Work of indentation approach for investigation of mechanical properties of YBCO bulk superconductor at cryogenic temperatures

In this study, depth sensing Vickers microindentation test was carried out for YBCO polycrystalline superconductor with the temperature of ranging from 50 to 293 K at the load of 4.9 N. The applied load (P)-displacement (h) curves and the energy data (the absolute, the total, the plastic, and the elastic energy) were analysed to evaluate the mechanical properties such as hardness and elastic modulus values. The values were calculated by the Oliver-Pharr method and the work of indentation approach. A comparison between the results obtained by the aforementioned two methods was made. The work of indentation approach performed well because of the fact that the error due to the pile-up was reduced. In addition, it was found that the hardness and elastic modulus increased with decreasing temperature. Some specific material constants describing the properties of materials were also suggested as total energy constant (νT), plastic energy constant (νP), elastic energy constant (νE), elastic-total energy constant (νET), plastic-total energy constant (νPT), and elastic-plastic energy constant (νEP).