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Skorohod and Olevsky's constitutive relation for viscous sintering (SOVS) is employed to simulate the shrinkage and relative density evolution of ceramics during the sintering process. While this model effectively simulates shrinkage and density evolution, the original formulation of the SOVS model does not explicitly incorporate grain growth or microstructural evolution. This paper introduces an enhanced version of the SOVS model, incorporating a novel calibration method to obtain the temperature dependence of the viscosity parameter. It considers grain growth as well as the evolution of the microstructure by adding new parameters. Simulations were conducted using Code_Aster, an open-source finite element software, in conjunction with MFront, a tool for formulating material behaviour equations. Dilatometer tests were performed with probes of porcelain stoneware composition to calibrate the model. The predictions of dimensional shrinkage and relative density evolution showed a high accuracy of the model (> 95%), enabling its use in the manufacturing process. [ABSTRACT FROM AUTHOR]

By dilatometry, the absolute change in the length of a sample is measured. As length, i.e., volume, is a state variable, its change can be monitored for long time ranges. This is the decisive advantage compared to the widely applied calorimetric methods which are based on a rate (change of heat) and where the maximum time range is determined by the resolution limit of the heat flow measurement. In contrast, if the measurement environment is kept at a constant temperature, dilatometric signals can be measured for very long time ranges down to very small changes with resolution in the nm range. The application of high‐stability isothermal dilatometry for studying precipitation phenomena in Al(Mg,Si)‐, Ti(V)‐, and Ti(Cr)‐alloys is summarized in the present review. Al(Mg,Si) turns out as a prime example where the various phases can unambiguously be distinguished by their characteristic length change features. For Ti(V), the influence of the oxygen impurity on the omega phase formation, and for Ti(Cr), the effect of Sn alloying on the omega phase formation can be revealed by dilatometry. The results on Al(Mg, Si) are compared with dilatometry on Al(Cu)‐alloys upon time‐linear heating, for which also the effect of microalloying with Au is studied. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of composition and heating rate on the fast-drying (∼60 min) of red ceramics obtained by extrusion using optical dilatometry and thermogravimetry to obtain the drying curve. Three different plastic clays were used in the four formulations investigated, as well as three heating rates with a total time of 60 min and a maximum drying temperature of 200 °C: 5.83, 3.89, and 2.92 °C/min. Based on the results obtained from the modified Bigot curves, a fast-drying curve (3 °C/min) was established in a static laboratory dryer with a total cycle of 60 min and a maximum temperature of 160 °C. The samples were characterised in terms of compressive resistance and visual aspects related to drying cracks. Formulation F5, containing 50 wt% AM clay and 50 wt% AV clay, exhibited the worst performance in fast-drying with drying cracks, whereas formulation F7, containing 33.3 wt% AC clay, 33.3 wt% AM clay and 33.3 wt% AV clay, exhibited the best performance. Formulations F7 and F8 (16.7 wt% of AC clay, 66.6 wt% of AM clay and 16.7 wt% of AV clay) were fired at 900 °C in an electric kiln, with a heating rate of 1.5 °C/min and a 2 h holding time, and then characterised in terms of firing shrinkage, water absorption and compressive strength. The results showed that Formulation F7 presented suitable behaviour in the fast-drying process at 160 °C for 60 min in a laboratory dryer at a heating rate of 3 °C/min, 0.9 wt% a residual moisture. It exhibited no drying cracks and a dry compressive strength of 0.94 ± 0.09 MPa. However, the combined analysis of optical dilatometry and thermogravimetry indicated that the drying conditions could be optimised for a residual moisture of 2 wt%, using a thermal cycle of 138 °C for 19 min (heating rate of 5.83 °C/min) if adequate control of the humidity of the chamber atmosphere in the first drying stage is employed to avoid drying cracks. The results also showed that the specimens of formulations F7 and F8 met the technological requirements defined by the Brazilian standard ABNT NBR 15270-1, demonstrating the feasibility of producing red ceramic bricks by extrusion with fast-drying. The combined optical dilatometry and thermogravimetry techniques used to obtain the Bigot curve applied to fast-drying showed very good agreement with those obtained in the laboratory dryer. These combined techniques represent promising approaches for studying the fast-drying of red ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

PrBaFe 2 O 6–δ (PBF) is considered as a promising material for mixed ionic-electronic conductors used in high-temperature applications. In the present work, PBF was used as a basis for two chemical modification approaches, including doping with cobalt, nickel and copper, as well as composite design with the addition of a BaCe 0.8 Sm 0.2 O 3–δ phase. The single-phase and composite materials were successfully prepared and characterized in terms of their functional properties. The two approaches were found to synergistically affect the functional properties of PBF, allowing a trade-off between thermomechanical and transport properties to be achieved. As a result, the prepared 70 wt% PrBaFe 1.9 M 0.1 O 6–δ (M = Co, Ni, Cu) + 30 wt% BaCe 0.8 Sm 0.2 O 3–δ composites exhibit acceptable electrochemical activity in the intermediate-temperature range. The best electrochemical activity was found for the sample with M = Cu, whose polarization resistance at 700 °C reaches 1.7 Ω cm2. Therefore, the designed PBF-based composites can be considered as promising electrode materials for solid oxide fuel cell applications. [Display omitted] • Homogeneous and heterogeneous doping strategies were used for PrBaFe 2 O 6–δ (PBF). • A partial substitution of iron-ions in PBF with nickel, cobalt or copper is made. • The Cu- and Ni-containing PBF samples exhibit better conductivity and reduced TECs. • Further modification of doped PBF is performed to create composite materials. • The as-prepared composites show acceptable polarization resistance values. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

In the present work the bulk-diffusion problem of electrochemically inserted solute particles, e.g. hydrogen, in planar or cylindrical electrodes is treated with a boundary condition, which considers simultaneously both a sinusoidal modulation of the particle flux as well as the reaction rate of particle insertion into the electrode. By solving this diffusion–reaction model with superimposed modulation the solute concentration inside the sample as well as the particle flux is obtained. For application to electrochemical charging, this flux is related to that which follows from the Butler-Volmer equation. The phase shift between the surface solute concentration modulated by electrochemical means and the bulk particle concentration provides information whether the particle flux through the electrode-electrolyte interface is influenced more strongly by the insertion reaction or the subsequent diffusion inside the electrode. The spatial and temporal concentration evolution within the sample is analysed. The present model catches not only the modulation behaviour in a stationary state but also the transient behaviour. Furthermore, the faradaic impedance, derived from the current density across the interface, intrinsically contains both, the interfacial transfer resistance and the diffusion impedance. The presented diffusion–reaction model is not only suitable to study solute insertion in electrodes and subsequent diffusion phenomena in the field of electrochemistry, but can also be applied for other types of loading, e.g. from the gas phase, and to other measuring techniques, e.g. dilatometry. [ABSTRACT FROM AUTHOR]

This study investigates the tempering behavior of bainite and martensite in a medium carbon, high silicon steel, with a focus on the microstructural evolution and the attainment of equilibrium, over a temperature range of 200–650 °C. The dissimilarities between the characteristics of the two initial microstructures, both comprising a C-saturated tetragonal ferrite matrix and retained austenite, are reflected in the differences observed in their evolution towards equilibrium as the tempering temperature increases. Therefore, while retained austenite plays a pivotal role in the bainitic microstructure, in the martensitic microstructure it is the ferritic matrix, which is highly dislocated and enriched in carbon, that plays a determinant role. The findings demonstrate that while both bainite and martensite can converge towards the same equilibrium state upon high-temperature tempering (600–650 °C), the pathway to this convergence is markedly different, with bainite exhibiting a slower transformation rate. This path to equilibrium has been characterised by means of high-resolution dilatometry, scanning electron microscopy and detailed X-ray diffraction analysis. This has provided a dynamic and detailed picture of the most relevant microstructural changes and tempering mechanisms in high silicon steels. It has also provided a foundation for tailoring heat treatment processes to optimise the mechanical properties of advanced bainitic and martensitic steels.

The paper presents the results of research on the influence of the material condition – HSLA steel with Ti and Nb microadditions – on the course of the austenitic transformation. In order to determine the kinetics of phase transformations occur in steel during individual stages of the austenitic transformation, tests were carried out using a Bähr 805 A/D dilatometer. In order to determine the influence of hot plastic deformation on the course of the austenitic transformation, plastometric tests were carried out using the Gleeble 3800 thermomechanical simulator. For detailed microstructural analysis, microscopic examinations were carried out using the light microscope and the scanning electron microscope. The obtained results were compared with hardness measurements. The tests carried out showed significant differences in the course of the austenitic transformation and the values of critical temperatures for steel before and after using the plastic deformation. The Ac1 temperature for steel in the as-cast state is 850°C and the Ac3 temperature is 950°C. As the annealing temperature increases, the hardness increases from 210 HV100 for a temperature of 700°C to 260 HV100 for a temperature of 920°C. Knowledge about the phase transformations of supercooled austenite is extremely important, especially for newly developed steels, hence the aim of the work is to analyze the atypical course of the austenitic transformation of HSLA steels and to determine the influence of deformation on the austenitic transformation during heating.

Low-carbon Cr-Ni-Mo steels widely used in mechanical engineering are studied: 18Kh2N4MA, 25Kh2N4MA, 25KhN3MA. Thermokinetic diagrams are plotted by a dilatometric method. Temperature-time ranges for microstructure constituent formation are established. It is shown that bainite within the steels studied may be formed both above and below the Ms temperature. Features of isothermal bainite transformation are investigated, kinetics of bainite transformation are determined, as well as the quantitative ratio of microstructure constituents formed as a result of austempering. It is established that the largest amount of bainite within the steel structures studied (80–95%) is achieved at a temperature near Ms. Mechanical properties (strength, ductility, impact strength) of the steels being studied are analyzed after various heat treatment methods: various cooling intensities, upper and lower bainite austempering. It is shown that formation of upper bainite has an ambiguous effect on steel impact strength. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the influence of the material condition - HSLA steel with Ti and Nb microadditions - on the course of the austenitic transformation. In order to determine the kinetics of phase transformations occur in steel during individual stages of the austenitic transformation, tests were carried out using a Bähr 805 A/D dilatometer. In turn, the influence of hot plastic deformation on the course of the austenitic transformation, were determined via plastometric tests carried out using the Gleeble 3800 thermomechanical simulator. For detailed microstructural analysis, microscopic examinations were carried out using the light microscope and the scanning electron microscope. The obtained results were compared with hardness measurements. The tests carried out showed significant differences in the course of the austenitic transformation and the values of critical temperatures for steel before and after using the plastic deformation. The Ac1 temperature for steel in the as-cast state is 850 °C and the Ac3 temperature is 950 °C. As the annealing temperature increases, the hardness increases from 210 HV100 for a temperature of 700 °C to 260 HV100 for a temperature of 920 °C. Knowledge about the phase transformations of supercooled austenite is extremely important, especially for newly developed steels, hence the aim of the work was to analyze the atypical course of the austenitic transformation of HSLA steels and to determine the influence of deformation on the austenitic transformation during heating. [ABSTRACT FROM AUTHOR]

Phase transformations in cold-rolled (CR) 304L austenitic stainless steel were studied using different techniques, including dilatometry, X-ray diffraction and scanning electron microscopy. During continuous annealing, the dilatometric measurements indicated that the evolution of the deformed microstructures led to an important anomaly constituted of two contractions. Quantitative processing of the X-ray diffraction results allowed the determination of the temperature-dependence of α′-martensite and austenite (γ), phase fractions, dislocations density and lattice strains on heating to 900°C. It is demonstrated that the first contraction is due to the recovery of α′- and γ-phases. In this temperature range, it is suggested that the recovery in CR γ has caused the growth of surrounding α′ particles which competes with the reversion of the smallest α′ particles. The second contraction, on the other hand, has been attributed to the α′ reversion and recrystallization in CR γ regions. [ABSTRACT FROM AUTHOR]

In this study, technical properties of 3 different clays from Doğanhisar/Konya region were determined to investigate their usage potential in glazed porcelain tile production of Yurtbay Seramik Company. For this purpose, mineralogical, chemical, and thermal characterization of the clays was performed using XRD, XRF, and dilatometric analyses. Furthermore, the use of Konya clays instead of Ukrainian clay in the porcelain tile compositions was studied. Ukrainian clay was substituted gradually by Konya clays in different tile body recipes. Samples, having these new compositions, were prepared by uniaxial pressing, and exposing to a firing regime at 1190 °C for 55 min. Fired samples were then characterized based on their dry strength, fired strength, water absorption, color, and firing shrinkage properties. Experimental results proved that the use of Konya clays instead of Ukrainian clay increased the strength of fired bodies. It would be possible to use Konya clays in tile bodies up to 6 wt.% with some modifications in the body compositions and firing regime. [ABSTRACT FROM AUTHOR]

The study of white cement-based mortar mixtures prepared according to ASTM C-109 with self-cleaning and heterogeneous photocatalytic properties after seven days of curing, prepared by mixing white cement 30 CPC 30 RB, water, and silica, is presented here. To achieve the self-cleaning property, titanium dioxide TiO2 P25 with a crystal structure of anatase and rutile (80:20) and particle size of 20 nm were added by weight proportion of 0.5, 1, 3.0, and 5.0%. X-ray diffraction and scanning electron microscopy coupled with structural characterization revealed that the material which presents the highest degree of cleanliness was the one containing 5% TiO2 because the presence of the photocatalyst gives a stronger self-cleaning property to the cement-based material, achieving a 26% degradation of Rhodamine B after 8 h of sun exposure. In addition, it was found that the cement containing TiO2 presented a compressive strength 8–12% lower than the reference material without TiO2. The thermal expansion coefficient of the specimens was 7.4 × 10–6 K−1. It is concluded that itis possible to obtain self-cleaning cement-based materials without affecting their physical–mechanical properties and maintain the expansion coefficient. [ABSTRACT FROM AUTHOR]

The work explores the phase transformation sequence and the kinetics of ω formation in a novel metastable β titanium alloy of Ti–3Al–5Mo–7V–3Cr (wt%) through dilatometer test and phase/microstructure characterizations. The phase transformation sequence has been identified as β → β + ω, β + ω → α + β, β → β + α, and α → β during the continuous heating. The formation of ω phase has underwent nucleation and growth stages revealed by the S-shaped kinetic curve. The diffusion controlled mechanism has been analyzed via Avrami exponent. The average activation energy for β → β + ω phase transformation has been evaluated 90.42 kJ/mol via Kissinger–Akahira–Sunose equation. The activation energy difference between early and late stages of ω formation has been compared among metastable β titanium alloys. The small value of Ti-3573 alloy may imply a thermo-kinetic inconvenience of ω assisted α formation.

The effect of austenite grain on the phase transformation of low‐carbon microalloyed steel during continuous cooling is investigated by using Gleeble thermal simulator. The austenite grain size is changed by altering the holding period at the peak temperature. The findings demonstrate that for a given cooling rate, the longer the holding time, the microstructure becomes finer, and bainite begins to show up in the microstructure. The critical temperature of phase transformation and the diagram of phase transformation reaction rate during continuous cooling are determined by dilatometry. The Johnson–Mehl–Avrami–Kolmogorov equation is used to fit the transformation volume fraction, and the variation of kinetic parameters k and n with prior austenite grain size under nonisothermal condition is determined. The n value is trending downward as the prior austenite grain size increases, while the kinetic parameter k barely changes at all. The activation energy of phase transition is calculated by Kissinger method. The activation energy of fine austenite grain increases from 248.6 to 286.3 kJ mol−1 with the increase of austenite grain size, while the activation energy of coarse austenite grain decreases to 176.5 kJ mol−1 due to the competitive nucleation mechanism. [ABSTRACT FROM AUTHOR]

A dilatometric study of supercooled austenite transformation in steel 20Kh2G2SNMA is conducted during various stepwise quenching versions with exposure in the martensitic region. Processes occurring during single-stage, two-stage quenching, and stepwise quenching with tempering are studied. It is shown that two-stage quenching makes it possible to stabilize up to 14% of retained austenite at room temperature within the structure of the steel studied. Values of mechanical properties (strength, ductility, impact strength) are determined. It is established that quenching of the steel studied and partitioning provides higher strength and elongation indices compared to oil quenching and low-temperature tempering with lower values of relative reduction of area and impact strength. [ABSTRACT FROM AUTHOR]

The complexity of gas pressure liquid phase sintering (GPS-LPS) of silicon nitride induces a certain savoir-faire. This highly challenging strong bond ceramic uses sintering additives of a liquid phase sintering under high temperatures close to the silicon nitride phase decomposition which requires a gas pressure. The sintering behavior encompasses various phenomena such as Ostwald ripening grain growth, phase transition, and swelling when the pore elimination approach close porosity. The aim of this study was to model such sintering behavior. In this aim, master sintering curves (MSC) were used to study the temperature and porosity dependence of the sintering model. Then, the grain growth sensitivity of the sintering model was incorporated. Finally, the swelling phenomenon responsible for transient de-densification and sintering rate limiting mechanism at final stage sintering was extracted by an inverse method. A comprehensive sintering model reproducing all the silicon nitride sintering complexity result this study. [Display omitted] • Gas pressure liquid phase sintering of silicon nitride. • Sintering kinetics analysis from optical dilatometry. • Comprehensive simulation of sintering with a sensitivity to grain growth and swelling phenomena. [ABSTRACT FROM AUTHOR]

A novel concept, consisting of the stabilization of retained austenite with Ni, Al, and Cu additions instead of using Si as the major alloying element to prevent carbide formation, is proposed to design nanocrystalline, cementite-free bainitic steels. In this work, the novel steel (wt.%) Fe-0.40C-0.50Mn-8.0Ni-2.65Al-0.8Cu was designed. Dilatometry investigations were performed to obtain the experimental CCT and TTT diagrams for this material. It was concluded that the bainitic reaction occurs between 400 and 225 °C during a transformation time ranging from 2 h to 66.5 h, respectively. An in-depth analysis performed on the resulting materials confirmed the presence of an ultrafine structure free of cementite consisting of carbon supersaturated laths of tetragonal bainitic ferrite and retained austenite with thin film and block morphologies. The use of Ni, Al and Cu as alloying elements leads to high carbon content in both populations of retained austenite, which prevents, the formation of fresh martensite during cooling to room temperature. The results of this research constitute a novel insight into the design of ultra-fine, cementite-free bainitic steels.

Li 2 TiO 3 (lithium titanate) is a material of interest in the field of fusion reactors due to its potential application as a tritium breeder material. Because of the extreme working conditions and temperature gradients involved, thermal expansion properties are critical to consider when assessing a material for a fusion reactor. The reactor is subjected to severe neutron flux, high temperature and thermal cycling, which can cause significant stress on the material. A low coefficient of thermal expansion (CTE) of Li 2 TiO 3 is important as it mitigates mechanical stress and minimized the risk of structural damage resulting from thermal cycling. Material degradation, cracking, or delamination might result from a mismatch in CTE between different materials in the reactor. Therefore the estimations of material's thermal expansion properties hold significance for the designing and fabrication of structural material. In this study, Li 2 TiO 3 material was compacted into pellets and high-temperature X-ray diffraction (HT-XRD) was employed to obtain X-ray diffraction patterns from room temperature to 1273 K at 100 K intervals. The lattice parameters (a, b, and c) of Li 2 TiO 3 polycrystals were determined and corresponding unit cell volumes were estimated at each temperature. The thermal expansion percentages for the lattice parameters a, b, and c between room temperature and 1273 K were found to be 1.21%, 1.84%, and 1.83% respectively. The calculated coefficient of thermal expansion (CTE) were determined as 12.5 × 10−6 K−1, 19 × 10−6 K−1, and 18.9 × 10−6 K−1for lattice parameters a, b and c respectively. The crystallographic density at room temperature was estimated to be 3.42 g/cm3. The molar volume was calculated to range between 32.12 and 33.72 cm3/mol from room temperature to 1273 K. Additionally, high-temperature dilatometry was employed to measure the thermal expansion of Li 2 TiO 3 , resulting in the estimation of coefficient of thermal expansion. From room temperature to 1290 K, the thermal expansion percentage and mean coefficient of thermal expansion were calculated to be 1.91% and 19.64 × 10−6 1/K, respectively. Furthermore, the temperature dependent mean and instantaneous thermal expansion values were also determined. The differential scanning calorimetry (DSC) method was used to estimate the temperature of the monoclinic to cubic transformation, which was determined to be 1416 K. This paper provides a comprehensive description of the conducted experiments, accompanied by the detailed analysis of the thermal expansion properties derived through the use of High-Temperature X-Ray Diffraction (HT-XRD) and HT-dilatometry (High-Temperature Dilatometry). [ABSTRACT FROM AUTHOR]

Special features of structural and phase transformations, position of critical points, quantitative parameters of the structure, and hardness under continuous transformation of supercooled austenite in steels 30KhNMFRA, 30KhGNMFRA and 30KhN3MFRA are determined. Thermokinetic diagrams of decomposition of supercooled austenite in the steels are plotted using a Gleeble 3500 research complex. Recommendations are developed for selection of chemical composition and cooling rate for billets in order to provide a high strength and enough impact toughness of the steels after quenching and low tempering. The results may be used for development of high-strength cold-resistant steels and modes of their heat hardening. [ABSTRACT FROM AUTHOR]

Ceramic composites (1 – x)ZrSiO4–xZrO2 with low thermal conductivity were obtained by sintering nanosized powders in the range 1000 – 1300°C in air. The fracture surface of ceramic samples was studied using electron microscopy after sintering at 1300°C; their thermal behavior, by dilatometry. The chemical resistance of the composites was evaluated by leaching in distilled water. In the future, such ceramic composites can be used as matrices for long-term environmentally safe storage and subsequent final isolation from the environment of individual isotopes of the actinide(rare-earth fraction of high-level waste (HLW). [ABSTRACT FROM AUTHOR]

Ultra‐stable amorphous fluoropolymers glasses were created using vacuum pyrolysis deposition (VPD). Glass films with thickness ranging from 90 to 160 nm were grown at a substrate temperature of 0.86 Tg, where Tg is the glass transition temperature of the virgin polymer and is in units of K. Atomic force microscope (AFM) dilatometry measurements were conducted to investigate density behavior of the ultra‐stable glasses. Thickness measurements were made in stepwise fashion over a range of temperatures from ambient to above the Tg. Results show that the intersections of the line for the equilibrium liquid and those for the rejuvenated and stable glasses identifying the fictive temperature Tf result in Tf, rejuvenated = 347.3 K and Tf, stable = 269.5 K, that is, nearly 80 K below the Tg of the rejuvenated material and well below the notional Kauzmann temperature as estimated from the Vogel‐Fultcher‐Tammann (VFT) analysis of the cooling rate dependence of the calorimetric glass transition temperature reported previously. The results corroborate the published calorimetric results on the same ultra‐stable fluoropolymer glasses that witnessed Tf reductions of up to 62.6 K below the Tg of the rejuvenated system. In addition, to demonstrate the versatility of the AFM dilatometry methodology for the thin film response, isothermal de‐aging experiments were carried out to illustrate the devitrification kinetics. We also carried out one of the Kovacs' signature key experiments, the asymmetry of approach, to further illustrate the method. [ABSTRACT FROM AUTHOR]

The tempering kinetics in a Cr–Mo–V medium-carbon low-alloy martensitic steel was determined by an analytical kinetic model of isochronous conversion and differential dilatometry under non-isothermal conditions. The tempering zone associated with stages II and III, and the degree of tempering was determined by dilatometric analysis and the lever rule on the transformation zone. In a first approximation, the effective activation energy was determined by a Kissinger-type method considering the criterion of peak temperatures at the points of the maximum rate. The Kissinger-type method demonstrated the presence of two overlapping stages. The isochronous conversion analytical kinetic model was proposed to separate and determine the tempering parameters, effective activation energy, and growth exponent by stages and as a function of temperature and tempering degree. The kinetic parameters calculated with the Kissinger-type method were consistent with those obtained with the isochronous conversion method. However, the isochronous conversion method allowed identifying the behavior of the parameters as a function of temperature and transformation degree during tempering. In contrast, with the Kissinger-type method, the parameters were constant throughout the transformation range. Finally, the isothermal conversion diagrams were constructed for each stage, emulating fast tempering conditions, and demonstrating the congruence between the kinetic parameters from continuous to isothermal conditions. [ABSTRACT FROM AUTHOR]

Metallic diamond (MD) is a new alloy class which hardness was found to surpass any current alloys at more than a twofold factor, up to 2500 HV (kgf mm−2). The alloy design employs simple metallurgical principles at the so-called Lattice Occupancy Project aided by Diamoy 1.0 software. The most important aspect of the alloy project considers the maximization of chromium equivalent values by selecting metallic elements for promoting body-centred cubic structures. Forming these alloys into parts is challenging, whereas powder metallurgy techniques appear as valid processing routes. The work studies the sintering behaviour of MD-4 and 5 alloy powders, being the hardest MD ones. High energy milled powder compacts were sintered in a dilatometer up to 1500 °C for 1 h under Ar-10%H2 atmosphere. Alloy MD-5 has shown intense shrinkage starting at 1150 °C, contrasting to marginal sintering of alloy MD-4. The latter has undergone transformations from 400 °C with strong expansion, which seems to block most of the sintering retraction at higher temperatures. Alloy powder MD-5 is a good candidate as a raw material for tool parts production by powder metallurgy, which can compete with cemented carbide hard tools. [ABSTRACT FROM AUTHOR]

Dilatometric experiments were conducted with the main purpose of measuring the transformation-induced coefficients of 13% chromium and 4% nickel, which are martensitic stainless steel base and filler materials used for hydraulic turbine manufacturing. To this end, a set of experiments was conducted in a quenching dilatometer equipped with loading capabilities. The measurement system was further improved by means of modified pushrods to allow for the use of specimens with geometries that are compliant with tensile test standards. This improvement allowed for the measurement of the materials' phases and respective yield strengths. The dataset was further used to determine the relationship between the applied external stress and the martensitic start temperature ( M s ) upon cooling. The TRIP coefficient's K values for both the S41500 steel and E410NiMo filler material were measured at 8.12 × 10 − 5 and 7.11 × 10 − 5 , respectively. Additionally, the solid phase transformation model parameters for both the austenitic and martensitic transformation of the filler material were measured. These parameters were then used to model austenitic-phase-transformation kinetics and martensite transformation, including transformation-induced plasticity effects. Good agreement was achieved between the calculation and the experiments. [ABSTRACT FROM AUTHOR]

Despite the large number of studies on the development of multilayered composites using accumulative roll bonding method (ARB), there are not enough available details concerning the effect of the temperature variation on the constituent layer microstructure and the nature and kinetics of the developed intermetallic compounds. The present work aims to process an Al/IF steel multilayered composite using ARB and to understand the effect of non-isothermal heating on its structural evolution. The elaborated material is characterized by using thermal Differential Dilatometry (DD), Scanning Electronic Microscopy (SEM) and x-ray Diffraction (XRD). The progress of the ARB leads to the dispersion of the Fe layers between the Al layers and does not lead to the formation of diffusion layer. The continuous heating leads, for temperature lower than 330 °C, to the occurrence of the recovery reaction in the Al layers, which produces a big contraction and causes a partial softening of the material. The formation of the intermetallic compound Al5Fe2 seems to occur at higher temperatures and leads to a significant expansion of the material. This effect is explained by the increase in the atomic specific volume. [ABSTRACT FROM AUTHOR]

A dilatometric study of the bainite transformation in 20Kh2G2SNMA steel during isothermal holding in the temperature range of 280–380°C was carried out. The kinetics of the bainite transformation is determined, and the values of the coefficients k and n of the Austin–Rickett equation are established. The fraction of retained austenite in the steel structure following isothermal hardening was estimated using X-ray diffraction analysis. It is shown that, at 320°C and higher, the carbon content in retained austenite is in satisfactory agreement with the theoretically predicted values, and below 320°C, there is a discrepancy associated with slower bainite transformation and carbon partitioning. A correlation has been established between the impact strength, the fraction of bainite and retained austenite, and the carbon content in the latter. It is shown that with an increase in the fraction of bainite during isothermal holding, the fraction of retained austenite in steel increases, and the carbon content in it decreases, which adversely affects the impact strength of steel. [ABSTRACT FROM AUTHOR]

Isothermal bainitic transformation is studied in commercial and experimental alloy steels of various compositions using dilatometry. The effect of the conditions of cooling to the temperature of isothermal quenching on the subsequent kinetics of the bainitic transformation is considered. The experimental kinetics of formation of bainite is described with the help of the Austin–Rickett (AR) equation. The temperature dependence of parameters n and ln (k) in the AR equation and their linear interrelationship are presented. It is shown that the dependences n = f [ln (k)] differ for steels of specific classes, and the difference may be associated with different stabilities of the supercooled austenite. It is shown that in a number of cases the kinetics of the isothermal bainitic transformation is describable adequately by the Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation. The suggested differential equation generalizing the AR and KJMA equations makes it possible to describe the kinetics of formation of bainite the most accurately. [ABSTRACT FROM AUTHOR]

The key thermophysical properties necessary for the successful design and use of CoCrFeNi alloy in thermophysical applications have been measured experimentally, and the results have been compared with literature values and results previously obtained for commercial Ni-Cr alloys and equiatomic CoCrFeNi alloy. In particular, the thermal diffusivity, coefficient of thermal expansion (CTE), and specific heat capacity were measured for the as-cast and homogenized equiatomic CoCrFeNi alloy over a temperature range allowing the thermal conductivity to be calculated up to 1173 K. The thermal conductivity and thermal diffusivity of the equiatomic CoCrFeNi alloy were found to deviate from monotonic behavior in the temperature range from 773 to 1100 K. Such a deviation was previously observed in the behavior of the temperature dependence of CTE and specific heat capacity of the equiatomic CoCrFeNi alloy. The non-linear behavior is primarily the result of order/disorder phenomena for the as-cast and homogenized sample, as well as non-equilibrium solidification under arc melting conditions for the as-cast sample. The measured data of thermophysical properties are provided for thermally differently treated samples, and it is shown that there is a difference in the behavior of the temperature dependences of CTE, thermal diffusivity, and heat capacity. [ABSTRACT FROM AUTHOR]

The unusual behavior observed in the coefficient of thermal expansion and specific heat capacity of CrFeNi, CoCrNi, and CoCrFeNi medium/high-entropy alloys is commonly referred to as the K-state effect. It is shown to be independent of the Curie temperature, as demonstrated by temperature-dependent magnetic moment measurements. CoCrFeNi alloy is chosen for detailed characterization; potential reasons for the K-state effect such as texture, recrystallization, and second-phase precipitation are ruled out. An examination of the electronic structure indicates the formation of a pseudo-gap in the Density of States, which suggests a specific chemical interaction between Ni and Cr atoms upon alloying. Hybrid Monte Carlo/Molecular Dynamic (MC/MD) simulations indicate the presence of non-negligible chemical short-range order (CSRO). Local lattice distortions are shown to be negligible, although deviations around Cr and Ni elements from those expected in a fully disordered structure are experimentally observed by X-ray absorption spectroscopy. The determined bonding distances are in good agreement with MC/MD calculations. A mechanism is proposed to explain the anomalies and calorimetric experiments and their results are used to validate the mechanism.

It was found that the high decomposition temperature of amorphous Al(OH)3 makes it possible to sinter corundum ceramics directly from aluminum hydroxide, bypassing the stage of its preliminary thermal dehydration. Using the cold isostatic pressing method at 200, 600, and 1000 MPa, compacts with densities of 62, 69, and 79% of the theoretical value were obtained. The temperature dependence of the shrinkage of amorphous Al(OH)3 compacts was studied as a function of the cold isostatic pressing pressure. An area of intense shrinkage was discovered in the range 1050 – 1150°C, which coincides with both the temperature of complete decomposition of amorphous Al(OH)3 and the transition γ → α-Al2O3. [ABSTRACT FROM AUTHOR]

The quality of the castings depends, among other influences, on the quality of the moulding mixture used. The silica sands used are characterized by high thermal expansion compared to other sands. The tendency to dilatation of the moulding mixture can be influenced by the choice of the granulometric composition of the basic sand and the grain size. The aim of this work is to present the influence of grain distribution of foundry silica sand BG 21 from Biala Góra (Poland) and the degree of sorting (unsorted, monofraction, polyfraction) on the degree of thermal dilatation of the sand and thus on the resulting quality of the casting and susceptibility to foundry defects. For the purpose of measuring thermal dilatation, clay wash analysis was performed, sieve analysis of the sand was carried out, and individual sand fractions were carefully sorted. The measurements confirmed a higher thermal expansion in the case of monofractional sand grading, up to 51.8 %. Therefore, a higher risk of foundry stress-strain defects, such as veining, can be assumed.

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.

The sequence of structural changes produced in two deformed microstructures of austenitic stainless steel elaborated by a multipass unidirectional cold rolling (CR) and a two‐step one, to a 75% thickness reduction, is followed by dilatometric experiments. The two materials show different dilatometric behaviors. X‐ray diffraction and microhardness measurements are performed to underlie the observed dilatometric behaviors. The material subjected to multipass unidirectional CR shows an unusual dilatometric behavior. The first heating stage leads to the occurrence of the recovery reaction in competition with the ε‐martensite reversion. When the temperature increases between 550 and 780 °C, the reversion of deformation‐induced α‐martensite takes place and leads to a complicated dilatometric anomaly. Further increase in temperature leads to the occurrence of the recrystallization transformation. However, the material subjected to two‐step CR shows a quite usual dilatometric behavior which is explained by the occurrence of several reactions in the following order: 1) T < 300 °C, the recovery reaction, 2) 300 < T < 680 °C, the ferro‐ to paramagnetic transformation of α‐martensite, the reversion of ε‐martensite, and the athermal reversion of α‐martensite, 3) 680 < T < 760 °C, thermal reversion of DIM, and then 4) at T > 760 °C, the recrystallization. [ABSTRACT FROM AUTHOR]

The kinetics of structural transformations in compacted graphite iron (CGI) during austempering has not been well studied, whereas its understanding is important for the reliable formation of the desired microstructures and consumer properties in austempered CGI. For this purpose, comparative dilatometry experiments have been performed on CGI and ductile iron (SGI) having various and approximately the same complex of alloying elements from the point of view of industrial technology. Using the typical austenitization temperature for SGI austempering at 900 °C and heating and cooling rates of 4 °C/min and 1 °C/min, it was found that CGI austenitization processes are much faster and at lower temperatures, so that the industrial technology of CGI austempering can be conducted at lower time and energy costs than SGI austempering. [ABSTRACT FROM AUTHOR]

The steel 30CrMnSiNiWMo used in the aircraft industry is studied. The temperature and time ranges of austenite transformation during continuous cooling are established using the dilatometric method. The dilatometric modeling of various modes of quenching–partitioning and austempering heat treatment is carried out. The features of transformations occurring in the studied steel at different stages of the heat treatment are revealed. The analysis of mechanical properties after austempering, quenching–partitioning and oil quenching and tempering is carried out. It is shown that the implementation of isothermal hardening does not lead to the expected increase in the level of mechanical properties of the studied steel. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of cryogenic treatment on the microstructure and properties of high-strength D6AC steel with a bainite and martensite structure. The transformations occurring in steel during heat treatment above and below 0°C was dilatometrically studied. Cryogenic treatment in liquid nitrogen is shown to lead to almost complete restoration of the sample size, which indicates a decrease in the fraction of retained austenite in the structure. This is confirmed by the results of X-ray diffraction analysis. Cryogenic treatment is established to lead to increasing the strength properties and reducing the ductility of D6AC steel. [ABSTRACT FROM AUTHOR]

This study aimed to explore the thermostructural properties of high-density polyethylene (HDPE) reinforced with multi-wall carbon nanotubes (MWCNTs) at various concentrations. Utilizing a range of analytical techniques, including X-ray diffraction, Raman spectroscopy, infrared spectroscopy, differential scanning calorimetry, thermogravimetry, and dilatometry, we found that the crystallinity of the HDPE samples slightly varied with the concentration of MWCNTs. Furthermore, the mass loss measurements showed that MWCNTs played a stabilizing role in the samples. Our results also indicated the anisotropic nature of the samples and the dominance of the polyethylene phase. Notably, this study provides an in-depth examination of the thermal expansion coefficient Alpha in two directions for HDPE reinforced with MWCNTs, a topic that has been largely overlooked in the literature. Our findings significantly advance our understanding of the thermostructural properties of these materials and have important implications for future research and practical applications. [ABSTRACT FROM AUTHOR]

The work was aimed to study the influence of multi-walled carbon nanotubes (MWCNT) on the thermostructural properties of aluminum matrix in a wide temperature range from 30 to 600 °C. To achieve this aim, a nanomaterial with a composition of Al + 1.5% MWCNT was elaborated by sintering and rolling from aluminum and MWCNT powders. This material has to combine the ductility and lightness of aluminum with the toughness and thermal properties of MWCNT, and it can replace classical metal materials. The mechanical and structural properties of Al + 1.5% MWCNT material were studied using different techniques: differential scanning calorimetry, X-ray diffraction, thermogravimetry, Raman spectroscopy, and dilatometry. The reaction between an Al matrix and nanotubes leads to the formation of the carbides and some carbon dissolution in the matrix's crystal network. These reactions also lead to a refinement of the matrix grain and a more homogeneous distribution of the residual MWCNT. These phenomena significantly influence the structure of the matrix as well as the mass and dilatometric stability of the material. Reduction of the dilatometric coefficients of the composite material was observed in the entire temperature range of 30–600 °C, especially a significant reduction was measured for temperatures higher than 200 °C. The results obtained by differential calorimetry showed a noticeable decrease in the calorific capacity of the nanocomposite compared to that of the pure material, especially for temperatures higher than 200 °C. The essential role of anisotropy in determining the thermal expansion characteristics of the nanocomposite was revealed. [ABSTRACT FROM AUTHOR]

High sintered density is desired for heavy-duty applications and there are different ways through which the sintered density can be improved. In the current study, nanopowder is blended to the conventionally used micrometre-sized water-atomised steel powder to evaluate its impact on sintering. Both the powder variants, without and with nanopowder, were subjected to thermogravimetry analysis, and uniaxially compacted to the same green density of 7.15 g/cc or 90% relative density and sintered at 1250°C in pure hydrogen. A comparative analysis was performed with respect to the microstructural evolution between the micro and micro/nano bimodal powder compacts. JMatPro and electron backscattered diffraction was used to understand the microstructural evolution. An attempt was made to understand the improved linear shrinkage in the micro/nano bimodal powder compact using a combination of microstructure analysis and chemical analysis. [ABSTRACT FROM AUTHOR]

Context: As a result of the diversity of microstructures encountered in cis-1,4-polybutadiene and the variety of measurement methods used, experimental values of variation of glass transition temperature (Tg) with pressure are relatively dispersed. However, atomistic simulations enable access to valuable information for very well-controlled chemistry and structures with a well-defined and systematic acquisition protocol. By varying the temperature and pressure, the specific volume of the melt was computed, yielding results that deviated by only 2% from experimental data. A linear relationship between Tg and pressure was observed, with Tg predicted to be 162 K at zero pressure and a rate of change of Tg with respect to pressure (dTg/dP) of 0.24 K/MPa. Method: The atomistic dilatometry experiments were conducted on a model of amorphous cis-1,4 polybutadiene with an approximate molecular weight of 5400 g/mol using the LAMMPS code and the all-atom forcefield pcff +. The dilatometry process involved cooling and heating at a rate of 9 × 1012 K/min. The specific volume was calculated by averaging over seven independent configurations for each temperature. The Tait equation was employed to fit the specific volume evolution within the temperature range of 10 to 700 K under different pressures of 0, 60, and 100 MPa. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the influence of quartz on the main physical and mechanical characteristics of composites based on high-density polyethylene. In order to improve the compatibility and properties of the mixed components of the mixture, a compatibilizer and plasticizer based on low molecular weight polyethylene with a molecular weight of 2500 were used. The selective effect of the compatibilizer and plasticizer on the complex of the most important physicomechanical, thermomechanical, and dilatometric characteristics of composites was studied. [ABSTRACT FROM AUTHOR]