Formation Of Microcracks Research Articles

Tribologically enhanced self‐healing hybrid laminates for wind turbine applications

AbstractWind turbines are subjected to extreme weather and load conditions; hence, high strength and impact resistance are required. Furthermore, wind turbine blades can be subjected to impact loads such as bird strikes, resulting in the formation of microcracks. Self‐healing capsules can be used to mend turbine blades for microscale damage. The incorporation of self‐healing capsules may cause a decrease in the mechanical characteristics of the composites prior to impact resistance, which can be compensated for with efficient fillers such as silicon carbide whiskers (SiCw). Thus, a novel hybrid composite structure is examined with the advantage of using a self‐healing mechanism and SiCw reinforcement. Tensile, tribological, and Charpy impact tests were performed to characterize the mechanical and tribological properties, which were supported with microscopic observations. Multiple experimental characterizations were performed to investigate the impact, and the ultimate tensile strength (UTS) and energy absorption capacity of the structure were shown to increase by 32% and 45%, respectively, with the addition of SiCw. The presence of self‐healing agents provides a 5% rise in UTS after enough time for healing following the collision. The structure's tribological performance is improved by 10% in wear resistance and 20% in friction coefficient.Highlights Hybrid laminated composite structure with silicon carbide whisker and self‐healing capsules. Tensile and Charpy impact tests conducted with microscopic observations Increased ultimate tensile strength and energy absorption capacity by 32% and 45%. Tribological improvement by 10% in wear resistance and 20% in friction coefficient.

Linear and nonlinear ultrasound parameters attributed to anisotropy in granite

The anisotropic nature of granite, a key factor affecting its mechanical properties, is inherently governed by its mineral alignment and the presence of orthogonal cleavage planes: rift, grain, and hardway. This study examines how these cleavage planes influence anisotropy, particularly in the context of microcracking formation and acoustic properties. A new measurement procedure for the acoustic nonlinearity parameter (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document}) is developed to address the well-known limitations of conventional linear ultrasound methods, including wave velocity and attenuation coefficient, in detecting microstructural changes induced by existing cleavage planes. Unlike other parameters, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document} exhibits remarkable changes depending on the plane type, highlighting its high sensitivity to the mineral distribution in each cleavage plane and to the microcracks. A correlation between the linear and nonlinear parameters provides further evidence of the superiority of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document} in detecting inherent microscale defects that develop in each plane and affect the anisotropic characteristics of granite. The findings of this study confirm that nonlinear ultrasound is capable of elucidating the mechanisms underlying the origin of anisotropy in granite due to microcracks, with broader implications for understanding unidentified chemical and mechanical phenomena in geological materials.

Application of 3D-printed resin guides for the removal of molar fiber posts.

To evaluate the digital guide technique for removing fiber posts from molars and compare it with the conventional microscope-assisted ultrasound method. Two mandibular dentition models, each comprising six extracted molars, were prepared. Two thick and straight canals distributed separately in the distal and mesial roots of each molar were selected for placing the fiber posts. The 24 posts in the two dentition models were removed using 3D-printed resin guides, or a microscope and an ultrasonic device. The time taken to remove the fiber post from each tooth was recorded. The volume loss, deviation values (angular deviation and horizontal and vertical deviations of the tip), and formation of microcracks before and after fiber post removal were determined using micro-computed tomography images. The digital guide technique took significantly less time than the microscope-assisted ultrasound technique (p < 0.05). No significant differences in horizontal and vertical tip deviations were observed between the two groups. The angular deviation and volume loss in the guide group were significantly lower than those in the ultrasound group (p < 0.05). New dentin microcracks were formed in the ultrasound group but not in the digital guide group. Using a 3D-printed resin guide plate can shorten the fiber post removal time and improve the stability and safety compared to the microscope-assisted ultrasound technique. 3D-printed resin guides can reduce the fiber post removal time and provide better stability and safety than the conventional method.

Enhanced strength-ductility synergy in a Ni–W–Co–Ta medium-heavy alloy via cryogenic supersonic fine particle bombardment

This study explores the influence of cryogenic supersonic fine particle bombardment (CSFPB) on a Ni–W–Co–Ta medium heavy alloy (MHA), and focus on the effect of gas pressure and impact time on the surface integrity, microstructural evolution, and mechanical properties of the MHA. CSFPB treatment creates a gradient structure, including surface layer with nanograins down to 9.0 nm due to severe plastic deformation, subsurface layer with high density dislocation structures and deformation twins due to weakened impact energy, and undeformed matrix. A key advantage of CSFPB is seen to be the cryogenic environment, which promotes superior surface integrity by reduced roughness. As the impact duration and gas pressure increase, the depth of deformation layer, surface hardness and strength of the MHA progressively rise. The optimal combination of strength and ductility is achieved at a gas pressure of 1.0 MPa for a duration of 90 s. This setting results in a maximum ultimate tensile strength of 1351 MPa and yield strength 796 MPa, with uncompromising elongation. However, excessively long treatment durations or high gas pressures can lead to the formation of surface microcracks, ultimately reducing the MHA's strength. Therefore, CSFPB offers the benefit of improved surface integrity through the cryogenic environment while maintaining a desirable balance between enhanced strength and ductility.

Creep-fatigue interactive behavior and damage mechanism of TP321 stainless steel under hybrid-controlled conditions

In this study, Hybrid-controlled creep-fatigue (HCCF) tests were conducted on TP321 austenitic stainless steel under a variety of test conditions. The effects of strain amplitude, holding time, holding stress and temperature on the creep-fatigue behavior of TP321 austenitic stainless steel were not only analyzed in detail but also revealed the creep-fatigue damage interactive mechanism. The results demonstrated that a rise in test temperature and load holding time markedly induced creep deformation, resulting in a notable reduction in failure life. Additionally, an increase in test temperature led to the cessation of the cyclic hardening phenomenon. Secondly, the analysis of fracture morphology and X-ray computed tomography (X-CT) scanning results demonstrated that the transgranular cracks expanded inwards and connected with the intergranular voids under creep-fatigue interaction, forming a mixed intergranular and transcrystalline fracture mode. The presence of large creep cavities impeded the propagation of fatigue cracks when creep damage was the dominant phenomenon. Subsequently, the damage evolution mechanism was elucidated through microstructural analysis, which revealed that the impact of the slip bands on the triangular grain boundaries and the precipitation of carbides facilitated the nucleation of voids and the internal formation of intergranular microcracks, thereby causing creep-fatigue damage interaction. Finally, the TP321 austenitic stainless steel creep-fatigue damage interactive mechanism diagram was proposed in conjunction with the fracture morphological characteristics and microstructure.

Damage mechanisms of Ti60 under different uniaxial/multiaxial thermo-mechanical loading modes

The fatigue experiments for titanium alloy Ti60 under different uniaxial/multiaxial thermo-mechanical loading modes found that the combined action of high temperature and tensile stress can cause the debonding of the second phase strengthening particles between grain boundary, reducing the ability to resist deformation of Ti60, which leads to a decrease in the fatigue life of the material. In addition, mean tensile stress increases the ability of cracks to break through intergranular barriers and the non-proportional additional hardening caused by multiaxial loading exacerbates the formation of microcracks. Both will increase the fatigue damage of the material. The fatigue damage mechanism identified in this investigation can reasonably explain the fatigue life law under multiaxial loading at high temperature, uniaxial and multiaxial thermo-mechanical fatigue loadings.

Family-based whole-exome sequencing implicates a variant in lysyl oxidase like 4 in atypical femur fractures.

Atypical femur fractures (AFFs) are rare adverse events associated with bisphosphonate use, having unclear pathophysiology. AFFs also cluster in families and have occurred in patients with monogenetic bone diseases sometimes without bisphosphonate use, suggesting an underlying genetic susceptibility. Our aim was to identify a genetic cause for AFF in a Caucasian family with seven members affected by osteoporosis, including three siblings with bisphosphonate-associated AFFs. Using whole-exome sequencing, we identified a rare pathogenic variant c.G1063A (p.Gly355Ser) in lysyl oxidase like 4 (LOXL4) among 64 heterozygous rare, protein-altering variants shared by the three siblings with AFFs. The same variant was also found in a fourth sibling with a low-trauma femur fracture above the knee, not fulfilling all the ASBMR criteria of AFF and in one of 73 unrelated European AFF patients. LOXL4 is involved in collagen cross-linking and may be relevant for microcrack formation and bone repair mechanisms. Preliminary functional analysis showed that skin fibroblast-derived osteoblasts from the unrelated patient with the LOXL4 variant expressed less collagen type I and elastin, while osteogenic differentiation and mineralization were enhanced compared with two controls. In conclusion, this LOXL4 variant may underlie AFF susceptibility possibly due to abnormal collagen metabolism leading to increased formation of microdamage or compromised healing of microcracks in the femur.

Initial temperature conduction process and fracture response of rock impacted by ultra-low-temperature fluid: A case study of polymethyl methacrylate

Injecting ultra-low-temperature fluids, such as liquid carbon dioxide (CO2) and liquid nitrogen (LN2), into deep, low-permeability reservoirs for fracturing is an emerging waterless fracturing technology. When these fluids enter the reservoir, they rapidly exchange heat with the fracture walls, triggering intense cold shock, which influences fracture development. Although many scholars have studied the effects of nitrogen freezing and thawing on coal seams, the initial thermal exchange and cold shock process when LN2 first enters the rock mass remains unclear. This paper uses the visualizable material polymethyl methacrylate (PMMA) as the research object, conducting low-temperature impact experiments under different preset temperatures (20 °C, 40 °C, 60 °C, and 80 °C) to investigate the impact of thermal exchange during cold shock on PMMA fracturing. The results show: (1) During LN2 impact, PMMA's temperature changes in three stages: slow cooling (micro-cracks initiation), rapid cooling (formation of long fractures), and temperature recovery (crack formation completion). (2) In prolonged impacts, PMMA temperature decreases linearly, while in short-term cyclic impacts, temperature decreases exponentially with faster recovery, increasing the likelihood of micro-cracks formation. (3) Temperature differences have a dual effect on crack formation and propagation: they significantly enhance internal thermal stress, leading to rapid micro-cracks initiation and expansion, while also causing uneven temperature gradients in the crack propagation region, shifting fracture modes from tensile to complex composite failures and promoting secondary crack formation. However, a significant temperature differential may result in the development of a singular crack propagation path, hindering the formation of complex fracture networks. These findings offer theoretical insights into fracture network formation in waterless fracturing of low-permeability reservoirs.

Achieving strength-ductility synergy of ODS-FeCrAl alloys via heterostructured strategy

Oxide dispersion strengthened (ODS)-FeCrAl alloys are candidate structural materials for advanced nuclear reactor applications, which have excellent strength and radiation tolerance but low ductility. In this study, a novel ODS-FeCrAl heterostructured composite, reinforced with FCC-structured ODS-CoCrFeNiMn high-entropy particles, was prepared by using mechanical alloying and spark plasma sintering to achieve the strength-ductility synergy. The effect of different reinforcement contents (0, 10, 15 and 20 wt.%, designated as RC-0, RC-10, RC-15, and RC-20, respectively) on the microstructure and mechanical properties of the composites was investigated. The results showed that the unreinforced reference alloy, RC-0, consists of BCC-structured ODS-FeCrAl matrix and high-density oxides. In the RC-10, RC-15, and RC-20 composites, in addition to the ODS-FeCrAl matrix and nanoscale oxides, FCC-structured ODS-CoCrFeNiMn high-entropy reinforcement with ultrafine grain size and FCC transition layer with gradient grain size are observed. As the reinforcement content increases, the thickness of transition region increases. The composites show an increase in ultimate compressive strength and compressive strain with increasing reinforcement content in the following order: 2951 MPa/33.6%, 3169 MPa/40.0%, 3290 MPa/43.2%, and 3489 MPa/48.8%. And the compressive yield strength exhibits an initial increase and subsequent decrease, i.e. 1523 MPa (RC-0), 1680 MPa (RC-10), 1635 MPa (RC-15), and 1355 MPa (RC-20), respectively. The increase in yield strength is mainly attributed to hetero-deformation induced (HDI) strengthening and reinforcement hardening. The improvement in ductility is mainly attributed to the HDI work hardening and the suppression of microcrack formation and propagation at prior powder boundaries.

The effect of soaking heat-polymerized acrylic resin denture base in avocado seed extract (Persea americana Mill.) on the inhibition of denture-plaque microorganisms biofilm growth

Background Heat polymerized acrylic (HPA) resins are known to have high porosity that contributes to increased surface roughness and microcrack formation in stress areas. This facilitates the attachment and growth of polymicrobial biofilms contributing to increased antimicrobial resistance. Many research had been carried out on avocado seeds, but no research that studies avocado seeds effect on denture-plaque microorganism biofilm on HPA resin has been found. Methods This study used 144 samples (n=144), namely HPA resin discs covered with mono-species and polymicrobial biofilms. The discs were soaked for 8 hours in the 5%, 10%, 15%, 20% avocado seed extract, positive control (alkaline peroxide), and negative control (aquadest). Each disc was shaken with a vortex mixer for 1 minute, and 100 μL was added into 96-well microplates with three times repetition and incubated for 24 hours. A microtiter plate biofilm formation assay was then conducted The inhibition values were determined from the percentage inhibition value formula which required absorption values from a microplate reader (595 nm). The research data were analyzed using a univariant test, and a one-way ANOVA test, accompanied by Welch ANOVA on non-homogenous data. Results In this research, it was found that the MBIC50 of avocado seed extract against the mono-species of C. albicans (5%), C. glabrata (5%), A. odontolyticus (15%), S. gordonii (15%), S. aureus (10%), while against polymicrobial was 20%. There was a significant effect of soaking HPA resin in avocado seed extract on the inhibition of mono-species and polymicrobial biofilms with a value of p&lt;0.001 (p&lt;0.05). Conclusion The MBIC50 of avocado seed extract in polymicrobial biofilm group was higher than that in the mono-species biofilm groups. Although alkaline peroxide showed higher inhibition value than that of the MBIC50 in polymicrobial biofilm group, 20% avocado seed extract was concluded effective as it inhibited &gt;50% polymicrobial biofilm.

Simulation of Autogenous Self‐Healing in Lime‐Based Mortars

ABSTRACTThroughout history, architectural heritage has been constructed using masonry, clay or stone elements, and lime‐based mortars. Over time, old buildings are subjected to different degrees of movement and degradation, leading to the formation of microcracks. Water dissolves and transports lime in mortar, but when the water evaporates, the lime is deposited and heals cracks in a process known as autogenous healing. Lime‐based mortars can regain some mechanical properties due to their healing capacity, given certain conditions. In the present work, a constitutive formulation has been developed to simulate cracking and healing in lime‐based mortars. The proposed model captures the residual displacements within cracks, associated with interacting crack surface asperities, as well as the healing effect on mechanical properties. A new approach is described which expresses these mechanisms mathematically within a micromechanical formulation. The proposed model was validated by comparing the outputs with experimental data. The results show that the new continuum micromechanical damage‐healing model could capture the damage‐healing cycle with good accuracy.

Microstructural Anisotropy, Mechanical Properties, and Fatigue Crack Growth Behavior of AA2050‐T84 Alloy

ABSTRACTThis study focuses on characterizing the microstructure and mechanical properties of AA2050‐T84 alloy produced in two different thicknesses, 20 and 130 mm. A comparative analysis between the two thicknesses aims to understand how the rolling operation for achieving thin plates influences the alloy's microstructure and overall mechanical performance. Microstructural analyses showed a highly anisotropic grain structure and preferred crystallographic orientation in the 20‐mm‐thick plate, causing anisotropic tensile properties. Also, a significant fatigue crack deviation was observed for the 20‐mm‐thick plate during fatigue crack growth tests due to its microstructure. This result was attributed to the microcrack formations perpendicular to the crack growth direction and slip bands at the intermediate ΔK, when the loading was parallel to the rolling direction. The findings from this study offer critical insights into how the rolling operation for achieving thin plates influences the microstructure and overall performance of the alloy.

Periodically Sinusoidal Magnetic Stray Field and Improved Film Quality of CoMnP Micro-Magnet Arrays for Magnetic Encoders by Electrodeposition with the Assistance of Ultrasound

Magnetic encoders are composed of a magnetic sensor, a hard magnetic recording medium and a signal processing circuit. Electrodeposited micro-magnet arrays produced by micro-fabrication are promising recording media for enhancing encoder performance. However, two major engineering issues have yet to be resolved. One issue is an unknown relationship between the feature sizes of micro-magnet arrays and their stray field shapes, and another issue is the formation of micro-cracks due to the built-up residual stresses of thick films. In this study, we investigated the effect of feature sizes on the emanating stray field shape at various observation heights. Feature sizes include two height (i.e., film thickness) values of 78 μm and 176 μm, and both width and spacing with three values of 360 μm, 520 μm and 680 μm. Ultrasound-assisted agitation was adopted for investigating the effects of electrodepositing current densities on the film crystalline microstructures and magnetic properties. Narrowing the width of micro-magnets helps the stray field to become a sinusoidal profile. Thinner film, i.e., thickness 78 μm in this study, supports the stray field taking on a sinusoidal profile. Moreover, the spacing between the micro-magnets plays a key factor in determining the shape of the stray field. Under 37 kHz/156 W ultrasound agitation, the optimal hard magnetic properties of electrodeposited CoMnP films are residual magnetization 2329 G and coercivity 968 Oe by a current density of 10.0 mA/cm2. Ultrasound-assisted electrodeposition, along with duly designed feature size, facilitates the micro-magnet arrays having a sinusoidal stray field shape using high quality films. Furthermore, for the first time, a systematic understanding of feature-size-dependent stray field evolution and improved polarities quality has been realized for the recording media of sinusoidal magnetic encoders.

Improving Cycling Stability of Ni‐Rich Cathode for Lithium‐Metal Batteries via Interphases Tunning

AbstractCombining Li‐metal anodes (LMAs) with high‐voltage Ni‐rich layered‐oxide cathodes is a promising approach to realizing high‐energy‐density Li secondary batteries. However, these systems experience severe capacity decay due to structural degradation of high‐voltage cathodes and side reactions of electrolyte solutions with both electrodes. Herein, the use of multi‐functional additives in fluoroethylene carbonate‐based electrolyte solutions that enable the operation of successfully rechargeable high‐voltage (4.5 V) Li‐metal batteries (LMBs) with high areal capacity (&gt;4 mAh cm−2) are reported. Customized electrolyte solutions are pivotal in passivating the electrodes, minimizing microcrack formation, and ensuring that current is uniformly distributed within cathode particles. The developed electrolyte solution protects the LMA by forming a very stable and effective solid–electrolyte interphase. Together with the Li[Ni0.78Co0.1Mn0.12]O2 cathode material, which is composed of radially aligned rod‐shaped primary particles, the developed high‐voltage LMB containing 20 mg cm−2 of cathode material delivers a high specific capacity of 230 mAh g−1 at 0.1 C and retains &gt;86% of its initial capacity after 200 cycles at 0.5 C. This study highlights the significance of controlling the interfacial structure via electrolyte solution modification and the use of cathode materials with engineered morphologies that enhance mechanical stability.

Preparation and properties of silica isophorone diisocyanate microcapsules for self-healing anticorrosive coatings

ABSTRACT Traditional anticorrosion coatings often suffer from reduced effectiveness or even complete failure due to the formation of microcracks. Isophorone diisocyanate (IPDI) can form a polyurea structure without a catalyst in the presence of water, which can protect the underlying metal from corrosion. In this study, an anticorrosion coating with self-healing properties was developed by incorporating microcapsules containing IPDI into the coating formulation. Silica-based self-healing microcapsules were synthesized via interfacial polymerization, using tetraethyl orthosilicate as the precursor and IPDI as the core material. The effects of core-to-wall ratio, reaction temperature, different emulsifiers, and emulsifier ratios on the microcapsule properties were investigated. The results demonstrated that microcapsules prepared using a composite emulsifier system of cetyltrimethylammonium bromide (CTAB) and OP-10 at a 1:1 ratio, with a core-to-wall ratio of 1:1, and a reaction temperature of 75°C, exhibited a smooth surface, spherical shape, and excellent encapsulation efficiency. The maximum core content achieved was 81.2 wt%. An epoxy coating embedded with these self-healing microcapsules was subjected to scratching damage. After applying water to the surface and allowing it to stand for 2 days, the scratches healed, and the steel plate surface remained free from corrosion, indicating excellent self-healing performance.

Microstructural evaluation and optimization of wear behaviour of vacuum arc melted AlFeCrNiSi high entropy alloy

High-entropy alloys (HEA) are equiatomic, multi-element systems that, while having several elements with various crystal geometries to form a single phase. In this study, a novel equiatomic AlFeCrNiSi HEA is prepared using the vacuum arc melting process. The resulting microstructure featured dendritic and inter-dendritic structures with formations of intermetallic compounds such as Al₃Fe₂Si, NiAl, and AlCrNi phases. EDS analysis confirmed the presence of alloying elements and EBSD analysis revealed refined grains with an average size of 1 ± 0.15 µm size. Pin-on-Disc wear test with varying test parameters is conducted to optimize the wear parameters. Signal-to-noise ratio and analysis of variance identified the most significant wear parameters, with load being the most influential, followed by sliding distance and velocity. The wear rate is minimum at the lowest conditions of applied load, sliding distance, and sliding velocity. The improved microhardness also contributed to the improved wear resistance of the cast alloy. The subsequent worn morphology revealed the formation of grooves, microcracks, and oxide layers on the worn surface.

Rotation bending high cycle fatigue behaviors of TC21 alloy with bimodal microstructure

The TC21 alloy has been extensively utilized in the aerospace structural components, making it crucial to investigate the fatigue damage mechanism of this alloy. In this study, a comprehensive investigation was conducted into the high-cycle fatigue damage mechanism of TC21 alloy under rotation bending, considering variations in primary equiaxed α (αp) phase contents and size in bimodal microstructure (BM). Results demonstrate that the TC21 alloy exhibits optimal strength-ductility and fatigue life at approximately 25 percent of the αp phase content. The content and dimension of the αp phase play a significant role in regulating the onset of fatigue fractures. Dislocation pile-up around the αp phase promotes the formation of microvoids and microcracks. Notably, when the content of the αp phase falls below 15%, there is an increased influence from secondary α phase (αs) on crack initiation. Moreover, excessive amounts of αp coupled with decreased size lead to a reduction in fatigue life. The aforementioned factors contribute to an intensified concentration of stress, facilitate a more uniform path for crack extension, and expedite the rate of fatigue crack propagation.

The investigation of micro-crack generation in cementitious mine seals via temperature and strain analysis

Mine seals are employed in underground coal mines to effectively isolate abandoned areas from active workings. The seals are engineered to prevent air movement and endure dynamic pressure events resulting from methane explosions. Mine seals are made from cementitious materials and undergo a curing process that involves an exothermic reaction known as hydration. The presence of moisture (hydration) may result in the mixture contracting, which could subsequently lead to cracking during the early phases of the curing process. Cracks in the seal can influence the performance and structural stability. This study examines the formation of micro-cracks in cementitious mine seals throughout the curing process by evaluating temperature and strain data collected from thermocouples and strain gauges that were installed during the pouring phase. The samples for the mine seal were prepared using two distinct mixtures: traditional concrete and pumpable products sourced from conventional suppliers. Heat evolution curves were produced for each sampling location corresponding to the three samples. The samples of Mixture A and B, prepared according to specifications, exhibited the anticipated heat evolution curves, with the maximum temperature occurring at the center of the samples. In contrast to the other mixtures, the samples of mixture C, which were prepared outside of the specified parameters, exhibited the highest temperature at the bottom of the sample. The strain measurements showed a correlation with temperature readings, indicating that mixtures A and B exhibited the highest strain at the center of the sample, while mixture C demonstrated the greatest strain at the bottom of the sample. The examination of the gathered data reveals a significant likelihood of micro-cracks forming in each of the samples.

Microstructural characterization and wear analysis of AlTiVZrMoCr HEA coating on SS410 steel by atmospheric plasma spraying

In recent research, noteworthy progress is made in developing Lightweight High Entropy Alloy (LWHEA) with superior performance and characteristics. A novel AlTiVZrMoCr LWHEA is synthesized through 50 h of ball milling with a 19 µm mean size of powders. The microstructural analysis of synthesized LWHEA powders revealed minor FCC and predominate BCC phases. The powders are coated on SS410 substrate by Atmospheric Plasma Spraying (APS) and the LWHEA coating significantly improves the structural characteristics of the substrate. Notably, the coated sample exhibits a uniform and homogeneous distribution across the substrate surface with an average grain of 1.71 µm. The microhardness of the coated sample is 1.67 times higher than the substrate, owing to the elemental bonding. Pin-on-disc tribometer is employed to measure the wear rate using different process parameters. Response Surface Methodology (RSM) is employed for the optimization of process parameters to obtain optimum wear rate. The technique of Analysis of Variance (ANOVA) is used to determine the most influential wear process parameter. Among various process parameters, the applied load is found to be the most influential factor in achieving an optimal wear rate. The worn morphology revealed the formation of grooves, micro-cracks, and oxides on the coated sample.

Stabilization of thermal storage ceramics via the phase reconstruction of ferrotitanium slag and migration of Mg element

AbstractIn this study, aluminum titanate/anorthite (Al2TiO5‐CaAl2Si2O8) ceramics were fabricated from ferrotitanium slag through phase reconstruction. Stabilization of the ceramic was achieved by migration of Mg element into Al2TiO5 phase. The results indicated that optimal performance was achieved with the addition of 4 wt% MgO and 60 wt% ferrotitanium slag at 1370°C. The ceramic exhibited bulk density of 3.11 ± 0.01 g/cm3, thermal storage density of 1.51 kJ/cm3, and thermal expansion coefficient of 3.40 × 10−6/°C (1000°C), respectively. Additionally, the solid solution of Mg2+ in the Al2TiO5 lattice reduced the formation of microcracks and enhanced the mass transfer process. Consequently, the sintering temperature decreased from 1415°C to 1370°C while the bending strength increased from 61.25 ± 1.05 MPa to 75.92 ± 7.72 MPa. Furthermore, finite element simulation demonstrated that higher thermal expansion led to concentrated thermal stress, potentially increasing the possibility of ceramic cracking. This research provides a new strategy for preparing low thermal expansion ceramics from titanium‐containing solid waste.