The paper analyzes the marginal cut-outs from two slabs of Ti-Nb microalloyed steel. The first slab was transitional with initial pulling rate 0.5 m.min -1 and final pulling rate 0.8 m.min -1 . The second slab was cast at real pulling rate 1.03 m.min -1 . The V-notch Charpy impact test showed that at low pulling rate 0.5 m.min -1 , the values of impact toughness (KCV) were higher than those at high slab pulling rates. When the pulling rate was 0.5 m.min -1 , mixed fractures were obtained, occasionally ductile, but mostly brittle. On the other hand pulling at rates 0.8 m.min -1 and 1.03 m.min -1 resulted only in brittle fractures with low KCV. Comparison of the mean ferrite grain size d ST , showed that the most fine-grained structure was achieved at a low pulling rate 0.5 m.min -1 , and the coarsest structure at pulling rate 0.8 m.min -1 . Furthermore, it was shown that, at high slab-pulling rates 0.8 m.min -1 and 1.03 m.min -1 , a greater amount of tertiary cementite was found on the boundaries of ferritic grains, compared with the lowest rate of slab pulling 0.5 m.min -1 . At the highest rate of slab pulling 1.03 m.min -1 , in addition to tertiary cementite, presence particles were observed here and there on the boundaries of ferritic grains, mostly oval shaped. On the fracture surfaces of brittle samples transcrystalline cleavage facets (TCF) dominated. In small amounts smooth facet intercrystalline decohesion (FID) was also identified with max. 0.2% , and also ductile transcrystalline failure with dimples (DDTF), usually present only in the form of narrow dimple bridges between cleavage facets. Observation of failures using scanning electron microscope (SEM) revealed the presence of either clusters of inclusions or individual particles, and EDX analysis confirmed the presence of Al, S, O, Mn, i.e. most probably oxides of aluminum and manganese sulphides. Aluminum can come from poorly-cleaned melt contaminated by fumes from deoxidation or from mould powders. There were also complex particles based on (C, Ti, Mn, O, Al, S, Nb, Zr, Ca) observed mainly on the TCF. Moreover, the impact of heterogeneous distribution of particles on embrittlement cannot be excluded - carbides, nitrides, and complex carbonitrides based on (Ti, Nb) (C, N).
The paper deals with the metallographic analysis of overlapped laser welds of dissimilar materials based on galvanized and ungalvanized steels in various combinations. In addition to a gallery of metallographic sections, the paper presents the monitoring of weld defects, the measurement of selected weld geometrical characteristics and changes in weld microstructure by measuring the microhardness profile across the joint. The mixing of materials was monitored by area and line EDX analysis in the melting zone. Subsequently, the load carrying capacity of the formed joints was determined and compared with FEM simulation. Finally, the dependences of hardness and strength of welds on carbon content and carbon equivalent were determined.
The aim of this work was to propose a simple method for synthesizing differently shaped AgNPs and to find a suitable stabilizing/capping agent to ensure the non-toxicity of AgNPs. Using a chemical method, by simply changing the volume of reducing agents, we successfully prepared colloids of differently shaped AgNPs (spherical (~10 nm), triangular (~40 nm), rodlike (~30 nm), and a mixture of these shapes). The nanoparticle sizes and shapes affect the solution color. UV-VIS spectroscopy was used to evaluate the colloidal solutions, and transmission electron microscopy was used to analyze the shape and size of the nanoparticles. To create non-toxic and stable AgNPs, it is necessary to modify the surface properties of the nanoparticles; one possibility is to create a biocompatible layer on the nanoparticle surface. We successfully applied a combination of trisodium citrate and polyvinylpyrrolidone, thereby preventing the release of silver ions, which are responsible for the toxic effects of AgNPs. The synthesized nanoparticles show very low, mostly negligible antibiofilm activity against the green algae Chlorella kessleri. AgNPs were used to prepare polymer-AgNP composite thin layers and fibers. It was proved that AgNPs can influence polymer matrix properties.
Abstract Sintering by viscous flow in a “kinetic window” between T g and T x temperatures was used to prepare bulk glass/glass‐ceramic luminescent materials from rapidly quenched glass microspheres in the system Y 2 O 3 –Al 2 O 3 doped with Ce 3+ ions. The glass microspheres were prepared from sol–gel synthesized precursor powders in a high‐temperature methane‐oxygen flame. The crystallization of the glasses was analyzed using differential scanning calorimetry and high‐temperature X‐ray diffraction. The crystallization behavior of quenched glass microspheres was found to be strongly dependent on glass composition. The glass microspheres were consolidated into bulk material by hot‐pressing technique at a temperature of up to 1100℃ with the applied pressure 40MPa. The optimized time‐temperature‐pressure regime enables the preparation of bulk glass, and glass‐ceramic with a high fraction of crystalline Ce 3+ ‐doped YAG phase embedded in the Al 2 O 3 ‐enriched glass matrix. The glass/glass‐ceramics emit blue/yellow light with high intensity under excitation in UV and/or blue spectral region.
The work analyses microstructures of ZnAl4Cu1, ZnAl27Cu2 and ZnAl40Cu2Si2 alloys in cast condition and after heat treatment in relation to microhardness HV 0 . 2 and purity of the alloys. As shown the microstructure of ZnAl4Cu1 alloy contained η phase and eutectoid, which consisted phases α + η. ZnAl27Cu2 alloy contained α phase, eutectoid and ε phase, and ZnAl40Cu2Si2 alloy had a similar composition, but moreover contained Si particles. Microhardness in the molten state in ZnAl4Cu1 alloy was HV 0 . 2 = 94, in ZnAl27Cu2 alloy it was HV 0 . 2 = 117, and in ZnAl40Cu2Si2 alloy it was HV 0 . 2 = 142 .
This paper investigated the magnetic properties of novel soft magnetic composite (SMC) with ferrite nanofibers. Material consists of FeSi powder covered by resin and different amounts of Ni 0.3 Zn 0.7 Fe 2 O 4 ferrite nanofibers. We prepared SMC with very high specific electrical resistivity. FeSi/resin (0.49 wt% ferrite) sample exhibits the highest electrical resistivity (6.05 Ω·m) due to low interparticle contacts. The image analysis of SEM pictures was used for the evaluation of effective area, in which local eddy currents are flowing. The FeSi/resin (0.49 wt% ferrite) sample displays the lowest total losses in the measured frequency range due to the highest specific electrical resistivity and appropriately covered FeSi particles. Loss separation and the analysis of movable magnetic objects were performed for all studied materials.
The aim of this work is indentation study of local mechanical properties of Cu-22Zn-4.6Al alloy, which has significant shape memory effect after quenching from dual α + β phase region. The study was carried out on the samples with thermoelastic and non-thermoelastic martensite in the structure, which were obtained by quenching from various temperatures. A different behavior concerning mechanical properties measurements of α phase and β phase transformed to martensite after quenching from various temperatures was found out. It was observed almost no change of mechanical properties of α phase, whereas indentation hardness H IT and indentation modulus E IT raised with increasing quenching temperature. Also some serious differences were observed at indentation test of thermoelastic and non-thermoelastic martensite.
