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In this study, metal matrix-based composite (MMC) was subjected to Equal Chanel Angular Pressing (ECAP) in several passes to determine the influence of deformation on the hardness of the samples. Composite based on A356 aluminum alloy and reinforced with Fly Ash (FA) particles was obtained by the compo casting method. The microstructural analyses and microhardness measurements were performed on the cast and pressed samples. Vickers hardness measurement of composite samples was performed with different indentation load sizes: HV0.02, HV0.05, HV0.1 and HV0.2. Results showed that hardness increases after each ECAP pass. The lowest hardness value of 42 (HV0.02) as well as the lowest arithmetical mean value of 46 (HV0.2) was measured at the cast composite. The greatest composite hardness of 107 (HV0.1) and the highest arithmetical mean value of 94 (HV0.1) was measured at the three-time pressed sample. The mathematical model named Meyer's law was used for data analysis. In the cast sample, a decrease in hardness was detected with increasing indentation load, termed Indentation Size Effect (ISE), was confirmed with Meyers index n = 1.9112 < 2. Pressed samples showed opposite behavior—an increase in hardness with increasing indentation load—where Meyers index n > 2 indicated Reverse Indentation Size Effect (RISE). For all samples, a high coefficient of determination R2 > 0.99 confirmed that Meyer's law described this phenomenon well. [ABSTRACT FROM AUTHOR]

In this study, metal matrix-based composite (MMC) was subjected to Equal Chanel Angular Pressing (ECAP) in several passes to determine the influence of deformation on the hardness of the samples. Composite based on A356 aluminum alloy and reinforced with Fly Ash (FA) particles was obtained by the compo casting method. The microstructural analyses and microhardness measurements were performed on the cast and pressed samples. Vickers hardness measurement of composite samples was performed with different indentation load sizes: HV0.02, HV0.05, HV0.1 and HV0.2. Results showed that hardness increases after each ECAP pass. The lowest hardness value of 42 (HV0.02) as well as the lowest arithmetical mean value of 46 (HV0.2) was measured at the cast composite. The greatest composite hardness of 107 (HV0.1) and the highest arithmetical mean value of 94 (HV0.1) was measured at the three-time pressed sample. The mathematical model named Meyer’s law was used for data analysis. In the cast sample, a decrease in hardness was detected with increasing indentation load, termed Indentation Size Effect (ISE), was confirmed with Meyers index n = 1.9112 < 2. Pressed samples showed opposite behavior—an increase in hardness with increasing indentation load—where Meyers index n > 2 indicated Reverse Indentation Size Effect (RISE). For all samples, a high coefficient of determination R2 > 0.99 confirmed that Meyer’s law described this phenomenon well.

P.Hamb. II 134 yields the remains of a declamation on a theme otherwise attested only by Quintilian (9, 2, 85-86); the declamation itself is to be dated to the beginning of the 4th century AD, and represents one of the earliest known instances of accentual Satzrhythmus in Greek prose. [ABSTRACT FROM AUTHOR]

Mechanical features of BiPbEuSrCaCuO superconductor samples ( x=0, 0.01, 0.03, 0.05, 0.07, 0.1, and 0.3) are elaborated by traditional solid-state reaction route. The deformation of the mechanical properties belonging to the Bi-2223 crystal structure by Eu impurities with the aid of Vickers hardness ( H) measurements are conducted at different indentation loads from 0.245 N to 2.940 N for the first time. Further, the H values extracted from experimental results are investigated using five different models so as to demonstrate the role of Eu addition on Bi-2223 samples. Based on these results, we observed that the undoped sample reveals the indentation size effect (ISE) feature, whereas the Eu-doped Bi-2223 superconducting core demonstrates the reverse indentation size effect (RISE) nature. Additionally, it is attained that the models (Meyer's law, EPD, and PSR) fail to determine the estimate of the microhardness with the applied load. Nonetheless, the HK approach is observed to be superior to other models for the pure sample showing the ISE feature, while the IIC model is found to be the most successful model for the explanation of the mechanical characteristics of the Eu impurities in Bi-2223 bulk ceramics obeying RISE nature. [ABSTRACT FROM AUTHOR]

Neodmium (Nd) inclusions at different stoichiometric ratios ( x=0.0, 0.001 %, 0.005 %, 0.01 %, 0.05 %, 0.1 %) are doped in the Bi-2212 superconducting samples and the samples obtained are subjected to the sintering process at 840 C constant temperature for 72 hours. The effect of Nd doping on the structural and mechanical properties of prepared samples is investigated by the standard characterization measurements. XRD and SEM measurements are performed to obtain information about surface morphology, phase ratios, lattice parameters and particle size. Moreover, Vickers microhardness ( H) measurements are exerted to investigate the mechanical properties of the all samples in detail. It is found that all the properties given above retrogress with the increase of the Nd concentration in the Bi-2212 superconducting core. However, the ISE nature of the materials improves systematically. Additionally, the experimental results of microhardness measurements are analyzed using Meyer's law, PSR, MPSR, EPD models and HK approach. The results show that Hays-Kendall approach is determined as the most successful model. [ABSTRACT FROM AUTHOR]

This study indicates the change of the electrical, microstructural, physical, mechanical and superconducting properties of Cu-diffused bulk MgB superconductors by means of scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness and dc resistivity measurements. The samples are prepared at different annealing temperatures in the range from 650 to 850 C. Electrical and superconducting properties of samples are estimated from the dc electrical resistivity measurements. Moreover, microhardness measurements are performed to investigate the mechanical properties. Further, phase composition, grain sizes and lattice parameters are determined from the XRD measurements. At the same time, the surface morphology and grain connectivity of the samples are examined by SEM investigations. The measurements conducted demonstrate that both the Cu diffusion into the MgB system and the increment in the diffusion-annealing temperature increase the critical transition temperatures. Similarly, microstructure and grain size improve while the voids and porosity decrease with the increase of the diffusion-annealing temperature. In addition, the experimental results of the microhardness measurements are investigated using the Meyer's law, PSR (proportional specimen resistance), modified PRS (MPSR), elastic-plastic deformation model (EPD) and Hays-Kendall (HK) approach. The obtained microhardness values of the samples decrease with the increase of the diffusion-annealing temperature up to 850 C. The Hays-Kendall approach is found to be the most successful model describing the mechanical properties of the samples studied in this work. [ABSTRACT FROM AUTHOR]