Degradation Of Mechanical Properties Research Articles

Structural Performance of Sisal Fiber Mat Retrofits for Post-Fire Damaged Reinforced Concrete Beams

Concrete experiences degradation in mechanical properties when exposed to high temperatures, leading to spalling, disintegration, and surface damage. Research shows a 26-40% reduction in structure strength under fire. While strengthening and restoring existing structures is a practical solution, a more sustainable approach is needed. This study evaluated the performance of sisal fiber mat retrofits for post-fire damaged beams and investigated natural fiber retrofits as a sustainable solution for fire-damaged structures, addressing challenges like elevated temperatures and moisture sensitivity to restore safety, stability, and functionality. The physical, chemical, and mechanical properties of the constituent materials used to fabricate the reinforced concrete beams and retrofitted material were characterized. The mechanical properties of 150×225×650 mm reinforced concrete beams exposed to 800 °C for 1 hour were assessed. The load-carrying capacity of the concrete beam was determined after it had been repaired with one or two layers of sisal fiber mat. The results indicated that the load-carrying capacity of concrete reinforced beams exposed to fire was reduced by 13.03%. However, the use of two layers of sisal fiber mat retrofits in the beams restored the load-carrying capacity by 33.86% and improved ductility by 43.56%. These findings demonstrate the feasibility of using sisal fiber mat retrofits to repair fire-damaged reinforced concrete beams, as the fiber mat enhances the load-carrying capacity by providing additional tensile strength to the structure.

A deformation-diffusion interactive model to study crack-tip behaviour and predict crack growth rate under fatigue and hydrogen-embrittlement conditions

Hydrogen is accepted as a cleaner and more sustainable energy source, since it carries abundant energy and does not produce any effluent gas from burning when compared to fossil fuels. However, long-term degradation in mechanical properties, attributed to hydrogen embrittlement, is reported for metallic materials exposed to gaseous hydrogen, leading to accelerated crack growth behaviour under fatigue. In this paper, a visco-plastic deformation-diffusion interactive model is developed to study fatigue crack growth behaviour in a nickel-based superalloy under hydrogen-embrittlement condition. In the model, cyclic deformation is described by visco-plasticity constitutive model, while hydrogen diffusion is simulated by a modified form of Fick’s first law of diffusion which can address hydrogen diffusion driven by the hydrostatic stress gradient. In particular, trapped hydrogen, expressed as dependent on both diffusible hydrogen concentration and inelastic strain, is considered in the modelling of hydrogen diffusion. The model also describes the effects of hydrogen concentration on mechanical deformation by considering its influence on the evolution of isotropic hardening as well as on the strain state. Interaction between cyclic deformation and hydrogen diffusion is therefore studied for a crack tip in a compact tension specimen subjected to fatigue and hydrogen attack, showing a strong dependency on both loading frequency and stress intensity factor range. Subsequently, a two-parameter criterion is proposed for fatigue crack growth prediction, which accounts for the contributions of both cyclic deformation and hydrogen diffusion. The predictions show a good agreement with experimental data in terms of crack growth rate under fatigue and hydrogen-embrittlement conditions.

A Brief Review of the Impact of Neutron Irradiation Damage in Tungsten and Its Alloys

Neutron irradiation poses a substantial challenge in the development and application of tungsten (W) and its alloys, predominantly in the framework of nuclear fusion and fission environments. Although W is well-acknowledged for its unique properties like its high melting temperature and higher resistance to sputtering, transmutation products, such as Re and Os, form and impact the alloy properties as a result of neutron irradiation. This transmutation effect accompanied by significant microstructure damage due to neutron irradiation can lead to the significant degradation of mechanical properties. This review surveys the literature focusing on the microstructural modifications post-irradiation and its impacts on the irradiation hardening. This review provides insights into the elaborative understanding on the neutron radiation damage on W and W alloys by exploring the microstructural evolution and hardness changes post-irradiation. The gaps and future opportunities for understanding neutron radiation damage in W are briefly summarized

A spatially-resolved model of neutron-irradiated tungsten coupling stochastic cluster dynamics and finite deformation plasticity

Structural materials used in nuclear reactors face severe degradation in mechanical properties, such as hardening and embrittlement. At the microscopic scale, this occurs due to creation and accumulation of irradiation-induced defects and their interaction with system dislocations. Although techniques exist which can model evolution of irradiation defects, for instance kinetic transport theory-based models, their interaction with mechanical deformation of the bulk material has not been investigated extensively. In this work, we demonstrate a novel spatially-resolved multiscale coupling between microscopic irradiation defect evolution, modeled using Stochastic Cluster Dynamics (SCD) and macroscopic mechanical deformation modeled using a finite-deformation plasticity model. SCD is used to determine the statistically averaged defect cluster spacing, dependent on operating conditions such as irradiation dose and temperature. This acts as an initial condition that governs the critical resolved shear stress of dislocation glide in the macroscopic plasticity model. This framework is used to predict mechanical behavior in post-mortem test of irradiated Tungsten samples, which has found its importance as structural material used in nuclear reactors. The results obtained using the coupled approach are in good agreement with experimental data of uniaxial tension tests. The model is able to capture the effect of temperature and irradiation dose on the material hardening. Two methods are proposed to estimate hardness – using Tabor's Law relating uniaxial yield stress to hardness and from flat-punch simulations. The results are in reasonable agreement with hardness data from micro-indentation experiments of irradiated Tungsten samples. The model is also able to reveal microstructural details such as spatial variation in defect density and local stress.

Environment aging of lignocellulosic fibers and their composites: Visual, mechanical, and microstructural aspects

The current experimental investigation reports the performance of intra-hybrid woven jute-sisal lignocellulosic fibers, and their polypropylene composites subjected to different aging conditions (distilled water, vegetable oil, and alkali solution) for a prolonged time of 6 months. The effect of different aging mediums on chemical composition of fibers, such as, variation in cellulose and hemicellulose content was analyzed to understand the degradation mechanisms and their structure property relationship established. Significant degradation in mechanical properties was observed with exposure to alkali followed by water mediums due to degradation of fibers and thereby results in poor interfacial characteristics, while sustained durability in terms of mechanical properties was observed with oil-based aging. Highest reduction was observed in tensile strength (11 % and 34 %), flexural strength (16 % and 20 %), tensile modulus (44 % and 58 %), and flexural modulus (51 % and 52 %) after 3-month and 6 months of alkali-aging, respectively as compared to un-aged specimens. Furthermore, the visual appeal of materials was significantly affected due to aging in an alkali solution followed by distilled water, while vegetable oil has not shown any visual degradation.

Microstructural Evolution and Damage Mechanism of Water-Immersed Coal Based on Physicochemical Effects of Inorganic Minerals.

Coal seam water injection technology enables seam permeability enhancement and facilitates outburst risk reduction. This study investigated the microscale effects of water infiltration on coal and the evolution mechanisms of its mechanical properties. To this end, we systematically analyzed dynamic changes (such as mineral composition, pore structure, and mechanical performance) in coal soaked for various durations using X-ray diffraction, low-field nuclear magnetic resonance (NMR), and uniaxial compression testing. The results indicate: (1) the coal NMR T2 spectrum displays three characteristic peaks, corresponding to rapid water absorption, uniform transition, and stabilization stages of soaking traditionally divided according to peak area variation trends. (2) The coal strength decreases with progressive soaking, influenced by water content, pore volume, mineral composition, etc. Its compressive strength and elastic modulus drop by 22.4% and 19.5%, respectively, compared to the initial values. (3) The expansion of clay minerals during immersion reduces average pore size. In contrast, quartz particle displacement, pore water movement, and soluble mineral dissolution increase pore volume, reducing the overall structure strength. (4) The dominant factors driving the degradation of mechanical properties vary across immersion stages, including water content and specific mineral concentration. This work offers new insights into how hydraulic technology alters coal seams, providing theoretical support for optimizing water injection strategies in the seam.

Chloride corrosion resistance of manufactured sand reinforced concrete prepared in plateau environment

The durability of manufactured sand concrete prepared in a simulated plateau environment was investigated. Several factors, such as preparation environment of the specimens, concrete strength and corrosion rate of steel bar, were considered in this study. In these experimental investigations, the accelerated corrosion test on specimens exposed to a chloride salt solution and thereafter the static tensile test on corroded steel bars retrieved from these specimens were carried out. The durability of different specimens was compared by analyzing the surface crack development on the concrete surface, the corrosion morphologies of embedded steel bars, the degradation of mechanical properties of steel bars, and the concrete microstructure. In addition, the differences observed in the crack development of concrete and the degradation of mechanical properties of corroded steel bars between plateau and normal exposure environments were quantified. The results show that the steel bars embedded in the specimens prepared in a simulated plateau environment are prone to non-uniform corrosion attack, especially for the specimens with low concrete strength. The preparation environment of specimens and concrete strength have little influence on the degradation of mechanical properties of steel bar when subjected to a theoretical corrosion rate less than 6 %. Compared with the specimens prepared in a normal environment, the yield strength, ultimate strength and elongation of corroded steel bars subjected to a theoretical corrosion rate in the range 2∼10 % in specimens prepared in a plateau environment decrease by 2.99 %, 4.44 % and 14.78 % on average, respectively. For the specimens prepared in a plateau environment the decreased durability of concrete is explained by insufficient hydration and low compactness inside concrete, so that it is easier for chloride ions to penetrate into concrete, resulting in early corrosion. As a result, the variation of average crack width of concrete with actual corrosion rate and the variation of nominal yield and ultimate strengths of steel bars with their maximum section loss rates no longer satisfy the linear relationship for the specimens prepared in plateau environment, which is different from the specimens prepared in a normal environment. Moreover, the protective effect of concrete on embedded steel bar can be significantly enhanced by improving the strength of concrete produced in a plateau environment.

Experimental Test and Analytical Calculation on Residual Strength of Prestressed Concrete T-Beams After Fire

High temperatures during a fire can lead to the evaporation of moisture and the degradation of hydration products within concrete, consequently compromising its mechanical properties. This paper thoroughly investigates the effect of fire-induced high temperatures on the residual load-bearing capacity of concrete structures, with a focus on prestressed concrete T-beams. By conducting constant temperature tests and residual load-bearing capacity tests, complemented by finite element modeling, this study examines the degradation of mechanical properties in prestressed concrete T-beams due to fire exposure and its impact on post-fire residual load-bearing capacity. Additionally, an equivalent concrete compressive strength method was employed to propose a calculation method for concrete material degradation under high temperatures and a corresponding concrete strength reduction factor. Simplified calculations were also performed for the high-temperature damage to reinforcement and prestressed tendons, leading to the derivation of a simplified formula for the residual load-bearing capacity of post-fire prestressed concrete T-beams. The results indicate that in prestressed concrete T-beams exposed to fire, an increase in holding time results in more severe damage modes, accelerated crack propagation, and wider crack widths during bending failure. Under the same load, a longer holding time corresponds to a more pronounced reduction in deflection. At holding times of 60 min, 120 min, and 180 min, the prestress losses were 48.17%, 85.16%, and 93.26%, respectively. The cracking load decreased by 15%, 27%, and 42%, while the residual load-bearing capacity decreased by 11%, 21%, and 28%. Comparison with experimental data demonstrates that both the finite element model and the simplified calculation formula exhibit high accuracy, offering a reliable reference for the performance evaluation of post-fire prestressed concrete T-beams.

Cracking of silty mudstone subjected to wetting-drying cycles

Cracking affected by wetting-drying cycles is a major cause of shallow failure of soft rock slopes. Knowledge of rock tensile properties and cracking behaviors helps better assess the stability of soft rock slopes. This study aims to examine the cracking behaviors and tensile strength of silty mudstone under wetting-drying cycles. The wetting-drying cycles and Brazilian splitting tests were performed on silty mudstone considering various cycle number and amplitude. The cracking behaviors of wetting-drying cycles were analyzed by digital image correlation, three-dimensional (3D) scanning technology, and scanning electron microscopy. The results reveal a spiral-like pattern of crack ratio escalation in silty mudstone, with a higher crack ratio observed during drying than wetting. Tensile strength and fracture energy correlate negatively with cycle number or amplitude, with cycle number exerting a more pronounced effect. The variance of the maximum principal strain reflects stages of initial deformation, linear deformation, strain localization, and stable deformation. The formation of strain localization zones reveals the physical process of crack propagation. Crack tip opening displacement progresses through stages of slow growth, exponential growth, and linear growth, delineating the process from crack initiation to stable extension. Failure modes of silty mudstone primarily involve tensile and tensile-shear failure, influenced by the geometric parameters of cracks induced by wetting-drying cycles. Fracture surface roughness and fractal dimension increase with cycle number due to mineral dissolution, physical erosion, and nondirectional crack propagation. Hydration-swelling and dehydration-shrinkage of clay minerals, along with absorption-drying cracking, initiate and merge cracks, leading to degradation of the rock mechanical properties. The findings could provide insights for mitigating shallow cracking of soft rock slopes under wetting-drying cycles.

Comprehensive study of Tolanene's mechanical properties: Effects of temperature, layering, orientation, and defects

This study explores the mechanical properties of both single-layered and multi-layered tolanene nanosheets via molecular dynamics (MD) simulations. The effects of critical parameters such as size, temperature, and defects on the mechanical behavior of armchair and zigzag configurations of single-layer Tolanene nanosheets are analyzed. Key mechanical properties, including Young's modulus, ultimate stress, fracture stress, and fracture strain, are evaluated based on the stress-strain curve. It is observed that the zigzag configuration exhibits a higher Young's modulus compared to the armchair configuration. However, the armchair structure shows greater ultimate stress than the zigzag configuration. An increase in temperature or the introduction of vacancy defects leads to a degradation of mechanical properties in both configurations. The sensitivity of Young's modulus to temperature is more pronounced in the zigzag configuration than in the armchair, even though the armchair configuration generally has a higher Young's modulus. Additionally, increasing the number of layers in the nanosheets results in an enhancement of Young's modulus, with the armchair configuration showing more significant improvement than the zigzag configuration. The variation in Young's modulus with increasing layers is minimal for the zigzag configuration.

Study on the decay laws and deterioration mechanism of mechanical properties of cement-stabilized gravel under water-heat-salt coupled conditions

A new type of asphalt pavement disease, known as arch expansion, has appeared in the saline soil regions of Northwest China. The emergence, as well as the evolution of the disease, is strongly related to the distribution of sulfate. However, the decay of Cement-stabilized gravel (CSG) mechanical properties is closely related to the onset and development of arch expansion. The relationship between CSG mechanical strength and salinity in the arch expansion area is analyzed based on field investigations to systematically study the mechanical property degradation law and mechanism of CSG. The mechanical strength and deterioration patterns of CSG with different coupling conditions were investigated. The mineral composition and micromorphology of the erosion products were analyzed. The results show that the mechanical properties of CSG in the area of the arch deteriorate more than those in the regular section. The mechanical strength of the specimens initially containing salt and partially immersed in salt solution decayed most severely. In terms of the deterioration mechanism of mechanical strength of CSG, the water-heat-salt erosion process is also divided into two parts, including the formation stage of gypsum and ettringite, the stage of C-S-H decomposition and thaumasite formation, respectively. The degradation mechanism of CSG is a combination of physical and chemical erosion.

Influence of hygrothermal aging on the lifetime and mechanical properties of GFRP/Al adhesive joints

The study aimed to investigate the impact of hygrothermal aging on the degradation of mechanical properties and predict the lifetime of adhesive joints between aluminum alloy (AA6061) and glass fiber-reinforced epoxy (GFRP) composites. The adhesive joints were prepared in a single lap joint (SLJ) configuration and subjected to hygrothermal conditions to induce aging. Immersion tests were conducted at a water temperature of 70 °C with varying aging periods (10, 18, 40, 54, 60, and 75 days) to assess the long-term performance and predict the lifetime of the joints. The tensile and shear strength of the adhesive joints were evaluated using a tensile test. The test was performed at room temperature (RT) with a speed rate of 1.3 mm/min. Among the different methods available for lifetime prediction, a semi-empirical approach was selected to analyze the changes in the mechanical properties of the adhesive joints. A comprehensive comparison was made between aged and unaged specimens. The experimental results revealed a reduction in the ultimate tensile and shear strength of the adhesive bonds over the 75-day aging period. The semi-empirical relationship used for long-term durability prediction of adhesive joint structures indicated a 78 % decrease in ultimate tensile strength for the adhesive joints over a one-year aging period. This highlights the significant influence of hygrothermal aging on the mechanical properties of the investigated adhesive joints. During the aged periods, various failure modes were observed, including adhesive failure, cohesive failure, and structural failure.

A synchronous improvement of strength and elongation caused by solid solution in low-silver SAC solder with superior necking resistance properties

The current SAC(Sn–Ag–Cu) solder often experiences rapid degradation of mechanical properties at high temperatures and is prone to fracture under dynamic loads, thus failing to meet the interconnection requirements of industrial electronic products that operate under high power and vibration loads. In light of this, this paper aims to enhance the overall performance of the alloy by reducing the fraction of the second phase in SAC305 alloy, altering the type of second-phase particles, and strengthening the matrix β-Sn phase. Additionally, based on thermodynamic calculations of phase diagrams, the internal phases and elemental solid solubility of the alloy under different temperature conditions are accurately designed, thereby improving the alloy's strength while maintaining its elongation almost unchanged. The experimental results indicate that the designed Sn1.0Ag0.7Cu–3Bi4In1.5Sb alloy exhibits a higher rate sensitivity factor m (0.0559), which is more than double that of the Sn1.0Ag0.7Cu–5Bi4In3Sb alloy (0.0239). This improvement is primarily attributed to the enhanced interaction between the matrix β-Sn and the solid solution effect. Larger compound phases, such as Cu6Sn5 and Ag3Sn, only play a role in the low-rate loading region. Additionally, the alloy demonstrates strong temperature dependence, which is also related to the dissolution of the In element in the matrix β-Sn. The solid solution of the In element significantly enhances the high-temperature elongation rate of the alloy, increasing from 11.9% at low temperatures to 21.3% at high temperatures. The successful development and implementation of this research provides a new solution for interconnection of electronic devices under high-speed dynamic loading and high-temperature service.

The formation of CaCO3-based binder by carbonating high-dosage Ca(OH)2 + slag + NaHCO3 (HCHSN) cement paste

Normally, carbonation can cause the decalcification of C-(A)-S-H gel of alkali-activated cement and the degradation of mechanical properties. While, we propose another possibility to form CaCO3-based binder by carbonating the alkali-activated slag cement of high-dosage Ca(OH)2 (30 %) + slag (70 %) + NaHCO3 (5.11 % by weight of Ca(OH)2 and slag) (HCHSN) in this study. The results supported that the compressive strength and volume stability of HCHSN cement paste can be improved by the carbonation curing and the carbonated HCHSN cement paste could reach a maximum compressive strength of 32.4 MPa. According to the micro-analysis of XRD, TGA, FTIR, 1H NMR, BSE and SEM, the carbonated HCHSN cement paste was developed into a CaCO3-based binder with a CaCO3 content approaching 60 % (based on the mass of the samples heated to 800℃). NaHCO3 played a key role in the formation of the CaCO3-based binder, which not only accelerated the carbonation rate, but also promoted the carbonation of slag. The eco-efficiency assessment showed that compared to the production of 12.5 kg CO2 /MPa/t from carbonated ordinary Portland cement, the carbonated HCHSN cement paste only produced 3.5 kg CO2 /MPa/t, making it a very green CaCO3-based cementitious materials.

Effect of Coating Treatment on the Properties of Extruded Mg-1.0Zn-0.3Zr-1.0Y-2.0Sn Alloys

The impact of fluoride-based coatings on the microstructure and mechanical integrity of extruded Mg-1.0Zn-0.3Zr-1.0Y-2.0Sn alloys was assessed utilizing optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), immersion testing, electrochemical analysis, and tensile testing. It was observed that the magnesium alloys could be immersed in hydrofluoric acid (HF) for varying durations to achieve coatings of distinct thicknesses, with the coating thickness stabilizing at approximately 8 μm after a 48 h immersion period. The application of the fluoride coating significantly enhanced the corrosion resistance of the alloys, with a corrosion rate (CRH) of 0.13 ± 0.012 mm/y. Upon a 20-day immersion in simulated body fluid (SBF), the degradation rates of the yield strength (YS), tensile strength (UTS), and elongation (EL) for the cast alloys were recorded as 62%, 59%, and 64%, respectively. For the extruded alloys, these rates escalated to 77%, 76%, and 95%. In contrast, the fluorine-coated alloys exhibited significantly lower degradation rates of 28%, 23%, and 39% after a 25-day immersion in SBF. Upon extrusion, the specimens exhibit a diminished corrosion resistance and a more substantial decline in mechanical properties compared to their as-cast state. Upon the application of the coating, there is a discernible reduction in the rate of mechanical property degradation observed in the specimens. This indicates that the fluorinated coating can mitigate the corrosion rate and enhance the corrosion resistance of magnesium alloys.

Molecular dynamics study on the influence of temperature on the mechanical properties of graphene reinforced magnesium-matrix composites

Magnesium and its alloys have been considered the lightest engineering structural metal materials, but their poor plasticity and the degradation of mechanical properties at high temperatures limit their wide application. Therefore, using molecular dynamics simulation, this work examines how the phase structure and mechanical characteristics of pure magnesium under compressive loading are affected by graphene and varying temperatures. The findings demonstrate that adding graphene can significantly increase magnesium's strength. As well as its Young's modulus, and have a great influence on the secondary strain's strengthening. It is noted that the Gr/Mg-based composites have the same plastic deformation behavior as that of pure magnesium, and both of them undergo a transition from a dense hexagonal structure to other structures during plastic deformation, and the introduction of graphene makes the transition more drastic. The number of embedded graphene layers governs the overall deformation of the Gr/Mg composites; however, it does not significantly affect the deformation behavior of the magnesium matrix in the upper and lower regions of the composites. When there is no graphene embedded, the phase transition of magnesium matrix occurs everywhere, while when graphene is embedded, the phase transition of magnesium matrix in the upper and lower parts of graphene extends along the near-interfacial position of graphene without passing through it, which means graphene has the role of changing the nucleation position of dislocations and blocking the movement of dislocations. In addition, the temperature decreases the phase transition step size of Gr/Mg composites, which is similar to that of pure magnesium, while the temperature affects the phase structure of pure magnesium Gr/Mg composites.

Research on mechanical property degradation model of equipment compartment floor under atmospheric corrosion condition

A mechanical property degradation model of material fatigue life varying with stress level and corrosion time was developed in this study. An acidified NaCl solution was used to accelerate the corrosion of stainless-steel samples, and the relationship between laboratory-accelerated corrosion and atmospheric corrosion was established using corrosion thickness loss parameters. Based on the results of a pre-corroded fatigue test, lgN–S–T surface models and a modified version of Miner’s rule for calculating nonlinear mechanical damage accumulation were proposed. Taking a real part of a high-speed train as an example, critical operating mileages considering material fatigue performance degradation under corrosion conditions were calculated, which were consistent with failure mileages of the census results.

Study on Mechanical and Microstructural Evolution of P92 Pipes During Long-Time Operation

To investigate the mechanical properties and microstructure evolution of P92 steel during long-term service, the operated P92 main steam pipes from the first ultra-supercritical units in China were sectioned into samples representing various service durations and stresses (0# (as-received state, 1# (82,000 h, 67.3 MPa), 2# (85,000 h, 78.0 MPa), and 3# (100,000 h, 80.3 MPa)). Thereafter, a comprehensive assessment of their mechanical properties, including tensile strength, impact, hardness, and creep resistance, as well as a detailed microstructure analysis, was carried out. The effect of stress on the aging of material properties during operation is discussed. The results show that the circumferential stress caused by the increase in the internal steam pressure can significantly promote the creep life consumption of P92 steel, resulting in the degradation of mechanical properties and the expedited aging of the microstructure. The Rp0.2 and Rm of the P92 main steam pipe at room temperature and 605 °C decreased with the service time increase, reflecting the influence of stress in operation, which is expected to be used for the residual life evaluation of P92 steel. The relationship between the impact absorption energy (FATT50), Brinell hardness, and the operating time of P92 operating pipes is non-monotonic, indicating that these parameters are not sensitive indicators of material aging due to stress. The evaluation of performance degradation in P92 operating pipes due to stress-induced aging is not reliably discernible through optical metallography alone. To achieve a thorough assessment, the use of transmission electron microscopy (TEM) is essential.

Influences of Zr and V Addition on the Crystal Chemistry of θ-Al13Fe4 and the Grain Refinement of α-Al in an Al-4Fe Alloy Based on Experiment and First-Principle Calculations

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al13Fe4, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with more compact structures, such as α-Al15(Fe,Mn)3Si2. The addition of alloying elements is a crucial strategy for modifying the microstructure during the solidification process of aluminum alloys. This study investigates the effects of adding vanadium (V) and zirconium (Zr) on the morphology and crystal chemistry of θ-Al13Fe4 in an Al-4Fe alloy, employing a combination of experimental observations, first-principle calculations, and thermodynamic analysis. Our findings indicate that zirconium significantly refines both the primary θ-Al13Fe4 particles and the α-Al grains. Additionally, a small amount of vanadium can be incorporated into one of the Wyckoff 4i Al sites in θ-Al13Fe4, rather than occupying any Fe sites, under casting conditions, in addition to the formation of binary Al-V phases.

Piezo1-driven mechanotransduction as a key regulator of cartilage degradation in early osteoarthritis.

Osteoarthritis (OA) is a prevalent degenerative disease characterized by pain and cartilage damage in its later stages, while early OA is marked by the loss of cartilage's mechanical function. Recent studies suggest that Piezo1, a mechanotransducer, may contribute to cartilage degradation under abnormal physical stress. This study investigates the mechanism by which Piezo1 mediates the loss of cartilage's mechanical properties. Using rat chondrocytes cultured in a 3D in vitro model, we found that fluid flow-induced physical stress activates constitutively expressed Piezo1, leading to increased catabolic activity and apoptosis, which, in turn, disrupts the matrix structure. Ex vivo cartilage experiments further demonstrated that the mechanical stress-induced loss of cartilage's physical properties (approximately 10% reduction in relaxation modulus) is mediated by Piezo1 and depends on cell viability. Notably, Piezo1 agonists alone did not alter the mechanical behavior of cartilage tissue. In vivo, using an OA rat model induced by anterior cruciate ligament transection, we observed cartilage integrity degradation and loss of mechanical properties, which were partially mitigated by Piezo1 inhibition. RNA sequencing revealed significant modulation of the PI3K signaling and matrix regulation pathways. Collectively, this study demonstrates that Piezo1-mediated catabolic activity in chondrocytes is a key driver of the loss of cartilage's mechanical function during the relaxation phase.