Effects of Ball Size and Microstructures on Indentation Curves of Fe9Cr Model Alloys and Tempered Martensitic Steel Eurofer97

Nano-indentation with spherical indenters is a test technique largely used to determine the elastic–plastic behavior of a very small volume of material. In this work, the indentation size effects under spherical indentation were investigated for Fe9Cr model alloys and reduced activation tempered martensitic steel Eurofer97. Experimental tests and finite element method (FEM) simulations were performed. Results and analysis of the experimental results and FEM simulations revealed that the indentation size effects depend on both the spherical indenter radius and the microstructures characterized by the initial dislocation density and the grain size of the tested materials. The observed difference in the indentation stress–strain curves was qualitatively discussed in terms of the relative effects associated with the ball radius and the microstructural length scale.