Changes In Grain Size Research Articles

Influence of hydrogen addition to sputtering ambient on the properties of AZO films deposited by sputtering

Abstract The influence of addition of H2 to sputtering ambient on the microstructural and electrical properties of AZO films deposited by r.f. magnetron sputtering at low temperature (100 °C) and high temperature (400 °C) have been investigated in comparison with each other. The grain size decreased with increase of H2 flow rate for both films deposited at 100 °C and 400 °C, but the order of decrease were different; the change of grain size for films deposited at 400 °C was more considerable compared with that at 100 °C, indicating that the addition of H2 into Ar leads to deterioration of crystalline, particularly for the films deposited at high temperature. For the AZO films prepared at comparatively low temperature around 100 °C, small addition of H2 to sputtering ambient was in favour of enhance of electrical properties of films, but for those at high temperature around 400 °C, addition of H2 was unfavourable at all. The origin of variations of microstructural and electrical properties by adding of H2 to sputtering ambient was discussed.

Pulse laser deposition prepared tin(IV) oxide thin films: effects of gamma radiation doses on their structural and optical characteristics

This work studied the effects of gamma radiation on the structural and optical properties of SnO2 thin films in a dose-dependent manner. The microstructural change was confirmed by peak shifting, peak broadening, and changes in grain size with an increase in radiation dose, as observed from X-ray diffraction analysis. Changes in the intensity of photoluminescence spectra and optical properties are due to radiation-induced defect states. The obtained results indicate that gamma irradiation can be used to tailor the characteristics of SnO2 for various applications. In contrast to previous works, this study quantitatively connects radiation dose to structural and optical transformations, thereby addressing the fundamental mechanisms of defect formation.

Gas invasion in stratified porous medium

A stratified porous medium appears to be the simplest type of heterogeneity found in natural and industrial structures. In this paper, we study the invasion of air in a stratified porous medium represented by a highly compacted granular material, where changes in grain size and shape occur across the boundary between the upper and lower layers. Laboratory experiments in a vertical Hele–Shaw cell show that smaller or irregularly shaped grains located in the upper layer prevent air from penetrating the boundary, resulting in the formation of an air layer. Invasion of air is controlled by the force balance among viscous forces, buoyancy, and capillary forces at the air–liquid interface. Therefore, as either the capillary number or the Bond number increases, the thickness of the air layer decreases because of the increased importance of the viscous forces or buoyancy. In contrast, the air layer becomes thicker with the smaller capillary number or the Bond number owing to the increased importance of the capillary forces. Direct numerical simulations are in good agreement with the experimental observation, confirming that the ability of air to penetrate the layer boundary depends on the viscosity of the liquid, the speed of air injection, and the shape and size of the grain. More importantly, on the basis of the simulation, we capture the critical values of the capillary number and the Bond number, below which air is trapped below the layer boundary instead of breaking into the upper layer.

Microstructural evolution and mechanical properties of Fe-12Mn-xAl-1.2C after aging treatment

Abstract This study investigates the influence of varying Aluminium contents on the microstructure and mechanical properties of high Manganese steel. Microstructural characterization was performed using optical microscopy (OM) and scanning electron microscopy (SEM). Mechanical property assessments included hardness testing, room temperature impact testing, and tensile testing. The results indicated that adding Aluminium content refines the austenite grains in high Manganese steel, causing a shift from coarse austenite to a more complex multiphase structure. The gradual increase of ferrite as well as other second-phase particles with increasing Aluminium content also has an effect on the hardness of high Manganese steel. The hardness of high Manganese steel is as high as 501.4 HBW when the Aluminium content is 11%. However, the impact and tensile properties initially increase and then decrease, which is attributed to changes in grain size and fracture mechanisms. The maximum impact toughness of high Manganese steel is 17 J at 4% Aluminium content.

Elucidation of the Nano-Mechanical Property Evolution of 3D-Printed Zirconia

Understanding the mechanical properties of three-dimensional (3D)-printed ceramics while keeping the parts intact is crucial for advancing their application in high-performance and biocompatible fields, such as biomedical and aerospace engineering. This study uses non-destructive nanoindentation techniques to investigate the mechanical performance of 3D-printed zirconia across pre-conditioned and sintered states. Vat photopolymerization-based additive manufacturing (AM) was employed to fabricate zirconia samples. The structural and mechanical properties of the printed zirconia samples were explored, focusing on hardness and elastic modulus variations influenced by printing orientation and post-processing conditions. Nanoindentation data, analyzed using the Oliver and Pharr method, provided insights into the elastic and plastic responses of the material, showing the highest hardness and elastic modulus in the 0° print orientation. The microstructural analysis, conducted via scanning electron microscopy (SEM), illustrated notable changes in grain size and porosity, emphasizing the influencing of the printing orientation and thermal treatment on material properties. This research uniquely investigates zirconia’s mechanical evolution at the nanoscale across different processing stages—pre-conditioned and sintered—using nanoindentation. Unlike prior studies, which have focused on bulk mechanical properties post-sintering, this work elucidates how nano-mechanical behavior develops throughout additive manufacturing, bridging critical knowledge gaps in material performance optimization.

Effects of Long‐Term Thermal Aging on the Microstructure and Mechanical Behaviors of the Safe End in CPR1000

This study systematically investigates the effects of thermal aging on the microstructural evolution and mechanical properties of forged Z2CND18.12N2 austenitic stainless steel (ASS) using small punch testing (SPT) and tensile testing. Prolonged thermal exposure at 400 °C for 10 000 h results in no significant changes in grain size or precipitated phase content, while α′‐phase formation is identified within individual shear bands in both aged and nonaged specimens. Fractographic analysis reveals a mixed‐mode failure mechanism involving cleavage fracture initiation at ferrite‐austenite interfaces, followed by microvoid coalescence in stress‐concentrated austenite regions. Contrastingly, mechanical characterization demonstrates that thermal aging enhances strength parameters (yield strength: 338.45–372.32 MPa; ultimate tensile strength: 540.65–588.33 MPa) but severely compromises ductility (elongation: 75.8–42.5%), with ferrite‐phase hardening evidenced by nanoindentation hardness increasing from 5.97 to 8.89 GPa. SPT results further corroborate this degradation trend through reduced total absorbed energy (2.24–2.12 J). The inverse strength‐ductility relationship is attributed to thermally induced ferrite hardening, providing critical insights into ASS degradation mechanisms and essential guidance for ensuring structural integrity in high‐temperature applications.

Microstructural evolution of Duplex stainless steel 2205 during single-point incremental sheet forming

The research investigates different phases and grain sizes in Duplex stainless steel 2205 through single-point incremental sheet forming processes using Electron Backscatter Diffraction methodology. Research probes the changes in grain size together with counts of high-angle boundaries and low-angle boundaries and relative proportions of face-centered cubic and body-centered cubic components throughout the sample. The study evaluates base metal structural properties against three tested Sample 1 (maximum formability), Sample 2 (moderate formability), and Sample 3 (minimum formability). SEM analysis reveals that the microstructure of Duplex stainless steel 2205 undergoes substantial change due to the application of Spirit forming. The magnitude of plastic deformation applied during single-point incremental forming controls how phases transform while it affects both fault formation and grain refinement patterns. The most formable sample (Sample 1) experiences major microstructural modifications which result in improved mechanical properties. The microstructural alterations in sample 2 create intermediate formability possibilities because it possesses moderate modifications compared to sample 3 which maintains its original structure thus resulting in reduced formability. The microstructural changes during SPIF appear in X-ray diffraction patterns. Microstructural changes triggered by plastic deformation determine phase transition behavior and both microstrain formation and grain refinement results. The mechanical properties improved substantially because Sample 1 showed marked refinement in grain size alongside increased microstrain along with substantial phase transformation into martensite. The microstructural changes in Sample 2 remain moderate while Sample 3 maintains most of its original structure with minimal observed modifications. The findings are supported by transmission electron microscopy which demonstrates the link between plastic deformation along with phase changes and dislocation density as well as grain refinement processes. The microstructure of Sample 1 exhibits major changes that include high densities of dislocations while showing extensive grain refinement and transforming its structural makeup to martensite. The microstructure of Sample 3 remains largely intact while Sample 2 shows average modifications because this sample displays lower formability.

Challenges in correlating the Hell Creek–Ludlow Formation contact: a lithostratigraphic study in northwestern South Dakota, U.S.A.

The Cretaceous–Paleogene (K–Pg) boundary marks a pivotal moment in Earth's history; understanding this transition at a regional scale provides critical insights into sedimentary processes and lithological changes during this period. This study focuses on the lithological transitions at the Hell Creek–Ludlow contact in northwestern South Dakota to establish a regional lithostratigraphic framework and improve understanding of depositional changes during the K–Pg transition. Field investigations concentrated on stratigraphic measurements and sedimentological analyses. Results reveal consistent lithological transitions, with the Hell Creek Formation being dominated by clay-rich paleosols and floodplain deposits transitioning into the sandier, fluvial-dominated Ludlow Formation. The formational contact is interpreted as facies transition across all sites and marked by abrupt changes in grain size and sediment color. While lignite beds, including the “Z-coal”, serve as markers in some locations, their absence or variability underscores the limitations of relying solely on lithological criteria to define the K–Pg boundary. This study highlights regional variability in the Hell Creek–Ludlow transition and establishes a lithostratigraphic framework for northwestern South Dakota. The findings emphasize the need for complementary methods, such as palynostratigraphy, geochemistry, and magnetostratigraphy, to refine the geochronologic placement of the K–Pg boundary.

Получение нанокомпозиционного материала с матрицей на основе алюминиевого сплава Al-7Si методом механического замешивания в стальную литейную форму с переменной толщиной стенок и исследование его характеристик

Introduction. The Al-7Si is considered one of the key aluminum alloys due to its favorable combinations of casting and mechanical properties. Metal matrix composites (MMCs) reinforced with ceramic particles are widely used in high-tech industries such as military, automotive, aerospace, and electrical engineering. The purposes of this study are threefold: (1) to investigate the feasibility of producing composite materials based on the Al-7Si alloy reinforced with varying amounts of TiO2 nanoparticles using a stir casting technique; (2) to investigate the effect of mold wall thickness on the microstructure and mechanical properties of the Al-7Si alloy during solidification; and (3) to analyze the influence of the reinforcing component content on the mechanical properties and wear resistance of the resulting composite materials. Methodology. Metal matrix composite materials based on the Al-7Si alloy, containing 0, 2, 4, and 6 wt. % TiO2 nanoparticles, were fabricated using a stir casting technique. Cylindrical specimens with a diameter of 15 mm and a length of 18 mm were prepared for metallographic and mechanical testing. Results and discussion. It is found that the solidification rate increases with increasing mold wall thickness. This leads to an increase in the cooling rate and, consequently, to the formation of a finer-grained structure. The microstructure of the casting demonstrates a change in grain size from fine to coarse when transitioning from the outer surface (adjacent to the inner mold wall) to the inner part of the casting. As a result, the microhardness near the inner mold wall is higher. Density measurements indicate that composites with a higher amount of reinforcing particles exhibit greater porosity. Furthermore, the results of hardness and wear tests reveal that an increase in the TiO2 particle content leads to increased hardness and a significant reduction in the wear rate of the composite materials.

Analysis of macroscopic cracks in triple cation perovskite films fabricated by the anisole antisolvent method.

The most efficient perovskite solar cells (PSCs) are currently developed using antisolvent-based fabrication technology. Despite extensive analysis of various aspects of the antisolvent method-such as the type of antisolvent, dropping time, and precursor compatibility-some antisolvents still produce uneven film surface morphology on centimeter-scale substrates. The decoupling of the relationship between local structural characteristics, such as grain boundaries and defects, and the optoelectronic performance of PSCs is currently one of the most highly regarded research issues in the field. In this study, we utilized high-resolution white light interferometry to characterize the morphological distributions of perovskite films from the center to edge, using anisole as an example of the antisolvent. We observed that macro cracks at the center of the film typically exhibit dense ridge morphology, while cracks toward the edges display a concave morphology. We analyze the stress mechanism by using EDS mapping and AFM in detail, attributing this phenomenon to the competitive attachment of 2D islands and boundaries for adatoms, which are influenced by changes in grain size. The devices at different locations were fabricated and their performance analyzed. Our findings indicate that these protruding cracks do not significantly affect the current and voltage of the photovoltaic device; however, concave cracks lead to a decrease in the device fill factor. We attribute this decrease to enhanced carrier recombination at the interface due to this morphology. This study provides valuable insights into the formation of perovskite film morphology under antisolvent treatment and the relationship between film local morphology and PSCs performance.

Effect of heat treatment parameters on microstructure and properties of GH4169 alloy hot-rolled sheets

Abstract The effects of different heat treatment schemes on grain size, microstructure evolution and properties of GH4169 alloy were studied in this paper. The changes of matrix microstructure, grain size, recrystallization ratio and orientation difference were observed by means of light microscope and EBSD. The effects of three heat treatment schemes on mechanical properties of the alloy were compared, which provided a theoretical reference for the heat treatment conditions of hot-rolled plates. The results show that different heat treatment conditions have significant effects on the microstructure and material properties. After heat treatment of scheme A (910 °C/ 30min, 90min), the matrix structure of GH4169 alloy hot-rolled sheet has no obvious change, and there are a lot of strips; After heat treatment in scheme B (980 °C/30min, 90min), the band structure gradually disappeared, and the grain structure became uniform; After heat treatment in Scheme C (1050 °C/30min, 90min), the matrix grain structure is more uniform and annealing twins appear. The strength of the material also decreases with the increase of heat treatment temperature, and the plasticity increases with the increase of heat treatment temperature.

A possible trail of dust from a young, highly extincted brown dwarf in the outskirts of the Trapezium Cluster

ABSTRACT We present the JWST discovery of a highly extincted ($A_V\sim 52$) candidate brown dwarf (${\sim} 0.018$ M$_\odot$) in the outskirts of the Trapezium Cluster that appears to be coincident with the end of a ${\sim} 1700$ au long, remarkably uniformly wide, dark trail that broadens only slightly at the end opposite the point source. We examine whether a dusty trail associated with a highly extincted brown dwarf could plausibly be detected with JWST and explore possible origins. We show that a dusty trail associated with the brown dwarf could be observable if dust within it is larger than that in the ambient molecular cloud. For example, if the ambient cloud has a standard ${\sim} 0.25$ $\mu$m maximum grain size and the trail contains micron-sized grains, then the trail will have a scattering opacity over an order of magnitude larger compared to the surroundings in NIRCam short-wavelength filters. We use a simple model to show that a change in maximum grain size can reproduce the high $A_V$ and the multifilter NIRCam contrast seen between the trail and its surroundings. We propose and explore two possible mechanisms that could be responsible for the trail: (i) a weak far ultraviolet radiation-driven wind from the circum-brown dwarf disc due to the O stars in the region and (ii) a Bondi–Hoyle–Lyttleton accretion wake. The former would be the most distant known case of the Trapezium stars’ radiation driving winds from a disc, and the latter would be the first known example of ‘late’ infall from the interstellar medium on to a low-mass object in a high-mass star-forming region.

Effect of lead and zinc composition on the optical and structural characteristics of PbZnS thin films fabricated by spray pyrolysis

In this study, PbZnS thin films with varying concentrations of lead (Pb) and zinc (Zn) were successfully produced using the spray pyrolysis method. The structural, optical and surface properties of the films were systematically investigated as a function of the Pb/Zn ratio. Xray diffraction (XRD) analysis confirmed the polycrystalline nature of the films, showing a cubic zinc blende structure with improved crystallinity as Pb content increased. Initially, with the increase in Pb concentration, larger crystallite sizes and decreased microstress were observed, but with the increase of Pb addition, the formation of secondary phases and the emergence of lattice distortions caused a decrease in grain size and an increase in microstress. Optical measurements showed a tunable bandgap in the range of 3.25 eV to 1.30 eV as Pb content increased. The narrowing of the bandgap is attributed to the lower energy gap of PbS compared to ZnS, which allows for enhanced absorption of longerwavelength light, especially in the visible and near-infrared regions. These findings highlight the potential of PbZnS thin films for optoelectronic applications, where the ability to tune the bandgap and enhance absorption through compositional adjustments is crucial for optimizing device performance. The surface morphology of the PbZnS thin films was analyzed using scanning electron microscopy (SEM). The SEM images showed notable changes in grain size and surface roughness as Pb content increased, with larger grains and a more distinct surface structure observed in films with higher Pb concentrations. This work demonstrates the versatility of spray pyrolysis in fabricating thin films with controllable properties, offering valuable insights for future applications in energy conversion technologies, including solar cells and photodetectors.

Influence of rapid thermal treatment on the mechanical properties of submicrostructures based on nickel and chrome films

The results of a study of the phase composition, surface morphology, grain size and mechanical properties of submicrostructures based on chromium and nickel before and after rapid thermal treatment (RTT) at temperatures from 200 to 550 °C are presented. Surface morphology and grain size were determined using atomic force microscopy. Mechanical properties were determined by nanoindentation. Rapid thermal treatment of nickel and chromium films significantly affects the change in phase composition, surface morphology, grain size and properties. The formation of silicides (according to the diffusion mechanism) and new phases occurs in the films: the CrSi2 phase is formed at temperatures of 350 °C and above, the Ni2Si phase at 300 °C, and the NiSi phase at 350 °C and above. When the phase composition changes, the grain size increases. In the RTT ranges from 200 to 300 °C and from 450 to 550 °C for chromium-based submicrostructures, the correlation between microhardness and grain size is carried out according to the Hall–Petch law – microhardness increases with decreasing grain size. For nickel-based submicrostructures, the Hall–Petch law is satisfied in the temperature range from 200 to 300 °C and from 500 to 550 °C. In the temperature range of 300–450 °C for chromium-based submicrostructures and 300–500 °C for nickel-based submicrostructures, microhardness decreases with decreasing grain size and vice versa, i.e. a “negative Hall– Petch effect” occurs. This effect is associated with the phase transitions Cr → CrSi2 and Ni → Ni2Si → NiSi, restructuring of submicrostructures due to the diffusion mechanism, morphological rearrangement of vacancy defects and annealing of point defects inside grains, as well as the corresponding reconstruction of grain boundaries. The considered submicrostructures based on chromium and nickel can be used in microelectronics for Schottky diodes, ohmic contacts and gates.

Predictive modeling of pulse-electrodeposited Cu–Zn alloy and dealloying for porous electrode fabrication†

Porous metals (PMs) have attracted significant attention in recent years due to their unique structural and functional properties, holding potential for a wide range of applications in catalysis, sensing, energy storage, and filtration. Among these, porous copper (PC), which is produced by dealloying copper–zinc (Cu–Zn) alloys has evolved as a particularly valuable material. In this study, a Cu–Zn alloy is electrochemically deposited onto a Cu wire in a sulphate-based electrolyte containing tri-sodium citrate as a complexing agent. To produce PC, the alloy has been subjected to chemical dealloying to dissolve the less noble element. We have implemented machine learning algorithms such as adaptive neuro-fuzzy inference systems (ANFIS), artificial neural networks (ANN), and response surface methodology (RSM) to model the interaction of process parameters and responses. Statistical modeling has been carried out to investigate the influence of operating parameters, including precursor reagent quantities (0.002–0.2 M), electrodeposition time (15–45 min), and dealloying time (16–24 h), on Zn content, dealloyed weight, and change in grain size. The test results confirm that both models fit the experimental data well, with the ANN model achieving high accuracy (R2 = 0.98, 0.96, and 0.96 for Zn content, dealloyed weight, and grain size change, respectively); however, the ANFIS model demonstrates superior performance with the highest R2 value (0.99) and the lowest MAPE (0.003, 0.002, and 0.001 for the respective responses). The RSM-BBD model is best suited for analyzing parameter interactions on responses, as it systematically evaluates the combined effects of multiple variables. By using potentiodynamic polarization curves to compare the corrosion resistance of Cu–Zn electrodes to bare Cu and PC electrodes, it was found that Cu–Zn electrodes have better corrosion resistance. Additionally, dealloying has resulted in a transition from a hydrophobic (110 ± 1°) to a hydrophilic (59 ± 0.5°) surface.

Morphosedimentary Response of Rivers Crossing Multiple Fault‐Controlled Subsiding Areas: Field Evidence and Laboratory Experiments

ABSTRACTDownstream changes of fluvial styles and related grain size triggered by localised tectonically‐induced changes in riverbed gradient are still poorly understood, especially in terms of their impact on the accumulation of alluvial successions. In this study, we analyse the morpho‐sedimentary response of rivers crossing multiple fault‐controlled subsiding areas, by using field data from the age‐constrained, fluvial deposits of the Pleistocene Dandiero Basin (Eritrea) to create scaled, controlled laboratory experiments performed at the Eurotank Stratigraphic Analogue Modelling Facility (Utrecht University, NL). With this experimental series, we quantified the impacts of degradational/aggradational fluvial dynamics showing that stream bed degradation occurs upstream of subsiding depocenters following the localised increase in river slope. Following a tectonic‐induced decrease in river slope, aggradation occurs downstream of the fault zones, and marked in‐channel aggradation promotes the branching of major river trunks into minor channels and the development of unchannelised tabular bodies. Experiments also show that highly subsiding areas promote the accumulation of fine‐grained deposits, but their accumulation zones shift downstream following localised bed aggradation. We show that where multiple subsiding areas occur along a river, localised depocenters separated by degradational areas occur, causing general starvation in the downstream subsiding reaches, where lacustrine deposition became common. These findings suggest that the role of active faults could have been significantly overlooked when studying how changes in allogenic forcings impact alluvial strata. The results obtained in this study offer a solid basis for creating a predictive model for facies distribution in river dynamics, providing insights into detecting neotectonic signatures in active rivers and identifying tectonic imprints on ancient fluvial successions.

Evolution of Crushing Surface of Ta-d Pumice in Triaxial Compression Tests

Crushable porous granular materials like volcanic pumice, distributed worldwide, cause various engineering problems, including slope hazards. These materials are often classified as problematic soils due to their complex mechanical properties, which arise from high compressibility and changes in grain size due to particle crushing. Consequently, their behaviour is typically discussed on a case-by-case basis, and a systematic understanding has yet to be established. This study aims to elucidate the relationship between the mechanical properties and particle crushing of porous granular materials through a series of tests on natural volcanic pumice. The intra-particle void ratio was measured alongside isotropic consolidation and CD/CU triaxial compression tests, with particle crushing assessed before and after the experiments. The results indicate that the intra-particle void ratio correlates with particle size, with larger particles generally having higher porosity. Additionally, the mechanical behaviour of these materials shows high compressibility, and their stress paths resemble those obtained from undrained triaxial tests on loose sand, ultimately reaching the critical state. The relationship between the amount of particle crushing and mean effective stress at the end of the tests can be represented by a single curve for isotropic consolidation tests, CD, and CU triaxial tests, respectively. The amount of crushing generally increases with the progression of axial strain during the compression process, and in CU tests, when reaching the critical state, no further increase in crushing occurs with increased axial strain. Furthermore, critical state and isotropic consolidation state of each material can be represented on its own unique surface, each referred to as a "Crushing Surface," defined by the crushing volume, void ratio, and mean effective stress for that specific soil.

Design and Optimization of W-Mo-V High-Speed Steel Roll Material and Its Heat-Treatment-Process Parameters Based on Numerical Simulation

W-Mo-V high-speed steel (HSS) is a high-alloy high-carbon steel with a high content of carbon, tungsten, chromium, molybdenum, and vanadium components. This type of high-speed steel has excellent red hardness, wear resistance, and corrosion resistance. In this study, the alloying element ratios were adjusted based on commercial HSS powders. The resulting chemical composition (wt.%) is C 1.9%, W 5.5%, Mo 5.0%, V 5.5%, Cr 4.5%, Si 0.7%, Mn 0.55%, Nb 0.5%, B 0.2%, N 0.06%, and the rest is Fe. This design is distinguished by the inclusion of a high content of molybdenum, vanadium, and trace boron in high-speed steel. When compared to traditional tungsten-based high-speed steel rolls, the addition of these three types of elements effectively improves the wear resistance and red hardness of high-speed steel, thereby increasing the service life of high-speed steel mill-roll covers. JMatPro (version 7.0) simulation software was used to create the composition of W-Mo-V HSS. The phase composition diagrams at various temperatures were examined, as well as the contents of distinct phases within the organization at various temperatures. The influence of austenite content on the martensitic transformation temperature at different temperatures was estimated. The heat treatment parameters for W-Mo-V HSS were optimized. By studying the phase equilibrium of W-Mo-V high-speed steel at different temperatures and drawing CCT diagrams, the starting temperature for the transformation of pearlite to austenite (Ac1 = 796.91 °C) and the ending temperature for the complete dissolution of secondary carbides into austenite (Accm = 819.49 °C) during heating was determined. The changes in carbide content and grain size of W-Mo-V high-speed steel at different tempering temperatures were calculated using JMatPro software. Combined with analysis of Ac1 and Accm temperature points, it was found that the optimal annealing temperatures were 817–827 °C, quenching temperatures were 1150–1160 °C, and tempering temperatures were 550–610 °C. The scanning electron microscopy (SEM) examination of the samples obtained with the aforementioned heat treatment parameters revealed that the martensitic substrate and vanadium carbide grains were finely and evenly scattered, consistent with the simulation results. This suggests that the simulation is a useful reference for guiding actual production.

Finite Element and Experimental Analysis of Microstructural and Hardness Variations in Plasma Arc Welding of AISI 304 Stainless Steel

AISI 304 is widely regarded as the most common austenitic stainless steel and is utilized in various household and industrial applications, including food handling equipment, machinery components, and heat exchangers. Its popularity stems from its excellent mechanical properties, corrosion resistance, and ease of manufacturing. Given its diverse applications, it is crucial to study the microstructural evolution and mechanical properties of the welded zone, especially considering the potential for weld decay during fusion welding. In this context, two critical thermal-dependent factors for ensuring high-quality welds are grain growth and hardness variation in the heat-affected zone (HAZ) during the welding process. This paper presents an innovative finite element (FE) model developed to analyze the grain growth and hardness reduction that occur in the HAZ during plasma arc welding (PAW) of AISI 304 steel for solid expansion tube (SET) technology. Using the commercial FE software SFTC DEFORM-3D™, a user subroutine was created that integrates a physics-based model with the Hall–Petch (H-P) equation to predict changes in grain size and hardness. This study introduces a comprehensive numerical model, encompassing the user subroutine, heat source fitting, and geometry, which accurately predicts the thermal phenomena associated with grain coarsening and hardness reduction in the HAZ during the welding of austenitic stainless steel. The results from the numerical model, including the customized user routines, show good agreement with experimental data, leading to a maximum error prediction of 10 HV in hardness, 30 µm in grain size, and 10% in HAZ extension.

Effects of casting mold temperature on tensile properties of Pb–Sn–Ca alloys for negative grids of lead-acid batteries

Abstract In this work grain structure and tensile properties of as-cast and aged Pb–Sn–Ca alloys (with tin-to-calcium content ratio ranged from 2.6 to 3.3) used to produce negative grids for lead-acid batteries were determined. The microstructure of the alloys was studied by scanning microscopic and quantitative metallographic analyses. Mechanical properties in terms of ultimate tensile strength, yield strength, Young’s modulus, and elongation were estimated at room temperature using TIRAtest 2,300 universal testing machine. Based on the tensile test results, average stress-strain curves for aged Pb–Sn–Ca alloys were plotted for the subsequent age-strengthening analysis. The studies showed that the significant casting process parameter was the mold temperature that markedly affected grain structure of the alloys. With mold temperature rising from 60 °C to 170 °C, an average grain size was increased by as much as two-fold. As a result, elongation increased by 55 %, but ultimate tensile strength decreased by 25 %. Ageing time affected grain structure of the alloys to a much lesser degree since the change in average grain size was negligible. Strengthening occurred rapidly within first 3 days of ageing during storage at ambient temperature. With ageing time prolonged up to 35 days no appreciable differences in the tensile properties’ values were found.