Effect of chemical composition and temperature on viscosity and structure of molten CaO-Al2O3-SiO2 system

The effects of the change of chemical composition and temperature on the viscosity of CaO-Al2O3-SiO2 oxide system with basicity from 0.78 to 1.63 were investigated in this paper. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1600. Viscosity was measured in a rotational mode during heating at the rate of 2.2 K/min in the temperature interval from 1673 to 1873 K. Viscosity is often sensitive to the structural changes in molten oxide systems, which implies that the analysis of viscosity is an effective way to understand the structure of molten oxide systems. Exact clarification of the change of structure of the oxide system caused by increased content of CaO was performed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD).Web of Science6042878287

Plastometric study of hot formability of hypereutectoid C – Mn – Cr – V steel

Formability of hypereutectoid C-Mn-Cr-V steel in hot condition was investigated with use of plastometric methods. A wide range of deformation temperatures 1 300 - 640 °C for hot tensile tests was proposed with use of nil-strength temperature (NST), determined by special plastometric method, and as well as with use of the calculated temperatures of phase transformations during heating of the investigated steel. Ultimate tensile strength of the investigated steel was increasing exponentially with the decreasing deformation temperature. Ductility of the investigated steel in hot condition increased with the increasing deformation temperature up to the temperatures ranging from 1 150 to 1 250 °C, after which a sharp decline of formability took place in investigated material.Web of Science55336836

Impact of Ni on the thermophysical and thermodynamic properties of Fe–C–Ni based alloys

Three model alloys based on Fe-C-Ni were studied containing carbon between 0.338 and 0.382 wt. % and nickel between 1.084 and 4.478 wt. %. Phase transition temperatures, heat capacity, enthalpy change, heat of fusion, coefficient of thermal expansion, and density were experimentally and theoretically determined in the high-temperature area from 1000 degrees C to 1595 degrees C. A number of techniques, namely differential thermal analysis (DTA), differential scanning calorimetry (DSC), and dilatometry, were used in this study, and the heat of fusion was determined by two approaches, that is, from the DSC peak area and from the enthalpy change. The experimental data were compared and discussed with the calculation results obtained using SW IDS, JMatPro, and Thermo-Calc operating with the commercially available TCFE8 thermodynamic database. The obtained experimental results show that the liquidus temperature and the coefficient of thermal expansion decrease with increasing nickel content. On the contrary, the density and heat of fusion values derived from the DSC peak increase with increasing nickel content. Furthermore, an ambiguous influence of nickel on the change in solidus temperature, heat capacity, enthalpy change, and heat of fusion obtained from the enthalpy change was observed.Web of Science204332431

Decomposition of γ-Fe in 0.4C–1.8Si-2.8Mn-0.5Al steel during a continuous cooling process: A comparative study using in-situ HT-LSCM, DSC and dilatometry

Continuous cooling transformation (CCT) diagrams represent roadmaps for producing all heat-treatable steels. CCT curves provide valuable information on the solid-state phase transformation sequence, depending on the defined cooling strategies, the alloying concept of the steel and previous processing steps. The experimental characterization of CCT diagrams is usually done on a laboratory scale applying thermal analysis of dilatometry. In current research studies, however, also other in-situ methods such as high-temperature laser scanning confocal microscopy (HT-LSCM) or differential scanning calorimetry (DSC) are frequently used to investigate phase transformations during thermal cycling. In the present study, HT-LSCM observations and DSC analysis are critically compared with dilatometry results by investigating the CCT diagram of a 0.4%C-1.8%Si-2.8%Mn-0.5%Al (in mass pct.) advanced steel grade. Furthermore, classical examinations by optical microscopy and hardness measurements were performed to support the analysis. In general, very good consistencies between all experimental techniques were identified in determining the transformation start temperature for pearlite, bainite and martensite. The optical microscopy confirmed the observed phase transformations and the results correlated with the measured hardness response. Based on the results, coupling of HT-LSCM and DSC is considered as a valuable novel approach to plot CCT diagrams in future research.Web of Science2

Graphitic carbon nitride/xylene soot metal-free nanocomposites for photocatalytic degradation of organic compounds

Graphitic carbon nitride and soot (g-C3N4/soot) metal-free nanocomposites were synthesized by a simple one-pot thermal synthesis from mixtures of dicyandiamide with different volumes of xylene. The soot nanoparticles of 17.7 ± 1.7 nm in size were observed on the g-C3N4 surface. The band gap energies of the synthesized nanocomposites decreased from 2.65 eV to 2.53 eV with the increasing content of soot nanoparticles. The photocatalytic activity of the g-C3N4/soot nanocomposites to degrade phenol, ofloxacin, and ampicillin under the LED irradiation of 420 nm was investigated. Time-resolved photoluminescence measurements, electrochemical impedance spectroscopy, and trapping experiments indicated that photoinduced electrons were accumulated in the soot particles, reacted with oxygen forming superoxide radicals, which decomposed the organic compounds. The degradation efficiency decreased in the sequence ofloxacin > ampicillin > phenol. The g-C3N4/soot nanocomposites were investigated for the photocatalytic degradation of organic compounds for the first time.Web of Science139art. no. 11043

Rheological Characteristics of Fe–C–Cr(Ni) Alloys

The principal objective of this project was to investigate the rheological properties of Fe–C–Cr and Fe–C–Ni-based low-alloy steels using an Anton Paar high-temperature rotational viscometer up to 1550 °C. The emphasis was placed on determining the liquidus temperatures and evaluating the flow and viscosity curves and the temperature dependence of dynamic viscosity. All were studied depending on the change in the content of chromium (0.010–4.863 wt%), nickel (0.001–4.495 wt%), and carbon (0.043–1.563 wt%). It was shown that the dynamic viscosity decreases with increasing nickel content and increases with increasing carbon and chromium content. The experimental data of the flow curves were fitted using the Herschel–Bulkley model with a good agreement between the measured and calculated values. Characterization of the internal structure was performed by SEM and EDX analyses, confirming non-significant changes in the microstructure of the original and remelted samples. The phase composition of the selected samples was also determined using JMatPro 12.0 simulation software (Sente Software Ltd., Guildford, UK)

Study of phase transformation temperatures of alloys based on Fe-C-Cr in high-temperature area

Three alloys based on Fe-C-Cr were studied. These alloys contained carbon in a range of 0.308-0.380 mass% and chromium 1.058-4.990 mass%. Temperatures of solidus (onward used as T (S)), liquidus (onward used as T (L)) and peritectic transformation (onward used as T (P)) were studied in the high-temperature region. These temperatures were obtained using two thermal analysis methods: differential thermal analysis (onward used as DTA) and simple thermal analysis (onward used as TA). The Setaram Setsys 18(TM) was used for experiments with employment of the DTA method. All measurements were taken in an inert atmosphere of pure argon at heating rate of 10 A degrees C min(-1), and simple TA method was used for the experiments with the use of the Netzsch STA 449 F3 Jupiter. Measurements were taken in inert atmosphere of pure argon at a heating and cooling rate of 5 A degrees C min(-1). Phase transformation temperatures were obtained by heating and cooling process and were approximated to "equilibrium conditions" (DTA method: zero heating rate and sample mass, standard, TA method: only standard) (A 1/2 aludova et al. in J Therm Anal Calorim 112:465-471, 2013a. The experimental data were compared and discussed with the calculation results using IDS (solidification analysis package) software (onward used as SW) Thermo-Calc and the TCFE8 (Thermo-Calc Fe-based alloys) database. The results of the two alloys were compared with those published for similar steels. The experimentally obtained transition temperatures were close to the calculated values. The solidus, liquidus and peritectic transformation temperatures were lowered with increasing carbon (range 0.308-0.380 mass%) and chromium content (range 1.058-4.990 mass%). The smallest difference between the experimental results and theoretical calculations was observed at the liquidus temperature for all alloys. Nonetheless, the difference measured for the solidus temperatures was much greater.Web of Science1331484

Liquidus and solidus temperatures and latent heats of melting of steels

The paper deals with the study of latent heats of melting of three real steels (one low-alloyed steel and two chromium steels) and temperatures of liquidus, peritectic transformation and solidus of these steels. All quantities were obtained using the differential scanning calorimetry method (DSC). The Setaram MHTC (multi-high-temperature calorimeter) Line 96 device equipped with 3D DSC sensor was used for all experiments. Measurements were done in alumina crucibles under inert atmosphere of pure argon. Controlled heating and cooling of steel samples was conducted at the rate of 5 K min(-1). All investigated quantities were also calculated using the Thermo-Calc software package with the use of the Thermo-Calc Fe-based alloys (TCFE) database. Comparison and discussion of experimental and calculated data was performed, and very good agreement was observed. The largest difference between measured and calculated values was 18 J g(-1) for latent heat of melting and up to 2 A degrees C for all investigated temperatures of phase transformation, except for one temperature of peritectic transformation.Web of Science127112812

Experimental and theoretical assessment of liquidus, peritectic transformation, and solidus temperatures of laboratory and commercial steel grades

The paper deals with theoretical and experimental study of phase transformation temperatures of steels in high temperature region (above 1000 degrees C), with focus on the solidus temperature, peritectic transformation temperature and liquidus temperature of multicomponent steels. Experimental data were obtained using Differential Thermal Analysis and direct thermal analysis. The experimental data were assessed by basic statistics. The calculations were performed using InterDendritic Solidification software and Thermo-Calc software. Also, selected empirically based models were used for calculations. The study presents the basic principles of theoretical and experimental methods, characteristics, advantages and disadvantages. Both used thermo-analytical methods are set correctly; the results are reproducible, comparable and close to equilibrium temperatures. Furthermore, comprehensive comparisons between the calculated and measured phase transformation temperatures show that the experimental data is satisfactorily accounted for by the present thermodynamic description.Web of Science4011039

Study of equilibrium and nonequilibrium phase transformations temperatures of steel by thermal analysis methods

This work deals with determining temperatures of phase transformations in steel S34MnV in a low-temperature region (below 900 A degrees C). Although S34MnV is a significant tool steel, in the literature, there are only a few works dealing with the study of the thermo-physical properties of this steel. For the study of phase transformation temperatures of steel S34MnV, a differential thermal analysis and dilatometry were used in this study. Both methods are used to determine the phase transformation temperatures of steel. Dilatometry, however, unlike differential thermal analysis, is commonly used to determine the temperature of nonequilibrium phase transformations during cooling. Temperatures of the eutectoid phase transformation (A (c1)) and temperatures of the end of the ferrite to austenite transformation (A (c3)) were obtained at heating, and temperatures of the start of the ferrite formation (A (r3)), the temperature of the start of the pearlite formation (A (r1)) and the temperature of the start of the bainite formation (B (S)) were obtained at cooling using these methods. The temperatures obtained using the both methods were compared and discussed. The original thermo-physical data on steel S34MnV were obtained under precisely defined conditions. For the complexity of the study of the steel, a metallographic analysis of samples was also conducted after thermal analysis, which enables determining the phases occurring in the final structure and their quantity. The experimentally obtained data were compared with data calculated by the software QTSteel.Web of Science127142942