strain rate remarkably. In situ scanning images showed a significant pile up around the indents, demonstrating that a highly localised plastic deformation occurred in the process of nanoindentation. Under different strain rates, contact stiffness and elastic modulus basically remain unchanged. However, the hardness decreases as indentation depth increases due to indentation size effect. For the same maximum load, serrations became less prominent as the loading rate of indentation increased. Similar serrations have been observed in the current alloy upon quasi-static compression.

Keywords:

• High entropy alloy
• Plastic deformation
• Serrations
• Nanoindentation