Differential barothermal analysis (DBA) of Ni-base alloys

The technique of differential barothermal analysis (DBA) combines the hot isostatic pressing technique and classical differential thermal analysis has been elaborated. This technique allows the study of the phase equilibria in the most of inorganic systems under pressure up to 200 MPa and temperatures up to 2000°C. The Ni-base alloy with the solidus, liquidus, g-phase and carbides dissolution temperatures of 1328, 1390, 1272 and 1255°C, accordingly, was chosen as a model material. By DBA technique the pressure coefficients of the above mentioned temperatures were established. The values of the obtained coefficients are 3-5 times larger than the melting point pressure coefficient for the pure Ni (the alloy base metal). The discussion of the data obtained is carried out. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of thermophysical properties of high temperature alloy IN713LC by thermal analysis

The presented paper deals with the study of thermophysical properties of cast and complex alloyed nickel based on superalloy Inconel 713LC (IN713LC). In this work, the technique of Differential Thermal Analysis was selected for determination of the phase transformation temperatures and for the study of the effect of varying heating/cooling rate at these temperatures. The samples taken from as-received state of superalloy were analysed at heating and cooling rates of 1, 5, 10, 20 and 50?°C?min^?1 with the help of the experimental system Setaram SETSYS 18_TM. Moreover, the transformation temperatures at zero heating/cooling rate were calculated. The recommended values for IN713LC after correcting to a zero heating rate, are 1,205?°C (T _?á?,solvus), 1,250?°C (solidus) and 1,349?°C (liquidus). Influence of heating/cooling rate on shift of almost all temperatures of phase transformations was established from the DTA curves. Undercooling was observed at the cooling process. The samples before and after DTA analysis were also subjected to the phase analysis by scanning electron microscopy using the microscope JEOL JSM-6490LV equipped with an energy dispersive analyser EDAX (EDS INCA x-act). Documentation of the microstructure was made in the mode of secondary (SEI) and backscattered (BEI) electron imaging. On the basis of DTA analysis and phase analysis it may be stated that development of phase transformations of the alloy IN713LC will probably correspond to the following scheme: melting?????? phase; melting???????+?MC; melting????eutectics ??/?á?; melting???????+?minority phases (e.g. borides); and matrix ???????á?.     

Thermodynamic properties of the NdBr3–MBr binary systems (M = Na,K)

Thixoforming involves heating different types of alloys to the semisolid state at high heating rates and forming in die-casting machines or conventional presses. At temperatures higher than the solidus and lower than the liquidus, the mush metal behaves like a high-viscosity thixotropic material. Therefore, determining the thermodynamic behavior of the solid-to-liquid transition is paramount to control thixoforming processes. This article describes a simple, novel experimental setup based on differential thermal analysis (DTA) for analyzing the phase transitions in an alloy heated using high heating rates typical of industrial applications. A365 alloy was chosen to demonstrate the effectiveness of the method as the phase transformations for this alloy in semisolid materials (SSM) processing are well understood. Samples were heated to 750 °C using constant linear heating rates of 5, 10, 15, 20, 25, 50, 75, 100 and 125 °C min in a Norax 25 kW 8 kHz induction furnace with an Omron E5CK temperature controller. AISI 316 austenitic stainless steel was used as the inert reference. Comparison of the results of DTA using the proposed method and the results of simulation with Thermo-Calc^® indicates that the proposed in situ DTA device and its method is suitable for analyzing phase transitions when high heating rates are used.     

Phase diagram study of CaBr2–CaHBr system

A study of binary, CaBr₂–CaHBr system was carried out by differential thermal analysis (DTA), covering the composition range from 100 % CaBr₂ to 100 % CaHBr between room temperature and 800 °C. From DTA results, the contour of solidus and liquidus temperatures with composition is plotted and the phase diagram of CaBr₂–CaHBr system is constructed. The system shows an eutectic reaction at 576 °C and the eutectic composition is 79.6 mol% CaBr₂. Co-existing phases in different phase fields are characterized by X-ray diffraction analysis.     

Calorimetric analyses on aged Al–4.4Cu–0.5Mg–0.9Si–0.8Mn alloy (AA2014 grade)

An Al–4.4Cu–0.5Mg–0.9Si–0.8Mn alloy (IADS 2014 grade) in the solution annealed and peak aged condition was exposed at 170°C for relatively long times (up to about 1800 h) in order to check the stability of the alloy. The investigated aging temperature was in the frame of a research on the long-term mechanical behaviour of such alloy. Microstructure evolution was monitored via calorimetric analyses, metallographic inspections and hardness measurements. Further, X-ray analyses were carried out on selected samples. The attention was focused on differential scanning calorimetry performed at different scanning rates, with the aim of evaluating the kinetics of the precipitation phenomena. Notwithstanding the wide industrial diffusion of this alloy, literature survey showed that there is not a consensus view on the precipitation sequences and on calorimetric peak identification. The present results show the progressive evolution of calorimetric peaks, corresponding to that of strengthening particles towards more stable phases, proved by the disappearance of exothermic peaks. Activation energy from Kissinger kinetic analysis in the case of aged samples provided scattered values that could be reasonably attributed to an overlapping of transformation peaks. Moreover, in these samples transformations partially occurred before DSC scans, providing non-constant transformation fraction at signal peak temperatures and resulting in different activation energies.     

Calorimetric investigation of order–disorder transition in Cu0.6Pd0.4 and Cu0.85Pd0.15 alloys

Order–disorder phase transitions in Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys have been investigated using differential scanning calorimetry and drop calorimetry. The differential scanning calorimetry measurements show that the transition in both these alloys are reversible in nature and the enthalpy increment measurements reveal that these transitions are first order in nature. The transition temperature of first-order phase transition in Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys have been evaluated to be 884(±2) and 799(±2) K, respectively, from drop calorimetric measurements. The latent heat of first-order phase transition in Cu_0.6Pd_0.4 alloy were evaluated to be 31.2(±0.6) and 28.9(±0.5) J g^?1, by enthalpy increment and differential scanning calorimetry measurements, respectively. Similarly, the latent heat of first-order phase transition in Cu_0.85Pd_0.15 alloy were evaluated to be 23.1(±0.6) and 21.3(±0.5) J g^?1, by enthalpy increment and differential scanning calorimetry measurements, respectively. The solidus temperatures of Cu_0.6Pd_0.4 and Cu_0.85Pd_0.15 alloys were found to be 1,457(±2) and 1,360 K, respectively.     

Calorimetric determination of head-to-head defect in poly(vinylidene fluoride)

Differential scanning calorimetric analyses were conducted on samples of poly(vinylidene fluoride) polymerized in an autoclave by tributylborane-oxygen by free-radical initiation at low temperature (-70-0°C). The peak melting points and the percent head-to-head defect in each polymer sample were determined by a reported calorimetric method. A commercial sample showed a melting temperature in the range 157–162°C and a percent head-to-head defect of 7.7%; whereas two experimental samples showed melting temperatures in the range 172–179°C with a percent head-to-head defect of 4.4 and 4.9%. The calorimetric procedure was modified by reducing annealing times to only 2 h, which saves time and, as shown in this study, avoids thermal polymer degradation.     

Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Ni functionally graded materials (FGM) obtained by centrifugal-slip casting method

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 °C for all investigated temperatures of phase transformation, except for one temperature of peritectic transformation.     

Thermal studies of copolymers of styrene and maleic anhydride

Copolymers of styrene and maleic anhydride prepared by a charge transfer mechanism have been studied thermally by thermogravimetry and differential scanning calorimetry. The copolymers degrade in two stages; the first stage accounts for about 85% of the degradation. Incorporation of maleic anhydride to styrene decreases the thermal stability of the later. Differential scanning calorimetric studies show two exotherms between 300° to 500 °C. Glass-transition temperatures for the copolymers are lower than that of polystyrene.     

Wärmekapazitätsmessungen Nach Scanning-Methoden Bis Zu Hohen Temperaturen

Scanning calorimetric methods permit determination of heat capacities at high temperatures up to 1600°C. For disk systems with power compensation application limits are in order of 700°C, and for cylindrical systems with electrical calibration up to 1000°C. For the high temperature range above 1000°C DSC plates and a cylindrical calorimetric systems based on the CALVET principle ('MULTI HTC’) are known. For cylindrical calorimetric systems the precision of the Cp data is between 2 and 5% even at high temperatures without any requirements on the kind and shape of samples. These results are better than data provided by DSC plate systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

A DSC study of precipitation hardening in a WE43 Mg alloy

The phase transformations leading to hardening a Mg-Y-Nd-Zr (WE43) alloy submitted to thermal treatments are followed by calorimetric and microhardness measurements. A double-stage thermal treatment is adopted, the first at 210°C for 8 h and the second at 150°C, on samples quenched from a temperature higher than the conventional one. A secondary precipitation of the metastable phase β″ in the second stage makes the hardness increase with respect to the primary precipitation.     

Determination of the kinetic parameters in magnesium alloy using TEM and DSC techniques

The effects of ageing treatment on phase transformations in Mg–Al alloy have been assessed. The techniques of scanning and transmission electron microscopy, microhardness and differential scanning calorimetric tests were used to characterize the materials obtained after application of artificial ageing. An ageing treatment at 175 °C causes the β-Mg₁₇Al₁₂ precipitation to become evenly distributed along the grain boundary and within the grain together with precipitation of the Al₆Mn and the Τ-Mg₃₂(Al,Zn)₄₉ phases. The transformation processes are associated with increased hardness values. The hardness value increases with the ageing time and attains maximum value after 10 h of ageing time. The presence of the β-Mg₁₇Al₁₂ phase acts as an effective barrier to dislocation motion, thus improving the mechanical properties of the alloy. Analysing the DSC data it is found a shift of peak temperatures to higher temperatures with increasing heating rates, which suggests that the solid state reactions are thermally activated and kinetically controlled. The fraction and the rate of transformation, the transformation function and the kinetic parameters such as activation energy and frequency factor for the alloy in artificial ageing conditions were determined.     

The surface oxidation behavior of Ni–45.16%Ti shape memory alloys at different temperatures

The isothermal oxidation behavior of Ni–45.16%Ti (composition in atomic percent) alloy was investigated by thermogravimetric analysis, and differential scanning calorimeter (DSC) methods. It was found that Ni-rich NiTi alloy exhibits a different oxidation behavior at temperatures above 400 °C in oxygen atmosphere. The alloy was exposed to oxygen atmosphere isothermally, i.e., between 400 and 800 °C, for 1 h. A gravimetric method was used to determine the oxidation kinetics and it was seen that the oxidation constant increases significantly with isothermal temperature. The activation energy of oxidation reaction for NiTi alloy was determined to be 65.47 kJ mol^?1. According to DSC measurements, the transformation temperature of alloy (M _s, M _f, A _s and A _f) was increased and also R phase disappeared above 500 °C. The formal oxides were determined by means of SEM–EDX measurements and obtained oxides are TiO and TiO₂ oxides.     

Fourier transform infrared investigation of the effects of irradiation on the 19 and 30°C phase transitions in polytetrafluoroethylene

Fourier transform infrared spectroscopy has been used in conjunction with differential scanning calorimetric measurements to investigate the nature of molecular degradation and its effect on the phase transition temperatures in irradiated polytetrafluoroethylene (PTFE). Both the 19 and 30°C transitions are observed to exhibit similar shifts to low temperatures upon irradiation. Infrared absorbance subtraction data from irradiated PTFE indicate a continual decrease in sample crystallinity accompanied by an increase in the number of free and bonded ? COOH groups with increasing dose consistent with molecular degradation by chain scission. By comparing infrared band intensities on a number of irradiated PTFE samples with those from short chain perfluoro n-alkanes, it was determined that the overall reduction in chain length caused by irradiation was primarily responsible for the observed reduction in both phase transition temperatures.     

Thermodynamic Properties and Melting Behavior of Bi–Sn–Zn Alloys

Summary. The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed. Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found at 135°C.     

Thermodynamic Properties and Melting Behavior of Bi–Sn–Zn Alloys

The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed. Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found at 135°C.     

DSC investigations of amalgam formation in Bi-Sn-Hg system doped with indium

Differential scanning calorimetric (DSC) measurements have been carried out on Bi-Sn based amalgam precursors to be used in compact fluorescent lamps (CFLs) to study the changes in melting and solidifying behaviour caused by In dopant. The phase and elemental compositions of the samples have been characterized by using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), respectively. One of the endothermic peaks of the liquid amalgam formation shifted from 121°C to 112 and 105°C, with increasing content of 2.5 and 4.8 mass% In of samples, respectively.     

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 °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 °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) (?aludová et al. in J Therm Anal Calorim 112:465–471, 2013a. doi: https://doi.org/10.1007/s10973-012-2847-8; J Therm Anal Calorim 111:1203–1210, 2013b. doi: https://doi.org/10.1007/s10973-012-2346-y). 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.     

Heat capacity,enthalpy and crystallinity for a linear polyethylene obtained by DSC

Journal of Thermal Analysis and Calorimetry - By means of computer-controlled DSC, heat-capacity measurements were performed on NBS SRM 1484 betweens-70°C and 250°C, in heating as well as...     

DSC and PVT measurements

The dissociation of gas and model hydrates was studied using a classical thermodynamic method and a calorimetric method, in various aqueous media including pure water, high concentration calcium chloride solutions and water-in-oil emulsions. Methane hydrate dissociation temperatures vs. pressure curves were determined using pressure vs. temperature measurements in a constant volume cell (PVT), and high pressure differential scanning calorimetry (DSC), at 5 to 10 MPa gas pressure and at temperatures ranging from -10 to +12°C. PVT and DSC results are in good agreement, and concordant with data available in literature. From a thermodynamic point of view, there are no measurable differences between bulk solutions and emulsions. From a kinetic point of view, due to the considerable surface of interface between the two phases, emulsions allow the formation of much greater amounts of hydrate than solutions, without any agitation. Model hydrate of trichlorofluoromethane was studied in 9 to 27 mass% calcium chloride solutions in emulsion in oil, using DSC under atmospheric pressure, at temperatures ranging from -20 to +5°C. A diagram of dissociation temperature vs. salt concentration is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.