Microstructural Observations Research Articles

Application of psyllium husk powder addition on the textural properties, oxidative stability and sensory attributes of non-phosphates luncheon meat.

This study assessed the textural properties, oxidative stability and sensory attributes of non-phosphates luncheon meat containing different concentrations (0.75%, 1.00%, 1.25%, 1.50% and 1.75%, w/w) of psyllium husk powder (PHP). The addition of PHP effectively promoted the emulsion stability and textural properties of non-phosphates luncheon meat, as verified by the changes noted in cooking loss and microstructural observations. Meanwhile, PHP successfully retarded lipid oxidation of non-phosphate luncheon meat during storage in a dose-dependent manner (P<0.05). Moreover, 1.50% PHP-addition overcame the quality defects in non-phosphates luncheon meat and was statistically no significant difference or better than the phosphate-added luncheon meat. Thus, 1.50% PHP-addition exhibited the optimal phosphates-replacing effect in luncheon meat. However, a higher concentration of PHP (1.75% in present work) exhibited a negative effect on the sensory attributes of non-phosphates luncheon meat. Additionally, hydrogen bonds and disulphide bonds were the major molecular forces in PHP-containing non-phosphates luncheon meat. Our results indicate that the application of PHP could be considered a feasible and practical strategy for processing non-phosphates luncheon meat with superior textural properties and sensory attributes.

Research on hot deformation characterization of a new weathering steel through processing map and microstructural observation

Investigations using hot compression tests on a new high-strength weathering steel revealed specific deformation behaviors across different conditions. These tests were performed at temperatures ranging from 850 to 1050 °C and at strain rates from 0.01 to 5 s−1. Results indicated that a decrease in the deformation temperature combined with an increase in strain rate notably enhanced both the maximum stress and strain achieved. Notably, above 900 °C and with strain rates below 0.1 s−1, the flow stress of the material reached a steady state at certain strain levels. At a strain rate of 1 s−1, irrespective of the temperature, the steel shows a continuous strain hardening behavior, achieving no stable flow stress state. Notably, when the true strain exceeds 0.8, an unusual increase in flow stress occurs, predominantly due to secondary work hardening effects. The microstructural changes in the deformed samples were examined using electron backscatter diffraction (EBSD), which helped elucidate the softening mechanisms inherent in this high-strength steel. Further, processing maps developed from true strains of 0.1–0.9, derived from the experimental flow stress data, suggest controlling the strain within 0.2–0.4 to minimize instability during hot working.

Effect of Hardness Distribution on Strength of Narrow-Gap Hot-Wire Laser-Welded Joint for High-Tensile Strength Steel.

Application of high-heat input welding on high-tensile strength steels causes deterioration of mechanical properties of the welded joint, due to softening and grain coarsening in the heat-affected zone (HAZ). In this study, low-heat input narrow-gap hot-wire laser welding was applied to 12 mm thick 780 MPa-class high-tensile strength steel plate. Conditions were optimized based on microstructural observations of joints produced at various welding speeds. Heat input was estimated from measured grain size. Evaluation of properties of joints welded at 0.5 m/min revealed sound toughness, tensile strength, and elongation. The effect of undermatched weld metal width on joint strength was analyzed using a finite element method. When the width of undermatched weld metal was 2.5 mm, the joint strength was 99% of the base metal strength; when it was 7.5 mm, the strength dropped to 95%. The effect of HAZ softening width on joint strength with even-matched weld metals was similarly analyzed, showing that even when the HAZ softening width was 2.0 mm, the joint strength was 98% of the base metal strength. The results of this study suggest that narrow-gap hot-wire laser welding can efficiently reduce heat input and the HAZ softening zone, thereby achieving both high strength and high toughness.

Optimization of Plasma Welding Sequence and Performance Verification for a Fork Shaft: A Comparison of Same-Direction and Reverse-Direction Welding.

The shift fork shaft is a key component in transmissions, connecting the shift fork in order to adjust the gear engagement. This study investigates the effects of different welding sequences on deformation and residual stress during plasma welding of the shift fork shaft. A temperature-displacement coupled finite element method, using ABAQUS simulation software and a double ellipsoid heat source model, was employed for the numerical analysis. The simulation results show that welding in the same and opposite directions leads to opposite deformation directions but similar deformation magnitudes. However, opposite-direction welding generates more significant stress concentration. After determining an optimal welding process, experimental welding was conducted. Microstructural observations of the weld seam and critical areas, along with mechanical property tests, revealed that the welds were well formed with no surface defects. The heat-affected zone (HAZ) exhibited a mixture of martensitic and non-martensitic phases, while the fusion zone (FZ) underwent phase transformation and recrystallization, forming fine-grained ferrite with martensite. Microhardness (HRC) in the weld seam ranged from 35 to 50, with the FZ and HAZ hardness higher than that of the base material (BM). The second weld pass showed significantly higher hardness in the FZ than the first pass. The tensile strength of the weld joint reached 94% of the base material strength, though plasticity and toughness were reduced. Fracture surface analysis indicated a combination of brittle cleavage and localized plastic deformation.

PHYSIO - ELECTRICAL CHARACTERISTICS OF Sn/Pb SOLDER AFFECTED ALUMINUM SUBJECTED TO PLASTIC DEFORMATION AND THERMAL TREATMENT

In the present work, the precipitation behaviour of solder affected Al - Sn - Pb alloy is investigated as a function of cold deformation and artificial ageing using microhardness measurements, electrical resistivity, differential scanning calorimetry, X-Ray diffraction analysis as well as microstructural observation. To compare the aforementioned properties three different types of aluminium have been selected for analysis: commercially pure aluminium, binary aluminium with tin, and binary aluminium with lead. It has been found that changes in such parameters like cold rolling and thermal treatment play a crucial role in influencing the physio-electrical qualities of alloys. The alloys exhibit two distinct processes: solid solution strengthening combined with strain hardening resulting from cold plastic deformation, and the softening mechanisms of recovery and recrystallization. The presence of solder positively influences the hardness of pure aluminium at lower aging temperatures, primarily due to solid solution strengthening from tin and lead, albeit at the cost of conductivity. The superior performance of BCC tin over the similar FCC lead structure to Al is attributed to its unique crystal structure. Furthermore, neither of the two elements forms any intermetallic with Al, while Sn and cast alloy impurities do form a variety of intermetallic. DSC and XRD study also confirm the presence of those elements. The micrographs study of cold rolled alloys has confirmed elongated grain at the rolling direction and relatively thick grain boundaries of minor alloying elements due to the presenceof different particles. All the alloys attain more or less re-crystallized state after ageing at 350oC for one hour.

Investigation of electric field-induced phase transitions in unfilled tungsten bronze relaxor ceramics designed by the high entropy concept

Electric field-induced phase transition behaviour, extensively studied in perovskite-structured ceramics, has not been previously reported in unfilled tetragonal tungsten bronze (TTB) structured ceramics. In this work, we present the first investigation of electric field-induced phase transitions in high entropy designed unfilled TTB structured Ca0.25Sr0.25Ba0.25Pb0.25Nb2O6 (CSBP) ceramics using dielectric and ferroelectric characterization techniques. The findings reveal that field-induced polarization in the CSBP ceramics evolve from irreversible to reversible with increasing temperature. Furthermore, relaxor ferroelectric behaviour was observed in the ceramics, attributed to the A-site cation disorders in the unfilled TTB structure, facilitated by the high entropy design. The absence of non-180° domain switching was indicated by microstructural observations and analysis of the strain-electric field (S-E) response. In-situ poling synchrotron studies and experimental S-E response measurements revealed an electrostrictive behaviour characterized by an electrostrain not originating from macroscopic structural transformations or long-range domain switching but more likely contributed by the reorientation of polar nanoregions. The results obtained provide a foundation for future studies investigating the electric field-induced phase transition and domain switching behaviour in the unfilled TTB structured ceramics.

Effect of surface condition on fatigue life of 7075 aluminium alloy

ABSTRACT This study investigates the effects of surface treatments on the mechanical properties of 4 mm thick flat test specimens made from annealed AA 7075 alloy in three conditions: as-received, shot-peened, and electropolished. Experimental investigations, including cyclic stress response, fatigue life, microstructural observations, and mechanical properties, are conducted to provide insights into the fatigue behaviour of the alloy. The surface roughness (Ra) values were measured at 546 nm for as-received, 830 nm for shot-peened, and 72 nm for electropolished samples. Push–pull fatigue tests conducted at a stress amplitude of 500 MPa with a load ratio (R) of -1 yielded average fatigue lives of 1200 cycles for as-received, 990 cycles for shot-peened, and 2700 cycles for electropolished samples. These results align with the general observation that smoother surfaces yield better fatigue life, which can be explained by the influence of surface conditions on stress–strain behaviour, microstructure, and fracture mechanisms. The smoother surfaces have lower stress concentration points, so the propensity for crack nucleation and propagation is lower in these samples, leading to improved mechanical properties.

Evaluation of the Microstructure and Properties of As-Cast Magnesium Alloys with 9% Al and 9% Zn Additions.

The need to reduce energy consumption means that it is necessary to reduce the weight of vehicles. However, a thick wall of massive elements promotes the formation of casting defects, which must be removed by either plastic processing (straightening) or welding methods (surface and internal discontinuities). Basic alloys contain Al and Zn as the main alloying elements. The studies involved an evaluation of the microstructure and properties of alloys at ambient and elevated temperatures. The microstructure observation revealed a dendritic structure with the presence of low-melting eutectic, and intermetallic and Laves phases in the interdendritic areas. The presence of these phases may pose significant limitations during welding work. Thermal conductivity coefficient measurements showed that it is constant at temperatures up to 200 °C and is 49 W/mK for 9% Al and 77 W/mK for 9% Zn. The tensile test reveal that the most favorable tensile strength (120 MPa) occurs at temperatures of 150 °C for the 9% Zn alloy and at 180 °C for the 9% Al alloy.

Liquid Metal Embrittlement Susceptibility and Crack Formation of the Zn-Coated Complex Phase Steel

In the resistance spot-welding (RSW) of galvanized complex phase (CP) steel, liquid metal embrittlement (LME) may occur, deteriorating the welded joint’s performance. Based on the Auto/Steel Partnership (A/SP) standard, the joints of galvanized CP steel welded with a welding current from 7.0 kA to 14.5 kA were evaluated. When the welding current increased to 11.0 kA, LME cracks began to appear. The longest type A crack was 336.1 μm, yet the longest type D crack was 108.5 μm, and did not exceed 10% of the plate thickness, which met the limitation of the A/SP standard. In light of the microstructural observation and element distribution, it was found that there existed an internal oxide layer adjacent to the surface of galvanized CP steel matrix, with the depth of about 4.1 μm. In addition, the simulation results show that the CP steel was under tensile stress throughout the RSW process, but the internal oxide layer could successfully lead to the low LME susceptibility of the Zn-coated CP steel.

Optimization of vacuum isothermal quenching process and microstructure analysis of die steel Cr12MoV

AbstractThis study first employed a vacuum isothermal gas quenching process to heat‐treat Cr12MoV in an attempt to achieve a mixed structure of martensite and lower bainite. Based on an analysis of the impact of different isothermal gas quenching process parameters on the properties and microstructure of Cr12MoV steel, with a focus on material impact toughness and Rockwell hardness, the particle swarm optimization method was used to optimize the vacuum gas quenching process parameters for Cr12MoV steel. Using the optimized process parameters, Cr12MoV steel was subjected to vacuum isothermal gas quenching treatment. Microstructure observations and phase analysis revealed that the post‐quenching structure consisted of an excellent combination of martensite and lower bainite dual‐phase structures, with reduced carbide content and even distribution. After two tempering processes, it was observed that the residual austenite content significantly decreased. The vacuum isothermal gas quenching‐tempering process effectively reduced material anisotropy and tool deformation.

Effects of ultrasonic-assisted osmotic pretreatment on convective air-drying assisted radio frequency drying of apple slices

Convective air-drying assisted radio frequency drying (CARFD) is an innovative method with the merits of rapid volumetric heating, energy efficiency, as well as high quality food products. However, knowledge about how pretreatment methods impact on the physicochemical characteristics of pretreated apples and the performance of subsequent CARFD is limited. In present work, apple slices were subjected to osmotic pretreatment (OP) and ultrasonic-assisted osmotic pretreatment (USOP) with different intensities (1.0, 2.0 and 3.0 W/g); and the physicochemical properties of pretreated samples (such as mass transfer behavior, water migration status, dielectric loss factor and the others) were compared. The drying duration, energy consumption and a series of quality characteristics (color index, texture, nutrient compositions, antioxidant activity, and so on) of the CARFD produced apple slices were also investigated. The microstructure observations revealed that acoustic waves induced the structural changes and created microchannels. Meanwhile, physicochemical properties of pretreated samples also demonstrated that OP and USOP methods significantly facilitated the water migration status and heightened the dielectric loss factor. In comparison with control and OP methods, three USOP methods were successful in reducing the drying time (14.6%∼27.1%) and total energy consumption (4.5 ∼ 19.8%) of entire processing steps. Concomitantly, USOP (2.0 W/g) samples after drying showed an enhanced quality characteristics in terms of good texture, higher retention of bioactive compounds, higher rehydration ratio, better antioxidant capacity. This study highlights the application of USOP as an effective pretreatment method for enhancing the process efficiency and quality of CARFD produced apple slices.

Prediction of the hot flow behavior of AISI 321 stainless steel during dynamic recrystallization using sine hyperbolic constitutive equation and artificial neural network

The hot compression deformation behavior of AISI 321 austenitic stainless steel were studied under the strain rate and temperature ranges of 0.001–1 s−1 and 950–1200°C. The single peak hot flow curves indicated the occurrence of dynamic recrystallization in AISI 321 steel at applied deformation conditions. The microstructural observations showing the development of equaxed austenite grains further approved the results of flow curve analysis. The average size of austenite grains, when deformation is carried out at strain rate of 1 s−1, increases from 8 μm at 950°C to 61 μm at deformation temperature of 1200°C. After microstructure analysis, the flow behavior of AISI 321 steel was modeled using sine-hyperbolic constitutive equation and feed-forward back propagation artificial neural network. The mean absolute error related to the predicted flow stress values at different strains with the sine-hyperbolic constitutive equation is more than 2, and this value is less than unity for the neural network method. The obtained results efficiently indicate that the ANN model is more accurate in predicting the flow behavior of AISI 321 austenitic stainless steel when the dynamic recrystallization is the prevailing softening mechanism.

Optimization of Aluminium Casting with Alumina Reinforcement via Stir Casting: Impact on Physical and Mechanical Properties

Aluminum casting using the stir casting method is a common practice in the industrial sector. This study aims to optimize the effect of stirring speed on the physical and mechanical properties of aluminum casting reinforced with alumina powder (Al2O3). The material used in this study is derived from discarded vehicle rim waste. The stir casting method was performed at varying speeds of 500, 600, and 700 rpm, with a mold temperature of 250°C and a pouring temperature of 700°C. Physical testing to examine the microstructure was conducted using optical metallography, hardness testing was performed using the Rockwell hardness scale B, and tensile strength was measured using a Universal Testing Machine. The microstructure observations showed that a stirring speed of 500 rpm yielded the best results, with minimal porosity. The highest hardness value recorded was 65 HRB at 500 rpm, consistent with the microstructure observations. The highest tensile strength was also recorded at 500 rpm, reaching 262 MPa.

Analysis of Fatigue Crack Propagation in AISI 4140 Steel with Multi-Austempering Treatment

This study examines the fatigue crack propagation behaviour of AISI 4140 steel subjected to multi-austempering heat treatments. Tensile test and fatigue crack propagation (FCP) specimens were prepared in accordance with ASTM E8 and ASTM E647, respectively. Multi-austempering was carried out by heating the specimen to an austenite temperature for 10 min using an induction heating coil. The specimen was then immersed in a salt bath for each isothermal transformation time of 60 min at three austempering temperature levels from 312°C to 412°C with a temperature increase of 50°C. Tensile and fatigue crack growth tests were performed on both annealed and multi-austempered specimens. It is observed that the multi-austempering heat treatment significantly improves the tensile properties and the FCP properties of AISI 4140 steel. Microstructural observations indicate that the bainitic phase and the retained austenite increase the tensile strength and reduce the fatigue crack propagation rate (da/dN). It is found that the bainitic structures are an effective barrier in reducing fatigue crack propagation as the fatigue loading cycle increases

Exploring the Solidification Sequence and Solid-State Transformations in High-Boron Multi-Component Cast Alloys by Differential Scanning Calorimetry

AbstractThe newly designed multi-component (Fe–5 wt.% W–5 wt.% Mo–5 wt.% V–10 wt.% Cr–2.5 wt.% Ti) cast alloys, containing 0.7–1.1 wt.% C and 2.7–3.6 wt.% B, are intended for tribological applications. The present work was aimed at studying the solidification sequence and phase transformation temperature intervals of the above-mentioned alloys, in order to elucidate their structural status and further develop an appropriate heat treatment regime. For this purpose, Differential Scanning Calorimetry (DSC), microstructure observation and thermodynamic modeling were applied. Two temperature ranges of exothermic reaction (caused by the release of latent heat during transformation) were revealed at 1200-1091 °C and ≤400 °C. The first range was caused by the primary carboboride (M(C,B), M2(B,C)5) precipitation, followed by sequential eutectic reactions with the formation of carboborides M2(B,C)5, M7(C,B)3, and M3(C,B). The temperature ranges of eutectic transformations decreased with the increase in carbon and boron contents. Low-temperature exothermic reactions (at 399-181 °C) referred to the transformation of austenite into bainite or martensite. The values of the latent heat of the transformations were calculated and discussed. Graphical Abstract

A Novel Objective Method for Steel Degradation Rate Evaluation.

This article introduces a novel approach for assessing microstructure, particularly its degradation after extended operation. The authors focus on creep processes in power plant components, highlighting the importance of diagnostics in this field. This article emphasizes the value of combining traditional microstructure observation techniques with image analysis. A non-destructive method of evaluating microstructure parameters (matrix replicas) is presented, and its accuracy is evaluated against the conventional destructive method. The assessment utilizes quantitative data derived from classical stereological principles and image analysis. Parameters like mean chord length, relative surface area, mean cross-sectional area, and mean equivalent diameter are compared for replica and metallographic specimens. The results show that the replica method accurately reproduces the microstructure. In their conclusions, the authors highlight the importance of developing visual methods alongside the application of artificial intelligence while indicating the challenges in achieving this goal.

Effects of γ-polyglutamic acid on the rheological, microstructural and sensory properties of low-fat yogurt.

While low-fat yogurt offers numerous health benefits, its texture and sensory qualities are poor. This study aimed to investigate the effects of γ-polyglutamic acid (γ-PGA) on the rheological, microstructural and sensory properties of low-fat yogurt using rheological tests, scanning electron microscopy (SEM) and sensory evaluation. The results showed that the syneresis of low-fat yogurt added with 0.15% γ-PGA was significantly (P < 0.05) reduced to 23.03%, compared to that of low-fat yogurt without γ-PGA (42.87%). An improvement in storage and loss moduli (G', G") and apparent viscosity was also observed. The power law model fitted to rheological data indicated that γ-PGA enhanced the viscoelasticity and strength of the gel network though interaction with casein gel, which might lead to changes in the moduli of yogurts. Microstructural observation via SEM confirmed the enhanced crosslinking between casein micelles and the filling effect of γ-PGA. Sensory liking scores were strongly correlated with rheological properties and apparent viscosity. The results of principal component analysis (PCA) confirmed the positive effects of γ-PGA on quality and rheological attributes of low-fat yogurt. The results of this study provided valuable references for the potential use of γ-PGA as a fat replacer to stabilize the sensory quality of low-fat yogurt. © 2024 Society of Chemical Industry.

Deformation mechanisms and geometries of superposed fault zones in dolostones

Understanding how heterogeneous rock volumes deform is crucial in structural geology, and several studies have addressed this issue by focusing on the impact that the mechanical stratigraphy of a layered stratigraphic sequence has on deformation. However, mechanical layering can also develop subparallel to fault surfaces within the upper crust, and how these anisotropies affect subsequent deformation has been much less explored. This work addresses this aspect by structurally and mechanically characterizing superposed fault zones developed in Triassic dolostones that crop out in the fold-and-thrust belt of the southern Apennines. We investigate how layering associated with an early, reservoir-scale, normal fault zone (F1), inherited from Upper Triassic−Lower Jurassic pre-orogenic extension, influenced the deformation mechanisms and the geometry of younger strike-slip faults (F2) that formed at an angle to it in the early Pliocene in association with out-of-sequence tectonics during the Apennine orogeny. We combined field surveys and laboratory analyses using a multiscalar and multimethodological approach. Meso- and microstructural observations and geomechanical, laboratory, and in situ tests were employed to describe fault rock attributes. We found that the architecture of the F1 normal fault primarily consists of four tens-of-meters-thick, subparallel fault rock units. They have a cataclastic core, and are bounded in the hanging wall by cemented micromosaic breccia, and in the footwall by high-strain and low-strain fault rocks. The younger F2 strike-slip faults developed alternatively as either cataclastic shear bands or compaction bands and occur in either localized or anastomosing geometries. By combining data, we demonstrate that the particle size distribution, porosity, and rock strength of the fault rock units related to older normal faults are the main controls on the deformation mechanisms (i.e., cataclasis versus compaction) and geometry (i.e., localized anastomosed) of the subsequent strike-slip faults. Our study highlights that preexisting highly porous fault rocks favor the development of compaction deformation bands. Conversely, low rock strength facilitates the formation of discrete and diffuse slip surfaces. These results can have significant implications for assessing fluid flow in multifaulted dolomite reservoirs.

Fabrication of Porous TiO2 with Aligned Pores Using Tert-Butyl Alcohol Based Freeze Casting

The effect of freezing conditions on the pore structure of porous TiO2 fabricated using a freeze casting process with tert-butyl alcohol slurry was investigated. The raw powder was heat treated to manufacture a porous body with stable shape by suppressing volume change induced by the phase transformation of TiO2 powder. The XRD analysis result indicated that the anatase phase fraction in the raw powder could be converted to 98.6% rutile phase by heating it at 800°C for 30 min. Porous TiO2 ceramics with unidirectionally aligned pore channels were prepared by freezing tert-butyl alcohol slurry containing 10 vol% TiO2 powder under different freezing temperatures of -20, -30 and -40°C, respectively. After removing the frozen tert-butyl alcohol by sublimation in vacuum, the green samples were sintered at 1100°C for 4 h in air. The porous body contains directional pores with a size of approximately 30 µm, and a hexagonal pore shape corresponding to the crystal structure of tert-butyl alcohol was observed in the cross-section of the pores. Small pores were observed at the bottom part of the porous body near the Cu plate where the solidification heat was released, but relatively large pores were present at the upper part. Both microstructure observation and pore size distribution indicated that the pore size and the strut thickness increased significantly with increasing freezing temperature. The change in pore characteristics was explained as being mainly due to the difference in the solidification behavior of the slurry and the rearrangement of the solid powder.

Glutaric anhydride esterification promotes wheat starch/glutein composite gel interaction: Formation, characterization, and oleogel applications.

This study constructed a composite system with different ratios (100:0, 95:5, 90:10, and 80:20) of glutein compounded with various esterified starch (3% and 6%). The results demonstrated that the esterification process enhanced the viscosity of the starch gel system. Furthermore, the optimal esterification level (3%) facilitated the formation of a dense composite gel network, as observed through microstructure observation. Conversely, elevated esterification levels (6%) resulted in reduced gel system ordering, a loss of crystal structure, and a decline in thermal stability (ΔH reduction). The introduction of glutein promotes interactions within systems, conferring a more continuous structure and positively improving the gel's oil adsorption capacity. NMR images and oil-water distribution curves can verify the ameliorative effect. However, an excessive protein ratio (≥10%) leads to a double decrease in adsorption performance and rheological properties. This porous and lipophilic gel network structure can provide insights for designing solid fats for food products and developing adsorbent templates for chemical industries.