Mechanical properties of Ag-added DyBa₂Cu₃O_y superconducting melt-textured bulks prepared by the single-direction melt growth method

Ag-added DyBa2Cu3Oy superconducting melt-textured bulks were prepared using the newly developed single-direction melt growth (SDMG) method with different pre-heat-treatment conditions. Clearly distinct microstructures were observed depending on the pre-heat-treatment conditions and thickness of the bulks. Their mechanical properties were evaluated by use of Vickers microhardness measurements at varying applied forces. Vickers microhardness increases with an increase in the applied force for each sample, up to an importantly high value of similar to 9 GPa at the saturated region, indicating all the prepared bulks demonstrate the untypical reverse indentation size effect (RISE) performance. In addition, the experimental results found from the saturation regions are examined by the mechanical methods such as Meyer's law, proportional sample resistance model, elastic/plastic deformation, Hays-Kendall (HK) approximation, and indentation-induced cracking (IIC) model. According to the mechanical modelling findings, the HK and IIC models are found as appropriate mechanical models describing the hardness values for all the studied bulks exhibiting RISE feature and the true values are suggested to lie between the estimated values of HK and IIC models.