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

Metallurgical preparation of Nb-Al and W-Al intermetallic compounds and characterization of their microstructure and phase transformations by DTA technique

The possibilities of metallurgical preparation of 40Nb-60Al and 15W-85Al intermetallic compounds (in at.%) by plasma arc melting (PAM) and vacuum induction melting (VIM) were studied. Both methods allow easy preparation of Nb-Al alloys; however, significant evaporation of Al was observed during the melting, which affected the resulting chemical composition. The preparation of W-Al alloys was more problematic because there was no complete re-melting of W during PAM and VIM. However, the combination of PAM and VIM allowed the preparation of W-Al alloy without any non-melted parts. The microstructure of Nb-Al alloys consisted of Nb2Al and NbAl3 intermetallic phases, and W-Al alloys consisted mainly of needle-like WAl4 intermetallic phase and Al matrix. The effects of melting conditions on chemical composition, homogeneity, and microstructure were determined. Differential thermal analysis was used to determine melting and phase transformation temperatures of the prepared alloys.Web of Science258art. no. 200

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

Study of Selected Thermophysical and Thermodynamical Properties of Ni-bassed Alloys

Import 13/12/2010V leteckém průmyslu se pro lopatky stacionárních i leteckých turbín často používá niklových superslitin. Je to proto, že na materiál je kladena řada extrémních požadavků, jako např. žárupevnost za vysokých teplot, odolnost vůči únavovému poškození, aj. Použité materiály bývají komplexně legovány a jsou ze strukturního hlediska značně komplikované. Tato práce je zaměřena především na studium teplot a latentních tepel fázových přeměn vybraných niklových superslitin (IN 713LC, IN 738LC, IN 792-5A) s využitím metody diferenční termické analýzy (DTA). Vzorky odebrané z litého stavu superslitin byly roztaveny řízenou rychlostí ohřevu (1, 5, 10, 20 a 50°C/min) a ihned po roztavení byly řízeně ochlazovány stejnou rychlostí. K analýzám byl použit laboratorní systém SETARAM Setsys 18TM. Z naměřených DTA - křivek byly rovněž stanoveny teploty fázových transformací při nulové rychlosti ohřevu/ochlazování. Teploty a latentní tepla fázových přeměn byly porovnány s daty uváděnými v dostupné literatuře. Vzorky před a po DTA - analýzách byly za použití elektronové skenovací mikroskopie podrobeny fázové analýze.The aircraft industry often uses nickel based super-alloys for blades of the jet-turbine engines. It is so because this material must satisfy numerous extreme requirements, such as e.g. heat-resistance at high temperatures, resistance to fatigue damage, etc. Used materials are usually alloyed in complex manner and their structure is very complicated. This work deals with an experimental investigation of phase transformation temperatures and phase transformation latent heats of selected nickel based super-alloys (IN 713LC, IN 738LC, IN 792-5A) with use of Differential Thermal Analysis (DTA method). Samples taken from as-received state of superalloys were heated with controlled ramp rates (1, 5, 10, 20 and 50°C/min) and immediately after melting they were cooled with the same controlled ramp rate with the help of the laboratory experimental system SETARAM Setsys 18TM. Moreover, the transformation temperatures at zero heating/cooling rate were determined. Phase transformation temperatures and phase transformation latent heats were compared with results presented in literature. The samples before and after DTA - analysis were also subjected to the phase analysis with use of scanning electron microscopy.Prezenční619 - Katedra fyzikální chemie a teorie technologických pochodůvyhově

Application of high temperature DTA to micro-alloyed steels

Paper deals with investigation of phase transitions temperatures for selected real grades of micro-alloyed steels. Temperatures of characteristic phase transitions were obtained using Setaram SETSYS 18TM. The DTA technique was selected for the study of micro-alloyed steels. Temperatures of phase transitions (liquidus, solidus etc.) were obtained. Infl uence of admixed and alloyed elements on shift of temperatures was investigated. Resulting data were compared with temperatures of phase transitions of Fe-C, Fe-Mn systems and with temperatures calculated according to relations published in available literature. Thermodynamic-kinetic solidifi cation model IDS was used to calculate characteristic equilibrium temperatures of investigated systems.Web of Science51112412

Thermophysical and structural study of IN 792-5A nickel based superalloy

The presented paper deals with study of phase transformations temperatures of nickel based superalloy IN 792-5A with application of DTA – method and use of experimental laboratory system for simultaneous thermal analysis SETARAM Setsys 18TM. Samples taken from as-received state of superalloy were heated with controlled ramp rates (1, 5, 10 and 20 °C·min-1) and immediately after melting they were cooled with the same controlled ramp rate. The samples before and after DTA-analysis were also subjected to the phase analysis with use of scanning electron microscopy on the microprobe (JCXA 733) equipped with energy dispersive analyser EDAX (EDAM 3).Web of Science511868

Teoretické základy fyzikální chemie v příkladech

OstravaE-vyuk

Phase transformation temperatures of pure iron and low alloyed steels in the low temperature region using DTA

The paper reports a study of temperatures of phase transitions of nine samples of real grades of low-alloyed steels, including one sample of pure iron, using differential thermal analysis. Temperatures of phase transitions were measured in the low-temperature interval (20–1000°C). Investigated systems were analysed at selected rates of heating/cooling and then temperatures of phase transitions for zero heating/cooling rate were determined. The results obtained are compared with temperatures of the equilibrium metastable diagram Fe–C, with results from the software IDS and with temperatures of phase transitions calculated according to relations published in available literature. It follows from the results that differences, sometimes considerable ones, still exist between experimental and theoretical data, which implies the necessity for further systematic research in this area

Phase transition temperatures of Sn-Zn-Al system and their comparison with calculated phase diagrams

The Sn–Zn–Al system was studied in connection with the possible substitution of lead-based solders for temperatures up to 350 °C. Ternary alloys with up to 3 wt% of aluminium were prepared. The investigated alloys lie close to the monovariant line (eutectic valley) of the Sn–Zn–Al system. The temperatures of phase transitions of six binary Sn–Zn reference alloys and fourteen ternary Sn–Zn–Al alloys using DTA method were investigated in this paper. DTA experiments were performed at the heating/cooling rate of 4 °C min−1 using Setaram SETSYS 18TM experimental equipment. The temperatures of phase transitions in the ternary Sn–Zn–Al system were obtained, namely, the temperature of ternary eutectic reaction T E1 (197.7 ± 0.7 °C), temperature of ternary transition reaction T U1 (278.6 ± 0.7 °C), temperatures of liquidus and other transition temperatures for studied alloys. Temperatures obtained during DTA heating runs were used as authoritative. DTA curves obtained during cooling enabled realising better differentiation of the obtained overlapped heat effects (peaks) during heating. Theoretical isopleths of the Sn–Zn–Al phase diagram were calculated using the Thermocalc software and MP0602 thermodynamic database. Experimental data were compared with the calculated temperatures, and a good agreement was obtained.Web of Science110137836