Dilatometric Method Research Articles

Investigation of phase transformation in Fe microalloyed Ti6Al4V alloy during continuous heating process

The phase transformation and dilatometric curves in Fe microalloyed Ti6Al4V alloy (Ti6Al4V-Fe) during continuous heating at 1 ℃ /min heating rate had been studied by dilatometer and metallographic methods, and β phase transition temperatures of alloy were obtained. In order to validate the accuracy of these β phase transition temperature and microstructure evolution, the relative phase concentration and the evolution of microstructure which were acquired by cooling after tempering were analyzed by metallographic microscope. The results illuminated that the expansion method was able to accurately measure the β transformation temperature of Ti6Al4V-Fe alloy. The lathy-shaped α phase decreased significantly disappeared in the range of 838℃ to 988℃, and the α→β phase transformation occurred.

Correlation between crystallinity and thermal expansion in LiAlSiO4 ceramics prepared by spark plasma sintering

LiAlSiO4 (LAS) ceramics are prepared by using the sol-gel method followed by spark plasma sintering. XRD patterns and SEM images verify that the ceramics contain amorphous and LAS phases and that microcracks appear in the sample prepared at 900 °C due to its larger grain size. Compared with applied pressure and soaking time, sintering temperature has a greater impact on the crystallinity and density of the ceramics during sintering. High-temperature XRD results reveal that the LAS phase exhibits its intrinsic negative thermal expansion independently in all samples regardless of crystallinity. The coefficients of thermal expansion (CTE) measured by the dilatometric method change from positive values in samples prepared at 600 and 650 °C to near zero in samples prepared at 700 and 800 °C and then to a negative value in the sample prepared at 900 °C. The combined effects of an amorphous phase with a positive CTE and the LAS phase with a negative CTE are responsible for the observed transformation of thermal expansion in the samples. The calculated total CTEs of the glass-ceramic bulks are in agreement with the results measured through the dilatometric method in samples prepared at 650–800 °C. Microcracks in the sample prepared at 900 °C cause a more negative bulk CTE than the calculated CTE.

An investigation into the effects of HIP after sintering of WC-ZrC-Co-Cr3C2 cemented carbides

The sintering behaviour of cemented carbides based on WC-ZrC-Co-Cr3C2 powder mixtures have been analyzed by dilatometric and calorimetric methods for different cobalt contents and WC/ZrC ratios. As expected, powder oxide reduction in these compositions is mainly of carbothermic nature. However, depending on the milling conditions, some highly stable Zr-rich oxides are retained in the binder phase after sintering. Hot isostatic pressing (HIP) cycles have been successfully applied for closing residual porosity after vacuum sintering. For a fixed amount of binder phase and a WC/ZrC ratio, the hardness of these materials depends on the amount of residual porosity and WC grain growth control. The best combination of hardness and toughness is found for alloys with 8 wt%Co and WC/ZrC wt. ratios of 6.46. HIP treatments induce the formation of a compact and well adhered layer mainly comprised of Zr oxides and WC grains. The cobalt binder phase migrates from this layer towards the sample bulk likely due to the loss of wettability on these Zr rich oxides. Hot hardness is higher for the alloy with higher WC/ZrC ratio suggesting that this property depends on both the volume fraction of (ZrxW1-x)C and WC phases and their degree of contiguity.

Experimental study of the titanium nickelide thermophysical properties complex

The article presents new experimental data on the thermal diffusivity (a), thermal conductivity (λ), heat capacity (Cp) and linear thermal expansion coefficient (α) of titanium nickelide (56.6 wt. % Ni, 43.4 wt. % Ti). The temperature interval from 293 to 872…962 K has been investigated by laser flash technique, method of differential scanning calorimetry and dilatometric method. The estimated errors of the received data were 2–4%, 3–5%, 2–3% and (1.5–2)×10−7 K−1 for a, λ, Cp and α, respectively. The approximation dependences and the reference table of investigated transport, caloric and thermal properties have been obtained.

Thermophysical properties of Inconel 718 alloy

The thermal diffusivity (a), linear thermal expansion coefficient (α), isobaric heat capacity (Cp) and phase transition enthalpy (ΔH) of Inconel 718 superalloy were determined by laser flash method, dilatometric method and differential scanning calorimetry in the temperature range of 298–1375…1473 К. The thermal conductivity (λ) has been calculated from the measurement results. The estimated errors of the obtained data were 2–5%, 3–5%, 2–3% and (1.5–2)×10−7 K−1 for a, λ, Cp and α, respectively. The approximation equations and a table of reference values for the studied properties have been obtained.

Synthesis and Inhibition Performance of a Fe3O4/Chitosan‐Supported Inhibitor

In this work, a magnetic inhibitor (MI) was first prepared by using p‐hydroxybenzaldehyde anchored onto magnetic chitosan (MCS). Its inhibition effect to the free‐radical polymerization was studied. The MI with a size of less than 1 μM was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and thermo gravimetric analysis (TGA). For potential application, MIs have been used to inhibit the thermal polymerization of styrene, and they can be removed from the monomers conveniently by magnetic separation. The corresponding inhibitory effect has been investigated through the measurement of the induction period with the dilatometer method. The results show that the inhibitory effect of MI was eight times higher than that of the nonadditive inhibitor for the equivalent volume of styrene. J. VINYL ADDIT. TECHNOL., 26:304–308, 2020. © 2019 Society of Plastics Engineers

Density and volumetric expansion of the Inconel 718 alloy in solid and liquid states

The density and thermal expansion of the solid and liquid Inconel 718 alloy are measured by the dilatometer method and gamma-ray attenuation technique over the temperature range 293.15–1730 K. The density change during the solid-liquid phase transition is directly measured. A comparison of the obtained results with literature data is carried out.

Density and Molar Volume of Molten GdCl3–NaCl and GdCl3–KCl Binary Mixtures

The densities of the salt melts of the GdCl3–NaCl and GdCl3–KCl systems are determined by the dilatometric method over the entire concentration range and in a wide temperature range. The molar volumes of the systems and their deviations from additivity are calculated. All electrolyte composition dependences are nonlinear. The results can be used in the manufacture of gadolinium and its compounds and for the refinement of the structures of the molten salt systems under study.

STUDY OF THE MICROSTRUCTURE OF MARTENSITE-BAINITE STEELS AND NICKEL ALLOYS WHEN MODELING HEAT TREATMENT MODES USING A DILATOMETRIC METHOD

We present the results obtained using the equipment available at the Center for collective use “Composition, structure, properties of structural and functional alloys” NRC “Kurchatov Institute” — CRISM “Prometey”: DIL 805A/D (TA Instruments) and DIL 402C (Netzsch) dilatometers. Dilatometric analysis which provides determination of the temperature coefficient of linear expansion and the temperature of phase transitions, as well as evaluation of the transformation kinetics, can also allow simulation of heat treatment modes to identify the size of the former austenitic grain using vacuum etching and conduct the research aimed at improving the technology of thermal and thermomechanical processing (TMO) of steels and alloys. The experiments were carried out both in vacuum and in dynamic helium atmosphere. The main methodological difficulties that we have faced with are described. For steels of martensite and martensite-bainite class (38KhMA, 38KhN3MFA, 20Kh3NMFA) conditions of vacuum etching in the chamber of the dilatometer are specified. The efficiency of the method for martensite-bainite steels in determination of the grain size compared to traditional methods of etching is deminstrated. The effect of thermodeformation parameters on the size of austenitic grain is estimated. When modeling the heat treatment modes by the dilatometric method, the microstructure of KhN55MVTs nickel alloy was also analyzed. Changes in the size and morphology of the grain structure at different stages of heat treatment are revealed. The obtained results were used to adjust the current modes of heat treatment and obtain a uniform fine-grained structure. The combined application of dilatometric and metallographic analyzes after vacuum etching of the material decreases the production costs attributed to obtaining the desired microstructure upon thermal and thermomechanical processing of the products and blanks.

DECAY OF SUPERCOOLED AUSTENITE OF LOW-CARBON PIPE STEEL WITH THE USE OF GLEEBLE 3500 COMPLEX

The promising direction in improving the strength properties of low-carbon steels is the use of controlled rolling providing formation of structures with prevalence of a bainite component. Analysis of the references has shown that now there are no detailed researches which allow to approve what morphological type of bainite provides the most optimal properties. In this regard in the present work the influence of cooling rate on the structure, properties, and structuralphase transformations of low-carbon complex-alloyed pipe steel containing 0.062 % C; 1.80 % Mn; 0.12 % Mo; 0.032 % Cr, 0.90 % Ni and other elements (Al, Cu, V, Nb, Ti) was studied. The dilatometric method was used to construct the CCT diagram of the decay of supercooled austenite of low-carbon complex-alloyed pipe steel. The qualitative and quantitative analysis of microstructure was carried out and hardness after various speeds of cooling was determined. There were identified the cooling rates providing bainite structures and increase in the strength properties of steel with specified composition. At a cooling rate since 0.05 to 6 °C/s, along with ferrite, a globular bainite is formed in the microstructure, consisting of bainitic α-phase and “islands” of martensite-austenite component ranging in size from 1 – 6 μm. At a cooling rate of 6 °C/s, conversion to reed bainite is observed, along with the borders of which the carbides and residual austenite are located. At cooling rates of more than 16 °C/s, bainite becomes bag-rack. With an increase in cooling rate from 50 to 150 °C/s, the average width of the bainite α-phase rails decreases from 2.22 to 1.32 μm.

Sorptive Deformation of Porous Sorbents

Deformations of granulated recuperative activated carbon AR-V (produced in granulated form from coal dust (coals mixture) and adhesion agents by steam treatment at the temperature of 1100 — 1200K) upon carbon tetrachloride adsorption has been studied. To solve this problem a dilatometer was used. Its main part was a line differential transformer, the core of which was connected to the adsorbent by means of a rod. Any changes in the adsorbent height caused a change in the core position in the transformer, which influenced the signal recorded from its secondary winding. These results were compared with the adsorption isotherms.Also deformations of cation – substituted vermiculite (Na form) upon water vapor sorption have been studied. The sorbent used was plate – formed, anisotropic, and swelled only in the direction perpendicular to the plane of the plates. The results obtained were compared with the sorption, calorimetry (a Calvet – type microcalorimeter with a microbalance attachment was used) and X-ray data. High sensitivity of the dilatometric method to the structural changes of the laminated silicates whose cell structures expand upon hydration has been shown. The dilatometer used allowed the measurement of absolute deformations in the range 1(10-7 to 3(10-3 m.

Study of the coefficient of heat expansion of TiNbTaZr alloy

This article describes the study of the thermal expansion coefficient of a TiNbTaZr alloy by a dilatometric differential method used to determine phase transformation temperatures. The object of the study was samples of an alloy of TiNbTaZr with a variable composition, which underwent homogenizing annealing and rotary forging. According to the obtained results, all the studied alloys have three temperature regions, which are distinguished in the graphs of uniform elongation with increasing temperature.

Evaluation of the continuous dilatometer method of silicon carbide thermometry for passive irradiation temperature determination

Silicon carbide (SiC) is a primary candidate for passive irradiation temperature monitoring, and continuous dilatometry (CD) has been proposed as the key method for extracting irradiation temperatures from SiC thermometry samples. The CD method was evaluated to determine the sensitivity of the technique to the analysis procedure, as well as its accuracy and precision. Analysis found that the CD method had a ±20 °C sensitivity to the algorithm used to determine the irradiation temperatures. Comparison of the CD method with the continuous length change method for SiC thermometry showed CD is a more viable method of extracting irradiation temperatures. A comparison of irradiation temperatures determined by CD with those from active thermocouple measurements further validated the CD method for accurately and precisely determining irradiation temperatures in materials test reactor irradiations.

Density of magnesium and magnesium-lithium alloys in solid and liquid states

Abstract New experimental data are presented on the density and thermal expansion of solid and liquid magnesium and ultralight magnesium–lithium alloys containing 23.03 and 30.02 at.% Li, respectively. The measurements were performed using the dilatometer method and the gamma-ray attenuation technique in the temperature range from 145 to 1244 K for magnesium and from 293 to ∼1000 K for the alloys. The density changes during the solid−liquid phase transition were directly measured for Mg and the Mg70Li30 alloy. The temperature dependences and reference tables of the investigated volumetric properties were developed. A comparison of the obtained results with literature data was made. The study showed that the eutectic composition in the magnesium− lithium system differs from 23 at.% Li. The concentration dependence of molar volume of the magnesium−lithium liquid system was found to be almost linear in the interval of 0−30 at.% Li and deviated noticeably from the corresponding dependence for an ideal mixture.

VOLUMETRIC CHANGES AT HEATING IN STEEL 60Si2CrV SUBJECTED TO Q&P TREATMENT

The paper presents results of the investigation of phasestructural transformations and volumetric changes that occur during heating in high-silicon spring steel 60Si2CrV subjected to Q&P(quenching and partition) treatment. Chemical composition of the steel was: 0.53 % C; 1.46 % Si; 0.44 % Mn; 0.95 % Cr; 0.10 % V; 0.016 % S; 0.013 % P. Steel samples were subjected to Q-n-P treatment as follows: a) austenitization at 880 °C; b) quenching with the cooling stop at 120, 160, 200 and 240 °C; c) subsequent holding at 220, 250 and 300 °С with duration from 10 to 3600 s; d) final cooling in water. The volumetric changes during heating were studied using an optical differential dilatometer at a heating rate of 1 K/s. As a reference, a sample of the same steel stabilized by high tempering was used. The amount of retained austenite was determined by X-ray diffraction using a diffractometer DRON-3 with Fe-radiation. It is found that on the heating curves of Q&P samples, the sections corresponding to different transformations during tempering are clearly identified. On dilatograms of the Q&P samples, dilatometric effect corresponding to the second transformation during tempering (270 – 430 °C) was found to be increased dramatically, indicating an increase in retained austenite amount compared to the quenched state as a result of Q&P treatment (as confirmed by Xray study). At the same time, value of the effect corresponding to the third transformation during tempering was found to be decreased. To obtain the maximum amount of retained austenite in 60Si2CrV steel, the partitioning temperature should be of 260 – 300 °С, while the quenching completion temperature should be of 160 – 240 °С. The amount of retained austenite rises substantially as the quenching temperature increases. Duration of the partitioning stage should be selected taking into account the extreme character of austenite dependence on the partitioning time. As a result of the work, an effective applicability of the dilatometric method for analyzing the steel structural state and choosing the optimal mode of Q&P treatment was demonstrated.

Austenite Decomposition Kinetics in Laser-Hybrid Welding of Steel of Strength Class K52

A modern technology for joining materials welding is commonly used in various industries. It is a process of interaction of thermal, mechanical and metallurgical properties and behaviors. Complex phenomena, such as solidification, microstructural changes and defect formation, have a great impact on the quality of welded joints. This article presents the results of studying the features of the austenite decomposition kinetics in the application of laser-hybrid welding technology, in a combination with multi-arc automatic submerged arc welding. The cooling rates are determined, affecting the change in properties of HAZ of welded joints on pipe steel of strength class K52. Using the dilatometric method, studies were conducted and thermo-kinetic and structural diagrams were constructed. Analysis of diagrams and microstructures showed that, as a result of the impact of the laser-hybrid welding process in the area of HAZ, the decomposition of austenite occurs mainly in the martensitic zone, followed by the formation of a bainite-perlite structure, due to recrystallization from the heat generated by the facing seams.

H-complexes in the “4-n-alkoxybenzoic acid: 4-pyridyl 4′-n-alkoxybenzoate” system. IR spectroscopy and quantum chemical calculations

IR spectra of individual 4-n-dodecyloxybenzoic acid (A) and 4-pyridyl 4′-n-dodecyloxybenzoate (B) compounds as well as IR spectra of 2A:1B and 1A:1B systems were recorded. For the assignment of the experimental vibrational spectra a series of quantum chemical calculations of DFT(B97-D)/6-311++G** level was carried out. Hydrogen-bonded complexes of types A⋯A, A⋯B, as well as various trimers that can be formed at different component ratios in system A-B were simulated. The geometric structure of these complexes was optimized and the vibrational frequencies were calculated. The conclusions on the molecular organization of system A-B for different ratios of the components A and B were based on the interpretation of IR spectra and the analysis of calculated thermodynamic characteristics of self-assembly processes. Thus, it is determined that the system A consists of cyclic A⋯Acycl dimers; in 1A:1B system the H-complexes of A⋯B type are formed. In the 2A:1B system in the process of self-assembly, instead of the complexes A⋯A⋯B and A⋯B⋯A of stoichiometric composition, the complexes A⋯B and A⋯Acycl are formed in the ratio 2:1. These results are confirmed by the dilatometric method data.

Generalization of the Temperature Dependence of Some Physical Properties of High-strength Polyethylene (HDPE) Using the Method of Given Parameters

In this paper, based on the study of HDPE by dilatometric and rheological methods in a wide range of temperatures and cooling and deformation rates, we generalized the temperature dependence of the physical properties of polyethylene using the specified parameters method. Test specimens (cylinder size: height 12 mm, diameter 9.3 mm) were obtained both in the dilatometer’s test cylinder itself and in a specially designed injection mold using injection molding on a TP-125 injection molding machineThe temperatures in the experiments were added and maintained with an accuracy of 3.2.°C. Defined by The dependence of ρ_0 T_0 / ρT (relative reduced density of the polymer) on the reduced temperature (T - T0). Test specimens (cylinder size: height 12 mm, diameter 9.3 mm) were obtained both in the dilatometer’s test cylinder itself and in a specially designed injection mold using injection molding on a TP-125 injection molding machine. It was found that a reliable characteristic of the dilatometric properties of the crystallizing polymer, physically correctly and completely reflecting the features of the crystalline structure, can be obtained only in the mode of stepwise temperature changes, when at each given temperature the equilibrium value of the specific sample of the primer is fixedThus, the practical value of the dilatometric method for studying crystallizing polymers is shown, especially when comparing the results of dilatometry with the results of rheological studies.

КІНЕТИЧНІ ДОСЛІДЖЕННЯ МЕТАКРИЛОВИХ МОНОМЕРІВ НА ОСНОВІ 2-СТИРИЛХІНОЛІНУ

Polymethylmethacrylate is widely use material in optics due to its atmosphere resistance, chemical stability, good mechanical properties, transparency and light transmission. Due to these properties, PMMA is often used as a polymeric matrix for creating photosensitive polymers and polymers with nonlinear optical (NLO) properties. Materials with NLO properties can be made by introducing moleculas of chromophores into the polymer chain. There are two fundamentally different ways of doing this. The first is to create composite material where the chromophore is a dispersed phase and is introduced into the system as a "guest". In the second case, the chromophore is introduced into the polymer chain covalently, and can be included in the side and the main chain. Studies of polymers containing NLO chromophore in the side chain have shown a number of advantages: better orientation of the chromophores under the action of an electric field; relaxation processes are much slower; increasing time and thermal stability; increasing the glass transition temperature of the polymer. Based on present knowledge we decided to design new methacrylic polymers with styrylquinoline chromophore in side chain. The polymerization ability of the new monomers for free radical homopolymerization was investigated kinetically by using dilatometric method. It was found that new 2-styrylquinoline containing monomers are able to homopolymerization with high conversions (63–83%). The polymerization was carried out in DMF using 2,2´-azobisisobutyronitrile as initiator at 80°C in argon atmosphere. The products of polymerization were characterized by 1H NMR spectroscopy. It was installed that all new monomers have bigger speed of polymerization (Ksum= 1.36–8.33×103 l/mol×s) then methylmethacrylate (Ksum= 0.5×103 l/mol×s), phenylmethacrylate (Ksum= 1.1×103 l/mol×s) and similar to polymerization of 2-methyl-8-oxyquinoline methacrylate (Ksum= 3.28×103 l/mol×s). It was found that speed of polymerization increases with increasing electron donating power of substitute in paraposition of the aromatic ring. It has been proven that presence of electron acceptor group reduces speed of polymerization.

Thermal and mechanical behavior of composite mortars containing natural sorptive clays and fly ash

Mineral additives are extensively applied as cement replacement materials in both construction concrete and mortar. Fly ash is one of the most commonly utilized additives which improve rheological properties, as well as thermal and mechanical behavior of mortar, and as such it has been widely investigated. This industrial byproduct comprises heavy metals in its composition; therefore further research is needed to optimize its effective dosage. Moreover, certain sorptive clays, such as natural zeolite and bentonite, can prevent migration of toxic elements from fly ash by immobilizing them in their structure. Ten experimental mortars are prepared with Portland cement, river sand and addition of fly ash, zeolite and/or bentonite in accordance with chemometric experimental design rules. The aim of the study was to investigate the effect of mineral additives on thermal and mechanical performances of mortar. Thermal characteristics were monitored via dilatometric analysis and DTA method. Principal component analysis was used on the results of physico-mechanical testing (workability, bulk density, water absorption, shrinkage, compressive and flexural strength) to enable the divisions of the observed samples into groups in the factor space. The performance of Artificial Neural Network was compared with the experimental data in order to develop rapid and accurate method for prediction of mechanical parameters of mortar. The ANN model showed high overall prediction accuracy (r2 = 0.989, during training cycle). The test results indicate that incorporation of the mineral additives gave cost effective mortars with sufficiently good properties. However, tools of analytical modeling highlighted mortar with zeolite and fly ash as the optimal composition regarding its mechanical performance.