Indentation size effect of stress exponent and hardness in homogeneous duplex eutectic 80Au/20Sn

• Creep stress exponent of homogeneous 80Au/20Sn with various indentation depths.
• A revised model for indentation size effect of hardness.
• Depth independent hardness and micro characteristic depth were determined.

The indentation size effect (ISE) of creep stress exponent and hardness in homogeneous duplex eutectic 80Au/20Sn was studied by nanoindentation, using constant load/holding (CL) and continuous multi-cycle (CMC) loading modes, respectively. The stress exponent of each fixed load decreases first and then increases as the indentation depth increases. The stress exponent for the same strain rate range increases with the indentation depth increasing. The result of CMC indicates that Nix-Gao's overestimates the hardness of 80Au/20Sn for small indentations. A revised model incorporating enlarged effective plastic zone and the maximum geometrically necessary dislocation density was achieved to describe the relationship between hardness and indentation depth.