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This paper employed squeeze-casting (SC) technology to develop a novel Al-7Si-1.5Cu-1.2Ni-0.4Mg-0.3Mn-0.15Ti heat-resistant alloy, addressing the issue of low room/high temperature elongation in traditional gravity casting (GC). Initially, the effects of SC and GC processes on the microstructure and properties of the alloy were investigated, followed by an examination of the evolution of the microstructure and properties of the SC samples over thermal exposure time. The results indicate that the SC process significantly improves the alloy's microstructure. Compared to the GC alloy, the secondary dendrite arm spacing of the as-cast SC alloy is refined from 50.5 μm to 18.5 μm. Meanwhile, the size and roundness of the eutectic Si phase in the T6-treated SC alloy are optimized from 11.7 μm and 0.75 μm to 9.5 μm and 0.85 μm, respectively, and casting defects such as porosity are reduced. Consequently, the ultimate tensile strengths (UTSs) at room temperature and at 250 °C of the SC alloy are 5% and 4.9% higher than that of GC alloy, respectively, and its elongation at both temperatures shows significant improvement. After thermal exposure at 250 °C for 120 h, the morphology of the residual second phase at the grain boundaries in the SC alloy becomes more rounded, but the eutectic Si and nano-precipitates undergo significant coarsening, resulting in a 49% decrease in UTS. [ABSTRACT FROM AUTHOR]

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility. [ABSTRACT FROM AUTHOR]

The microstructure evolution under over-temperature （1070-1250 ℃） and tensile/compressive stress （30-90 MPa） conditions of IC10 alloy was analyzed to simulate the alloy deterioration process during over-temperature operation of gas turbine blades.The results show that the degeneration of secondary γ' phase in IC10 alloy during thermal exposure without stress includes spheroidizing， coarsening， and redissolution. As thermal exposure temperature and time increase， the shape of secondary γ' phase transforms from flower-like to rounded cubic and spherical， driven by the decrease of γ/γ' phase interface energy. The area fraction of secondary γ' phase decreases with the increase in temperature and the prolonging of time. The secondary γ' phase is completely redissolved after thermal exposure at 1225-1250 ℃ for more than 50 h. The size of secondary γ' phase increases with the increase in temperature and time. The coarsening of γ' phase conforms to the Lifshitz-Slozov-Wagner theory controlled by diffusion. Under the overtemperature and stress condition， the rafting of γ' phase gradually intensifies with the increase of temperature. The tensile stress promotes the N-type rafting of γ' phase perpendicular to the stress axis， while the compressive stress promotes the P-type rafting of γ' phase parallel to the stress axis. The γ' phase rafting process is faster under the tensile stress state than under the compressive stress. The microstructure of IC10 alloy under over-temperature and stress conditions can be used to evaluate the service conditions of the blade after service.

The microstructural stability and property evolution of high-temperature titanium alloys under long-term high-temperature conditions has been a critical scientific issue in the field of advanced titanium alloys. In this work, we systematically investigated the precipitation behavior of silicides and ordered α2 phase, which are closely related to the microstructural stability of Ti65 high-temperature alloy, during thermal exposure at 650 °C for different periods of time. Furthermore, the effects of thermal exposure on mechanical properties were evaluated using room temperature and high temperature tensile tests, and subsequently, the correlation between the microstructural thermal stability and the mechanical characteristics was discussed. The results reveal that (Ti, Zr)6Si3 silicides initially precipitate within the residual β film and then start to precipitate in the α platelet. A large number of fine spherical α2 precipitates were formed inside the α platelet after a short thermal exposure. The number density of ordered α2 decreased significantly after 1000 h due to Ostwald ripening. The precipitation of silicides and ordered α2 phases during thermal exposure improves the tensile strength but deteriorates the ductility, and the room-temperature ductility is slightly restored due to α2 ripening after long-time thermal exposure. Ti65 high-temperature titanium alloy consistently maintains favorable room-temperature tensile properties throughout long-term thermal exposure. [ABSTRACT FROM AUTHOR]

To establish the correlation between thermal conditions imposed on bloodstains and visualizing effect of enhancement techniques, infrared photography and four chemical enhancement reagents were used to visualize bloodstains following thermal exposure. A black tile was selected as the substrate to intensify the visualization challenge, with a Cone Calorimeter serving as the standardized heating source to control thermal conditions. Compared with standard photography, infrared photography is proven to be a valuable complement to chemical reagents, showing significant advantages in visualizing bloodstains after thermal exposure. However, it is worth noting that infrared image fell short of standard image when bloodstains displayed raised, embossed morphology or when bloodstains almost disappeared under specific conditions. The enhancement effectiveness was found to be strongly correlated with thermal conditions imposed on bloodstains, and the morphology evolution of bloodstains during heating affected the chemical enhancement effect additionally, especially when the bulge morphology was formed, and it was observed that reagents were more effective after removing the dense shell of the bulge. Among the four selected chemical enhancement reagents, fluorescein performed exceptionally well, maintaining its effectiveness even for bloodstains heated at 641°C for 10 min. TMB demonstrated its visualizing ability for bloodstains heated at 396°C for 5 min and heated at 310°C for 20 min. BLUESTAR® followed afterwards, while luminol performed worst. The correlation between thermal conditions imposed on bloodstains and the corresponding visualizing effectiveness of enhancement techniques provides important references for detecting bloodstains at fire scenes. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work investigates the effect of Ru on the precipitation of the topologically close-packed (TCP) phase from the γ-γʹ microstructural degradation analysis. The addition of Ru is found to delay the precipitation time of the TCP phase from 100 h to 1000 h after thermal exposure at 950 °C. The effect of Ru on the γ-γʹ microstructural degradation is also investigated. Adding Ru slightly decreases the coarsening rate of the γʹ size and promotes the reduction of the volume fraction of γʹ phase. The reduction of the volume fraction of γʹ phase causes the ''inverse partitioning'' effect and increases the solution limit of the TCP forming element in the matrix. These help inhibit the precipitation of the TCP phases in Ni-based single crystal superalloys during thermal exposure.

The microstructural characteristics of brazing seams significantly influence the mechanical properties of brazed joints. In this study, a novel Ni3Al-based single crystal superalloy(Alloy 1) with high Mo content was brazed with a Ni–B–Si–Ti filler. The evolution of microstructure and mechanical properties of brazed joints were investigated after thermal exposure at 1000 °C up to 300h. The brazed joint was mainly composed of the athermally solidified zone (ASZ), isothermal solidification zone (ISZ), diffusion affected zone (DAZ), and base metal (BM). As the increase of thermal exposure time, the tensile strength of the joint at 980 °C decreases from 625 MPa at 0h of thermal exposure to 443 MPa after 300h of thermal exposure. It is suggested that as the duration of thermal exposure increases, the skeleton phases gradually aggregate at the ASZ/ISZ interface, reducing the relative barrier effect of the skeleton in ASZ. Simultaneously, the ASZ/ISZ interface becomes smoother over time, which in turn leads to rapid crack propagation.

Widespread species experience a variety of climates across their distribution, which can structure their thermal tolerance, and ultimately, responses to climate change. For ectotherms, activity is highly dependent on temperature, its variability and availability of favourable microclimates. Thermal exposure and tolerance may be structured by the availability and heterogeneity of microclimates for species living along temperature and/or precipitation gradients – but patterns and mechanisms underlying such gradients are poorly understood. We measured critical thermal limits (CTmax and CTmin) for five populations of two sympatric lizard species, a nocturnal gecko (Chondrodactylus bibronii) and a diurnal skink (Trachylepis variegata) and recorded hourly thermal variation for a year in three types of microclimate relevant to the activity of lizards (crevice, full sun and partial shade) for six sites across a precipitation gradient. Using a combination of physiological and modelling approaches, we derived warming tolerance for the present and the end of the century. In the present climate, we found an overall wider thermal tolerance for the nocturnal species relative to the diurnal species, and no variation in CTmax but variable CTmin along the precipitation gradient for both species. However, warming tolerances varied significantly over the course of the day, across months and microhabitats. The diurnal skink was most restricted in its daily activity in the three driest sites with up to six daily hours of restricted activity in the open (i.e. outside refugia) during the summer months, while the impacts for the nocturnal gecko were less severe, due to its higher CTmax and night activity. With climate change, lizards will experience more months where activity is restricted and increased exposure to high temperatures even within the more sheltered microhabitats. Together our results highlight the importance of considering the relevant spatiotemporal scale and habitat for understanding the thermal exposure of diurnal and nocturnal species. [ABSTRACT FROM AUTHOR]

The present study investigated microstructural evolution and changes in tensile properties of an Al-Si piston alloy subjected to thermal exposures at 250 and 350 °C for 150, 300, and 500 h. Microstructural and nanoscale precipitates were characterized using a combination of high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) images and scanning electron microscopy (SEM). The tensile testing was performed. The results demonstrated that the thermal exposure induced granulation of the δ-Al3CuNi particles, alongside precipitation of the θ-Al2Cu phase particles and AlCu clusters within the matrix. Specifically, an increase in the size and number density of the θ-Al2Cu phase particles was observed with exposure time at 250 °C. Conversely, at 350 °C, the θ-Al2Cu particles exhibited a gradual increase in size with prolonged thermal exposure, coupled with a decrease in their number density. AlCu clusters precipitated solely at a thermal exposure temperature of 350 °C, with precipitation intensifying over time. Moreover, a decrease in the alloy's tensile strength and an increase in elongation were noted after thermal exposure. Finally, the present study discussed the precipitation mechanisms of θ-Al2Cu particles and AlCu clusters within the grains, suggesting that the AlCu clusters exerted a more effective strengthening effect compared to the θ-Al2Cu particles. [ABSTRACT FROM AUTHOR]

Abstract Background Guided bone regeneration (GBR) involves collecting bone autografts with high bio-quality and efficiency. The current non-irrigated low-speed drilling has been limited for broader application in bone autograft harvest due to its low efficiency, inability to conduct buccal cortical perforation, and dependence on simultaneous implant placement. Increasing the drilling speed helps improve the efficiency but may incur thermal-mechanical bone damage. Most studies have addressed thermal reactions during bone drilling on non-vital models, which is irrelevant to clinical scenarios. Little has been known about bone’s in vivo thermal profiles under non-irrigated higher-speed drilling and its influences on the resulting bone chips. Aim A novel technique for bone harvest and cortical perforation via in-situ non-irrigated higher-speed drilling was proposed and investigated for the first time. Methods The third mandible premolars of eight beagles were extracted and healed for three months. Sixteen partial edentulous sites (left and right) were randomized into four groups for bone autograft harvest without irrigation: chisel, 50 rpm drilling, 500 rpm drilling, and 1000 rpm drilling. Bone chips were harvested on the buccal plates of the missing tooth. An infrared camera and an implantable thermocouple collaboratively monitored in vivo real-time bone temperature at the drilling sites. In vitro performances of cells from bone chips, including cell number, viability, proliferation, migration, ALP activity, in vitro mineralization, mRNA transcriptional level of osteogenic genes and heat shock protein 70 (HSP-70), and HSP-70 expression at the protein level were also studied. Results 500 rpm produced mild local hyperthermia with a 2–6 °C temperature rise both on the cortical surface and inside the cortical bone. It also held comparable or enhanced cell performances such as cell number, viability, proliferation, migration, ALP activity, in vitro mineralization, and osteogenic genes expression. Conclusions In-situ non-irrigated higher-speed drilling at 500 rpm using a screw drill is versatile, efficient, and thermal friendly and improves the bio-quality of bone chips. Our novel technique holds clinical translational potential in GBR application.

7A85-T74 forged aluminum alloy was chosen as the experimental material, and the microstructure, tensile properties and impact energy of the alloy were investigated after 5 h of thermal exposure at room temperature to 240℃. The mechanism of the influence of the microstructure on the mechanical properties of 7A85-T74 aluminum alloy was also analyzed by transmission electron microscopy. The results show that the grain size of 7A85-T74 aluminum alloy does not change much in the temperature range of 80-240℃, but the precipitation phase changes significantly with the increase of temperature. Below 120℃, the precipitate size, tensile properties and impact absorption energy do not change significantly with increasing thermal exposure temperature, and the precipitation strengthening mechanism is a mixture of dislocation cutting precipitates and dislocation bypassing precipitates. With the increase of the thermal exposure temperature from 120℃ to 240℃, the precipitate average radius increases from 3.8 nm at room temperature to 12.3 nm, and the precipitate changes from η' phase to η phase. The yield strength and tensile strength of the alloy decrease significantly by 45.7% and 33.5% respectively compared with that of room temperature and the elongation, reduction of area and impact energy of the alloy increase significantly. The precipitation strengthening mechanism changes to dislocation bypassing precipitates, and the fracture mode changes from mixed fracture consisting of intergranular fracture and dimple transgranular fracture to dimple transgranular fracture. The effect of precipitate size on the strength and impact energy of the alloy discusses based on the precipitation strengthening theory, and the results of the theoretical analysis are consistent with the experimental results.

Introduction: Deep burns, primarily caused by thermal exposure such as fire and hot liquids, result in severe tissue injuries with enduring consequences, prompting extensive research into their etiology, treatment, and ramifications. Surgical intervention is pivotal, though its efficacy varies based on diverse factors. Technological advancements and global collaboration are paramount for enhancing treatment efficacy and patient outcomes. Research Aim: The research aim involves a retrospective analysis of burn cases, particularly those involving respiratory tract involvement, with a focus on elucidating current diagnostic and treatment modalities. Materials and Methods: A patient cohort of 110 individuals, predominantly male (ratio 3:1), aged 40-80, underwent examination. Key criteria evaluated encompassed gender, age, pre-treatment diagnosis, intervals between surgeries, hospitalization duration, burn severity and extent, blood transfusions, burn types and locations, treatment modalities, and post-treatment complications. Result: Findings revealed a male predominance and increased susceptibility among individuals aged 40-60 and 60-80. Surgical approaches varied, encompassing excisional debridement, skin grafting, and, in some cases, amputation. Common causes of deep burns, such as fire and hot liquids, were identified, along with associated complications like infections and coagulation abnormalities. Effective management of these complications, including systemic inflammatory response syndrome and post-hemorrhagic anemia, proved pivotal for optimal patient outcomes. Conclusions: In conclusion, deep burns pose significant challenges, particularly for middle-aged and older individuals. Surgical interventions necessitate individualized and comprehensive approaches. Efficient management of associated complications is imperative for ensuring optimal patient recovery.

Research on how thermal exposure affects the microstructure and mechanical properties of the Ti–48Al–3Nb–1.5Ta (at. %) alloy, which is prepared via powder hot isostatic pressing (P–HIP), is essential since this low-density alloy shows promise for use in high-temperature applications, particularly for aero-engines, which require long-term stable service. In this study, a P–HIP Ti–48Al–3Nb–1.5Ta (at. %) alloy was exposed to high temperatures for long durations. The phase, microstructure and mechanical properties of the P–HIP Ti–48Al–3Nb–1.5Ta alloy after thermal exposure under different conditions were analyzed using XRD, SEM, EBSD, EPMA, TEM, nanomechanical testing and tensile testing. The surface scale is composed of oxides and nitrides, primarily Al2O3, TiO2, and TiN, among which Al2O3 is preferentially generated and then covered by rapidly growing TiO2 as the thermal exposure duration increases. The nitrides appear later than the oxides and exist between the oxides and the substrate. With increasing exposure temperature and duration, the surface scale becomes more continuous, TiO2 particles grow larger, and the oxide layer thickens or even falls off. The addition of Ta and Nb can improve the oxidation resistance because Ta5+ and Nb5+ replace Ti4+ in the rutile lattice and weaken O diffusion. Compared with the P–HIP Ti–48Al–3Nb–1.5Ta alloy, after thermal exposure, the grain size does not increase significantly, and the γ phase increases slightly (by less than 3%) with the decomposition of the α2 phase. With increasing thermal exposure duration, the γ phase exhibits discontinuous coarsening (DC). Compared with the P–HIP Ti–48Al–3Nb–1.5Ta alloy, the hardness increases by about 2 GPa, the tensile strength increases by more than 50 MPa, and the fracture strain decreases by about 0.1% after thermal exposure. When the depth extends from the edge of the thermally exposed specimens, the hardness decreases overall. [ABSTRACT FROM AUTHOR]

The effect of thermal exposure under high vacuum conditions on the chemical composition of the surface layers of the VT6 alloy with the mixed implantation of N+ ions by a carbon film is investigated. It is shown that under the conditions of thermal exposure the change in the concentration profiles of the distribution of elements is determined by the processes of chemical interaction, in which the diffusion of carbon and nitrogen into deeper layers does not occur. On the contrary, their concentration decreases and this is due to the formation of volatile compounds CO, CO2, or (CH)2 under thermal exposure. Titanium in the surface analyzed layer is in an oxidized state with various degrees of oxidation. Up to a depth of about 10 nm, the oxidation states of titanium are Ti4+ and Ti3+; in the transition region of the film/substrate, Ti2+. [ABSTRACT FROM AUTHOR]

The residual flexural behavior of reinforced concrete (RC) beams strengthened with a fabric-reinforced cementitious matrix (FRCM) composite system after exposure to elevated temperatures was analyzed and discussed in the paper. Ten RC beams, two unstrengthened and eight strengthened with a polypara-phenylene-benzo-bisthiazole (PBO) FRCM system, were tested at ambient temperature (20°C) under three-point bending after being exposed to temperatures of 100°C, 200°C, and 300°C. Test results were analyzed in terms of failure modes, failure loads, load–deflection curves, strain, stress distributions, and ductility. The obtained results evidenced that the load-bearing capacity of the strengthened beams remained roughly constant for temperatures ranging from 20°C to 200°C (from 13% to 23% higher than that of the unstrengthened beams). On the other hand, the collapse of PBO FRCM-strengthened beams exposed to a temperature of 300°C occurred for load values that were, on average, 12% lower than those of strengthened beams at room temperature. The effects of exposure to elevated temperatures on the PBO FRCM-to-concrete debonding were also discussed. A semiempirical model based on the experimental results was defined to estimate the residual debonding strain of the composite system as a function of temperature. The accuracy of the proposed model as well as those of some different analytical procedures available in the literature was assessed through a comparison with experimental results. [ABSTRACT FROM AUTHOR]

The microstructural stability and property evolution of high-temperature titanium alloys under long-term high-temperature conditions has been a critical scientific issue in the field of advanced titanium alloys. In this work, we systematically investigated the precipitation behavior of silicides and ordered α2 phase, which are closely related to the microstructural stability of Ti65 high-temperature alloy, during thermal exposure at 650 °C for different periods of time. Furthermore, the effects of thermal exposure on mechanical properties were evaluated using room temperature and high temperature tensile tests, and subsequently, the correlation between the microstructural thermal stability and the mechanical characteristics was discussed. The results reveal that (Ti, Zr)6Si3 silicides initially precipitate within the residual β film and then start to precipitate in the α platelet. A large number of fine spherical α2 precipitates were formed inside the α platelet after a short thermal exposure. The number density of ordered α2 decreased significantly after 1000 h due to Ostwald ripening. The precipitation of silicides and ordered α2 phases during thermal exposure improves the tensile strength but deteriorates the ductility, and the room-temperature ductility is slightly restored due to α2 ripening after long-time thermal exposure. Ti65 high-temperature titanium alloy consistently maintains favorable room-temperature tensile properties throughout long-term thermal exposure.

Background: Guided bone regeneration (GBR) involves collecting bone autografts with high bio-quality and efficiency. The current non-irrigated low-speed drilling has been limited for broader application in bone autograft harvest due to its low efficiency, inability to conduct buccal cortical perforation, and dependence on simultaneous implant placement. Increasing the drilling speed helps improve the efficiency but may incur thermal-mechanical bone damage. Most studies have addressed thermal reactions during bone drilling on non-vital models, which is irrelevant to clinical scenarios. Little has been known about bone's in vivo thermal profiles under non-irrigated higher-speed drilling and its influences on the resulting bone chips. Aim: A novel technique for bone harvest and cortical perforation via in-situ non-irrigated higher-speed drilling was proposed and investigated for the first time. Methods: The third mandible premolars of eight beagles were extracted and healed for three months. Sixteen partial edentulous sites (left and right) were randomized into four groups for bone autograft harvest without irrigation: chisel, 50 rpm drilling, 500 rpm drilling, and 1000 rpm drilling. Bone chips were harvested on the buccal plates of the missing tooth. An infrared camera and an implantable thermocouple collaboratively monitored in vivo real-time bone temperature at the drilling sites. In vitro performances of cells from bone chips, including cell number, viability, proliferation, migration, ALP activity, in vitro mineralization, mRNA transcriptional level of osteogenic genes and heat shock protein 70 (HSP-70), and HSP-70 expression at the protein level were also studied. Results: 500 rpm produced mild local hyperthermia with a 2–6 °C temperature rise both on the cortical surface and inside the cortical bone. It also held comparable or enhanced cell performances such as cell number, viability, proliferation, migration, ALP activity, in vitro mineralization, and osteogenic genes expression. Conclusions: In-situ non-irrigated higher-speed drilling at 500 rpm using a screw drill is versatile, efficient, and thermal friendly and improves the bio-quality of bone chips. Our novel technique holds clinical translational potential in GBR application. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of an alumina‐silica ceramic fiber after thermal exposure at 1100–1300°C were investigated by X‐ray diffraction, nuclear magnetic resonance, scanning electron microscopy, transmission electron microscopy analyses and room temperature tensile strength test. The results showed that the fiber was composed of γ‐A12O3 and amorphous SiO2. A phase reaction of γ‐A12O3 and amorphous SiO2 occurred when thermal exposure temperature exceeded 1150°C, and a new mullite phase formed. The grain size of the newly formed mullite increased with the increase of exposure temperature. Both the phase transition and grain growth of mullite had a significant impact on the mechanical properties of the fiber. Tensile strength of the fiber decreased slightly when thermal exposure temperature was below 1150°C, while the strength retention of the fiber decreased sharply to 65.36% as exposure temperature rose to 1200°C. A higher dispersion of tensile strength was also observed at higher exposure temperatures, as revealed by the Weibull statistical model. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of thermal exposure at 1000 ℃ to 1200 ℃ on the properties of porous matrix Al2O3/Al2O3 ceramic matrix composites was studied. The results show that the thermal exposure at 1000 ℃ for 100 h has no effect on the tensile strength of the composites. After 100 h at 1100 ℃, the tensile strength of the composites decreases slightly, and after 100 h at 1200 ℃, the tensile strength of the composites decreases obviously. The effects of different thermal exposure durations at 1200 ℃ on the properties of Al2O3/Al2O3 composites, alumina fibers and alumina matrix are further studied, and the micro morphologies of the samples are characterized by optical microscopy and SEM. The results show that the thermal exposure at 1200 ℃ for 100 h has little effect on the performance of alumina fiber, but has a great effect on the alumina matrix. After the thermal exposure at 1200 ℃ for only 10 h, the porosity of alumina matrix is significantly reduced and the density is significantly increased. It can be seen from the SEM morphology of the matrix fracture that with the increase of thermal exposure time at 1200 ℃, the alumina grain size of the matrix gradually increases and the matrix is further sintered. Correspondingly， it can be seen from the fracture morphology of the Al2O3/Al2O3 composite that the length and number of fibers pulled out also decrease significantly. The degradation of the properties of the composites after high temperature thermal exposure is mainly due to the further sintering of alumina matrix, and the densification of porous matrix reduces the toughening effect of the composites.

The article presents a study into the effect of long-term thermal exposure on the structure and properties of the PKh13M2-BN composite material, designed for seal structures of a flow-through section of steam turbines. Data on the temperature-resource zones of its performance and microstructure, as well as physical and mechanical properties before and after thermal exposure, is provided. [ABSTRACT FROM AUTHOR]

The microstructure and room temperature tensile properties of heat-treated TC25G alloy after thermal exposure were investigated. The results show that the α2 phase dispersed in the α phase, and silicide precipitated firstly at the α/β phase boundary and then at the dislocation of the αp phase and on the β phase. When thermal exposure was 0–10 h at 550 °C and 600 °C, the decrease of alloy strength was mainly due to the dominant effect of dislocations recovery. With the rise and extension of thermal exposure temperature and time, the increasing quantity and size of precipitates played an important role in the improvement of alloy strength. When thermal exposure temperature rose to 650 °C, the strength was always lower than that of heat-treated alloy. However, since the decreasing rate of solid solution strengthening was smaller than the increasing rate of dispersion strengthening, alloy still showed an increasing trend in the range of 5–100 h. When thermal exposure time was 100–500 h, the size of the α2 phase increased from the critical value of 3 nm to 6 nm, and the interaction between the moving dislocations and the α2 phase changed from the cutting mechanism to the by-pass mechanism (Orowan mechanism), and thus alloy strength decreased rapidly. [ABSTRACT FROM AUTHOR]

The present study investigated microstructural evolution and changes in tensile properties of an Al-Si piston alloy subjected to thermal exposures at 250 and 350 °C for 150, 300, and 500 h. Microstructural and nanoscale precipitates were characterized using a combination of high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) images and scanning electron microscopy (SEM). The tensile testing was performed. The results demonstrated that the thermal exposure induced granulation of the δ-Al3CuNi particles, alongside precipitation of the θ-Al2Cu phase particles and AlCu clusters within the matrix. Specifically, an increase in the size and number density of the θ-Al2Cu phase particles was observed with exposure time at 250 °C. Conversely, at 350 °C, the θ-Al2Cu particles exhibited a gradual increase in size with prolonged thermal exposure, coupled with a decrease in their number density. AlCu clusters precipitated solely at a thermal exposure temperature of 350 °C, with precipitation intensifying over time. Moreover, a decrease in the alloy’s tensile strength and an increase in elongation were noted after thermal exposure. Finally, the present study discussed the precipitation mechanisms of θ-Al2Cu particles and AlCu clusters within the grains, suggesting that the AlCu clusters exerted a more effective strengthening effect compared to the θ-Al2Cu particles.

The influence of long-term thermal exposure on microstructure evolution and tensile behavior of a new wrought γ′-hardened Ni-base superalloy at different temperatures are investigated. The experimental superalloys are thermal exposure at 650 °C for different times up to 2300 h and tensile tests are performed in both heat treatment and thermal exposure conditions. The results show that some discontinuous carbides precipitate at the grain boundaries and spherical γ′ precipitates homogeneously disperse within the γ matrix after heat treatment. During thermal exposure, the γ′ precipitates remain spherical morphology, and the coarsening behavior of γ′ conforms to the LSW model. The tensile strength of the experimental superalloy after heat treatment generally shows a downward trend with the increase of tensile temperature while the elongation reaches a maximum at 650 °C. After thermal exposure, the tensile strength of the experimental superalloy has improved while the elongation slightly decreases.

The Ti47Al2Cr2Nb alloy fatigue specimens were prepared by investment casting, and three kinds of surface processes were applied to fatigue specimens. These three processes were sand-blasting (SB), sand-blasting and shot-peening (SBSP) and sand-blasting and mechanical grinding (SBMG). The surface characteristics before and after thermal exposure at 700 °C for 24 h were investigated. The high cycle fatigue behaviors of specimens after thermal exposure were evaluated. The results showed that the surface roughness (Ra) values after SB, SBSP and SBMG processes were 1.71, 0.99 and 0.06 μm, respectively. After thermal exposure, they increased slightly for all three processes. The SB process caused work hardening in the near-surface region and the work hardening reached saturation after the SB process. Due to the mechanical grinding process removing an uncertain thick hardening layer, the maximum hardness after SBMG process was noticeably lower than those after SB and SBSP processes. After thermal exposure, the maximum hardness after all three processes significantly recovered. Deformed layers were formed beneath SB and SBSP surfaces. After thermal exposure, a depth-dependent gradient microstructure was formed in the surface layer. The SBMG specimens had the highest fatigue limit of 350 MPa. This was attributed to the SBMG specimens having very smooth surfaces and keeping some work hardening in the surface layers. The fatigue fractures were typical brittle cleavage fractures. The fracture modes included interlamellar and trans-lamellar fractures. The dislocation slip and mechanical twins were the main deformation mechanisms.

Confirmatory identification of hair colorants can be used to establish a connection between a suspect and the crime science or demonstrate the absence of such connections. A growing body of evidence shows that surface‐enhanced Raman spectroscopy (SERS) could be a confirmatory, minimally destructive, and fully noninvasive analysis of hair colorants. In SERS, a signal that provide the information about the chemical structure of both permanent and semipermanent dyes present on hair is enhanced by a million‐fold using noble metal nanostructures. However, it is unclear whether the information of hair colorants can be revealed if hair was contaminated or exposed to harsh environments such as sunlight and heat. In this work, we determine the effect of a short‐ and long‐term heat exposure on SERS‐based analysis of hair colored with blue and red permanent and semipermanent dyes. We found that short and especially long‐term heat exposure at 220°C could alter chemical structure, and consequently SERS spectra, of permanent and semipermanent colorants. This thermal degradation of permanent dyes complicates their direct identification using SERS. We also found that partial least squares discriminant analysis can be used to overcome this issue allowing for highly accurate identification of both permanent and semipermanent dyes on colored hair that was exposed to 220°C for 6–12 min. These results show that heat exposure of colored hair should be strongly considered upon their SERS‐based examination to avoid both false positive or false negative identification of chemical dyes. [ABSTRACT FROM AUTHOR]

The corrosion mechanism evolution of four low silicon-cast aluminium alloys exposed to heat treatment at 200°C for 0–50 h was studied by means of immersion corrosion, intergranular corrosion and electrochemical test, SEM, EDS and EBSD analysis methods. The correlation of corrosion resistance with composition and the thermal exposure time was investigated. The results show that the corrosion mechanism of all aluminium alloys changed after thermal exposure at 200°C. Before thermal exposure, intergranular corrosion was the main corrosion, and after 200°C thermal exposure, serious pitting corrosion and spalling corrosion occurred in the local area. The contents of Si and Mg in the grain boundary increased obviously. The contents of elements in the poor zone of the grain boundary increased, and the electrical potential difference between the grain and the grain boundary reduced. The intergranular corrosion sensitivity of the alloy was reduced. But the degree of pitting gradually becomes serious. The electrochemical test of the aluminium alloy with 3.5 wt% Si showed that its corrosion potential increased with the increase inthermal exposure time, and its corrosion current density increased with the increase inthermal exposure time. After the EBSD test, it was found that the large angle grain boundary decreased gradually and the proportion of large grain size increased with the increase in thermal exposure time to 50 h. [ABSTRACT FROM AUTHOR]

Microstructural stability at elevated temperatures is one of the main concerns for the service reliability of aero-engine turbine blades. Thermal exposure, as an important approach to examine the microstructural degradation, has been widely studied in Ni-based single crystal (SX) superalloys for decades. This paper presents a review on the microstructural degradation induced by high-temperature thermal exposure and the associated damage in mechanical properties in some typical Ni-based SX superalloys. The main factors affecting the microstructural evolution during thermal exposure and the influencing factors in the degradation of mechanical properties are also summarized. Insights into the quantitative estimation of the thermal exposure-affected microstructural evolution and the mechanical properties will be beneficial for the understanding and improvement of reliable service in Ni-based SX superalloys. [ABSTRACT FROM AUTHOR]

The effect of thermal exposure at 1000 °C to 1200 °C on the properties of porous matrix Al2O3/Al2O3 ceramic matrix composites was studied. The results show that the thermal exposure at 1000 °C for 100 h has no effect on the tensile strength of the composites. After 100 h at 1100 °C, the tensile strength of the composites decreases slightly, and after 100 h at 1200 °C, the tensile strength of the composites decreases obviously. The effects of different thermal exposure durations at 1200 °C on the properties of Al2O3/Al2O3 composites, alumina fibers and alumina matrix are further studied, and the micro morphologies of the samples are characterized by optical microscopy and SEM. The results show that the thermal exposure at 1200 °C for 100 h has little effect on the performance of alumina fiber, but has a great effect on the alumina matrix. After the thermal exposure at 1200 °C for only 10 h, the porosity of alumina matrix is significantly reduced and the density is significantly increased. It can be seen from the SEM morphology of the matrix fracture that with the increase of thermal exposure time at 1200 °C, the alumina grain size of the matrix gradually increases and the matrix is further sintered. Correspondingly, it can be seen from the fracture morphology of the Al2O3/Al2O3 composite that the length and number of fibers pulled out also decrease significantly. The degradation of the properties of the composites after high temperature thermal exposure is mainly due to the further sintering of alumina matrix, and the densification of porous matrix reduces the toughening effect of the composites. [ABSTRACT FROM AUTHOR]

TiAl alloys offer strong potential for replacing conventional nickel-base alloys in structural applications at high temperatures, which requires good high temperature performance. This study analyzes the creep performance and thermal exposure characteristics for a powder hot isostatic pressing (P-HIP) Ta-contained TiAl alloy. The microstructure characteristics, creep performance, and thermal exposure properties of the nearly lamellar (NL) alloy with a size of about 145 μm were investigated. The alloy remains 0.72 % fracture strain at room temperature after exposure at 750 ℃ for 1000 h. The fitting results of creep curves show that the creep stress index n is 15.82 at 750 ℃, indicating the power law creep mechanism. By reducing the interfacial energy, Ta can facilitate the formation of metastable structures and achieve refinement. The enrichment of Ta element at the lamellar edge, both observed after thermal exposure and creep, inhibits the growth of lamellae and hinders the expansion of cavities due to its low diffusion rate, improving the thermal stabilities and creep performance. The P-HIP Ta-contained TiAl alloy shows exciting high temperature performance. • A powder metallurgy Ti–48Al–3Nb–1.5Ta alloy with excellent high temperature performance is obtained with simple heat treatment process. • The mechanism of Ta for this alloy to improving the thermal stabilities and creep performance is revealed. The enrichment of Ta element at the lamellae edge has an effect of inhibiting the growth of lamellae and hindering the expansion of pores. • The fitting results of creep curves show that the creep stress index n is 15.82 at 750 ℃, indicating power law creep mechanism. • After exposure at 750 ℃ for 1000 h, the lamellae have no obvious coarsening and the material still has 0.72 % tensile fracture strain at room temperature, indicating favorable microstructure stability and mechanical performance. [ABSTRACT FROM AUTHOR]

The microstructure morphology and evolution of mechanical properties are investigated in this study. The results show that the phases displayed no clear change after thermal exposure at 250 °C for 200 h. The tensile strength of the as-cast alloy showed a downward trend in different degrees with the increase in the tensile temperature, while the influence of elongation was opposite to the tensile strength. In addition, the tensile strength tended to be stable after thermal exposure at 250 °C for 100 h. The main creep mechanism of the as-cast alloy at a low temperature and low stress (T ≤ 250 °C; σ ≤ 40 MPa) is grain-boundary creep. The Monkman–Grant empirical formula was used to fit the relationship between the creep life and the minimum creep rate, and the fitting results are:   t r · ε ˙ m i n 0.95 = 0.207 . [ABSTRACT FROM AUTHOR]

Thanks to its high weldability, Inconel 625 (IN625) can be easily processed by laser powder bed fusion (LPBF). After production, this alloy is typically subjected to specific heat treatments to design specific microstructure features and mechanical performance suitable for various industrial applications, including aeronautical, aerospace, petrochemical, and nuclear fields. When employed in structural applications, IN625 can be used up to around 650 °C. This limitation is mainly caused by the transformation of metastable γ″ phases into stable δ phases occurring under prolonged thermal exposure, which results in drastically reduced ductility and toughness of the alloy. Because the microstructure and mechanical properties change during thermal exposure, it is essential to study the material simulating possible service temperatures. In the current study, LPBFed IN625 samples were solution-annealed and then subjected to thermal exposure at 650 °C for different times up to 2000 h. The characterization focused on the evolution of the main phases, γ″ and δ phases, and their influence on the hardness evolution. The microstructure and hardness of the heat-treated LPBFed IN625 samples were compared with data related to the traditionally processed IN625 alloy (e.g., wrought state) reported in the literature. [ABSTRACT FROM AUTHOR]

Precipitate evolution characteristics of a Ni-based alloy containing tungsten during thermal exposure at 850 °C from 100 to 3000 h and its influence on the impact toughness were investigated. Transmission electron microscopy, scanning electron microscopy, and precise chemical analysis were used to analyze precipitate shape, type, composition, and growth mechanism. Experimental results proved that the μ, σ, M23C6, and M6C phases were formed and grew during thermal exposure at 850 °C. The μ phase was mostly formed within the grain or around the grain boundary in a strip-like or irregular shape and a stacking fault interior. M23C6 was formed at twin boundaries in a quadrilateral shape with one pair of parallel sides. However, at the grain boundary, the precipitate was mainly M6C and shaped in an irregular polygon. In addition, during long-term thermal exposure at 850 °C, M6C grew along the grain boundary and formed a chain-like structure. The μ phase can nucleate and grow independently or in clusters. Particularly, M6C and Ti(CN) or TiC can be the nucleation core for the μ phase. The precipitate size and quantity both increased with longer exposure time. Meanwhile, mechanical property testing indicated that the impact toughness worsened at the initial stages of aging, but remained relatively constant during thermal exposure from 500 to 3000 h. Microchemical phase analysis and EDS results showed that impact toughness deterioration for samples exposed to less than 500 h thermal treatment may be caused by the coarsening of grain boundary carbides and chemical composition fluctuation of the precipitate. [ABSTRACT FROM AUTHOR]

In the present work, thermal exposure was performed on the 7B50-T7451 aluminium alloy friction stir welding (FSW) joints at different temperatures (150 °C, 175 °C and 220 °C) for 200 h. The results show that the microstructure and mechanical properties of as-welded joints along the thickness direction of the plate are heterogeneous. The hardness and strength of FSW joints decrease while the elongation continuously increases with increasing thermal exposure temperature. Compared with the base material, the joints present much higher hardening capacity which is further increased with increasing temperature. The precipitates in the heat-affected zone (HAZ) exhibit continuous coarsening and the precipitate distribution becomes broader as the temperature rises. The transformation from η′ phase to η phase is obvious at 220 °C. The weld nugget zone (WNZ) re-precipitates a large number of nano-scale η particles subjected to 200 h thermal exposure at 150 °C and re-precipitated η phase in WNZ of the double-sided joint has reached micron-sized at 175 °C and 220 °C. When exposed at different temperatures, all FSW joints show typical ductile fracture features. Fracture positions at different thermal exposure temperatures are inconsistent and this variation is closely related to different microstructural characteristics.

Abstract Background Lightweight rowers commonly utilize weight loss techniques over 24-h before competition to achieve the qualifying weight for racing. The objective was to investigate, using a quasi-experimental design, whether changes in weight resulting from dehydration practices are related to changes in proxies of bodily systems involved in rowing and whether these relationships depend on the dehydration technique used. Methods Twelve elite male rowers performed a power test, an incremental VO2max test, and a visuomotor battery following: weight loss via thermal exposure, weight loss via fluid abstinence and then thermal exposure, and no weight loss. The total percent body mass change (%BMC), %BMC attributable to thermal exposure, and %BMC attributable to fluid abstinence were used to predict performance variables. Results Fluid abstinence but not thermal exposure was related to a lower total wattage produced on a incremental VO2max test (b = 4261.51 W/1%BMC, 95%CI = 1502.68–7020.34), lower wattages required to elicit 2 mmol/L (b = 27.84 W/1%BMC, 95%CI = 14.69–40.99) and 4 mmol/L blood lactate (b = 20.45 W/1%BMC, 95%CI = 8.91–31.99), and slower movement time on a visuomotor task (b = -38.06 ms/1%BMC, 95%CI = -62.09–-14.03). Conclusions Dehydration related weight changes are associated with reductions in some proxies of bodily systems involved in rowing but depend on the dehydration technique used.

Geopolymers offer increasingly better physico-mechanical properties concerning thermal exposure at high temperatures compared to ordinary Portland cements (OPC). This paper aims to comprehensively study the use of different types of fillers with different particle size distributions in terms of type (silica sands and cordierites) and surface area, loaded at different temperatures and dwell times (30 min and 180 min). After thermal exposure in the temperature range of 100–1000 °C, geopolymer samples were evaluated regarding physico-mechanical properties compared to samples without thermal exposure, using OPC as a reference material. Geopolymer samples were found to have a denser microstructure than OPC, supporting their better resistance to elevated temperature conditions. In addition, the influence of different filler compositions on the resulting internal structure and porosity was demonstrated. Samples containing fillers in two particle size ranges showed better densification than samples with one particle size range. Conversely, OPC samples showed the least favourable results. In addition, the mechanical behaviour of the geopolymers under static loading, especially in bending and compression tests, showed that the prepared geopolymers exhibited better properties than Portland cement at elevated temperatures, especially in the range of 500–1000 °C. In conclusion, appropriately designed geopolymer compositions have the potential to be a sustainable material, a high-performance alternative to traditional building materials. • Geopolymers (GP) with cordierite and silica sand exposed to 100–1000 °C were studied. • The physico-mechanical properties of the samples after thermal loading were investigated. • The results of the GP samples were compared with ordinary Portland cement (OPC) ones. • GP results suggest solid phase reactions and/or partial sintering at higher temperatures. • GP show better overall properties than OPC in the 500–1000 °C range. [ABSTRACT FROM AUTHOR]

It is a long-standing challenge to balance the structural load capacity and toughness in the design of lightweight multi-cell tubes. To tackle this challenge, we provide two kinds of complex lattice-inspired composite multi-cell tubes. The composite multi-cell tubes consist of inner polylactic acid (PLA) complex lattice-inspired multi-cell tubes and outside aluminum tubes. The energy absorption capacity of these multi-cell tubes was evaluated under quasi-static axial compression. The effect of cross-sectional topology and thermal exposure were considered in the experiment. The results show that the integration of PLA tubes within aluminum tubes significantly enhances their energy absorption performance, effectively addressing the limitations posed by the low fracture strain of PLA. The synergistic effect between the aluminum and PLA tubes mitigates the fracture instability and distributes the load more evenly, resulting in improved specific energy absorption (SEA) and mean crushing force (MCF) up to 103.32 % and 184.38 %, respectively. In these composite tubes, a global self-similar layout can markedly enhance its energy absorption. However, their mechanical properties decrease significantly at 323K compared to room temperature. In contrast, local self-similar composite multi-cell tubes exhibited relatively less reduction in mean crushing force due to the weaker synergistic effects. Overall, this research provides a novel approach to enhancing the mechanical performance of PLA tubes, paving the way for their application in engineering fields requiring lightweight and high-strength structures. [Display omitted] [ABSTRACT FROM AUTHOR]