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Keywords = low-temperature impact fracture behavior

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20 pages, 8746 KB  
Article
Fatigue Performance of Q500qENH Weathering Steel Welded Joints at Low Temperature
by Lei Kang, Xuanming Shi, Tao Lan, Xiaowei Zhang, Chen Xue, Xiaopeng Wang, Zhengfei Hu and Qinyuan Liu
Materials 2025, 18(19), 4515; https://doi.org/10.3390/ma18194515 - 28 Sep 2025
Abstract
A systematic study was conducted on the fatigue performance of Q500qENH weathering steel welded joints under low-temperature conditions of −40 °C in this paper. Low-temperature fatigue tests were conducted on V-groove butt joints and cross-shaped welded joints and S-N curves with a 95% [...] Read more.
A systematic study was conducted on the fatigue performance of Q500qENH weathering steel welded joints under low-temperature conditions of −40 °C in this paper. Low-temperature fatigue tests were conducted on V-groove butt joints and cross-shaped welded joints and S-N curves with a 95% reliability level were obtained. A comparative analysis with the Eurocode 3 reveals that low-temperature conditions lead to a regular increase in the design fatigue strength for both types of welded joints. Fracture surface morphology was examined using scanning electron microscopy, and combined with fracture characteristic analysis, the fatigue fracture mechanisms of welded joints under low-temperature conditions were elucidated. Based on linear elastic fracture mechanics theory, a numerical simulation approach was employed to investigate the fatigue crack propagation behavior of welded joints. The results indicate that introducing an elliptical surface initial crack with a semi-major axis length of 0.4 mm in the model effectively predicts the fatigue life and crack growth patterns of both joint types. A parametric analysis was conducted on key influencing factors, including the initial crack size, initial crack location, and initial crack angle. The results reveal that these factors exert varying degrees of influence on the fatigue life and crack propagation paths of welded joints. Among them, the position of the initial crack along the length direction of the fillet weld has the most significant impact on the fatigue life of cross-shaped welded joints. Full article
(This article belongs to the Section Metals and Alloys)
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26 pages, 18754 KB  
Article
Integrated Documentation and Non-Destructive Surface Characterization of Ancient Egyptian Sandstone Blocks at Karnak Temples (Luxor, Egypt)
by Abdelrhman Fahmy, Salvador Domínguez-Bella, Ana Durante-Macías, Fabiola Martínez-Viñas and Eduardo Molina-Piernas
Heritage 2025, 8(8), 320; https://doi.org/10.3390/heritage8080320 - 11 Aug 2025
Viewed by 748
Abstract
The Karnak Temples are considered one of Egypt’s most significant archaeological sites, dating back to the Middle Kingdom (c. 2000–1700 BC) and were continuously expanded until the Ptolemaic period (305–30 BC). As the second most visited UNESCO World Heritage archaeological site in Egypt [...] Read more.
The Karnak Temples are considered one of Egypt’s most significant archaeological sites, dating back to the Middle Kingdom (c. 2000–1700 BC) and were continuously expanded until the Ptolemaic period (305–30 BC). As the second most visited UNESCO World Heritage archaeological site in Egypt after the Giza Pyramids, Karnak faces severe deterioration processes due to prolonged exposure to environmental impacts, mechanical damage, and historical interventions. This study employs a multidisciplinary approach integrating non-destructive testing (NDT) methods to assess the physical and mechanical condition and degradation mechanisms of scattered sandstone blocks at the site. Advanced documentation techniques, including Reflectance Transformation Imaging (RTI), photogrammetry, and Infrared Thermography (IRT), were used to analyze surface morphology, thermal stress effects, and weathering patterns. Ultrasonic Pulse Velocity (UPV) testing provided internal structural assessments, while spectral and gloss analysis quantified chromatic alterations and surface roughness. Additionally, the Karsten Tube test determined the water absorption behavior of the sandstone, highlighting variations in porosity and susceptibility to salt crystallization. In this sense, the results indicate that climatic factors such as extreme temperature fluctuations, wind erosion, and groundwater infiltration contributed to sandstone deterioration. Thermal cycling leads to microcracking and granular disintegration, while high capillary water absorption accelerates chemical weathering processes. UPV analyses showed substantial internal decay, with low-velocity zones correlating with fractures and differential cementation loss. Finally, an interventive conservation plan was proposed. Full article
(This article belongs to the Section Materials and Heritage)
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14 pages, 4123 KB  
Article
Research on the Impact Toughness of 3D-Printed CoCrMo Alloy Components Based on Fractal Theory
by Guoqing Zhang, Junxin Li, Han Wang, Congcong Shangguan, Juanjuan Xie and Yongsheng Zhou
Biomimetics 2025, 10(5), 292; https://doi.org/10.3390/biomimetics10050292 - 6 May 2025
Viewed by 552
Abstract
In order to obtain high-performance 3D printed parts, this study focuses on the key performance indicator of impact toughness. The parametric modeling software Rhino 6 is used to design impact specimens, and the laser selective melting equipment DiMetal-100, independently developed by the South [...] Read more.
In order to obtain high-performance 3D printed parts, this study focuses on the key performance indicator of impact toughness. The parametric modeling software Rhino 6 is used to design impact specimens, and the laser selective melting equipment DiMetal-100, independently developed by the South China University of Technology, is used to manufacture impact specimens. Subsequently, the CoCrMo alloy parts were annealed using an MXQ1600-40 box-type atmosphere furnace and subjected to impact testing using a cantilever beam impact testing machine XJV-22. Fractal theory was applied to analyze the fractal behavior of the resulting impact fracture surfaces. The research results indicate that the 3D-printed impact specimens exhibited excellent surface quality, characterized by brightness, low roughness, and the absence of significant defects such as warping or deformation. In terms of annealing treatment, lower annealing temperatures did not improve the impact performance of SLM-formed CoCrMo alloy parts but instead led to a decrease in toughness. While increasing the annealing temperature can improve toughness to some extent, the effect is limited. Furthermore, the relationship between impact energy and heat treatment temperature exhibits a U-shaped trend. The fractal dimension analysis shows that the parts annealed in a 1200 °C furnace have the highest fractal dimension and better toughness performance. This study introduces a novel approach by comprehensively integrating advanced 3D printing technology, annealing processes, and fractal theory analysis to systematically investigate the influence of annealing temperature on the impact properties of 3D-printed CoCrMo alloy parts, thereby establishing a solid foundation for the application of high-performance 3D printed parts. Full article
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19 pages, 7174 KB  
Article
Phase Transformation and Deformation Mechanisms of 304L Stainless Steel Under Tensile and Charpy Impact Testing at Varying Temperatures
by Gang-Ho Lee, Gwangjoo Jang, Byoungkoo Kim, Changyong Choi, Hee-Sang Park, Jong-Bae Jeon, Changwoo Lee, Sanghoon Noh and Byung Jun Kim
Crystals 2025, 15(4), 360; https://doi.org/10.3390/cryst15040360 - 15 Apr 2025
Cited by 1 | Viewed by 1338
Abstract
This study examines the mechanical behavior and deformation mechanisms of hot-forged 304L stainless steel for cryogenic applications such as LNG storage and low-temperature structural systems. Tensile testing revealed a significant strength increase from 618 MPa at room temperature to 1432 MPa at cryogenic [...] Read more.
This study examines the mechanical behavior and deformation mechanisms of hot-forged 304L stainless steel for cryogenic applications such as LNG storage and low-temperature structural systems. Tensile testing revealed a significant strength increase from 618 MPa at room temperature to 1432 MPa at cryogenic temperatures, with elongation decreasing from 83.7% to 23.3%. Charpy impact testing showed a 28% reduction in absorbed energy at cryogenic temperatures due to enhanced strain-induced martensitic transformation (SIMT). The observed mechanical responses are attributed to reduced stacking fault energy (SFE) at lower temperatures, which promotes SIMT, deformation twinning, and dislocation interactions, affecting material strength and toughness. SEM and EBSD analysis confirmed extensive martensitic transformation, increased deformation twinning, and reduced remaining austenite, indicating a γ → ε → α’ transformation pathway that governs strain hardening. The high strain rate during Charpy impact testing induced localized adiabatic heating, partially suppressing SIMT and modifying fracture behavior by enhancing localized plasticity. These findings emphasize the interplay between SFE, strain rate, and phase transformation in governing the cryogenic mechanical performance of 304L stainless steel. Full article
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24 pages, 6078 KB  
Article
Impact of Thermal Variations on the Fatigue and Fracture of Bi-Material Interfaces (Polyimide–EMC, Polyimide–SiO2, and Silicon–EMC) Found in Microchips
by Pedro F. C. Videira, Renato A. Ferreira, Payam Maleki, Alireza Akhavan-Safar, Ricardo J. C. Carbas, Eduardo A. S. Marques, Bala Karunamurthy and Lucas F. M. da Silva
Polymers 2025, 17(4), 520; https://doi.org/10.3390/polym17040520 - 17 Feb 2025
Cited by 1 | Viewed by 1234
Abstract
As the trend towards the densification of integrated circuit (IC) devices continues, the complexity of interfaces involving dissimilar materials and thermo-mechanical interactions has increased. Highly integrated systems in packages now comprise numerous thin layers made from various materials. The interfaces between these different [...] Read more.
As the trend towards the densification of integrated circuit (IC) devices continues, the complexity of interfaces involving dissimilar materials and thermo-mechanical interactions has increased. Highly integrated systems in packages now comprise numerous thin layers made from various materials. The interfaces between these different materials represent a vulnerable point in ICs due to imperfect adhesion and stress concentrations caused by mismatches in thermo-mechanical properties such as Young’s modulus, coefficients of thermal expansion (CTE), and hygro-swelling-induced expansion. This study investigates the impact of thermal variations on the fracture behavior of three bi-material interfaces used in semiconductor packaging: epoxy molding compound–silicon (EMC–Si), silicon oxide–polyimide (SiO2–PI), and PI–EMC. Using double cantilever beam (DCB) tests, we analyzed these interfaces under mode I loading at three temperatures: −20 °C, 23 °C, and 100 °C, under both quasi-static and cyclic loading conditions. This provided a comprehensive analysis of the thermal effects across all temperature ranges in microelectronics. The results show that temperature significantly alters the failure mechanism. For SiO2–PI, the weakest point shifts from silicon at low temperatures to the interface at higher temperatures due to thermal stress redistribution. Additionally, the fracture energy of the EMC–Si interface was found to be highly temperature-dependent, with values ranging from 0.136 N/mm at low temperatures to 0.38 N/mm at high temperatures. SiO2–PI’s fracture energy at high temperature was 42% less than that of EMC–Si. The PI–EMC interface exhibited nearly double the crack growth rate compared to EMC–Si. The findings of this study provide valuable insights into the fracture behavior of bi-material interfaces, offering practical applications for improving the reliability and design of semiconductor devices, especially in chip packaging. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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14 pages, 6487 KB  
Article
Application of Surface-Cracking Process to Improve Impact Toughness of High-Strength BCC Steel at Low Temperatures
by Minha Park, Gang Ho Lee, Byoungkoo Kim, Sanghoon Noh, Jong Bae Jeon, Changwoo Lee and Byung Jun Kim
Crystals 2025, 15(1), 69; https://doi.org/10.3390/cryst15010069 - 12 Jan 2025
Viewed by 1128
Abstract
At very low temperatures, typically ductile materials, especially body-centered cubic (BCC) steels, often exhibit an abrupt transition to brittle fracture, significantly limiting their applicability in cryogenic and low-temperature environments. This challenge arises from the inherent properties of BCC steels, where ductility is drastically [...] Read more.
At very low temperatures, typically ductile materials, especially body-centered cubic (BCC) steels, often exhibit an abrupt transition to brittle fracture, significantly limiting their applicability in cryogenic and low-temperature environments. This challenge arises from the inherent properties of BCC steels, where ductility is drastically reduced, leading to unexpected failures under mechanical stress. Despite the advantages of high-strength BCC steels, including cost-effectiveness and mechanical robustness, their susceptibility to brittle fracture restricts their use in demanding low-temperature applications. To address this limitation, we developed an innovative surface-cracking process to enhance the impact toughness of BCC steels. The introduction of controlled surface cracks redistributes stress and energy dissipation mechanisms, improving the toughness of high-strength BCC steels at cryogenic temperatures. Microscopic observations and finite element analyses reveal that these surface cracks not only dissipate crack formation energy but also alter stress triaxiality at crack tips. This causes the stress state to transition toward a plane stress condition, effectively mitigating stress concentrations typically observed in plane strain states. By reducing localized stress severity and promoting uniform energy distribution, the surface cracks encourage failure mechanisms favoring ductile behavior over brittle fracture. Full article
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11 pages, 15241 KB  
Article
Achieving Strength and Toughness in Dual-Phase Mg-8Li Alloys Through Phase Structure Control and Composite Fracture
by Lei Zhao, Shuaipu Wang, Mingjian Wu, Chengxiang Liu and Zhilin Wu
Materials 2024, 17(23), 5984; https://doi.org/10.3390/ma17235984 - 6 Dec 2024
Cited by 1 | Viewed by 1063
Abstract
The rising industrial demand for ultra-lightweight materials with exceptional strength and toughness has intensified interest in dual-phase Mg-Li alloys due to their low density and high specific strength. While much of the research on Mg-Li alloys has concentrated on conventional strengthening methods, such [...] Read more.
The rising industrial demand for ultra-lightweight materials with exceptional strength and toughness has intensified interest in dual-phase Mg-Li alloys due to their low density and high specific strength. While much of the research on Mg-Li alloys has concentrated on conventional strengthening methods, such as grain refinement and solid-solution strengthening, overcoming the challenge of plastic deformation compatibility between the α- and β-phases remains unresolved. This study focuses on Mg-8Li binary alloy, systematically investigating the impact of rolling deformation temperature and strain on the phase structures. A detailed analysis of fracture behavior reveals a novel brittle–tough composite fracture control strategy that enhances both strength and toughness simultaneously. This work advances the understanding of phase structure control and its role in strengthening and toughening mechanisms, offering critical insights for the development of next-generation dual-phase magnesium alloys. Full article
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22 pages, 8368 KB  
Article
Low-Velocity Impact Analysis in Composite Plates Incorporating Experimental Interlaminar Fracture Toughness
by Gyeong-Han Lee, Ji-Yoon Yang, Sang-Woo Kim and Soo-Yong Lee
Materials 2024, 17(23), 5768; https://doi.org/10.3390/ma17235768 - 25 Nov 2024
Cited by 1 | Viewed by 1041
Abstract
Reliable performance of composite adhesive joints under low-velocity impact is essential for ensuring the structural durability of composite materials in demanding applications. To address this, the study examines the effects of temperature, surface treatment techniques, and bonding processes on interlaminar fracture toughness, aiming [...] Read more.
Reliable performance of composite adhesive joints under low-velocity impact is essential for ensuring the structural durability of composite materials in demanding applications. To address this, the study examines the effects of temperature, surface treatment techniques, and bonding processes on interlaminar fracture toughness, aiming to identify optimal conditions that enhance impact resistance. A Taguchi experimental design and analysis of variance (ANOVA) were used to analyze these factors, and experimentally derived toughness values were applied to low-velocity impact simulations to assess delamination behavior. Sanding and co-bonding were identified as the most effective methods for improving fracture toughness. Under the identified optimal conditions, the low-velocity impact analysis showed a delamination area of 319.0 mm2. These findings highlight the importance of parameter optimization in enhancing the structural reliability of composite adhesive joints and provide valuable insights for improving the performance and durability of composite materials, particularly in aerospace and automotive applications. Full article
(This article belongs to the Special Issue Impact Behaviour of Materials and Structures)
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17 pages, 8611 KB  
Article
Micrographite (μG) and Polypropylene (PP) Composites: Preparation and Influence of Filler Content on Property Modifications
by Rabindra Dharai, Harekrushna Sutar, Rabiranjan Murmu and Debashis Roy
J. Compos. Sci. 2024, 8(8), 298; https://doi.org/10.3390/jcs8080298 - 1 Aug 2024
Cited by 2 | Viewed by 2566
Abstract
It is difficult to select low-cost filler materials. Specifically, carbon-based filling materials are a matter of concern, and developing a carbon-filled polymer composite with enhanced properties is necessary. In this study, the authors developed a polymer composite using virgin polypropylene (PP) as a [...] Read more.
It is difficult to select low-cost filler materials. Specifically, carbon-based filling materials are a matter of concern, and developing a carbon-filled polymer composite with enhanced properties is necessary. In this study, the authors developed a polymer composite using virgin polypropylene (PP) as a matrix and affordable micrographite (µG) as a filler. The developed composite has many potential applications in the automotive, aerospace, and electronic industries. To prepare the test specimens, the composite was prepared using a twin-screw extruder containing 3, 6, 9, 12, or 15 wt.% µG powder (BET surface area ≈ 29 m2/g; particle size > 50 µm) followed by injection molding. Different mechanical properties like the tensile, flexural, and impact strengths were determined. The prepared composites were further characterized by means of XRD, TGA, DSC, FTIR, DMA, FESEM, and PLM tests. The results were analyzed and compared with those for PP. Improved tensile (up to ≈ 34 MPa) and flexural (up to ≈ 40 MPa) strength was observed with an increase in the µG content. However, the impact strength continuously decreased (maximum ≈ 32 J/m for PP) with fractures. These findings underscore that graphite plays a significant role in controlling the deformation behavior and ultimate strength of composites. An XRD analysis revealed that adding graphite restructured the crystalline arrangement of PP and altered the composite’s crystallographic properties. Nonetheless, no induction effect (β-phase formation) was observed. A moderate enhancement in the thermal stability was observed owing to a small increase in the melt (Tm), onset (Tonset), and residual (TR) temperatures. A microstructural analysis showed that the micrographite powder strongly prevented spherulite growth and modified the graphite powder’s rate of dispersion and agglomeration in a polymer matrix. The results show that graphite could be a viable low-cost alternative carbon-based filler material in polypropylene matrices. Full article
(This article belongs to the Special Issue Progress in Polymer Composites, Volume III)
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20 pages, 12602 KB  
Article
The Mechanical Properties of Geopolymers as a Function of Their Shaping and Curing Parameters
by Camille Zoude, Elodie Prud’homme, Kévyn Johannes and Laurent Gremillard
Ceramics 2024, 7(3), 873-892; https://doi.org/10.3390/ceramics7030057 - 25 Jun 2024
Cited by 2 | Viewed by 1475
Abstract
This study investigates the impact of curing conditions, porosity and shaping techniques on the mechanical properties of metakaolin-based geopolymers. Geopolymers offer versatility in shaping, including 3D printing, yet the influence of curing conditions after printing on mechanical properties remains unclear. This is assessed [...] Read more.
This study investigates the impact of curing conditions, porosity and shaping techniques on the mechanical properties of metakaolin-based geopolymers. Geopolymers offer versatility in shaping, including 3D printing, yet the influence of curing conditions after printing on mechanical properties remains unclear. This is assessed by measuring the bending properties of 3D-printed metakaolin-based geopolymer filaments cured under varied humidity and temperature conditions. The influences of porosity and of shaping technique are observed by comparing the compression properties of molded and 3D-printed samples of various porosity. Samples cured at low humidity exhibit unusually high mechanical properties, which decrease when moved from a dry to a humid environment. This behavior may be due to the presence of PEG within the composition and/or to residual stresses due to the too rapid evacuation of water. High humidity is therefore necessary to ensure optimal curing and stable properties. Increasing the curing temperature helps accelerate geopolymerization without significantly compromising mechanical properties. Direct ink writing offers design flexibility and suitable porosity, but the samples appear to exhibit different failure mechanisms than the molded samples. Additional studies are necessary to understand the interactions between PEG and the geopolymer as well as to better identify the fracture mechanisms within the different samples. Full article
(This article belongs to the Special Issue Innovative Manufacturing Processes of Silicate Materials)
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21 pages, 41754 KB  
Article
Study on Fracture Behavior and Toughening Mechanisms of Ultra-High-Strength Pipeline Steel
by Ba Li, Xiaoshun Zhou, Shujun Jia, Xiaoping Chen, Song Fu, Dongliang Zhao, Haonan Zhang and Jie Guo
Metals 2024, 14(6), 666; https://doi.org/10.3390/met14060666 - 4 Jun 2024
Cited by 5 | Viewed by 2156
Abstract
In this paper, a series of low-temperature CVN (Charpy V-notch impact test) and DWTT (drop-weight tear test) experiments were carried out to deal with the intensifying contradiction of strength and toughness of ultra-high-strength pipeline steel. The fracture behavior and toughening mechanisms of ultra-high-strength [...] Read more.
In this paper, a series of low-temperature CVN (Charpy V-notch impact test) and DWTT (drop-weight tear test) experiments were carried out to deal with the intensifying contradiction of strength and toughness of ultra-high-strength pipeline steel. The fracture behavior and toughening mechanisms of ultra-high-strength pipeline steel were investigated using scanning electron microscopy, transmission electron microscopy and backscattered electron diffraction systems. The results show that DWTT fractures in ultra-high-strength pipeline steel had a variety of unconventional morphological features compared to CVN fractures, including ridge protrusion in ductile fracture conditions and a large-size fracture platform in brittle fracture conditions. Therefore, DWTT fractures contained more information about the material fracturing process, and could better reflect the actual process of material fracturing. In ultra-high-strength pipeline steel, fine-grained granular bainite caused cracks to undergo large deflections or frequent small transitions, which consumed additional energy and improved toughness. In contrast, large-sized granular bainite, which consisted of low-angle grain boundaries, did not effectively prevent crack propagation when it encountered cracks, which was not conducive to improved toughness. Moreover, the M/A constituents in large-sized granular bainite aggregated, cracked, or fell off, which could easily lead to the formation of microcracks and was also detrimental to toughening. Full article
(This article belongs to the Special Issue Design, Preparation and Properties of High Performance Steels)
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13 pages, 13083 KB  
Article
Experimental Study on the Fatigue Crack Propagation Rate of 925A Steel for a Ship Rudder System
by Li Yu, Wenyong Guo, Chenghao Cao, Min Li, Zhe Wu, Te Wang, Hantao Chen and Xinglong Pan
Materials 2024, 17(8), 1808; https://doi.org/10.3390/ma17081808 - 15 Apr 2024
Cited by 5 | Viewed by 1522
Abstract
The low-temperature fatigue crack propagation rate of 925A steel, as a rudder steel for polar special ships, has a crucial impact on the evaluation of the fatigue strength of polar ships. The purpose of this article is to study the fatigue crack propagation [...] Read more.
The low-temperature fatigue crack propagation rate of 925A steel, as a rudder steel for polar special ships, has a crucial impact on the evaluation of the fatigue strength of polar ships. The purpose of this article is to study the fatigue crack propagation rate of 925A steel under different low-temperature conditions from room temperature (RT) to −60 °C. The material was subjected to fatigue crack propagation tests and stress intensity factor tests. The experimental tests were conducted according to the Chinese Standard of GB/T6398-2017. The results show that as the temperature decreases, the lifespan of 925A increases. Within a certain stress intensity factor, as the temperature decreases, the fatigue crack propagation rate decreases. At −60 °C, it exhibits ductile fracture; within normal polar temperatures, it can be determined that 925A meets the requirements for low-temperature fatigue crack propagation rates in polar regions. However, in some extreme polar temperatures below −60 °C, preventing brittle failure becomes a key focus of fatigue design. Finally, the fatigue crack propagation behavior at the microscale of 925A steel at low temperatures was described using fracture morphology. The experimental data can provide reference for the design of polar ships to further resist low-temperature fatigue and cold brittle fracture. Full article
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13 pages, 8490 KB  
Article
Low-Temperature Impact Fracture Behavior of Medium Manganese Steel with Bcc-fcc Duplex Microstructures
by Yu Du, Xiuhua Gao, Xiaonan Wang, Hongyan Wu, Chao Sun, Guosheng Sun and Linxiu Du
Metals 2024, 14(3), 293; https://doi.org/10.3390/met14030293 - 29 Feb 2024
Cited by 2 | Viewed by 2342
Abstract
Impact fracture behavior at low temperatures was investigated in medium manganese steel with bcc-fcc duplex microstructures. The impact energy was above 150 J (−80~20 °C) and the fractography showed dimples for inter-critical annealing at 630 °C (QHA) because of the high retained austenite [...] Read more.
Impact fracture behavior at low temperatures was investigated in medium manganese steel with bcc-fcc duplex microstructures. The impact energy was above 150 J (−80~20 °C) and the fractography showed dimples for inter-critical annealing at 630 °C (QHA) because of the high retained austenite stability and low martensite dislocation density. The impact energy was from 180 J (20 °C) to 60 J (−80 °C) and the fractography was intergranular for inter-critical annealing at 610 °C (QLA) because of the low stability of RA and carbides precipitated at the prior austenite grain boundaries. The impact energy was below 60 J (−80~20 °C) and the fractography showed cleavage for direct quenching (DQ) because of the high dislocation density of martensite. Full article
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19 pages, 5764 KB  
Article
The Cold-Brittleness Regularities of Low-Activation Ferritic-Martensitic Steel EK-181
by Nadezhda Polekhina, Valeria Osipova, Igor Litovchenko, Kseniya Spiridonova, Sergey Akkuzin, Vyacheslav Chernov, Mariya Leontyeva-Smirnova, Nikolay Degtyarev, Kirill Moroz and Boris Kardashev
Metals 2023, 13(12), 2012; https://doi.org/10.3390/met13122012 - 14 Dec 2023
Cited by 1 | Viewed by 1604
Abstract
The behavior of the EK-181 low-activation ferritic-martensitic reactor steel (Fe–12Cr–2W–V–Ta–B) in the states with different levels of strength and plastic properties after traditional heat treatment (THT) and after high-temperature thermomechanical treatment (HTMT) in the temperature range from −196 to 25 °C, including the [...] Read more.
The behavior of the EK-181 low-activation ferritic-martensitic reactor steel (Fe–12Cr–2W–V–Ta–B) in the states with different levels of strength and plastic properties after traditional heat treatment (THT) and after high-temperature thermomechanical treatment (HTMT) in the temperature range from −196 to 25 °C, including the range of its cold brittleness (ductile–brittle transition temperature, DBTT) is studied. The investigations are carried out using non-destructive acoustic methods (internal friction, elasticity) and transmission and scanning electron microscopy methods. It is found that the curves of temperature dependence of internal friction (the vibration decrement) of EK-181 steel after THT and HTMT are similar to those of its impact strength. Below the ductile–brittle transition temperature, it is characterized by a low level of dislocation internal friction. The temperature dependence curves of the steel elastic modulus increase monotonically with the decreasing temperature. In this case, the value of Young’s modulus is structure-sensitive. A modification of the microstructure of EK-181 steel as a result of HTMT causes its elastic modulus to increase, compared to that after THT, over the entire temperature range under study. The electron microscopic studies of the steel microstructure evolution near the fracture surface of the impact samples (in the region of dynamic crack propagation) in the temperature range from −196 to 100 °C reveal the traces of plastic deformation (increased dislocation density, fragmentation of the martensitic structure) at all of the temperatures under study, including those below the cold brittleness threshold of EK-181 steel. Full article
(This article belongs to the Special Issue Thermomechanical Treatment of Metals and Alloys—Second Edition)
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20 pages, 3805 KB  
Article
Investigation of Self-Healing Performance of Asphalt Mastic—From the Perspective of Secondary Aging
by Bo Li, Yu Wang, Peng Xiao, Aihong Kang, Yao Zhang and Zhengguang Wu
Materials 2023, 16(24), 7567; https://doi.org/10.3390/ma16247567 - 8 Dec 2023
Cited by 5 | Viewed by 1560
Abstract
Reclaimed asphalt pavement (RAP) has been widely utilized because it is an environmentally friendly and economical material. The performance of recycled asphalt mixtures will deteriorate gradually with the secondary aging process of asphalt, including the self-healing property. To further understand the self-healing characteristics [...] Read more.
Reclaimed asphalt pavement (RAP) has been widely utilized because it is an environmentally friendly and economical material. The performance of recycled asphalt mixtures will deteriorate gradually with the secondary aging process of asphalt, including the self-healing property. To further understand the self-healing characteristics of asphalt after secondary aging, taking 70# petroleum asphalt, SBS-modified asphalt, and extracted old asphalt mastics as objects, the fatigue self-healing test and fracture self-healing test were conducted to simulate the intermediate-and low-temperature healing behaviors of different asphalt mastics. The impact of healing time, healing temperature, and aging degree of mastics on the healing performance was systematically investigated. The results show that the original unaged asphalt mastics present excellent fatigue healing properties with an index of 0.796 and 0.888 for 70# petroleum and SBS-modified asphalt mastics, respectively. The secondary aging process causes significant impact on the healing properties, leading to a great drop in the corresponding index, which decreased to 47.5% and 72.5% of that of the unaged ones. The fracture healing ability of all mastics was much inferior to the fatigue healing. After secondary aging, the fracture healing index values of 70# petroleum asphalt, SBS-modified asphalt, and extracted old asphalt mastics were all as low as around 0.3, indicating similar performance can be found in the secondary aged SBS-modified asphalt mastics and 70# asphalt mastics. Overall, after secondary aging, the fatigue damage of SBS-modified asphalt mastics can be cured effectively by self-healing, but the fatigue and fracture self-healing properties of 70# asphalt mastics are difficult to recover. These results could provide an innovative view to understand the fatigue and fracture healing characteristics of recycled asphalt pavement after secondary aging. Full article
(This article belongs to the Special Issue Green and Sustainable Infrastructure Construction Materials)
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