Reverse Indentation Size Effect Behavior Research Articles

Comparison of Vickers microhardness of undoped and Ru doped BSCCO glass ceramic materials

In this study, effect of substitution ratio on the mechanical and structural properties of Bi1−xRuxPb0.2Sr2CaCu2O10+δ system, that is prepared in the ratios of x = 0.0, 0.025, 0.050, 0.075, is investigated. Samples are prepared with glass ceramic method and sintered at 845 °C. XRD and SEM measurements are performed for structural analyses, and Vickers micro-hardness measurements are carried out at different applied load (0.245 ≤ F ≤ 2.940 N) in order to investigate the mechanical performance of the Ru doped Bi1−xRuxPb0.2Sr2CaCu2O10+δ system. Experimental results of Vickers micro-hardness analyses are performed using the Meyer’s law, the proportional samples resistance model, the elastic/plastic deformation model, the Hays–Kendall approach and the indentation induced cracking (IIC) model. All analyses results are exhibited reverse indentation size effect behavior. The measured hardness values increase with increasing the applied load. Finally, IIC model is determined as the most successful model describing the mechanical properties of our samples.

Changes in mechanical and structural properties of Bi-2212 added MgB2 superconductors

In the present study, we investigate the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) addition on structural and mechanical properties of bulk MgB2 obtained by hot-press method by means of X-ray diffraction, the Scanning Electron Microscopy and Vickers microhardness measurements. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 8 and 10 wt%) of the total MgB2. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano boron (B) powder and Bi-2212 powder which are produced by hot-press method. As a result of the hot-press process, the compact pellet samples were manufactured. The microhardness results were analyzed by Meyer’s law, Proportional Sample Resistance Model, Elastic–Plastic Deformation Model, Hays Kendall Approach, and Indentation Induced Cracking (IIC) Model. IIC model was identified as the most appropriate model for samples exhibiting the reverse indentation size effect behavior.

Significant change in micro mechanical, structural and electrical properties of MgB2 superconducting ceramics depending on argon ambient pressure and annealing duration

In this study, the effects of different Ar pressure (vacuum, 0, 10 and 20 bar) and different annealing times (0.5 and 1 h) on microstructural, mechanical and superconducting properties of the bulk superconducting MgB2 are investigated. The samples are produced using the solid state reaction method. X-ray diffraction and scanning electron microscopy measurements are performed for phase formation, crystal structure, lattice parameters, particle size analysis, grain orientations, grain connectivity, and surface morphology of MgB2 samples. The superconducting properties are studied by dc resistivity measurements. In this study we have focused on microhardness measurements to investigate the mechanical properties. Vickers microhardness test is employed for determination of mechanical properties of the samples. The experimental microhardness results are analyzed by Meyer’s law, proportional sample resistance model, elastic–plastic deformation model, Hays Kendall (HK) approach, and indentation induced cracking (IIC) model. HK approach is identified as the most appropriate model for MgB2 superconducting samples exhibiting the indentation size effect behavior; for the other samples that have reverse indentation size effect behavior IIC model is appointed as the most appropriate model.

Effect of Zn content on microstructure and mechanical performance in Bi1.8Sr2Ca2Cu3.2−xZnxO10+δ glass ceramic

In this study, we have investigated the effects of Zn doping on structural and mechanical properties of Bi1.8Sr2Ca2Cu3.2−xZnxO10+δ ceramic samples with x = 0.0, 0.1, 0.5, 1.0. The prepared samples were characterized by using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffractometer (XRD) and static microhardness indenter. Surface morphology, orientation of grains and elemental composition analysis of the samples were investigated by SEM and EDS measurements, respectively. Texturing and lattice parameters a, b and c were determined from the XRD measurements. In this work we focused on Vickers microhardness measurements in order to characterize the mechanical properties. Experimental results of Vickers microhardness measurements were analyzed by using Meyer’s law, the elastic/plastic deformation model, proportional sample resistance model (PSR), modified PSR model, Hays–Kendall (HK) approach and indentation induced cracking (IIC) model. According to the obtained results, HK approach is the most suitable model for the CZn00 sample showing indentation size effect behavior and IIC Model is the most suitable model for the CZn01, CZn05 and CZn10 samples showing reverse indentation size effect behavior.