Microstructural Studies Research Articles

In-situ study of microstructure and mechanical properties of GH3536 alloy manufactured by selective laser melting at 750 °C

Nickel-based GH3536 alloy exhibits high strength but low ductility when produced by selective laser melting (SLM), which hinders its widespread application in aerospace. This paper employed a ‘two-step’ method of heat treatment to optimize the microstructure of the SLM GH3536 alloy and investigated the mechanical properties. Tensile tests were conducted on SLM GH3536 alloy before and after heat treatment at 750 °C, using an in-situ high-temperature tensile stage. The relationship between the microstructural evolution and deformation behavior of the alloys was investigated by combining the in-situ tensile experiments and crystal plasticity finite element method (CPFEM). The results suggested that the elongation can be increased by 80% without a significant reduction in tensile strength. The improved elongation is attributed to the complete recrystallization, formation of annealed twins and serrated grain boundaries after heat treatment. The study also investigated the deformation behavior and fracture mode of the alloy before and after heat treatment. Discussion was done on the influence of the microstructure, particularly the twin and serrated grain boundaries on the alloy's plastic deformation. This study enhanced the understanding of plastic deformation of SLM GH3536 alloy and provided a valuable reference for the design and post-treatment of superalloy.

STUDY OF THE PROCESS OF PLANT RAW MATERIAL EXTRACTION IN A STATIC-TYPE CAVITATION INLINE MIXER

Abstract. The flowering heads of calendula have a significant content of biologically active substances (BAS) with a wide range of pharmacological activities. Traditional methods for obtaining their aqueous extracts include maceration or percolation. However, these methods have significant drawbacks. The rational choice of equipment and the study of the influence of thermophysical conditions on the extraction process of specific plant raw materials to intensify mass transfer processes are relevant. The aim of the study is to investigate the transition of solid substances of calendula flowers into a soluble state in a flow cavitation mixer of a static type to intensify mass transfer processes in obtaining aqueous extracts. For the research, previously ground dry calendula flower heads, swollen in distilled water at a hydro module of 1:15 and reduced to 0,1-2 mm, were used. The work was carried out on an experimental cavitation mixer of the Venturi tube type with a variable cavitation reactor with a nozzle throat diameter ranging from 0,006 m to 0,12 m. The efficiency of extraction was determined by the amount of water-soluble substances, and the cavitation phenomenon was characterized by the cavitation number. Results: The overall design of the cavitation apparatus, the profile and geometric parameters of the nozzle, the flow parameters, as well as the properties of the plant material, significantly affect the hydrodynamic conditions and the development of cavitation effects during processing. The Venturi-type flow cavitation mixer used in the research showed high efficiency in processing mass transfer processes during the extraction of a water suspension of calendula flower heads. The results obtained indicate that the most significant impact of cavitation effects is observed at nozzle throat diameters of 0,08 m and 0,10 m, with cavitation numbers χ = 0,53 and χ = 0,84, respectively. In this case, the process duration can be limited to 60 seconds. The obtained conclusions are confirmed by microstructure studies.

Vacuum sealing-assisted processing of titanium–zirconium alloys: synthesis, microstructure, hardness, friction, wear, and corrosion studies for biomedical application

Vacuum sealing-assisted processing of titanium–zirconium alloys: synthesis, microstructure, hardness, friction, wear, and corrosion studies for biomedical application

Genome-wide Association Study of Cerebellar White Matter Microstructure and Genetic Overlap with Common Brain Disorders (P11-4.013)

Genome-wide Association Study of Cerebellar White Matter Microstructure and Genetic Overlap with Common Brain Disorders (P11-4.013)

Evaluation of microbially induced carbonate precipitation in repairing process of cement mortars by Raman spectroscopy

The use of microorganisms that stimulate the precipitation of carbonates, which can fill the cracks that form in the structure of cementitious composites [MICP], has been gaining interest in recent years as an alternative method of self-healing of these materials. This article analyses the effectiveness of surface application of repair agents composed of zeolite NaX and bentonite, Bacillus subtilis bacteria spores and cementing solutions [precursors of precipitation reactions] as a method of repairing cracked cement mortar surfaces. The effects of this method were evaluated by image analysis and microstructure studies of precipitates precipitated under controlled conditions and on the surfaces of healed composites. Raman spectroscopy and X-ray diffraction were used to characterize the microstructure. The conducted tests confirmed the precipitation of carbonates in the breakthrough of the healed cracks [maximum 31.9% occupation of the surface by the precipitate produced], which proves the effectiveness of the MICP process incident, at the same time indicating the participation in the mechanism of abiotic precipitation of crystalline forms present in the cementing solutions. Additionally, the effectiveness of using Raman spectroscopy to characterise the surface of the cement composite and the carbonates precipitated by microorganisms was confirmed.

Evaluation of Locally Available Calcined Clay-Based Geopolymer for the Stabilization of Expansive Soils

Geopolymers (GPs) have been effectively used as an alternative to traditional calcium-based stabilizers for treating problematic expansive soils over the last decade. However, the high cost of precursors and limited availability of traditionally manufactured GPs pose significant challenges for commercial implementation. Utilizing locally available sources to manufacture GPs could address such limitations and promote sustainable development. A research study was designed and implemented to evaluate the efficacy of locally available calcined clay-based GP stabilizers to improve the performance of expansive soils and the results were compared with lime-treated and untreated soils. An array of laboratory studies was conducted using two natural clayey soils and two types of GPs to assess improvements in several engineering properties, including unconfined compressive strength before and after capillary soaking, resilient moduli, and moisture-induced strains. Supplemental microstructural studies using X-ray diffraction, optical microscopy, and scanning electron microscope imaging were conducted to identify the mineralogical changes and detect the precipitation of new reaction products. The engineering studies demonstrated that the application of GP significantly enhanced the strength, durability, and stiffness while reducing the swelling and shrinkage strains in the GP-treated soils. Microstructural analysis revealed that the precipitated GP gels effectively coated the soil particles and provided a uniformly bonded GP–soil matrix that enhanced the engineering performance. Overall, this study provides a comprehensive understanding with respect to the potential of using locally available calcined clay-based GPs as a sustainable and durable alternative in enhancing the engineering properties of expansive soils for the long-term performance of transportation infrastructures.

Study of microstructure and electrical heterogeneity of Ho and Mg co-doped CaCu3Ti4O12 lead free ceramics

Study of microstructure and electrical heterogeneity of Ho and Mg co-doped CaCu3Ti4O12 lead free ceramics

Effects of instant controlled pressure drop treatment combined with refractance window drying on infusion quality of made green tea.

The study aimed to determine the effects of instant controlled decompression of steam pressure, termed as ICPD (instant controlled pressure drop) on fresh tea leaves, when combined with refractance window drying (RWD) of rolled green teas during green tea manufacturing. The ICPD steam treatment pressure (TP; 0.1-0.3 MPa), treatment time (TT; 10-20 s) and refractance window drying temperature (RWDT; 70-90 °C) were used as the processing parameters for manufacturing of green tea. Response surface methodology was employed to enumerate the effects of ICPD process conditions and temperature of RWD on total phenolic content (TPC), total flavonoid content (TFC) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity of the green tea infusion. An optimum condition for green tea processing was found at TP 0.2 MPa, TT 20 s with RWDT at 70 °C. In comparison to made green tea manufactured without ICPD treatment, the ICPD treated green tea showed enhanced TPC, TFC and DPPH radical scavenging activity along with better colour and sensory attributes. The microstructural study of ICPD treated green tea samples showed more deformed cell surface integrity, larger stomatal pore size and cracks at the leaf surface in comparison with non-treated green tea sample. Present study reveals that an ICPD treatment at 0.2 MPa for 20 s can be used as an alternative to the traditional enzyme inactivation step of hot water treatment, for green tea leaves to improve the infusion quality in terms of increased levels of TPC and TFC and DPPH radical scavenging activity. © 2024 Society of Chemical Industry.

Fracture Toughness Investigation of AL6082-T651 Alloy under Corrosive Environmental Conditions

The crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.

Study of the effect of onion husk ethanol extract on the chemical composition and microstructure of meat pates

The wide use of antioxidants is due to their involvement in free radical processes in foods and human body. Interest in the use of low-value raw materials providing products with functional properties and increasing their shelf life is rapidly increasing. However, any changes in the formulation and technology may affect the properties and composition of the finished product. During the work, the effect of replacing 34% (sample 1) or 17% (sample 2) beef broth with 70% water-ethanol extract of yellow onion peels in the formulation of the experimental meat pates was investigated. The control product contained only beef broth as liquid. The total antioxidant capacity by the DPPH radical method (TACDPPH), fatty acid composition and amino acid composition were determined; microelement content analysis, proteomic and microstructural studies of meat pate samples with and without the addition of extract were also carried out. For 14 days, TACDPPH values of experimental pates were higher than in control by at least 2.32 times (P<0.10). Samples 1 and 2 were characterized by a decrease in the concentrations of zinc, manganese and magnesium by no more than 14% (P<0.10), with a simultaneous increase in selenium, copper, potassium and calcium of 8% to 17.35% (P<0.10) depending on the microelement. The mass fraction of protein in experimental pates 1 and 2 was higher by 6.76% and 2.73% (P<0.10), respectively, which was due to a decrease in moisture because of ethanol evaporation. Replacing the broth in the formulation affected the decrease in the protein biological value, as evidenced by a decrease in amino acid scores (AASs). However, a decrease in the AAS difference coefficient in experimental pates 1 and 2 by 7.71% and 3.07%, respectively, led to an increase in the biological value of the pates by 7.7% and 3.06%, respectively. Based on the results of proteomic and histological analysis, it was revealed that the addition of ethanol extract did not lead to significant changes in the protein composition and microstructural characteristics of the test samples.

Influence of the internal structure of straight microchannels on inertial transport behavior of particles

The rapid advancement of Micro-Electro-Mechanical Systems (MEMS) technology has established microfluidics as a pivotal field. This technology marks the onset of a new era in various applications, including drug testing, cell culture, and disease monitoring, underscoring its extensive practicality and potential for future exploration. This research delves into the intricate behavior of particle inertial migration within microchannels, particularly focusing on the impact of different channel structures and Reynolds numbers (Re). Our studies reveal that particles in microchannels with one-sided sharp-cornered microstructures migrate towards the sharp corner at a relative position of 0.4 under low flow rates, and towards the straight wall side at a relative position of 0.8 under high flow rates. The migration pattern of equilibrium positions varies with different arrangements of sharp-corner structures, achieving stability at the channel's center only when the sharp corners are symmetrically arranged on both sides. Our investigation into the shape of microstructures indicates that sharp-cornered structures generate a more stable secondary flow compared to rectangular and semi-circular structures, preventing particle aggregation at the outlet. To address the challenges associated with handling variable cross-section geometries and solid-wall boundaries in dissipative particle dynamics methods effectively, we have developed a dissipative particle dynamics model specifically for analyzing such microchannels. Building upon our previous research, this model introduces a conservative force coefficient for particles within the microstructured region and an interaction zone that only involves repulsive forces, aligning well with experimental outcomes. Through the study of microstructures' geometric shapes, this paper offers guidance for designing microchannels for particle enrichment. Furthermore, the dissipative particle dynamics model established for the particle flow and solid structure interaction within microstructured channels provides insights into the mesoscale dynamics of liquid-solid two-phase flow and particle motion. In conclusion, this paper aims to enhance particle motion sample preparation techniques, thereby broadening the scope of microfluidic applications in the biomedical field.

Microstructure, mechanical and corrosion study of friction stir processed Inconel 625 additive layers deposited via wire arc direct energy deposition

This study explores the application of friction stir processing (FSP) as an effective post-deposition surface treatment technique for improving the mechanical and corrosion properties of wire arc direct energy deposited (WA-DED) Inconel 625 additive layers. The coarse and cube-oriented microstructure observed in as-built Inconel 625 components results in anisotropic mechanical properties. The non-equilibrium solidification in WA-DED Inconel 625 leads to severe micro-segregation of alloying elements, forming large Nb and Mo-rich Laves and carbide phases in the inter-dendritic areas. This causes a heterogeneous distribution of vital alloying elements within the γ-Ni matrix of the material, adversely affecting its mechanical properties and corrosion resistance, thereby restricting the utility of this manufacturing technique in critical applications. The incorporation of FSP has been observed to successfully eradicate the presence of typical coarse and highly oriented microstructure through grain refinement, achieving a more uniform microstructure. Through severe plastic deformation (SPD), coarse eutectic phases are broken down and redistributed within the γ-Ni matrix, enhancing the uniformity of material properties. The research thoroughly investigates the changes in microstructure, mechanical performance, and corrosion resistance of both WA-DED and FSP-enhanced WA-DED Inconel 625 samples. A Thermo-Calc simulation using the classical Scheil model was conducted to understand the solidification pathway and the formation mechanism of the Laves phase in the WA-DED sample. The grain size was significantly reduced by 98.23%, from 138 µm in the WA-DED sample to 2.44 µm in the stir zone (SZ) of the FSP-treated area, due to dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and the Zener pinning effect. This grain refinement led to remarkable enhancements in the yield strength (YS) by approximately 113%, ultimate tensile strength (UTS) by about 37% and micro-hardness by around 60% compared to the WA-DED sample. In a 3.5 wt% NaCl solution, the FSP-treated sample demonstrated superior corrosion resistance by forming a stable, thicker passive film than the as-built sample. The results of this study will offer valuable insights into utilizing the FSP technique as post-weld surface treatment of WA-DED deposited IN625 superalloy.

RETRACTED: Tribological and microstructure studies of LM26/SiC metal matrix composite materials and structures for high temperature applications

This study aimed to investigate the tribological and microstructural characteristics of LM26 composites reinforced with silicon carbide to evaluate their suitability for high-temperature applications. For the sample fabrication, the modified stir-casting method was optimized using a Taguchi L16 orthogonal array. The wear rate and friction behavior were evaluated using the Taguchi’s S/N ratio analysis. When SiC was incorporated into the composite, the wear resistance increased by up to 15 wt%. The wear resistance of the LM26/SiC composite was improved compared to that of the pure LM26 aluminum alloy. The results of this study provide useful information to improve the wettability of metal matrix composites made from commercial-grade LM26 aluminum alloy by adjusting the SiC weight percentage. This type of composite has the potential as a replacement material for traditional applications such as heat sinks, heat exchanger fins, and electronic packaging.

A Petrological and Microstructural Study of Ten Brachinites: A Cumulate Texture?

AbstractBrachinites are igneous, ultramafic and unbrecciated primitive achondrites mainly composed of olivine and pyroxene, with a partial melt residue or cumulate origin that is still debated. This study presents a petrological and microstructural study of 10 brachinite meteorites to identify igneous and deformation processes responsible for their formation. Detailed microstructural analyses were performed using secondary electron microscopy, electron probe microanalysis, and electron backscatter diffraction. The olivine‐spinel and two‐pyroxene closure temperatures of these brachinites ranged from 814 ± 27 to 909 ± 20°C. Olivine [001] axes coincide with the elongation of olivine grains and the crystallographic preferred orientations (CPO) of clinopyroxene [001] axes, which led us to infer lineation as olivine [001] axes parallel to X for all samples. Olivine CPO displays a strong or medium concentration of [001] axes parallel to X and [010] axes parallel to Z pointing to a B‐type fabric. Limited internal deformation of olivine grains and slip systems identified from low‐angle boundary misorientation analyses are inconsistent with the CPO and grain misorientation distributions are close to those found in untextured rocks. Olivine B‐type fabrics may therefore result not from plastic deformation but rather from rigid crystal rotation or preferential crystal growth during compaction. Olivine subgrain boundary misorientation axes imply limited activation of [001](100) and [100](001) slip systems, which could be due to primary plastic deformation during or after crystal settling. These new results reveal that brachinites developed a cumulate texture and accommodated only weak plastic deformation during early differentiation processes in the parent body.

Mesoscale effects of trader learning behaviors in financial markets: A multi-agent reinforcement learning study.

Recent advances in the field of machine learning have yielded novel research perspectives in behavioural economics and financial markets microstructure studies. In this paper we study the impact of individual trader leaning characteristics on markets using a stock market simulator designed with a multi-agent architecture. Each agent, representing an autonomous investor, trades stocks through reinforcement learning, using a centralized double-auction limit order book. This approach allows us to study the impact of individual trader traits on the whole stock market at the mesoscale in a bottom-up approach. We chose to test three trader trait aspects: agent learning rate increases, herding behaviour and random trading. As hypothesized, we find that larger learning rates significantly increase the number of crashes. We also find that herding behaviour undermines market stability, while random trading tends to preserve it.

Effect of nano-Ag addition on the superconducting properties of MWCNT doped magnesium diboride superconductor

Bulk MgB2 superconductor added with nano silver (Ag), multiwalled carbon nanotube (MWCNT) and both the added (i.e., nano-Ag and MWCNT) samples were synthesized. The influence of nano-Ag and MWCNT addition on the structural and superconducting properties were studied. The XRD analysis confirms the formation of hexagonal MgB2 superconductor. Microstructural studies of all the synthesized samples are carried out by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). The superconducting properties such as critical temperature (Tc), magnetic critical current density (Jc), irreversibility field (Birr) and flux pinning properties of all the synthesized samples were investigated at 10 K and field up to 7 T. Nano Ag added MWCNT doped MgB2 shows maximum enhancement in the critical current density i.e., 5.83 × 104 A/cm2 at 5 T and 10 K.

Friction Stirs Processing - State of The Art Process to Fabricate Metal Matrix Composites

Friction stir processing(FSP) is the solid state method to fabricate the surface metal matrix composites(MMC). This process has been derived from the concept of Friction stir welding. As this process is performed in solid state, many defects related to phase transformation can be avoided. As this process is done below the melting point temperature of metal or alloy, it is easier to control the process. Machine variables (tool rotational speed, tool traverse speed, tool tilt angle etc.), tool design variables (diameter, profile and height of probe and shoulder of the FSP tool), and material properties are the main process variables to perform FSP in order to fabricate Metal matrix composite. In addition to these variables number of passes, tool traverse patterns, reinforcement particles’ content and its’ types also can be considered as process variables. Tribological properties’ comparison can be done between alloy and MMC fabricated by FSP for different combinations of process parameters. Microstructural study also can be carried out in order to see the effects of above process parameters. In this paper the above aspects are summarized and performance assessment done by various researchers has been covered.

DIRECT METAL LASER SINTERING TO DEVELOP COMPLEX CONTOURS OF AlSi10Mg ALUMINIUM ALLOY — BUILD PARAMETERS OPTIMIZATION

In the recent years, Additive Manufacturing (AM) has become a very demanding process utilized by majority of the manufacturing industries due to its complex geometrical capabilities, high accuracy, minimal material usage and better build quality. Among the various types of AM methods, Direct Metal Laser Sintering (DMLS) is a feasible method with many applications and a lot of scope for research. This paper focuses on optimizing the important parameters of DMLS process for better build quality of AlSi10Mg Aluminium alloy. The parameters identified are laser power, hatch distance, scanning speed, and layer thickness. Grey–Taguchi multi response optimization method has been used. Experimental specimens were fabricated and tested. Micro-Vickers hardness and average surface roughness were studied. Experiments were analyzed to determine the best combination of parameters of the DMLS process. A detailed micro-structural study was conducted on the specimens. Also, crystallographic study was made. The resultant specimen thus produced had a better build quality along with satisfying micro-structural characteristics.

A STUDY ON MULTI-OBJECTIVE OPTIMIZATION OF PULSED TIG WELDING PARAMETERS AND THEIR EFFECT ON JOINT PROPERTIES OF HIGH MANGANESE STEELS USING TAGUCHI-BASED GRA APPROACH

This investigation focuses on the study of the effect of process parameters like peak current ([Formula: see text], base current ([Formula: see text], pulse frequency ([Formula: see text], shielding gas flow rate ([Formula: see text] on mechanical properties like yield strength (YS), ultimate tensile strength (UTS) and flexural strength (FS) of the welded joints during pulsed TIG welding of SAILMA 450 and EN14 B steels. Taguchi’s L[Formula: see text] orthogonal array has been used for conducting the tests. Multi-objective optimization has been performed using Grey relational analysis (GRA) in order to maximize the mechanical strength and to find out the optimal set of parameters. The optimum parametric combination is obtained at a peak current of 220[Formula: see text]Amps, base current of 120[Formula: see text]Amps, pulse frequency of 5[Formula: see text]Hz and shielding gas flow rate of 17[Formula: see text]l/min. Analysis of variance (ANOVA) is used to predict the significant process parameters. It has been observed from the ANOVA analysis that peak current and pulse frequency have more influence on the output responses than the shielding gas flow rate and base current. The results of the confirmatory test show an improvement of 0.5801 in the GRG, which is satisfactory. A microstructure study has been performed using scanning electron microscopy (SEM) for the optimal set of process parameters.

A study of some relevant properties of concrete incorporating waste ceramic powder as a cement replacement agent

Cement, the key ingredient in concrete, is responsible for 8% of the world's CO2 emissions. Thus, reducing the amount of cement used in concrete is highly desirable to lower the total embodied carbon in concrete manufacturing. Furthermore, an increasing amount of ceramic waste powder (CWP) is generated during the ceramics manufacturing process, which can result in severe environmental problems such as soil, air, and groundwater pollution. This paper reports the use of CWP as a cement replacement agent in concrete to reduce environmental pollution in both concrete production and CWP waste management fields. For this purpose, comprehensive laboratory work was carried out to replace different levels of cement with CWP. It was found that changes in compressive strength and water absorption value are within the acceptable tolerance when 20% CWP replaces cement. In addition, there was an improvement in thermal conductivity, and no significant damage to the mechanical properties of concrete after 30 min of fire exposure when CWP replaced 20% of cement was observed. Therefore, using up to 20% of CWP to replace cement in concrete manufacturing is feasible without compromising the essential properties of the finished products. The microstructural studies of the test specimens further proved that the added CWP was evenly scattered in the concrete matrix.