Thermal Deformation Characteristics Research Articles

Microstructure evolution and fracture characteristics of GH4079 superalloy during high-temperature tensile process

An investigation of the thermal deformation characteristics and fracture mechanisms of the GH4079 superalloy was conducted through a series of hot tensile experiments conducted across a range of strain rates (from 0.01 s−1 to 1 s−1) and temperatures (from 970 °C to 1160 °C). The impact of MC carbides on the thermal deformation characteristics and dynamic recrystallization (DRX) of GH4079 superalloys, which are known for their challenging deformability, was analyzed to provide insights into enhancing the thermal workability of these formidable superalloys. The results suggest that DRX consistently preferentially occurs near MC carbides. The MC carbide plays a nucleation role in the particle-induced dynamic recrystallization mechanism, as determined via EBSD analysis. In addition, the primary grain boundary is the preferred nucleation site for DRX initiation. The promotion of DRX within the GH4079 alloy is considerably facilitated by the increased stored energy and nucleation site density resulting from the larger and more numerous carbides present at the grain boundaries. Moreover, the presence of carbides leads to uncoordinated deformation of the alloy during tensile deformation, which is also the induction factor of alloy cracking. With increasing strain rates and temperatures, the window of control over the hot deformation structure of the alloy diminishes. During the high-temperature deformation process of the GH4079 alloy, it is necessary to control the temperature within the range of approximately 1120 °C–1140 °C and the strain rate within the range of 0.1 s−1 to 1 s−1 to obtain a fine and uniform grain structure, delay material failure, and thus enhance the thermal processing performance of the material.

ИССЛЕДОВАНИЕ ТЕРМОДЕФОРМАЦИОННЫХ СВОЙСТВ ПОЛИТЕТРАФТОРЭТИЛЕНА

In this paper, comparative studies of the thermal and thermal deformation characteristics of PTFE presses obtained from the initial powder and chips are carried out. The work carried out comprehensive studies using methods of differential thermal and thermomechanical analyses. The results obtained are important for the development and improvement of technologies for processing polymer waste.

Unveiling the Microstructural Features during Compression of a High-Modulus Mg-15Gd-8Y-6Al-0.3Mn Alloy Reinforced by a Large Volume of Al2RE Phases

Magnesium alloys with a high volume fraction of secondary phases exhibit inferior formability. Therefore, investigating their thermal deformation characteristics is critical for optimizing thermal processing techniques. In this work, isothermal compression experiments were performed on a Mg-15Gd-8Y-6Al-0.3Mn alloy with an elastic modulus of 51.3 GPa with a substantial volume of aluminum-rare earth (Al2RE) phases. The rheological behavior and microstructural evolution of the material were systematically investigated at varying temperatures (350–500 °C) and strain rates (0.001–1.000 s−1). The calculated thermal processing diagram indicates that the unstable region gradually enlarges with increased strain, and all unstable regions appear within the high-strain-rate, low-temperature domain. The ideal thermal processing range of the alloy is 350–500 °C at strain rates ranging from 0.001 to 0.016 s−1. Particle-stimulated nucleation and discontinuous dynamic recrystallization are both verified to be responsible for the recrystallized microstructure of the alloy. The recrystallized grains exhibit a relatively random crystallographic orientation. As recrystallization proceeds, the texture gradually transitions from a typical [0001] texture in the compression direction to a random texture accompanied by decreased texture intensity. This work sheds new light on the thermo-mechanical processing of high-modulus Mg alloys, which could help design suitable processing techniques for related materials.

Research on temperature field and thermal deformation characteristics of casting rollers in twin-roll casting process

The twin-roll casting (TRC) process is considered a revolutionary technology in the metallurgical field and has garnered significant attention and research in recent years. The casting rollers used in the TRC process are crucial for achieving the desired shape of the casting strip. This study investigates the temperature distribution and thermal deformation of casting rollers in the TRC process using numerical simulation. A novel model for predicting the thermal resistance distribution at the circumferential interface between the casting roller and the molten pool has been introduced. The study examined the effects of various factors including casting roller diameter, water channel position, number, and diameter on temperature, thermal deformation, and heat flux. The findings reveal that increasing the casting roller diameter from 460 mm to 500 mm or augmenting the distance from the water channel to the casting roller surface from 35 mm to 55 mm resulted in a 37 % and 30 % increase in the maximum surface temperature of the casting roller, respectively. Additionally, an increase in the number of water channels from 30 to 50 and a growth in their diameter from 20 mm to 28 mm resulted in the average heat flux of the casting roller remaining stable, with fluctuations less than 1 MW/m2. Leveraging the insights gained from the thermal deformation behavior of the casting roller and the ideal shape of the casting strip, a comprehensive control approach for the casting roller profile was developed. The outcomes of this research provide a valuable theoretical framework for enhancing the design of casting roller structures in the TRC process.

Radial dependence of thermal, structural and micro deformation characteristics in Cu-Zr-Al bulk metallic glass subjected to high pressure torsion

Disk of a Cu38Zr54Al8 bulk metallic glass was subjected to severe plastic deformation by high pressure torsion up to 25 revolutions. X-ray diffraction was utilized to investigate the microstructure of the deformed sample, while the thermal behavior of the glass was analyzed by differential scanning calorimetry. To examine the effect of plastic straining on structural changes, micropillars were fabricated on the cross-section of the disk along the radius at specific locations, i.e. center, half radius and perimeter. Compression tests of these micropillars were conducted in a scanning electron microscope with simultaneous recording of continuous acoustic emissions. Present paper captures the effect of competition between thermal relaxation and deformation induced structural changes. Specifically, probability distributions were constructed for a series of acoustic emission events, revealing that the occurrence of acoustic emission bursts at larger deformations is in correlation with the shift of the X-ray diffraction halos and change in thermal characteristics. Accordingly, a transition was identified from random to correlated acoustic emission behavior parallel with a progressive increase in the accumulation of excess free volume from negative to positive values.

Long-term thermo-mechanical performance evolution of a 15-cell solid oxide fuel cell stack

Understanding mechanical performance evolution and failure mechanism of solid oxide fuel cell stack (SOFCs) during long-term operation period are essential to prolong operation life and advance commercialization. In this study, based on the structural mechanical model, the evolution characteristics of thermal stress, failure probability, strains, and deformation of SOFCs fueled by partially pre-reformed CH4 during 3000 h' operation are revealed. It's found the maximum thermal stresses of anodes, sealants, and frames/ICs decease respectively by 82.9%, 74.1%, and 88.4%, while those of electrolytes and cathodes firstly fluctuate then increase. The failure probabilities of sealant and anode decrease by 6∼10 orders of magnitude, while increase by 1 order of magnitude and 1.5 times for electrolyte and cathode. 300 h later, sealant may fracture by creep strain, while the component most likely to fail due to thermal stress changes from sealant to cathode. The maximum deformation of positive electrode-electrolyte-negative electrode (PEN) locates in anode of cell 15. It is suggested creep resistance of sealant be improved to avoid creep fracture, mechanical strength of cathode/sealant be increased to decrease failure probability, and the temperature unevenness be decreased to avoid larger deformation.

Applying the MIMO BP Neural Network and Cloud-Based Monitoring of Thermal Behavior for High-Speed Motorized Spindle Units

Understanding the temperature–working condition relationship is crucial for optimizing machining processes to ensure dimensional accuracy, surface finish quality, and overall spindle longevity. Monitoring and controlling spindle temperature through appropriate cooling systems and operational parameters are essential for efficient and reliable machining operations. This paper presents an in-depth analysis of the thermal equilibrium and deformation characteristics of a high-speed motorized spindle unit utilized in grinding machine tools. Through a series of thermal equilibrium experiments and meticulous data acquisition, the study investigates the nuanced influence of various working conditions, including spindle speeds, coolant types, and coolant flow rates, on spindle temperatures and thermal deformations. Leveraging the power of Artificial Neural Networks (ANNs), predictive models are meticulously developed to accurately forecast spindle behavior. Subsequently, the models are seamlessly transitioned to a cloud computing infrastructure to ensure remote accessibility and scalability, facilitating real-time monitoring and forecasting of spindle performance. The validity and reliability of the predictive models are rigorously assessed through comparison with experimental data, demonstrating excellent agreement and high accuracy in forecasting spindle thermal behavior. Furthermore, the study underscores the critical role of key working condition variables as precise predictors of spindle temperature and thermal deformation, emphasizing their significance in optimizing overall spindle efficiency and performance. This comprehensive analysis offers valuable insights and practical implications for enhancing spindle operation and advancing the field of grinding machine tools.

ВЗРЫВНОЕ ПРЕССОВАНИЕ ПОЛИСУЛЬФОНА

In work research results of a study of the effect of the initial porosity, the intensity of explosive pressing on the density, porosity and thermal deformation characteristics of polysulfone.

Thermal deformation characteristics of composites based on fibrous basalt and polypropylene

Thermal deformation characteristics of composites based on fibrous basalt and polypropylene

Thermal Deformation Characteristics and Dynamic Recrystallization Mechanism of Incoloy 800H Alloy under Different Deformations

Incoloy 800H alloy has excellent high‐temperature mechanical properties and broad application prospects. However, the dynamic recrystallization (DRX) behavior of this alloy at different deformations has been little studied. The thermal deformation characteristics and DRX mechanisms of Incoloy 800H alloy are studied by thermal compression tests. Quantitative analysis of grain size, DRX fraction, misorientation distribution, and twin boundaries under different deformation degrees is conducted using electron‐backscattered diffraction. Furthermore, the evolution characteristics of dislocations and grains are observed through transmission electron microscopy. It is found that the proportion of DRX improves with increasing deformation significantly. In the DRX process, discontinuous DRX (DDRX) is the main nucleation mechanism, while continuous DRX (CDRX) serves as an auxiliary nucleation mechanism. As the deformation increases, the CDRX + DDRX mechanisms can also be observed simultaneously in the high‐density dislocation region near the grain boundary. In addition, the ratio of ∑3 boundaries first decreases and then increases as the deformation increases. The initial twins gradually disappear due to the increase in deformation, and new twins are formed within the DRX grains. Twins can promote grain boundary bulging, provide more nucleation sites for DRX, and have a significant promoting effect on DRX.

Comparison of Thermal Deformation Behavior and Characteristics of Mg-Gd-Y-Zn Alloys with and without Bulk LPSO Phase.

Alloys Mg-8Gd-4Y-0.6Zn-0.5Zr (referred to as 0.6Zn) without the bulk long-period stacking ordered (LPSO) phase and Mg-8Gd-4Y-1.1Zn-0.5Zr (referred to as 1.1Zn) containing the bulk LPSO phase were prepared and a series of hot compression tests were conducted to examine and evaluate the influence of the bulk LPSO phase on the thermal deformation behavior and characteristics of the Mg-Gd-Y-Zn-Zr alloy. The bulk LPSO phase affects the dynamic recrystallization behavior, resulting in differences in flow stress between two alloys under different conditions. Specifically, in the temperature range of 380~460 °C, compression at lower strain rates is beneficial for the LPSO phase to promote dynamic recrystallization, while compression at a high strain rate inhibits the dynamic recrystallization due to the severe deformation of the bulk LPSO phase to release the stress concentration instead. The increase in temperature helps the LPSO promote dynamic recrystallization. As a result, the LPSO phase promotes dynamic recrystallization at all experimental strain rates at 500 °C. Furthermore, the thermal processing maps of the 0.6Zn and 1.1Zn alloys are established, and their optimal processing windows are located at 500 °C/0.001~0.01 s-1 and 500 °C/0.01 s-1, respectively. In addition, the instability zones for the 1.1Zn alloy are much larger than that for the 0.6Zn alloy, which corresponds to the microcracks generated at the interfaces between α-Mg and bulk LPSO phases.

Evolution of Grain Structure and Dynamic Precipitation during Hot Deformation in a Medium-Strength Al-Zn-Mg-Er-Zr Aluminum Alloy.

The hot deformation behavior of Al-Zn-Mg-Er-Zr alloy was investigated through an isothermal compression experiment at a strain rate ranging from 0.01 to 10 s-1 and temperature ranging from 350 to 500 °C. The constitutive equation of thermal deformation characteristics based on strain was established, and the microstructure (including grain, substructure and dynamic precipitation) under different deformation conditions was analyzed. It is shown that the steady-state flow stress can be described using the hyperbolic sinusoidal constitutive equation with a deformation activation energy of 160.03 kJ/mol. Two kinds of second phases exist in the deformed alloy; one is the η phase, whose size and quantity changes according to the deformation parameters, and the other is spherical Al3(Er, Zr) particles with good thermal stability. Both kinds of particles pin the dislocation. However, with a decrease in strain rate or increase in temperature, η phases coarsen and their density decreases, and their dislocation locking ability is weakened. However, the size of Al3(Er, Zr) particles does not change with the variation in deformation conditions. So, at higher deformation temperatures, Al3(Er, Zr) particles still pin dislocations and thus refine the subgrain and enhance the strength. Compared with the η phase, Al3(Er, Zr) particles are superior for dislocation locking during hot deformation. A strain rate ranging from 0.1 to 1 s-1 and a deformation temperature ranging from 450 to 500 °C form the safest hot working domain in the processing map.

Field investigation on the spatiotemporal thermal-deformation characteristics of a composite embankment with two-phase closed thermosyphons on a permafrost slope

Field investigation on the spatiotemporal thermal-deformation characteristics of a composite embankment with two-phase closed thermosyphons on a permafrost slope

Thermal Expansion and Adsorption Characteristics of Coal Based on Temperature Change and Its Influence on the Slippage Effect

The slippage effect is an important phenomenon of coalbed methane (CBM) migration. As the exploitation of CBM, the slippage effect becomes more and more obvious. For exploring the evolution of the slippage effect as CBM extraction by heat injection, the thermal expansion test and the temperature increasing desorption test under different stress states, as well as the seepage test under variable temperature conditions, were conducted by operating the high-temperature multifunctional triaxial test system. The effect rules for temperature and pore pressure on the slippage effect were analyzed, and then the evolution mechanism of the slippage factor at the united action of pore pressure and temperature was comprehensively analyzed based on thermal expansion deformation and adsorption characteristics. The results showed that: first, the influence of pore pressure on the slippage effect is mainly caused by the molecular mean free path and effective stress when pore pressure is greater than 0.8 MPa in the range of 30–150 °C. With the pore pressure increase, the slippage effect decreases. Second, the temperature influence on the slippage effect is mostly induced by the variation of cracks in coal due to thermal expansion deformation created by temperature. With the increase in temperature, the slippage factor average increases first from 30 to 60 °C is 19 times and then decreases from 60 to 90 °C is 36%. Finally, at the combined influence of temperature and pore pressure, the slippage effect is mainly influenced by thermal expansion deformation, desorption deformation, and effective stress. At 30–60 °C, the slippage factor is principally affected by thermal expansion deformation. At 60–90 °C, the slippage factor is mostly influenced by desorption deformation and effective stress. The research results provide a foundation for the technology of CBM exploitation by heat injection.

Thermal Deformation Characteristics of Nanocomposites Based on Polypropylene and Household Waste Thermal Ash

Thermal Deformation Characteristics of Nanocomposites Based on Polypropylene and Household Waste Thermal Ash

Mechanical properties of fluoroplastic seals of axial-piston pumps in relation to the operating conditions of a hydraulic drives

The article considers the issues associated with the elastic and plastic properties of fluoroplastic in the state of delivery and radiation hardened. The statement about the radiation hardening of fluoroplastic improves thermal deformation characteristics is substantiated. The results of kinetic microindentation are studied in comparison with the initial state in the temperature range of 80 - 400 0C. The effect of temperature on the ratio of the work of the elasticity and plasticity forces is analyzed. Particular attention is paid to the elastic properties of fluoroplastic. The assumption is substantiated that it is possible to improve the elastic properties of fluoroplastic by radiation treatment at elevated temperatures, which are typical for high-speed axial piston pumps. On the basis of the study, it was found that the use of radiation hardening treatment of fluoroplastic is promising for increasing the durability of movable seal rings.

Secondary Thermal Deformation Characteristics of Stiffened Plate Exposed to Fire

The material and structural thermal deformation characteristics of a steel stiffened panel under various fire-extinguishing methods were investigated experimentally. Propane gas was used to generate jet fires for steel stiffened panels widely used as offshore installation structures. The characteristics of the initial imperfection (initial deflection and residual stress) occurring during fabrication were measured and analyzed before and after the fire experiment. In addition, the serviceability limit values were analyzed in terms of the maximum and permanent defections of the steel stiffened plate. The experimental results can be used as basic data for establishing various maintenance/ retention systems in the event of fire accidents on offshore installations.

Thermal deformation and microstructure characteristics of low-heat Portland cement-based concrete in a high plateau environment

In this study, low-heat Portland cement concrete (LHPC-C) and ordinary Portland cement concrete (OPC–C) were prepared in a plateau region above 3000 m of altitude. The physical properties and thermal and deformation characteristics of the two types of concrete were studied. A JMZX-215HAT sensor was used to record the concrete strain and temperature in a plateau region. XRD, TG, SEM and MIP were employed to evaluate the product of concrete and micro-structure analysis. Results showed that Fresh LHPC-C displayed physical properties superior to fresh OPC-C in the plateau environment. And the rate of release of hydration heat and the total heat release of OPC-C were higher than those of LHPC-C. What's more, OPC-C exhibited a large contraction deformation, whereas LHPC-C exhibited a small fluctuation. Besides, LHPC-C exhibited a denser structure than OPC-C after 180 days.

Analysis of the fluid-solid-thermal coupling of a pressurizer surge line under ocean conditions

To investigate the effects of ocean conditions on the thermal stress and deformation caused by thermal stratification of a pressurizer surge line in a floating nuclear power plant (FNPP), the finite element simulation platform ANSYS Workbench is utilized to conduct the fluid-solid-thermal coupling transient analysis of the surge line under normal “wave-out” condition (no motion) and under ocean conditions (rolling and pitching), generating the transient response characteristics of temperature distribution, thermal stress and thermal deformation inside the surge line. By comparing the calculated results for the three motion conditions, it is found that ocean conditions can significantly improve the thermal stratification phenomenon within the surge line, but may also result in periodic oscillations in the temperature, thermal stress, and thermal deformation of the surge line. Parts of the surge line that are more susceptible to thermal fatigue damage or failure are determined. According to calculation results, the improvements are recommended for pipeline structure to reduce the effects of thermal oscillation caused by ocean conditions. The analysis method used in this study is beneficial for designing and optimizing the pipeline structure of a floating nuclear power plant, as well as for increasing its safety.

Thermal deformation characteristics of AlMo0.8NbTiW0.2Zr refractory multi-principal element alloy

Thermal deformation characteristics of a multiphase AlMo0.8NbTiW0.2Zr refractory multi-principal element alloy (RMPEA) prepared by powder metallurgy (P/M) were investigated using isothermal compression at temperature range of 1150–1350 °C and the strain rate of 10−4–10−2 s−1. The apparent activity energy (Q) for high-temperature deformation of AlMo0.8NbTiW0.2Zr was evaluated as 293–323 kJ mol−1 from the stress-strain data obtained from the hot-compression tests. The values of the stress exponent (n) were in a range of 2.51–2.84 at the strains of 0.35–0.69. At higher deformation strain rate, the discontinuous dynamic recrystallization (DDRX) mechanism became more obvious with increasing temperature. While at higher deformation temperature, the dominant dynamic recrystallization (DRX) mechanism gradually changed to the continuous dynamic recrystallization (CDRX) mechanism with decreasing strain rate. The intermetallic-growth-induced unidirectional bulging grain boundaries at low deformation temperature and high strain rate were beneficial to the nucleation of DDRX. The precipitated needle-like Zr-rich phase would promote the processing of CDRX at the deformation condition of high deformation temperature and low strain rate.