Thermal Cycling Treatment Research Articles

Microstructure evolution and strain rate sensitivity of ductile Hf20Nb10Ti35Zr35 medium-entropy alloy after thermal cycling

The medium-entropy alloy Hf20Nb10Ti35Zr35 has a ductile BCC structure in the as-solution-treated state and could be age-hardening with fine precipitates. In this study, the thermal stress produced by thermal cycling was found to accelerate the precipitation of the α" and the evolution of ω → α phase of Hf20Nb10Ti35Zr35. The α''-martensite phase of Hf20Nb10Ti35Zr35 tended to grow in the (001)β plane, with the misorientation angle being concentrated around 52° after 10 thermal cycles. Moreover, the misorientation angle tended to have a bimodal distribution after 50 thermal cycles. Nanomechanical testing was performed to measure the strain rate sensitivity (SRS) at room temperature. The result shows that SRS of Hf20Nb10Ti35Zr35 changed from a small positive value of 0.09247 to a small negative one of either −0.02125 or −0.0445. This was mainly attributable to the decrease in the volume of the β phase or the increase of the α" + α composite phase. This demonstrates that thermal cycling treatment of the present alloy could induce more precipitation of the second phase for hardening and enhance uniform deformation behavior.

Bonding effectiveness of multi-step adhesive resin cements to CAD/CAM blocks: impact of thermal cycling and surface treatment methods

BackgroundTo investigate the effects of thermal cycling and surface treatment methods on the bonding effectiveness of multi-step resin cements to CAD/CAM blocks.MethodsA total of 198 slices, 66 each from CAD/CAM blocks (feldspathic ceramic: Vitablocs TriLuxe Forte, V; resin matrix ceramics (RMCs): Cerasmart, C; and Shofu Block HC, S), were obtained and randomly divided into two subgroups for etching with hydrofluoric acid (HFA) and sandblasting with Al2O3 (SB). After the surface treatments, one etched and one sandblasted sample of each CAD/CAM block was observed via SEM analysis at 500× magnification. The remaining 32 etched and 32 sandblasted samples of each CAD/CAM block were divided into two subgroups to be cemented with total-etch (TE) and self-etch (SE) resin cements. Then, half of the 16 samples in all the subgroups were subjected to aging (TC) for 5000 cycles (n = 8). The shear bond strength (SBS) of each sample was measured. Four-way analysis of variance (ANOVA) and Tukey tests were used to analyze the data (p < 0.05).ResultsWith or without TC, the highest SBS values for V were obtained with the HFA-TE and HFA-SE interactions, respectively. C presented the highest SBS values with HFA-SE and SB-TE interactions, whereas S presented the highest SBS values with SB-TE and HFA-TE interactions. Except the SB-SE interaction, C presented lower SBS values after TC than other materials. HFA created less porosity on the C and S surfaces than V. SB visibly roughened the surfaces of all the materials but caused fractures, cracks, and damage to the surfaces.ConclusionSimilar SBS values can be achieved between feldspathics, RMCs, and multi-step adhesive resins with both HFA and SB treatments. However, the SBS values obtained from the SB-SE interaction may be below the recommended threshold values for all materials after TC. SB can cause distinctive cavities, fissures, and damage, especially on the surfaces of RMCs.

Effect of cryogenic thermal cycling treatment on the mechanical properties of FINEMET amorphous nanocrystalline alloy

The brittleness of FINEMENT amorphous nanocrystalline alloys caused by annealing is an urgent problem to be solved because it limits the scope of their engineering application. We are herein to investigate the rejuvenation behavior of the as-annealed samples that not only are in a relaxed state but also the nanocrystals are precipitated in the amorphous matrix. The results show that the thermal temperature for cryogenic thermal cycling (CTC) treatment should not be larger than 483 °C in order to recover the enthalpy of relaxation. Further, the more suitable temperature for CTC treatment differs with the time that the as-annealed ribbon is employed. Meanwhile, the improvement of mechanical properties of the rejuvenated samples was examined with the help of hardness, flat plate bending, and nanoindentation experiments, and the results correspond well to the maximum of the relaxation enthalpy recovery. In addition, molecular dynamics simulations were used to visualize the changes in the local structure and found that the increased local five-fold symmetric clusters have increased the amorphousness of the amorphous nanocrystalline ribbon through CTC treatment.

Coarsening of alloy carbides during a cyclic heat treatment for grain refinement in ultrahigh-strength steels

Strength–ductility trade-off dilemma is acute in materials science, especially for ultrahigh-strength steels. The improvement of toughness requires careful tuning of grains and precipitates. Thermal cyclic treatment and annealing before quenching are two effective ways of microstructural refinement for steels. However, a combination of the two methods has never been studied. Complex alloy carbides form in the process of annealing, but their effects on grain refinement in the subsequent quenching are unclear. Here, a systematic comparison of microstructure and mechanical properties is established between a thermal cyclic treatment with annealing (CHT) and traditional quench-temper treatment (QT). The results indicate that the CHT treatment leads to the coarsening of alloy carbides and subgrains, and the decrease in strength and toughness.

Evaluation of pore characteristics evolution and damage mechanism of granite under thermal-cooling cycle based on nuclear magnetic resonance technology

During the development process of deep geothermal energy (Hot dry rock, HDR), the high-temperature granite matrix in the wellbore needs to withstand thermal-cooling cycles, easily leading to wellbore instability and collapse. Considering the actual drilling engineering using different types of drilling fluid, thermal-cooling cycle experiments (cycles of 1, 2, 4, 8, 12 times) of granite were conducted using natural, water, and liquid nitrogen (LN2) cooling methods. Based on the low-field nuclear magnetic resonance measurement, the development and evolution of pore size, quantity, and distribution under different cooling ways and thermal cycles were studied, and the changes in rock mechanical parameters under different cooling methods and thermal cycling conditions were quantified. Then, the rock damage coefficients based on the variation patterns of different types of pores were calculated, and a quantitative relationship was established among T2 spectrum, pore, and mechanical damage. Finally, the proton weighting method was used to analyze the changes in the internal bearing area of rocks, revealing the deterioration mechanism of rock mechanical properties under different cooling ways and thermal cycling conditions. The results showed that the porosity increased with thermal cycles during the thermal-cooling cycle treatment, and the growth rate was first fast and then slow. Under the same number of thermal cycles, the groundwater cooling porosity was the highest, followed by LN2 and natural cooling. The relationship between T2 spectral area and rock damage was established on this basis, and the rock damage value increased with thermal cycles in an exponential function, and the proportion of large pores significantly affected the pore damage. A relationship (positively proportional linear) between pore damage and the mechanical degradation coefficient of high-temperature cooling cycle granite and a method for predicting rock degradation through pore damage were established, the deterioration mechanism of rock mechanical properties under thermal cycle treatment was revealed.

Simple processing via thermal treatment and catalyst infiltration to enhance nickel electrode performance for liquid alkaline water electrolyzers

Two simple processes for enhancing liquid alkaline water electrolyzer performance are demonstrated. Both enhance 3D Ni electrodes by introducing a micron-scale rough structure throughout the bulk of the electrode. Oxidation/reduction relies on a simple thermal treatment cycle to create surface roughening through the volumetric expansion during NiO formation and volume contraction during reduction back to Ni metal. Catalyst infiltration introduces a washcoat of additional metal particles throughout the electrode, by flooding the electrode with catalyst precursor and converting it to micron-scale particles via a reducing thermal treatment. The largest improvement in performance (211 mV at 1.8 A cm−2) is observed for infiltrated NiFe-3x catalyst. For Fe-free Ni-only electrodes, oxidation/reduction provides a larger improvement (157 mV at 1.8 A cm−2) than infiltrated Ni-3X (106 mV at 1.8 A cm−2). For both processes, the observed electrode surface structure and performance is quite sensitive to the thermal treatment temperature.

The Impact of Multiple Thermal Cycles Using CMT® on Microstructure Evolution in WAAM of Thin Walls Made of AlMg5

Wire Arc Additive Manufacturing (WAAM) of thin walls is an adequate technology for producing functional components made with aluminium alloys. The AlMg5 family is one of the most applicable alloys for WAAM. However, WAAM differs from traditional fabrication routes by imposing multiple thermal cycles on the material, leading the alloy to undergo cyclic thermal treatments. Depending on the heat source used, thermal fluctuation can also impact the microstructure of the builds and, consequently, the mechanical properties. No known publications discuss the effects of these two WAAM characteristics on the built microstructure. To study the influence of multiple thermal cycles and heat source-related thermal fluctuations, a thin wall was built using CMT-WAAM on a laboratory scale. Cross-sections of the wall were metallographically analysed, at the centre of a layer that was re-treated, and a region at the transition between two layers. The focus was the solidification modes and solubilisation and precipitations of secondary phases. Samples from the wall were post-heat treated in-furnace with different soaking temperatures and cooling, to support the results. Using numerical simulations, the progressive thermal cycles acting on the HAZ of one layer were simplified by a temperature sequence with a range of peak temperatures. The results showed that different zones are formed along the layers, either as a result of the imposed thermal cycling or the solidification mode resulting from CMT-WAAM deposition. In the zones, a band composed of coarse dendrites and an interdendritic phase and another band formed by alternating sizes of cells coexisted with the fusion and heat-affected zones. The numerical simulation revealed that the thermal cycling did not significantly promote the precipitation of second-phase particles.

Получение покрытий с высокой инфракрасной излучательной способностью

Introduction. One of the promising modern methods of coating formation is detonation gas dynamic sputtering. Coatings obtained by this method have high adhesion to the substrate, dense structure and specified functional properties. Development of technology for obtaining functional coatings with high emission coefficient in the infrared range is an urgent need for the development of high-temperature industrial processes and technologies. High-temperature industrial processes consume a large amount of energy, so improving the energy efficiency of industrial equipment is considered as one of the ways to overcome the ever-growing energy crisis. To this end, coatings with high infrared emissivity have been developed for industrial furnaces. These coatings are usually applied to the furnace walls, which significantly improves energy efficiency by increasing heat transfer from the heat-emitting surfaces of the furnace. The purpose of the work is to obtain coatings with high emission indices in the infrared range for further recommendation of its use in baking ovens of Shebekinsky machine-building plant. Methods for studying coating specimens obtained by detonation gas-thermal method: scanning electron microscopy, X-ray phase analysis, energy dispersive analysis, infrared spectroscopy. Results and discussion. The microstructure, phase composition, emissivity and thermal cycling resistance of Fe2O3; Al2O3 + 10 % Fe2O3; Ti + 10% Fe2O3 coatings obtained by detonation gas-dynamic powder spraying are investigated in this work. The results of the study showed that the obtained coatings have a dense structure, increased emissivity and resistance to thermal treatment cycles, as a result of which the structure of the crystal lattice of the coatings does not change.

Accelerated improvement in tensile superelasticity of electron beam directed energy deposition manufactured NiTi alloys by artificial thermal cycling combined with low temperature aging treatment

ABSTRACT The low-temperature aging treatment at 250°C can significantly improve the tensile superelasticity of NiTi alloys fabricated by electron beam directed energy deposition (EB-DED). However, it requires a very long aging duration (up to 200 h) to achieve excellent tensile superelasticity due to inherent coarse grain size. To accelerate the aging process, the high-density dislocations are introduced by artificial thermal cycling treatment prior to the aging treatment (the original dislocation content in EB-DED processed NiTi alloys is very low), which will promote the subsequent uniform precipitation of nanoscale Ni4Ti3 particles during low-temperature aging treatment. The phase transformation behaviour always maintains a stable two-stage martensitic phase transformation. Under a cyclic tensile test at 6% strain, 24 h aged sample with thermal cycling maintains a recovery rate exceeding 90% even after 10 cycles, comparable to the performance of the sample aged for 200 h without thermal cycling, indicating a substantial improvement in aging efficiency.

Thermal cycle stability and microstructure of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ferroelectric single crystals have been commercially available as important components in medical ultrasound transducers due to their excellent piezoelectric and electromechanical coupling performance. The variation in piezoelectric and dielectric properties of PMN-PT single crystals with ambient temperature is an important application indicator. In this work, the PMN-PT single crystals after direct current poling (DCP) and alternating current poling (ACP) were subjected to the cyclic thermal treatment process. The thermal cycling stability and microstructural changes in PMN-PT single crystals were investigated. The ACP single crystals exhibit a higher dielectric constant ε33T/ε0 (6500–7600) and piezoelectric coefficient d33 (2100–2500 pC N−1) compared to the DCP single crystals (ε33T/ε0 of 4100–5000, d33 of 1200–1300 pC N−1). Under thermal cycling at 60 °C, the DCP and ACP single crystals exhibit good thermal cycling stability after 150 cycles. Microstructural observations show that the domain structure of the DCP single crystals exhibits “staggered domain walls, inhomogeneous domain size, variety of domain structure,” while the relatively homogeneous stripe-like domains were observed in the ACP single crystals. After thermal cycling, new fine striped domains appear in both the DCP and ACP single crystals due to the instability of rotated polarization, but the piezoelectric and dielectric properties are not greatly affected. This work provides an intensive understanding of the effects of thermal cycling on the domain structure, which is useful for applications.

Study on the factors affecting the performance of oil-filled pressure sensitive core

PurposeThe performance of oil-filled pressure cores is very much affected by the corrugated diaphragm and the oil filling volume. The purpose of this paper is to show the effects of different corrugated diaphragms, different oil filling volumes and different treatments of the corrugated diaphragms on the performance of pressure sensors.Design/methodology/approachPressure-sensitive cores with different diaphragm diameters, different diaphragm ripple numbers and different oil filling volumes are produced, and thermal cycling is introduced to improve the diaphragm performance, and finally the performance of each pressure-sensitive core is tested and the test data are analyzed and compared.FindingsThe experimental results show that the larger the diameter of the corrugated diaphragm used for encapsulation, the better the performance. For pressure-sensitive cores using smaller diameter corrugated diaphragms, the performance of one corrugation is better than that of two corrugations. When the number of corrugations and the diameter are the same size, the performance of the outer ring of the diaphragm with concave corrugations is better than that with convex corrugations. At the same time, the diaphragm after thermal cycling treatment and appropriate reduction of encapsulated oil filling can improve the performance of the pressure-sensitive core.Originality/valueBy exploring the effects of corrugated diaphragm and oil filling volume on the performance of oil-filled pressure cores, the design of oil-filled pressure sensors can be guided to improve sensor performance.

Failure mechanism of hot dry rock under the coupling effect of thermal cycling and direct shear loading path

Inducing shear failure in reservoir rocks is a critical strategy for enhancing hot dry rock resource exploitation, as it promotes the development of an extensive fracture network. In this study, granite was subjected to direct shear tests under three distinct temperatures and five thermal cycling treatments. Utilizing acoustic emission (AE) and digital image correlation (DIC) techniques, the shear failure traits and the evolutionary patterns of cracks in granite under diverse thermal cycling treatments were probed. Experimental results reveal that the direct shear strength of granite initially decreases, subsequently rebounds with increasing thermal cycles, and exhibits a steady decrease with temperature increase. Effects of thermal shock provoke a surge in AE counts and energy during the initial half of the shearing process, steering the failure mode of the samples from brittle to plastic. Furthermore, the macro crack morphology changes from a singular shear crack to a pair of parallel shear cracks, becoming intricately complex at elevated temperatures (600 °C). Additionally, the initiation of the main shear crack in granite consistently manifests a mixed tensile-shear failure, with the proportion of shear action displaying a positive correlation with temperature. In contrast, the proximal secondary cracks are purely tension-initiated. Finally, a competitive mechanism between rock strengthening and weakening induced by thermal cycles treatment was proposed to explain the remarkable rebound in direct shear strength following thermal cycling treatment. The current work provides insights for the mechanism of shear failure in rocks under different thermal cycling conditions in geothermal reservoir stimulation.

Experimental Research on the Permeability of Granite Under Different Temperature Cycles

In this paper, through the permeability test of granite under different temperature cycles, the change law of porosity and permeability of rock samples after different temperature cycles was studied, and the relationship between the P-wave velocity and porosity and permeability was established by regression analysis. The results show that the porosity and permeability of the granite samples decreased significantly in one to three high-temperature cycles, showing a logarithmic change, and with the increase of the number of cycles, the decreasing rate gradually decreased after five to 10 thermal cycles, which is beneficial to the long-term development of deep geothermal resources. Under thermal cycles at different temperatures, the P-wave velocity of granite has a logarithmic correlation with permeability and porosity. As the number of cycles increases, the relationship between permeability, porosity, and P-wave velocity changes from a logarithmic relationship between one to three cycles to a linear relationship between five to 10 cycles. After thermal cycle treatment at different temperatures, there is an excellent logarithmic relationship between the P-wave velocity and porosity and permeability, and it has a high correlation. The porosity and permeability of granite can be estimated nondestructively by measuring the wave velocity. Using a scanning electron microscope (SEM) to observe the granite at 450℃, trivial particles appeared between the pore structure, and the internal structure of the rock sample was destroyed under the action of the thermal cycle. The change mechanism of physical property deterioration in deep geothermal energy mining is revealed, guiding deep geothermal energy mining.

Analysis of the influence of thermal and thermocyclic technology on the properties of maraging steel

The article presents experimental data obtained by studying the influence of changes in the geometry of parts made of maraging steels, depending on the modes of thermal and thermal cycling treatment with heating in the temperature range of α-γ transformation. The experiments were carried out on samples cut from hot-rolled sheets, pre-hardened at a temperature of 1000°C for 1 hour. Using the accelerated testing method, the relative change in resistance to stress corrosion damage was determined depending on the phase composition and aging temperature (strength) of maraging steel.

Friction behavior of 30CrNi2MoVA gun barrel steel after thermo-cyclic treatment: Air and simulated seawater

The influence of gun barrel erosion has been proposed, but the research on the wear behavior of gun steel during the initial extrusion phase remains limited. This study employed an experimental approach to investigate the wear of 30CrNi2MoVA gun steel after untreated (25 °C) and thermal cycling treatments (400 °C and 800 °C) under both air and simulated seawater environments. In the air environment, abrasive wear and adhesive wear mechanisms were prominently observed. In the simulated seawater, abrasive wear mechanism was predominant. In both environments, the surface morphology and wear profiles of the untreated samples were similar, exhibiting a negative interaction phenomenon. After thermal cycling treatment, the corrosion wear resistance of 30CrNi2MoVA steel were significantly reduced. Among them, the material performance is the lowest at 800 °C. Therefore, this study provides theoretical and experimental evidence for improving the friction and wear performance of gun barrel rifling during the bullet extrusion process.

Estimation of Thermal Stability of Si-SiO2-W Nanolayered Structures with Infrared Spectrometry.

Nanolayered coatings are proposed for use in microelectronic devices where the size/performance ratio is becoming increasingly important, with the aim to achieve existing quality requirements while reducing the size of the devices and improving their ability to perform stably over multiple cycles. Si-SiO2-W structures have been proposed as a potential material for the fabrication of microelectronic devices. However, before such materials can be implemented in devices, their properties need to be carefully studied. In this study, Si-SiO2-W nanolayered structures were fabricated and subjected to numerous thermal treatment cycles at 150 °C. A total of 33 heating cycles were applied, resulting in a cumulative exposure of 264 h. The changes in chemical bonds and microstructure were monitored using Fourier Transform Infrared spectrometry (FTIR) and scanning electron microscopy (SEM). The FTIR signal at 960 cm-1, indicating the presence of W deposited on SiO2, was selected to characterize the thermal stability during the heating cycles. The estimated signal intensity variation closely resembled the normal inhomogeneity of the nanolayers. The increase in slope intensity was estimated to be 1.7 × 10-5.

Ways of energy saving during thermal and chemicalthermal treatment of steel due to acceleration of diffusion processes

Some technical and economically effective ways of energy saving in the processes of thermal and chemical‑thermal treatment of steels are analyzed. A classification of ways to save energy by activating structural‑phase transformations in steels is proposed. The results of work on accelerating diffusion processes in steels during thermal improvement, thermal cycling treatment, thermal diffusion galvanizing, nitriding and carburization are summarized. A high potential for energy saving and increased productivity by reducing the time of thermal and chemical‑thermal treatment was noted.

Effect of cyclic thermal stimulation on the pore structure and fluid space of coal and inspiration for coalbed methane production

Based on the modified programmed temperature-raising system, cyclic thermal stimulation with different temperature gradients was carried out for lignite, bituminous and anthracite coal, and each group of coal samples after thermal stimulation cycle was subjected to nuclear magnetic resonance (NMR) testing. The NMR T1-T2 spectra and the fractal dimensions of coals in different ranks during thermal simulation quantitatively described the dynamic evolution of the pore fluid storage space of coals. The variation of T2 distribution and pore throat were used to reflect the pore development process of coals. The results shows that the pores and pore throat of lignite developed the best among the three coal ranks and the structure of the pore is complete after the cyclic thermal simulation; the T1-T2 signal peaks increased from 17.05 at 30 °C to 163.00 at 180 °C; the seepage of lignite increased from 6.54 % to 12.43 %; total pore fractal dimension DT has a decreasing trend, indicating reduced inhomogeneity of pores. This indicates that the cyclic thermal stimulation treatment can promote the growth of seepage pores to a greater extent, improve the seepage space, and enhance the connectivity of the pores in the coal samples.

Effects of thermal cycling treatment on load bearing and friction behavior of SiCp/A356 composites

During bench tests and actual service, the Al-MMC (metal matrix composite) brake discs used in urban rail transit vehicles experienced problems such as poor wear resistance, compromising the brake discs' stability and safety. While braking, the brake disc material will bear the thermal cycling loads, leading to a certain degree of degradation in the material's performance. In this study, the degradation of the material's performance by the thermal cycling treatment was investigated. The results showed that all material performance degraded to some extent after thermal cycling treatment, with a strong correlation with cycling temperature. The degradation of material performance was caused by a combination of matrix mechanical damage and interface damage. At the same time, the tribological performance of the material also decreased to some extent. The main effect of thermal cycling treatment on tribological performance was its effect on material performance. The increase of hard particles in the abrasive debris resulting from the mechanical damage of the material and the aggravation of the dynamic changes in the TBL (third body layer) were the basic reasons for the surface scratches. The results further help to explore the application of Al-MMCs in high-temperature and long-term service.

Sequential double anionic substitution through synthesis of perovskite-type AB(O,N,F)3 with A = Ca, Sr, Ba and B[dbnd]Ti, Zr

For the synthesis of perovskite-type oxynitrides AB(O,N)3 in most cases cationic substitution is applied for charge compensation, while anionic substitution, e.g., using fluoride is by far less investigated. Herein, we have investigated the possibility to use sequential double anionic substitution for charge compensation while forming perovskite-type oxynitride fluorides AB(O,N,F)3 with A = Ca, Sr, Ba and BTi, Zr. As expected from Goldschmidt's tolerance factor, the cubic SrTi(O,N,F)3 and BaZr(O,N,F)3 were found to be easily formed. The synthesis required a lower number of rigorous thermal treatment cycles to obtain single-phase materials. The non-cubic crystal structures favored a factor six to ten higher nitrogen content of e.g., up to 0.06 per formula unit in SrZr(O,N,F)3, while the fluoride content did not change within measurement uncertainty. Overall, the amount of anionic substitution remained low and a presence of oxygen vacancies in the range of 0.1 per formula unit was indicated in all cases. In comparison to the corresponding oxides the double anionic substituted oxynitride fluorides displayed a band gap reduction by about 0.7 eV on average, however, the obtained band gap values of around 3 eV were still too large for a potential application in solar water splitting (SWS). Nonetheless, a clear correlation of the nitrogen content and the band gap reduction was obtained, e.g., SrZr(O,N,F)3 revealing the highest nitrogen content also showing the highest band gap reduction. While no band gap change was observed in CaZr(O,N,F)3 showing a negligible nitrogen amount. The main drawback of a sequential double anionic substitution strategy using consecutive heterovalent substitution by F− and N3− is found to be the need of intermediate charge compensation. In parallel the Fermi level is altered. Both allowed only for a very limited substitution of the anionic sublattice. Instead, alternative synthesis pathways enabling a simultaneous anionic double substitution will be needed to realize increased partial substitution of nitride and fluoride in perovskite-type AB(O,N,F)3 reducing the band gaps to values suitable for SWS.