High Temperature Thermal Cycling Research Articles

Damage evolution and acoustic emission characteristics of hard rock under high temperature thermal cycles

Damage evolution and acoustic emission characteristics of hard rock under high temperature thermal cycles

Thermal Cycling Stability of Ti-Zr-Nb-Al Shape Memory Alloy

Shape memory alloys, as a novel class of intelligent materials, possess substantial application potential in the field of petroleum engineering at elevated temperatures. However, the complex downhole environment necessitates the alloy to endure alternating cycles of cold and heat, demanding both a high phase transformation temperature and excellent thermal cycling stability. This study focuses on a quaternary Ti-Zr-Nb-Al shape memory alloy, examining the thermal cycling stability of the Ti-20Zr-10Nb-xAl (x=1, 2, 3, 4 at%) alloys after subjecting them to 50 thermal cycles. Results indicate that the alloy composition, post 50 cycles, transitions from a single martensite α'' -phase to a duplex microstructure comprising α''-phase and β-phase. Changes in Al content did not significantly affect the phase composition of the alloy in its thermally cycled state. As Al content increases, both the tensile strength and shape memory effect of the alloy initially improve before declining. In terms of shape memory properties, the Ti-20Zr-10Nb-2Al alloy sample exhibits the most favorable thermal cycling stability, characterized by a tensile strength of 692 MPa, an elongation of 6%, a shape memory effect of 0.96% under 4% pre-strain, a shape memory recovery rate of 38%, and a Vickers microhardness of 381 HV.

Reversing relaxation-induced embrittlement by high-temperature thermal cyclic annealing in Zr-based metallic glass

Annealing usually induces structural relaxation and reduction of liquid-like regions, leading to embrittlement in bulk metallic glasses (BMGs). Here, we find that the short-term high-temperature thermal cycling (HTC) annealed Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) BMG shows an improved plasticity without sacrificing their yield strength. And only relaxation behavior with increased hardness is observed after HTC, which is different from the rejuvenation effect usually observed in cryogenic thermal cycling (CTC). We revealed that this embrittlement reversal is attributed to enhanced fluctuations of full width at half maximum (FWHM) of the hardness’ distribution at micrometer and larger scales induced by short-term HTC. The enhanced fluctuations of mechanical heterogeneities across the diameter on a cross-section of the short-term HTC sample may increase the number and decrease the size of shear transformation zones (STZs) activated at high stress and promote the deflection of shear bands (SBs) during their propagation to form multiple SBs. The enhanced plasticity after HTC induced relaxation contradicts the common sense that relaxation accompanying with annihilation of free volume or liquid-like region usually causes embrittlement. Present results indicate that short-term HTC could be a powerful mean to tune the mechanical performance, shedding new lights on the interplay among relaxation, mechanical/structural heterogeneity, and plasticity of MGs.

Microstructure evolution and micromechanical behavior of solvent-modified Cu–Ag composite sintered joints for power electronics packaging at high temperatures

With the increased deployment of power modules in demanding conditions, sintering materials, especially composite sintering materials, have raised growing interest due to their cost-effectiveness and suitability. Therefore, this study explores the viability of Cu–Ag composite sintering material, focusing on solvent influence through microstructure and mechanical behavior analysis. Micron-sized particle-based Cu–Ag composite pastes were designed and compared using eight solvents (four epoxy-free and four epoxy-added) based on fluidity and thermal stability. The sintered joints' performance, assessed through shear strength analysis, showed comparable values to pure silver sintering for both epoxy-free and epoxy-added samples. Optimized samples from each solvent system underwent reliability analysis, demonstrating that Cu–Ag joints with epoxy resin exhibited significantly higher shear strength after high-temperature storage and thermal cycling tests. Micromorphology and elemental composition analysis revealed differences in aging mechanisms, primarily attributed to variations in porosity due to oxide formation and pore filling by epoxy resin under different solvent systems. Further nanoindentation characterization of micromechanical properties, including hardness, modulus, and creep properties, during high-temperature aging, established constitutive models for insights into reliability evolution. In conclusion, the optimized epoxy-added Cu–Ag sintered joints proposed in this study demonstrated exceptional reliability and acceptable micromechanical properties, presenting a promising option for high-temperature power packaging.

Microstructure evolution of Incoloy 800H in industrial environment and correlation with creep mechanisms from literature

ABSTRACT The microstructures of 800 H samples affected by natural corrosion within industrial-like environmental conditions have been studied, and their potential effects on the creep response have been investigated based on literature information. Smooth cylindrical specimens of the alloy extracted from rolled sheet material have been placed into an industrial furnace, where they were exposed to high temperature thermal cycles within an air atmosphere. Samples spending 0 to 5 years inside the furnace underwent a microstructural characterisation campaign. Optical microscopy images reveal no grain coarsening. Macroscopic Vickers hardness shows a relatively wide surface hardness range (115≲HV10≲140). Compared to as-received material, micro-hardness profiles from specimens after years of high-temperature exposure exhibit a surface hardening trend within the vicinity of the edge exposed to the environment. Scanning electron microscopy analyses revealed two coexisting corrosion mechanisms: oxidation and nitridation. The latter is identified as the cause of the micro-indentation hardening trend.

ADVANCED HYBRID SOLAR THERMOELECTRIC GENERATOR THEORETICAL ANALYSES

Due to the fact that much of the world’s best solar resources are inversely correlated with population centers, significant motivation exists for developing the technology, which can deliver reliable and autonomous conversion of sunlight into electricity. Thermoelectric generators (TEG) are gaining incremental ground in this area due to its extensive use in solar thermal application as power generators, known as solar thermoelectric generators (STEG). STEG systems are gaining significant interest in both, concentrated and non-concentrated systems and have been employed in hybrid configurations with the solar thermal and photovoltaic systems. In this dissertation, mainly studies of Hybrid Solar Thermoelectric Generators (HSTEG) configuration are presented. HSTEG systems are much less studied both experimentally and theoretically, despite their clear technoeconomic advantages. There is a scope for significant improvement in the performance (efficiency) and a need for detailed performance analysis to understand the fundamentals of the energy transfer process. HSTEG systems (conventional) reported till date, initially the solar energy is utilized by the TEG for generating electricity and then transferred to other low temperature thermal cycles (heating or cooling). As an alternative one can design an advanced HSTEG system, in such way to first utilize the solar energy in the heat transfer fluid (HTF), which can run high temperature thermal cycle for heating or cooling or power generation) and then generate electricity by using TEG. Further, there is no advanced HSTEG system is available in the literature, which could deliver high temperature heat output from the hot side of the HSTEG system. Key Words: optics, photonics, light, lasers, stencils, journals

Experimental and numerical analysis of CMCs mechanical properties under high-temperature thermal gradient environment

This paper carried out a high-temperature thermal gradient cycling test of ceramic matrix composites (CMCs), investigating the failure characteristics of CMCs in non-uniform high-temperature environments. The result shows that the damage characteristics of CMCs under thermal gradient environments are significantly different from those under uniform temperature environments. The SiC fiber pull-out lengths at different yarn fractures have obvious differences in the thermal gradient direction. The thermal stress damage propagation pattern of CMCs under the thermal gradient environment is revealed by numerical analysis, and its residual mechanical properties under different thermal gradient environments are predicted. The numerical results could be adopted as a theoretical basis and suggestions for temperature control of CMCs components in practical applications.

Hybrid Bond Interconnect and Advanced Packaging Solutions

Hybrid bond interconnect is a scalable technology that offers significant improvements over the incumbent Cu mbump technology. The notable advantages include, enhanced reliability of elemental metal interconnect, improved thermal performance of an inorganic bond interface and the high-speed performance with a low capacitance and inductance pad structure. Currently, the industry is adopting this technology for high-performance compute applications; however, we anticipate a broader adoption once the technology is readily available within the full supply chain. In this paper, we present the performance of our hybrid bond interconnect on multiple test vehicles including single 1 to 8-die stacks with various pad-pitch sizes, die sizes and configurations. We share die to wafer assembly yield results using our manufacturing worthy process where die are prepared on tape frame using standard pick and place equipment. The test vehicles cover a range of pad sizes (2-15 um), with pitches (4-40 um) and have different x,y dimensions from 1mmx1mm to 9mmx12mm. Reliability tests include MSL-3 precondition, high temperature storage and thermal cycling and on the various test structures

Multi-factor coupled failure mechanism of W–Cu functionally graded material under thermal shock service

The stability of W–Cu functionally graded material (FGM) as a heat sink connecting material is of significant importance for long-term service under high-temperature thermal cycling conditions. In this study, W–Cu FGM was successfully fabricated by powder metallurgy method. Various thermal shock experiments were performed on the samples at different temperatures and cycles, and a comprehensive investigation was conducted into its service failure mechanisms. The findings demonstrate that as the temperature increases to 1000 °C, the layer with low copper content gradually developed microcracks, and the microstructure changed from the original uniform distribution to a copper granular exudation, ultimately forming a network-like copper layer. The layer with high copper content undergoes a transition from slight undulations and roughness to the emergence of numerous cracks and pores, accompanied by the formation of a larger area of copper pool structures. After 1000 °C thermal shock for 200 cycles, the thermal conductivity decreases from 215.33 W m−1 K−1 to 168.24 W m−1 K−1, the bending strength decreased from 686.75 MPa to 115.77 MPa at room temperature, with reductions of 22.4 % and 81.2 %, respectively. At this point, the sample severely failed. The study highlights that the thermal shock failure mechanism of the gradient W–Cu samples is a novel multifactor coupled failure mechanism. It is influenced by the combined effects of crack initiation and propagation induced by thermal stress and the evolution of microstructural changes.

Early detection of thermal instability in railway tracks using piezo-coupled structural signatures

Rail accidents caused by rail track derailments have been a growing concern due to repetitive thermal changes resulting from high temperature stresses in rails due to rail traction and environmental thermal variation. This leads to thermal buckling, which can result in catastrophic failure. Structural health monitoring (SHM) using the electromechanical impedance (EMI) technique has emerged as a promising technology to detect structural deterioration and its severity before it leads to failure. This study used piezoelectric sensors to collect piezo-coupled structural signatures of different rail-joint bars for high-temperature repetitive thermal cycles, which were then analyzed using an impedance analyzer. The results show that the piezo-coupled signatures could identify structural changes, and the damage metric, could be employed for continuous monitoring of structural rail defects due to excessive thermal stress and residual strain. The method also derived piezo-equivalent structural parameters, such as mass, stiffness, and damping, which were very satisfactory in detecting significant changes and consequent damage. Overall, this study presents a pre-emptive experimental method that can see thermal deterioration and instability in rails and rail joints, thereby reducing the risk of rail accidents caused by derailments.

A Study on Long-Term Oxidation and Thermal Shock Performance of Nanostructured YSZ/NiCrAlY TBC with a Less Dense Bond Coat.

This paper focused on studying the performance of a nanostructured thermal barrier coating (TBC) system deposited by APS, which had a bond coat with inter-lamellar porosities that resulted during the manufacturing process. The higher porosity level of the bond coat was studied as a possible way to keep the thickness of the TGO under control, as it is distributed on a higher surface, thereby reducing the chance of top-coat (TC) spallation during long-term oxidation and high-temperature thermal shock. The TBC system consisted of nanostructured yttria partially stabilized zirconia (YSZ) as a top coat and a conventional NiCrAlY bond coat. Inter-lamellar porosities ensured the development of a TGO distributed on a higher surface without affecting the overall coating performance. Based on long-term isothermal oxidation tests performed at 1150 °C, the inter-lamellar pores do not affect the high resistance of nanostructured TBCs in case of long-term iso-thermal oxidation at 1150 °C. The ceramic layer withstands the high-temperature exposure for 800 h of maintaining without showing major exfoliation. Fine cracks were discovered in the ceramic coating after 400 h of isothermal oxidation, and larger cracks were found after 800 h of exposure. An increase in both ceramic and bond-coat compaction was observed after prolonged high-temperature exposure, and this was sustained by the higher adhesion strength. Moreover, in extreme conditions, under high-temperature thermal shock cycles, the TBC withstands for 1242 cycles at 1200 °C and 555 cycles at 1250 °C.

Development and thermo-mechanical reliability assessment of fiber reinforced polymers in lightweight PV modules towards vehicle-integrated photovoltaics

Weight reduction by omitting the use of bulky glass in c-Si photovoltaic (PV) modules is an important consideration of module development for vehicle-integrated photovoltaics (VIPV). Various approaches to achieve lightweight modules are proposed, yet there are many concerns regarding the reliability of such modules compared to standard glass-glass or glass-backsheet configurations. In this work, we investigate the thermo-mechanical behavior of LW modules with a multiwire design specifically aiming to VIPV applications. The developed modules consist of a commercially available carbon-fiber reinforced polypropylene backsheet and are compared to glass-fiber reinforced polypropylene backsheet modules. To enhance the thermo-mechanical reliability, polymer encapsulant and interconnection foil are substituted by glass-fiber reinforced composite encapsulant with the carbon-fiber reinforced polypropylene backsheet, thereby leading to ∼2.9% fill factor (FF) decrease with a limited degradation after 200 thermal cycles. A failure mechanism analysis using electroluminescence and X-ray-based micro-tomography is carried out after thermal cycling tests, clearly demonstrating that thermal stresses introduce deformation of wire interconnects. A modified high-temperature thermal cycling test (- 40 to 110 °C, 3.5 h) is implemented to observe the fast degradation of interconnects in compliance with VIPV conditions. The resulting fatigue stresses account for wire breakage in-between cells in the glass-fiber reinforced polypropylene module, while this effect is less pronounced in the carbon-fiber reinforced polypropylene backsheet module, indicating better thermo-mechanical reliability of the carbon-fiber reinforced polypropylene backsheet module. Herein, the current results could provide guidelines for lightweight PV module design (with a weight of 4.8 kg/m2) in the thermo-mechanical aspect. This research sheds light on the potential of lightweight modules specifically for VIPV applications.

Microstructure, mechanical characteristics, and electrochemical behavior of the wide-area stir zone fabricated in Al5083 by friction stir processing with overlapping technique

In the current study, a wide-area stir region was created in Al5083 aluminum alloy using multi-pass friction stir processing (FSP) with 50% pin overlapping. Microstructural investigations such as grain structure analysis and intermetallic particle (IMPs) distribution were carried out on processed alloys using optical and scanning electron microscopy (SEM). Recrystallized fine grains were developed after FSP due to the intense plastic straining and dynamic recrystallization. It was also identified that the grain refinement was uniform in the stir region of all overlapping passes, resulting in uniform hardness over the wide-area stir region. Three different types of IMPs, such as needle shape iron-based IMPs, round shape magnesium-based IMPs, and the very fine magnesium-based IMPs along the grain boundaries, were identified from the SEM analysis. The tensile test findings showed that the elongation improved drastically after overlapping FSP, while the hardness and tensile strength were found to be decreased due to high temperature thermal cycles. Electrochemical investigations revealed that the corrosion rate decreased after FSP due to the formation of uniform grain structure and dissolution of iron-based IMPs.

Corrosion Behaviour of NiCr/TiO2 coated 316L stainless steel before and after thermal shock exposure

ABSTRACT Understanding the impact of high-temperature thermal cycle on coating composition and its corrosion characteristics is essential for coating development. The present study investigated NiCr/TiO2-coated 316L austenitic stainless steel (316L SS) under thermal shock exposure and their corrosion behaviour in 3.5% NaCl solution. The electrochemical parameters were evaluated using potentiodynamic polarisation and electrochemical impedance spectroscopy techniques to understand the corrosion characteristics. Various techniques, viz. field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, were employed to examine the morphology, elemental composition, crystalline and oxidation characteristics of all the samples. The NiCr/TiO2-coated 316L SS demonstrated thermal resistance up to 9-h oxidation period and five thermal cycles. Afterwards, with gradual weight loss, TiO2 spallation appeared on the coated samples. The as-deposited sample revealed an increased pitting potential of 118.76% and improved corrosion resistance over ten times in magnitude than the bare sample. This improvement in the coated sample is attributed to high charge transfer resistance and chemically stable coating layer between the metal matrix and corrosive solution. In contrast, the delaminated sample revealed over four times greater resistance than the bare sample, which is credited to the limited surface area for possible redox reactions and passive NiCr bond coat layer over the metal matrix.

The effect of multiple thermal cycles on Ti-6Al-4V deposits fabricated by wire-arc directed energy deposition: Microstructure evolution, mechanical properties, and corrosion resistance

Thermal cycles have an important effect on the microstructure and properties of the components fabricated by wire-arc directed energy deposition (wire-arc DED). In this study, a Gleeble thermal-mechanical simulator was adopted to create closer-to-reality thermal cycles with the assistance of a numerical simulation model and experimental Ti-6Al-4V deposition. Step-by-step microstructure evolution, including αm, retained β, and GB α, microhardness gradual variation, and the corrosion resistance change before and after the entire thermal cycle were investigated. Therefore, combining phase orientation and high-magnification morphology, transformed and untransformed α that occurred in low- and medium-temperature thermal cycles can be distinguished. After the entire thermal cycle, αm laths coarsened from ∼1 µm to ∼1.2 µm, and the content of retained β phase became more and more. The αm formed around grain boundaries partially disappeared and was occupied by α laths from the inner grain. GB α was more continuously distributed along prior β grain boundaries due to its lower formation temperature during the subsequent thermal cycles that were occurring incomplete α→β transformation. The severe preferential orientation of α phases formed after the deposition and high-temperature thermal cycle was also alleviated through the twice low-temperature thermal cycles. Besides, the microhardness decreased from 318.78 ± 7.5 HV to 285.17 ± 5.3 HV after the high-temperature thermal cycle but eventually increased significantly to 330.5 ± 6.4 HV after experiencing the final low-temperature thermal cycle. The corrosion resistance decreased after the entire thermal cycle, indicating a performance difference between the top and bottom regions of the Ti-6Al-4 V component fabricated by wire-arc DED.

Role of headspace environment for phase change carbonates on the corrosion of stainless steel 316L: High temperature thermal storage cycling in concentrated solar power plants

Role of headspace environment for phase change carbonates on the corrosion of stainless steel 316L: High temperature thermal storage cycling in concentrated solar power plants

Microstructure evolution of thermally grown Al2O3 on NiCrAlY bonding coating for high-temperature thin-film sensors

Thermal stability is an important aspect of thermally grown alumina (TGA) for high-temperature thin-film sensors on nickel-based superalloys. In this paper, a thermodynamic coupled model was used to calculate the vacuum diffusion and the oxidation of aluminum atoms in NiCrAlY bonding coatings (BCs). The calculation results show that the thickness of the outer Al-rich β-NiCrAl layer gradually increases during the vacuum diffusion process and reaches the maximum at 1050 °C for 6 h, while the thickness of NiCrAlY BCs is 15 µm. The scanning electron microscope results show that the surface of TGA is mainly composed of metastable alumina (θ and γ-Al2O3) at high oxygen partial pressure (1 ×105 Pa). At lower oxygen partial pressure (10–1 ×103 Pa), the TGA is mainly composed of equiaxed α-Al2O3. The experimental results show that the oxygen partial pressure is the main factor determining the crystal phase of TGA. The energy-dispersive X-ray spectroscopy shows that the TGA thickness is about 500 nm after 12 h of oxidation at 950 °C and 100 Pa, which are consistent with the calculation results. Finally, to verify the improvement of thermal stability of the TGA, Pt/Pt-10%Rh thin-film thermocouples (TFTCs) with Al2O3 insulating layer, TGA and NiCrAlY BCs were fabricated on the surface of the turbine blade by magnetron sputtering. The insulating layer has an excellent insulation resistivity (exceeded 2 ×109 Ω·cm at 1000 °C) during three consecutive high-temperature thermal cycling tests. This result suggests that the TFTCs with thermally grown α-Al2O3 possesses have excellent reliability and stability at high temperature.

On the Microcrack Propagation and Mechanical Behavior of Granite Induced by Thermal Cycling Treatments

Deep geothermal energy is a renewable and environmentally friendly resource, and the hot dry rock in a geothermal reservoir is subjected to thermal cycling treatment. Thermal cycling treatment can cause thermal stresses in the rock matrix and result in thermal cracking, which significantly influence the physical and mechanical properties of a rock. To investigate the influence of thermal cycling treatment on the microcrack propagation and mechanical behavior of a granite rock, a series of physical and mechanical tests were performed on nontreated and treated granite samples. The testing results show that the mass, density, and P-wave velocity of granite decrease with heating temperature and cycling time increase, while the volume of the samples increases significantly. The UCS and elastic modulus of the granite declined from 178.65 MPa and 20.09 GPa to 24.58 MPa and 3.81 GPa after treatment at 500 °C for 30 thermal cycling times, respectively. The degradation trends of the UCS and the elastic modulus of the granite can be characterized by the heating temperature and the thermal cycling times. High temperature and frequent thermal cycling treatment can induce microcrack propagation within the granite, which causes the failure of the samples and leads a transformation of granite from brittleness to ductility.

Thermo-mechanical stability of concrete containing steel slag as aggregate after high temperature thermal cycles

Thermal energy storage represents a crucial element to increase solar power dispatchability. Within sensible heat storage in solid media, concrete is considered a low-cost alternative to be further developed and therefore, this has been addressed in this paper. Four concrete dosages were designed, combining each type of considered cement, ordinary Portland and calcium aluminate cement, with each type of considered aggregate, silico-calcareous and a steel slag. Thermo-mechanical properties of concrete were studied before and after 10 thermal cycles from 290 °C to 700 °C. Maximum operating temperature and heating rates were selected accordingly to the targeted application, a concentrating solar power (CSP) tower plant. At macro-level, results show thermal cycle stability of concrete with steel slag aggregate in both cement types. On the contrary, at micro-level, the petrography analysis shows the lack of bonding between steel slag aggregate and the cement paste. In contrast, concrete mixtures containing silico-calcareous aggregates collapse after thermal cycling.

A custom designed modular, scalable test system for an efficient performance evaluation of thermoelectric devices

• A modular, scalable test rig capable of evaluating unicouple, devices and modules. • Ability to handle most thermoelectric (TE) performance evaluation criterion’s including real-world endurance high temperature thermal cycling, thermal soaking and identifying defective devices is demonstrated. • Evaluated three different TE systems viz. Bismuth Telluride, Skutterudites and Half Heusler alloys across different temperature gradients. • Single software platform interacting with DAQ with special features like automatic temperature stability control, high vacuum control, inert gas purging to minimize high temperature oxidation/sublimation of TE device. Reliable and efficient performance evaluation of thermoelectric (TE) elements and devices is critical for developing high performance and robust thermoelectric generator. Due to the inherent thermomechanical coupling, testing thermometric devices is a challenge and requires design of customized test rigs for a thorough evaluation. This article discusses design and development of a modular, scalable customized test rig for performance evaluation of TE devices of different proportions. Various standard TE specifications like harvested power, specific power, instantaneous device resistance, power–current relationships, device efficiency/competence measured against time/temperature difference can be readily evaluated. Further, the test rig is also employed for mimicking real-world endurance thermal cycling tests, high temperature thermal soaking and using measured data to potentially identifying defective devices which have not been addressed in detail before. All these test results together can help determine the effectiveness of TE materials in an actual real world application setting. The scalability and robustness aspects of the proposed test rig is demonstrated by evaluating three different classes of TE systems viz. Bismuth Telluride, Skutterudites and Half Heusler alloys across different temperature gradients and various TE material/legs, devices or modules. The test is capable of handling other TE material systems, geometric configurations and temperature gradients that are not discussed in this work.