Materials science communication: Analysis of data on indentation load against penetration depth for bulk MgB2 crystal using indentation work and Oliver-Pharr approaches

Vickers microindentation tests were carried out on a bulk MgB2 superconductor with the load of ranging from 300 to 1500 mN at a room temperature. The load-penetration depth curves and the energy data (the absolute, the total, the plastic, and the elastic energy) were analyzed to evaluate the mechanical properties. Hardness and elastic modulus values were calculated by the Oliver-Pharr method and the work of indentation approach. The work of indentation hardness and elastic modulus were calculated directly from the energy of indentation without the need for estimating displacement, areas or volumes, which can be time consuming and inaccurate. It was found that the hardness and elastic modulus increased with decreasing load (i.e. indentation size effect). In addition, the hardness and elastic modulus calculated from the work of indentation approach seem to correlate very well with Oliver-Pharr method at high peak load. Some specific material constant describing the properties of materials were also calculated as total energy, plastic energy, elastic energy, elastic-total energy, plastic-total energy and elastic-plastic energy constants.