Compositional Zoning Research Articles

Investigation of the 4D Multi-Material 316L/FeNi36 Obtained by Selective Laser Melting

Multi-material can have functional properties, which are not typical for the materials of which they are composed (for instance, shape-changing effect). This can be used in robotics, micromachines, aerospace, and other fields. In this work, the 316L/FeNi36 multi-material produced by selective laser melting was investigated. The results show that the interfacial zone of the multi-material exhibits mixing regions of the two alloys but no defects. The microstructure is constituted by large grains with epitaxial growth, which propagate in a directional manner from the 316L alloy through the interfacial zone to the FeNi36 region. The multi-material sample displays three different zones of chemical composition: the FeNi36 composition zone; the interfacial zone; and the 316L zone. The size of the interfacial zone is approximately 50 µm. The multi-material sample exhibits the presence of three distinct phases: γ-Fe; γ-Fe64Ni36; and α-Fe. The hardness of the FeNi36 zone is approximately 163 HV, followed by an interfacial zone with a hardness of approximately 200 HV and then, the 316L zone with a hardness of approximately 214 HV. Functional tests demonstrate that the shape-changing effect is directly correlated with the variation in the FeNi36 thermal expansion coefficient with temperature. For achieving the most pronounced shape-changing effect, the temperature range of 25–215 °C is more suitable.

Microstructure and mechanical properties of Ti60–Ti2AlNb functionally graded materials fabricated by laser directed energy deposition

The increasing demands for materials that service under high temperature environments in advanced aero-engines with high thrust-to-weight ratios have led to the exploration of functionally graded materials, which can offer unique advantages for addressing these challenges, such as the ability to achieve multiple properties at different positions of the components. In this study, Ti60–Ti2AlNb functionally graded materials were fabricated via laser directed energy deposition (L-DED) with 20% compositional step and various step widths in the transition zone. The distribution of chemical composition, microstructure, and microhardness in the transition zone of functionally graded materials with different compositional paths along the deposition direction were investigated. Meanwhile, the mechanical properties and fracture mechanisms were also evaluated. Smooth composition transition has been achieved in the joint zone between Ti60 and Ti2AlNb. By decreasing the width of each composition zone in the transition area or removing the Ti60-60% Ti2AlNb zone, the precipitation of the hard and brittle α2 phase can be effectively suppressed, thereby enhancing the tensile strength of the graded material. Through this approach, Ti60–Ti2AlNb functionally graded material with a tensile strength of 1030.9 MPa and elongation of 2.0% was fabricated.

Spatial and temporal mush heterogeneity during eruptions recorded in clinopyroxene from the 2021 paroxysms at Mt. Etna, Italy

Textural and compositional zoning of volcanic minerals archives pre-eruptive magma processes. Crystals erupted simultaneously may be sampled from different regions of the plumbing system and hence record variable histories due to complex magma dynamics. In addition, crystals erupted throughout the course of an eruption may record temporal variations in the plumbing system. To resolve mush variability on both spatial and temporal scales, we investigate clinopyroxene erupted during a series of paroxysmal episodes between February–April 2021 at Mt. Etna, Italy. Using a combination of high-resolution geochemical techniques, we observe that Cr enrichments in clinopyroxene mantle zones, grown upon eruption-triggering mafic rejuvenation, exhibit both temporal and spatial (sample-scale) variability. Temporal variability correlates with changes in glass compositions, attesting to the ability of clinopyroxene to track magma maficity throughout an eruption. Spatial variability, indicated by the scatter of Cr concentrations, is greatest for the first event and lowest for the final paroxysm. In conjunction with core textures, degree of sector enrichment and thermobarometry, our data suggest that the onset of the paroxysms was preceded by the remobilisation of a mid-crustal clinopyroxene mush (534 ± 46 MPa) by hot, mafic magma causing variable resorption of mush-derived crystal cores. Towards the end of the eruption, waning magma supply led to less efficient mush remobolisation and mixing, resulting in homogenous crystal populations. Our results highlight that clinopyroxene Cr contents and sector enrichment can be used to track mafic rejuvenation and magma evolution throughout eruptions, while also reflecting spatial heterogeneities within the plumbing system.

Chemical and isotopic investigation of the I-type Bega Batholith, southeastern Australia: Implications for batholith compositional zoning and crustal evolution in accretionary orogens

Cordilleran granitic batholiths represent significant episodes of crustal growth and differentiation, and commonly display lateral isotopic and chemical variations. Establishing the tectono-magmatic processes responsible for generating this compositional asymmetry is important for understanding crustal evolutionary processes throughout the Phanerozoic. The Bega Batholith, an example of a ‘Cordilleran style’ granite batholith, is the largest I-type Siluro-Devonian granite complex in the Lachlan Fold Belt (LFB) of southeastern Australia and comprises seven granite supersuites that display systematic lateral isotopic and chemical asymmetry. From west to east towards the present-day continental margin, an increase in the content of Na2O, Sr, Al2O3, and P2O5, with concomitant decreases in CaO, Sc, Rb, and V are observed. In the same direction, whole-rock initial 87Sr/86Sr decreases from 0.7098 to 0.7039, εNd values increase from −8.3 to +4.4, and δ18O decreases from 10.2 ‰ to 7.9 ‰. Depleted-mantle model ages also decrease from ca. 1800 Ma in the west to 600 Ma in the east. Here, we address whether these chemical and isotopic variations were generated by interaction between two distinct components (mantle-derived magmas and supracrustal sources) or were alternatively produced by partial melting of infracrustal source rocks formed sequentially by much earlier episodes of crustal underplating. Combined whole-rock Nd-Sr-O isotopic and geochemical analyses indicate that several I-type supersuites exhibit chemical and isotopic correlations consistent with two-component magma mixing. This new evidence challenges the long-held view that I-type granites derive exclusively from the melting of infracrustal sources, and that granite terranes represent wholesale crustal reworking rather than new crustal growth. Our results show that the compositional zoning within the Bega Batholith is multifaceted. Firstly, the presence of two discrete mantle sources endows chemically and isotopically distinct eastern and western segments in the batholith. Secondly, within these compositionally distinct regions the lateral compositional changes across supersuites derives from mixing between mantle-derived and supracrustal sources. Finally, progressive extension within a developing back-arc environment regulates the ratio of crust-mantle contributions and compositional architecture of each I-type supersuite.

Features of the continental volcanic-plutonic belts of the Junggar-Balkhash fold system

Purpose. The study aims to investigate the formation composition and structural-formation zoning of the Late Paleozoic continental volcanic and volcano-sedimentary formations of the Junggar-Balkhash fold system (JBFS). It also seeks to define the geological-geophysical characteristics and metallogenic specialization of the volcanic-plutonic belts (VPB) in the region. Methods. The research utilizes data from detailed mapping and analysis of Late Paleozoic magmatites in JBFS over the past 10-40 years. Structural-formation zoning of the region was performed from an actualistic perspective, along with the formation typification of stratified and intrusive ore formations. The study of metallogenic specialization was conducted considering modern geophysical research methods. Findings. Two main volcanic-plutonic belts have been identified: the Carboniferous marginal-continental Tasty-Kusak-Kotyryasan-Altunemel Belt and the Carboniferous-Permian intracontinental Balkhash-Ili Belt, which together cover about 80% of the JBFS territory. The geological-geophysical characteristics and metallogenic specialization of these belts have been defined. In particular, the findings highlight significant prospects for epithermal gold-silver and copper-porphyry mineralization. Originality. For the first time, a structural-formation zoning of JBFS has been conducted, and the typification of volcanic-Plutonic Belts has been substantiated. Additionally, their metallogenic specialization has been determined, revealing patterns of localization for epithermal gold-silver and copper-porphyry deposits. Practical implications. The study’s results are of great importance for exploration geology, contributing to the improved efficiency of searching for ore deposits in the region, particularly epithermal gold-silver and copper-porphyry targets.

Micromechanical and Tribological Performance of Laser-Cladded Equiatomic FeNiCr Coatings Reinforced with TiC and NbC Particles.

This paper discusses a comparative micromechanical and tribological analysis of laser-cladded equiatomic FeNiCr coatings reinforced with TiC and NbC particles. Two types of coatings, FeNiCr-TiC (3 wt.% TiC) and FeNiCr-NbC (3 wt.% NbC), were deposited onto an AISI 1040 steel substrate by means of short-pulsed laser cladding. The chemical composition, microstructure, and micromechanical and tribological characteristics of the coatings were systematically investigated via optical and scanning electron microscopy, Raman spectroscopy, and mechanical and tribological tests. The average thicknesses and compositional transition zones of the coatings were 600 ± 20 μm and 150 ± 20 μm, respectively. Raman spectroscopy revealed that both coatings are primarily composed of a single FCC γ-phase (γ-FeNiCr). The FeNiCr + 3 wt.% TiC coating exhibited an additional TiC phase dispersed within the γ-FeNiCr matrix. In contrast, the FeNiCr + 3 wt.% NbC coating displayed a more homogeneous distribution of finely dispersed NbC phase throughout the composite, leading to enhanced mechanical behavior. Micromechanical characterization showed that the FeNiCr + 3 wt.% NbC coating possessed higher average microhardness (3.8 GPa) and elastic modulus (180 GPa) compared to the FeNiCr + 3 wt.% TiC coating, which had values of ~3.2 GPa and ~156 GPa, respectively. Both coatings significantly exceeded the AISI 1040 steel substrate in tribological performance. The FeNiCr + 3 wt.% TiC and FeNiCr + 3 wt.% NbC coatings exhibited substantial reductions in both weight loss (37% and 41%, respectively) and wear rate (33% and 42%, respectively) compared to the substrate material. These findings indicate that more finely dispersed NbC particles are better suited for hardening laser-cladded equiatomic FeNiCr-NbC coatings, making them advanced candidates for industrial applications.

Synthesis and Characterization of a Novel Chitosan-Based Nanoparticle-Hydrogel Composite System Promising for Skin Wound Drug Delivery.

As a natural preservative, nisin is widely used in the food industry, while its application in biomedicine is limited due to its susceptibility to interference from external conditions. In this study, a nanoparticle-hydrogel composite system was designed to encapsulate and release nisin. Nisin nanoparticles were identified with a smooth, spherical visual morphology, particle size of 122.72 ± 4.88 nm, polydispersity coefficient of 0.473 ± 0.063, and zeta potential of 23.89 ± 0.37 mV. Based on the sample state and critical properties, three temperature-sensitive hydrogels based on chitosan were ultimately chosen with a rapid gelation time of 112 s, outstanding reticular structure, and optimal swelling ratio of 239.05 ± 7.15%. The composite system exhibited the same antibacterial properties as nisin, demonstrated by the composite system's inhibition zone diameter of 17.06 ± 0.83 mm, compared to 20.20 ± 0.58 mm for nisin, which was attributed to the prolonged release effect of the hydrogel at the appropriate temperature. The composite system also demonstrated good biocompatibility and safety, making it suitable for application as short-term wound dressings in biomedicine due to its low hemolysis rate of less than 2%. In summary, our nanoparticle-based hydrogel composite system offers a novel application form of nisin while ensuring its stability, thereby deepening and broadening the employment of nisin.

Exploring constituent redistribution in irradiated U-19Pu-14Zr fuel via electron probe microanalysis

The phenomena of constituent redistribution, wherein a previously homogeneous metallic fuel forms discrete, radially concentric compositional zones upon irradiation was investigated by examining an irradiated U-19Pu-14Zr fuel (where numbers represent wt. %) with a burnup of 11.5 at.% with electron probe microanalysis (EPMA) and quadruple inductively coupled plasma mass spectroscopy (Q-ICP-MS).EPMA-generated U, Pu, and Zr compositional data obtained from a diameter traverse of the sample was converted to mass and was used to: 1) compare the overall fuel element analysis results between the two methods, 2) determine the number of compositionally distinct zones forming as a result of constituent redistribution; and 3) quantify the post-irradiation loss or gain of U, Pu, and Zr atoms in each distinct compositional zone.Weight percent concentrations of U, Pu, and Zr for the overall cross section compare favorably between the two analytical methods, suggesting that the spatially resolved EPMA analysis complements bulk chemical analysis.Among the four identified compositional zones, post-irradiation quantification of U, Pu, and Zr elemental atom content changes shows that the quantity of U atoms lost from the innermost zone is slightly less than the quantity of U atoms gained by the middle two zones, and the quantity of Zr atoms lost from the high-U third zone is slightly less than is gained by the two innermost zones. Pu is lost from all four zones, although the innermost zone and the high-U third zone lose a significantly higher percentage (> 22 %) of their initial Pu atoms than the other two zones. For all three elements, EPMA cannot distinguish between atoms lost due to transport to a different zone from atoms lost due to nuclear processes; however, the insight gained from using this process can be used to experiment with new modeling techniques to predict constituent redistribution in U-Pu-Zr fuels.

Bayesian frameworks for integrating petrologic and geochronologic data

Constraining the absolute time and duration of geologic processes is one of the great challenges and goals in Earth sciences. Increasingly, the integration of geochronologic constraints with petrologic information is being qualitatively applied to understanding the timescales of metamorphic, igneous, tectonic, and fluid-related processes. Many rocks and geochronometers preserve relative age constraints such as compositional zoning or cross cutting relationships. This prior information can be formalized in a Bayesian statistical framework to generate a probabilistic posterior chronology. As we show here, these “age-sequence” models can enhance precision on geochronologic dates and rates and insight into tectonic models. Bayesian modeling of complex, concentrically, zoned monazite from the northern Appalachian orogen was used to develop a detailed temperature-time history through the Acadian (∼405–395 Ma) and Neoacadian (∼380–350 Ma) orogenies with significantly reduced uncertainties (40–70 %). Modeling of zoned monazite from a southern Trans-Hudson orogen granulite yielded durations of 0.5+9/-0.4 Ma and 20+5/-8 Ma for biotite-dehydration melting and suprasolidus conditions, respectively. The relatively short intervals of heating and peak conditions are consistent with a back-arc tectonic setting. A complementary approach, Bayesian change point detection, provides a framework to constrain the timing of compositional changes that can be linked with metamorphic reactions. Applying this approach in the northern Appalachian orogen demonstrates contrasting durations of low-Y monazite crystallization (∼10 vs ∼30 myr) in regions with different pressure-temperature histories. Compositionally distinct monazite domains can be linked with garnet stability, which provides a key constraint on tectonic models. Bayesian statistical analysis represent a powerful tool that can be widely applied to refine the absolute time and duration of geologic processes. A more objective and reproducible set of interpretations are produced by this more formal, although not necessarily complex, statistical analysis.

Integrated textural and geochemical analysis of igneous zircon by atom probe tomography

Mechanisms relating to growth and/or compositional modification of zircon occur at the atomic scale. For felsic igneous systems, processes responsible for growth patterns in zircon have previously remained elusive as the volume of material needed to analyze these compositional features using traditional in-situ methods is considerably larger than the typical sub-micron scale distribution of trace elements. To illuminate some of these driving forces, we characterize and quantify minor and trace element concentrations in igneous zircon grains by combining methods of cathodoluminescence (CL) imaging, electron microprobe microanalysis (EMPA) elemental maps for Hf, Y, Yb and U or Th, and atom probe tomography (APT). We focus on igneous zircon from the Chon Aike Silicic Large Igneous Province (Patagonia) that provide novel insights into (1) dissolution and re-crystallization during crustal anatexis, (2) crystallization to produce oscillatory zonation patterns that are typical of igneous zircons, and (3) the incorporation of trace element impurities (e.g., P, Be, and Al) at the nanoscale. Significantly, these APT volumes provide nanoscale sampling of boundaries between oscillatory growth zones in an igneous zircon to reveal compositional zoning of Y and, to a lesser extent P, which appear as high-angle, planar features. These concentration boundaries measured on the order of 10 to 12 nm are difficult to reconcile with proposed mechanisms for generating fine-scaled oscillations. Lastly, we fit diffusional profiles to measured Y concentrations to provide an estimate on the maximum timescales of zircon growth prior to eruption, as a function of the temperature at which diffusion occurred. When combined with known pressure-temperature-time paths for the magmatic system considered, these extremely short diffusion profiles that are resolvable by APT provide a powerful method to constrain timescales of crystal growth.

Olivine Time-Capsules Constrain the Pre-Eruptive History of Holocene Basalts, Mount Meager Volcanic Complex, British Columbia, Canada

Abstract The Canadian segment of the Cascade Volcanic Arc (i.e. the Garibaldi Volcanic Belt) comprises more than 100 eruptive centres, spanning the entire Quaternary period (Pleistocene to Holocene in age), and with deposits ranging in composition from alkaline basalt to rhyolite. At least one of the volcanoes is currently active; Mount Meager / Q̓welq̓welústen erupted explosively 2360 years BP and has ongoing fumarolic activity. Long-term forecasting of eruption frequency and style depends on reconstruction of the history and timescales of magmatic processes preceding previous volcanic eruptions. Utilising diffusion chronometry, we investigate the Mount Meager Volcanic Complex focusing on Holocene olivine-phyric basalts (Lillooet Glacier basalts) exposed by the retreat of the Lillooet Glacier. We identify two distinct olivine populations in samples of quenched, glassy basalt lavas that record different magmatic processes and histories. Glomerocrysts of Fo83 olivine phenocrysts, entrained and transported by a hot mafic input, form Population 1. These exhibit resorption and normally zoned outermost rim compositions of Fo76–78; a third of them also show interior reverse compositional zoning. A second population of skeletal microphenocrysts have the same composition as the phenocryst rims (i.e. Fo76–78) and are in equilibrium with the adjacent matrix glass. We estimate the pre-eruptive temperature-fO2 conditions in a shallow reservoir (100 MPa; ~3 km) for a melt with H2O content of 0.5 to 1 wt % as ~1097°C to 1106°C (± 30°C), and NNO + 0.5 (±1.1), respectively. Using these input parameters, we report Fe-Mg diffusion chronometry results for 234 normally zoned profiles from 81 olivine phenocrysts. Diffusion modelling of compositional profiles in oriented crystals indicates pre-eruptive magmatic residence times of 1 to 3 months. These remarkably short residence times in shallow reservoirs prior to eruption suggest very short periods of unrest may precede future eruptions.

Innovate, insulate, integrate: Embracing circular economy in innovative insulations for reduced air conditioning expenses and carbon mitigation in fly ash brick buildings

Global demand for energy in the construction sector has increased drastically. A substantial portion of this energy belongs to fulfilling the heating, ventilation, and air-conditioning requirements of buildings, which are essential for maintaining the well-being of people. The development of zero-energy or environmentally friendly structures is required to attain a sustainable future. Strategic design of the building’s envelopes in green energy buildings can reduce air conditioning expenses. This article focuses on several insulation-integrated fly ash brick wall envelopes that have been designed to reduce CO2 emissions, reduce air conditioning expenses, and figure out payback times in warm-temperate and hot-arid regions. The degree-hour technique for heating and cooling, as well as unsteady heat transfer characteristics, are taken into consideration in this research. This is achieved by incorporating thirteen innovative insulation materials into fly ash bricks in three distinct configurations, (i.e., insulation layer near to the outer end of the fly ash block, on the middle of the fly ash block, and near to the inside end of the fly ash block). Experimental measurements were carried out to determine the thermo-physical characteristics of insulation materials. The analytical findings are confirmed through experimental validation. In hot-arid and composite climatic zones, placing an insulation layer (cloth-40/foam-60) near the outer end of the fly ash block resulted in the highest savings on air-conditioning costs of 0.89 $/m2 and 0.90 $/m2, respectively. They also achieved the highest carbon mitigation values at 17.2 and 16.8 kg/kWh. Insulation-integrated wall envelopes represent the pinnacle of energy efficiency in green building design, seamlessly combining advanced insulation materials with cutting-edge construction techniques to minimise energy consumption and maximise sustainability.

Steel-concrete-steel sandwich composite cable-pylon anchorage of cable-stayed bridges: horizontal bearing capacity

Steel-concrete-steel sandwich composite cable-pylon is preliminarily applied to bridge engineering due to its excellent mechanical properties and high degree of assembly. However, the stress behavior of the steel-concrete-steel sandwich composite cable-pylon anchorage zone under the strong horizontal component force of the cable force is relatively unknown. In this paper, a 1:4 scaled-down steel-concrete-steel sandwich composite cable-pylon model test under horizontal force is designed and carried out to investigate the strain distribution in inner and outer steel plates, and the horizontal displacements in the pylon wall, and the crack development in the concrete pylon wall. Subsequently, a simplified analysis method is proposed for facilitating the calculation of the load distribution ratios of both steel plates and concrete, and the pylon wall stresses are obtained based on the force method. Furthermore, aiming to improve the problem of excessive stress in the anchorage region of the outer steel plate, the effects of various parameters on the mechanical properties of the anchorage region are investigated through parametric analysis, and the investigated parameters include the diameter of the reinforcement bar, area of the bearing plate, concrete strength, the thicknesses of the steel plate and perfobond ribs. The results indicate that increasing the diameter of the reinforcement bar is insignificant in improving the stress distribution and value of the outer steel plate, and appropriately increasing the bearing area, concrete strength, thicknesses of the steel plate and perfobond ribs can reduce the stress peak value of the outer steel plate, among which changing the thickness of the steel plate and bearing area is the most significant effect. The research results can provide experimental data and theoretical support for the design and optimization of steel-concrete-steel sandwich composite cable-pylon anchorage zones.

Using waste to improve the weak: Recycled seashell as an ideal way to regulate the interfacial transition zone in biochar-cement composites

The strategy of partially substituting cement with carbon-negative biochar to fabricate biochar-cement composites can represent a promising approach to reducing the carbon emissions of the construction industry. However, the detrimental impact on strength development from excessive biochar incorporation remains a significant challenge. To address this issue, this study pioneers a strategy to modify wood waste-derived biochar using seashell waste for enhancing its binding with the cement matrix. Employing a mechanochemical process, the shell-modified biochar was synthesized using oyster shell (OS) and wood waste (WW). The compressive strength of cement composites incorporating 5 wt% modified biochar improved by 3.9–17% compared to the referenced biochar. Even with high biochar incorporation (30 wt%), the compressive strength increased by 58.2% upon modifying the biochar at the OS/WW ratio of 1:9 (10SBC). The modified biochar refined the pore structures, accelerated the hydration kinetics, improved the degree of hydration, and fostered the development of the C-S-H gel network with a longer silicate chain and a higher polymerization degree. Furthermore, the strength enhancement of the biochar-cement composites was attributed to the improved micro-mechanical properties at the interfacial transition zone (ITZ), which increased the volume fraction of high-density C-S-H by 64.4–112% and decreased the low-density C-S-H fraction by 41.8–52.6%. Notably, 10SBC demonstrated a superior improvement due to its cohesive bond with the C-S-H gel and the concurrent densification of C-S-H in the ITZ, which was facilitated by the growth of Ca-/Al-rich hydration products. Overall, this study synergistically upcycled wood and seashell waste into value-added cement additives, thereby achieving strength enhancement of the cement composites.

Non-destructive detection of the useful zone in Boron carbide-reinforced metal matrix composites laminated plates

Non-destructive detection of the useful zone in Boron carbide-reinforced metal matrix composites laminated plates

Inhibition of interfacial cracks in 304L-Inconel718 bimetal fabricated via laser powder bed fusion

Multi-material additive manufacturing is crucial for intricate component fabrication, yet challenges, such as interfacial cracks and weak bonding, persist. This work investigated the laser powder bed fusion (L-PBF) of bimetallic components (stainless steel 304L-nickel-based alloy Inconel718) crucial in aerospace and nuclear applications. It is found that the interfacial cracks predominantly occur within the compositional transition zone where the proportion of 304L is between 45wt.% and 75wt.%, characterized by brittle Laves phases along grain boundaries. Experimental and finite element simulations of melt pool reveal that a higher ratio of temperature gradient (G̅) to the grain growth rate (R̅) (G̅/R̅) results in straight grain boundaries with underdeveloped secondary dendrites. This leads to the formation of continuous liquid film and strip-like Laves phase at grain boundaries, causing interfacial cracks during L-PBF. To suppress these cracks, this work proposes manipulating grain boundaries into a tortuous morphology through promoting the growth of secondary dendrites. By controlling the G̅/R̅ ratios below the critical value (<147.9×106K∙s/m2) and combining with a high cooling rate (G̅×R̅) during L-PBF, a well-developed secondary dendritic structure and grain refinement are achieved, significantly enhancing grain boundary tortuosity and forming discretely distributed Laves phases. As a result, interfacial cracks are completely suppressed, enabling the successful manufacturing of crack-free 304L-Inconel718 bimetallic components. The approach of tailoring the distribution of brittle precipitates through manipulating grain boundary morphology proposed in this work provides a novel and practical pathway for inhibiting cracks in multi-material additive manufacturing.

Experimental and FEM study on the feasibility of PBL connectors in the composite cable-pylon anchorage zone of cable-stayed bridge

This study investigates the joint between the steel wall plate and the concrete pylon wall in the cable-pylon anchorage zone of cable-stayed bridges, utilizing perfobond rib (PBL) connectors. Finite element analysis (FEM) was conducted on the steel wall plate-concrete joint under various conditions, including cable force, concrete shrinkage, overall warming, and overall cooling, with PBL connectors modeled as spring elements. The results indicate that vertical shear force in the PBL connectors peaks in the steel bracket web plates, with cable force and concrete shrinkage having the most significant impact on stress. Scaled-down local model tests and corresponding solid element FEM analysis were performed to evaluate the load performance of these joints. During tests, deformation between the steel plate and concrete wall remained minimal, and no cracks appeared under loads up to 1.7 times the design load. The ultimate load capacity was 2.9 times the design load, with failure occurring through pullout damage. FEM analysis showed good agreement with test results, and overall stress levels remained low, meeting design requirements. Material yielding only occurred in joint areas under large loads, confirming the feasibility of PBL connectors in composite cable-pylon anchorage zones.

Residual stress evaluation in innovative layer-level continuous functionally graded materials produced by Powder Bed Fusion-Laser Beam

The main objective of this study is to evaluate residual stresses in AISI 316L and 18Ni Maraging 300 functionally graded materials with continuous variation of composition within a single layer using the contour method. The manufacture of this kind of layer-level continuous functionally graded materials by employing a Powder Bed Fusion-Laser Beam system utilizing a blade/roller-based powder spreading technique has only been recently devised and a proper residual stress analysis is still required. In fact, as the mechanical properties of additively manufactured samples are significantly influenced by the direction of construction, the same holds true for the direction along which the compositional variation is made. Furthermore, in this study, the impact of solution annealing and aging heat treatment, which are necessary for enhancing the mechanical properties of martensitic steel, on residual stresses was explored. Additionally, the effect of adopting material-differentiated process parameters was investigated. The results indicated that each specimen displayed areas of tensile stress concentration on the upper and lower surfaces, balanced by compression in the center. The application of heat treatment led to a decrease in the maximum tensile stress of 8% and provided a uniform and significant stress reduction within the maraging steel. Finally, the implementation of material-specific process parameters for the three composition zones in conjunction with the heat treatment resulted in a reduction in the maximum residual stress of 35% and also a significantly lower residual stress field throughout the specimen.

Compositional zoning and evolution of symplectite coronas in jadeitite

Abstract Multistage fluid activities play an important role in the interaction between jadeitite and symplectite coronas; therefore, we studied the compositional zoning and evolution of representative Myanmar jadeitite. Under the influence of multistage Ca-, Na-, and Si-rich fluid activity, some minerals in Myanmar jadeitite formed symplectite coronas with concentric rings and multilayer metasomatic reaction rim structures. Additionally, the concentrations of Cr and Fe decrease from the core to the peripheral jadeite minerals, whereas the concentration of Si markedly increases. There is almost no Si or Ca in the chromite core, and the concentrations of Si and Ca increase sharply in rims composed of uvarovite. Due to Cr diffusion, the edge of the jadeite adjacent to kosmochlor is Cr-rich and Al-poor. The different element concentrations indicate that the uvarovite formed from the presence of a chromite and jadeite interaction, Si in the kosmochlor after metasomatism or an external Ca-rich fluid. One possible explanation for the formation of kosmochlor is the interaction between chromite and a Na- and Si-rich fluid. Also, Ca-rich fluid could have first interacted with chromite and formed uvarovite; subsequently, a Na-rich fluid could have entered and become saturated with kosmochlor, leading to the formation of kosmochlor surrounding the uvarovite.

Reaction Rims on Ilmenite and Chromite: Implications for Volatile Behavior and Crystallization Conditions of Kimberlite Magma

Abstract Significant uncertainty surrounds the crystallization conditions and the composition of kimberlite melts, including the role of volatiles (H2O and CO2) due to their hybrid nature, intense alteration, and volatile loss during emplacement. In this study, we address these uncertainties by investigating the interaction between oxides (ilmenite and chromite) and kimberlite magma. During kimberlite ascent, mantle minerals react with the magma and develop dissolution textures, compositional zoning, and rims of secondary mineral phases in response to crystallization conditions and the composition of kimberlite magma. We examined oxides from several lithologies within the BK1 and AK15 kimberlites of the Orapa cluster in Botswana, where diamonds demonstrate distinct dissolution styles in each lithological unit owing to differences in magma saturation with volatiles. Here we discovered a strong correlation of the reaction products on ilmenite and chromite with the dissolution style of diamonds in the same kimberlite unit. Diamonds with glossy, low-relief surface features indicative of fluid-rich magma occur in the kimberlite units where ilmenite and chromite develop reaction rims of Ti-bearing phases. Diamonds with corrosion sculptures implying a volatile-undersaturated magma occur in kimberlite units with heavily resorbed chromite and ilmenite completely replaced by a MUM (magnesio-ulvöspinel-magnetite)–perovskite symplectite. Furthermore, the composition of ilmenite reaction rims depends on kimberlite lithology, where MUM co-exists with perovskite or its break-down product anatase in the two coherent kimberlite units, or with perovskite and titanite in the massive volcaniclastic unit. We examine how decompression, cooling, degassing, or assimilation of crustal rocks by kimberlite magma could have shifted conditions from perovskite to titanite stability in the volcaniclastic kimberlite unit. We propose perovskite replacement by anatase-calcite pseudomorphs in the top coherent unit, from which diamonds exhibit an overprint of fluid resorption with a melt resorption. Composition of ilmenite reaction rims provides estimates of kimberlite crystallization temperatures of 730–1275 °C and oxygen fugacities of +0.5 to −3.5 relative to the nickel-nickel oxide buffer, which are validated through controlled experiments. Our study shows that preservation of ilmenite, the type of Ti-phase in its reaction rim, the relative rate of chromite dissolution, and compositional re-equilibration with kimberlite can help model the eruption process as well as the style and rate of diamond dissolution.