Influence Of Grain Size Research Articles

Effect of Sb-induced oxygen octahedral distortion on piezoelectric performance and thermal stability of Pb(In,Nb)O3-Pb(Hf,Ti)O3 ceramics

The combination of excellent thermal stability and outstanding electrical performance is of great significance for piezoelectric ceramics. Herein, we have prepared 0.11Pb(In0.5Nb0.5)O3-0.89Pb(Hf0.47Ti0.53)O3-Sb2O5 (PIN-PHT-xSb) ceramics by solid-phase method and investigated the effect of oxygen octahedral lattice distortion on microstructure and macroscopic electrical properties. The distortion index of oxygen octahedra is studied by Rietveld refinement, showing that optimal octahedral distortion can soften B-O repulsion, disrupt long-range ordered ferroelectric domains, and enhance local heterogeneities, significantly increasing piezoelectric properties. Moreover, outstanding thermal stability and ultrahigh piezoelectric response of PIN-PHT-1.2Sb ceramics are realized under the synergistic influence of octahedral distortion, excellent density, and large grain size. Compared with PIN-PHT ceramics, PIN-PHT-1.2Sb ceramics exhibit ultrahigh piezoelectric responses (d33 = 706 pC/N, kp = 0.68, εr = 3244), a high Curie temperature (TC) of 300 °C, excellent thermal stability, and anti-fatigue properties.

The Effect of Grain Size and Silicon Content on Non-Oriented Grain Steel Anomalous Loss Through Frequency Excitation in The Medical Healthcare by Using Big Data Analysis

Using steels for commercial electromagnetic purposes produced by the Jordan Steel Group, the current research will look into the effects of grain size and excitation frequency on anomalous losses and the characteristics of the hysteresis curve of the anomalous loss. The final heat treatment of 21 steel samples for commercial electromagnetic purposes, divided into three groups differing in chemical composition, was carried out in the laboratory to determine the influence of electrical resistivity, grain size, and excitation frequency on total, hysteretic, and seek a better understanding of the effect of these variables on the anomalous loss portion. Compare the experimental data to the hypothesized constitutive equations in the literature and study to create the parasitic loss plus hysteretic loss curve using interpolation, superimpose it on the total loss hysteresis curve, then correlate the areas between the curves with anomalous loss and energy dissipation processes. It is possible to determine from micrographs and grain sizes that there was an increase in grain size due to normal brain development and a minor fraction of aberrant growth at high temperatures.

Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer’s Lactate Solution

Cobalt-chromium-molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer's lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear.

Analysis of the Mechanical Properties of Electrical Steel

Abstract This paper presents the microstructural aspects of strips cold rolled laminar and the influence of grain size on the total magnetic loss at 1T respectively 1.5T, for silicon steel strips with non-oriented grains after decarburized and annealed treatment. We find that the hardness at the head of the rolls is higher for all 5 analyzed rolls, on the other hand, for the rolls from batch II the hardness at the ends is higher than the hardness at the head. The hardness values are included in the EN standards 10106. The regression equations drawn for Rc in the raw state, as well as in the aged state, show us significant correlation coefficients very close to the value of 1, that is 0.98 for Rc raw and 0.97 for Rc aged.The regression equations plotted for Rm in the raw state for the batch of bands analyzed, as well as in the aged state, show us significant correlation coefficients very close to the value of 1, i.e. 0.91 for Rm raw and o.98 for Rm aged.

A unified model for ductile-to-brittle transition in body-centered cubic metals

Ductile-to-brittle transition (DBT) is a well-known phenomenon in body-centered-cubic (BCC) metals, intermetallics and semiconductor materials. A quantitative prediction of the DBT temperature, however, has so far remained intractable. Here, we propose a unified model based on the efficacy of dislocation multiplication as the controlling factor for DBT, with the dislocation source efficiency governed by the relative mobility of screw versus edge dislocations. The model successfully predicts the DBT temperature of iron, molybdenum and tungsten, and also covers the influence of grain size, initial dislocation density, and the multiplicity of dislocation sources. A comparison with experiments indicates that the model captures the key DBT features, providing new insight into the toughness of BCC metals.

Machining performance and wear behaviour of polycrystalline diamond and coated carbide tools during milling of titanium alloy Ti-54M

Polycrystalline diamond (PCD) is currently under development as a new generation of cutting tool material for titanium alloy machining applications. The unrivaled high temperature hardness possessed by PCD offers the potential for higher levels of productivity compared to tungsten carbide, the current industry standard tool material, through facilitating higher cutting speeds. This study investigates the performance of various PCD tool grades during square shoulder milling of Ti-54M. The influence of PCD grain size on dominant wear mechanism has been established, revealing that a smaller, sub 1 μm, grain size offers improvements in tool life due to superior fracture toughness compared to larger grained material. For fine grained PCD, loss of tool material through a cyclic process of workpiece adhesion followed by grain pull-out was identified to be the predominant wear mechanism, contrasting the mechanical fracture dominated wear observed for the larger grained PCD grades. The influence of insert microgeometry was also investigated through honing of the cutting edge radii. An increased tendency for edge fracture was demonstrated when machining with larger radii tooling which was attributed to increased cutting forces. Finally, the study has compared the surface integrity response of the workpiece following PCD and carbide machining, revealing considerably lower levels of microstructural damage and cutting forces when machining with PCD. This highlights the potential benefits of PCD in finishing applications, whereby high speed machining can be employed to reduce the impact on component surface integrity.

Development of Hall-Petch and Hollomon models for thermo-mechanically treated Al-Cu-Mg alloys with trace additions of Sn

ABSTRACT Present study aims to develop Hall-Petch and Hollomon models for Al-6.2 wt.%Cu-0.6 wt.%Mg alloys microalloyed with varying Sn contents, under different thermo-mechanical treatments. Average grain sizes were microscopically determined, and uniaxial tensile tests were conducted to generate flow curves and evaluate yield strength of the alloys. Average grain diameter of Al-Cu-Mg base alloy decreased (by 19.9 %), while yield strength concomitantly increased (by 17.6 %), with increasing Sn content up to 0.06 wt.%. Rolled peak-aged alloys recorded highest average grain refinement and increase in yield strength by 41% and 98.8% respectively, among all thermo-mechanical treatments. Influence of grain size on mechanical strength was analytically modelled through Hall-Petch equation, using Weighted Least Square methodology. Hall-Petch parameters of the alloys were evaluated for first time, considering separate processing conditions. Yield strengths computed from Hall-Petch models were successfully compared with experimental results with fairly good accuracy, to validate estimated Hall-Petch parameters. Flow curves obtained from uniaxial tensile tests were mathematically modelled through Hollomon equation, by determining strain hardening exponent and strength coefficient, first time for investigated alloys under different processing conditions. Trace contents of Sn and processing parameters had significant potential to refine grain structure and enhance mechanical strength of the Al-Cu-Mg alloy.

The influence of grain size and catalytic doping on magnesium hydride nanocrystals for hydrogen storage

Magnesium hydride (MgH2) nanocrystals of different sizes were constructed by a facile hydrogenated ball milling method. X-ray diffraction (XRD) analysis showes that the size of MgH2 nanocrystals decreased gradually with the increasing milling time. The as-prepared MgH2 nanocrystals started to release and take up hydrogen from 281 to 119 °C, respectively. By doping the prepared Nb2O5@MOF into MgH2 nanocrystals, the initial hydrogen desorption and absorption temperatures were further reduced to 228 and 25 °C. Microstructure analysis revealed that the uniform distribution of Nb2O5 on MgH2 nanocrystals contributed to the greatly enhanced de/hydrogenation kinetics of modified MgH2 system.

Influence of Grain Size and Volume Fraction of η/δ Precipitates on the Dwell Fatigue Crack Propagation Rate and Creep Resistance of the Nickel-Base Superalloy ATI 718Plus

Recently, it was found that the orientation of the η/δ plates in the Ni-base superalloys ATI 718Plus has a huge impact on the fatigue crack propagation behavior (Huenert et al. in Superalloys pp.781–792, 2016). However, the targeted alignment of η/δ precipitates in components with complex geometry can be challenging in certain applications. Therefore, the effect of other microstructural features of ATI 718Plus, which are easier to manipulate, is tested with respect to their fatigue crack propagation behavior and creep strength. The grain size, the γ′ precipitate size, as well as the γ′ and η/δ volume fraction are varied by applying different heat treatments. An increase in the η/δ volume fraction as well as the γ′ volume fraction and precipitate size enhanced the crack growth resistance, but worsened the creep properties. On the contrary, increasing the grain size leads to better creep properties and better fatigue crack growth resistance. The impact of the different microstructures investigated in this study on the mechanical properties is smaller compared to microstructures with strongly aligned η/δ plates. These results enable to design the desired microstructures that meet the particular demands of the given application regarding crack propagation and creep resistance.

Influence of grain size, organic carbon and organic matter residue content on the sorption of per- and polyfluoroalkyl substances in aqueous film forming foam contaminated soils - Implications for remediation using soil washing

A soil that was historically contaminated with Aqueous Film Forming Foam (AFFF) was dry sieved into size fractions representative of those produced during soil washing. Batch sorption tests were then conducted to investigate the effect of soil parameters on in situ per- and polyfluoroalkyl substances (PFAS) sorption of these different size fractions: < 0.063 mm, 0.063 to 0.5 mm, 0.5 to 2 mm, 2 to 4 mm, 4 to 8 mm, and soil organic matter residues (SOMR). PFOS (513 ng/g), 6:2 FTS (132 ng/g) and PFHxS (58 ng/g) were the most dominant PFAS in the AFFF contaminated soil. Non-spiked, in situ Kd values for 19 PFAS ranged from 0.2 to 138 L/Kg (log Kd −0.8 to 2.14) for the bulk soil and were dependant on the head group and perfluorinated chain length (spanning C4 to C13). The Kd values increased with decreasing grain size and increasing organic carbon content (OC), which were correlated to each other. For example, the PFOS Kd value for silt and clay (< 0.063 mm, 17.1 L/Kg, log Kd 1.23) were approximately 30 times higher compared to the gravel fraction (4 to 8 mm, 0.6 L/Kg, log Kd −0.25). The highest PFOS Kd value (116.6 L/Kg, log Kd 2.07) was found for the SOMR fraction, which had the highest OC content. Koc values for PFOS ranged from 6.9 L/Kg (log Koc 0.84) for the gravel fraction to 1906 L/Kg (log Koc 3.28) for the silt and clay, indicating that the mineral composition of the different size fractions also influenced sorption. The results here emphasize the need to separate coarse-grained fractions and fine-grained fractions, and in particular the SOMR, to optimize the soil washing process. Higher Kd values for the smaller size fractions indicate that coarser soils are better suited for soil washing.

Influencing factors of rock thermal conductivity and applicability evaluation of its mixing law predictive models

The thermal conductivity (TC) of rocks is a very important parameter in geothermal theory and applied research, its value is related to rock composition, mineral grains characteristics, rock porosity, and pore fluid etc., and simultaneously is affected by formation thermodynamic environment (temperature, pressure,etc.). Statistical analysis results of the thermophysical property parameters of borehole samples from Jizhong Depression indicated that the TC is mainly controlled macroscopically by lithology, compared with sandstone, mudstone, conglomerate, and gneiss, dolomite has a greater TC. In the dry state, the TC of dolomite samples showed a decrease with increasing temperature, the values of TC decreased by 12.3–27.5% in the temperature interval of 30–130 °C. Moreover, under the same temperature conditions, excluding the effects of water content and mineral fraction, the TC of medium–coarse crystalline dolomite, medium–fine crystalline dolomite, microcrystalline dolomite, and mud-powder crystalline dolomite decreased successively, reflecting the influence of the mineral grain size on TC. The validity and applicability of six commonly used mixing law predictive models for TC were evaluated based on X-ray diffraction (XRD) data from 70 borehole samples. The results showed that Geometric mean model displayed the best fit (goodness of fit, R2 = 0.878) for rocks, and Voigt-Ruess-Hill average also showed a good fit, with an R2 of 0.868, and had the best prediction for mudstone (AME = 10.16, RMSE = 0.25). In cases where the calculated values deviate significantly from the measured values, it may reflect the limitation that the mixing models consider only the composition of minerals but ignores the structural characteristics of rocks.

The role of initial grain size on bimodal-grained microstructure and mechanical properties of an extruded Mg-Gd-Y-Nd-Zr alloy

Influence of initial grain size on the formation of bimodal-grained microstructure and mechanical properties of a Mg-11Gd-3Y-0.5Nd–Zr alloy was investigated. The results indicate that the fraction of unrecrystallized (un-DRXed) grains in bimodal-grained microstructure was governed by the initial grain size, and the fraction increases with the increasing of initial grain size. Formation of un-DRXed grains in samples with a small initial grain size is induced by the uneven distribution of grain size, in which coarser grains is more difficult to recrystallize. However, the recrystallization behavior in samples with large initial grain size is mainly affected by the difference in orientation among grains, and grains with orientation that are not favored for slip are difficult to recrystallize. The strength increases while the elongation decreases with the increasing of initial grain size. The sample with the highest initial grain size (178 μm) accordingly shows the best ultimate tensile strength of 459 MPa. The higher strength is mainly due to the higher texture strengthening and hetero-deformation induced (HDI) strengthening provided by higher fraction of un-DRXed grains.

Influence of Grain Size on Mechanical Properties of a Refractory High Entropy Alloy under Uniaxial Tension

There is a growing interest in High Entropy Alloys (HEAs) due to their outstanding mechanical properties. Most simulation studies have focused on face-centered cubic (fcc) HEAs; however, bcc HEAs can offer a larger elastic modulus and plastic yielding, thus, becoming possible candidates for the next generation of refractory materials. In this work, we focus on molecular dynamics (MD) simulations of bcc HfNbTaZr nanocrystalline samples, with a grain size (d) between 5 and 17 nm, deformed under tension at 300 K. The elastic modulus increases with the grain size and reaches a plateau near 10 nm. We find the typical inverse Hall–Petch (HP) behavior with yield strength, ultimate tensile stress (UTS), and flow stress increasing with d. Up to 12 nm, there are contributions from dislocations and twins; however, grain boundary (GB) activity dominates deformation. For the 5 nm grains, the GB disorder extends and leads to extensive amorphization and grain size reduction. For d&gt;10 nm, there is a HP-type behavior with dislocations and twinning controlling deformation. For this regime, there is hardening at large strains. Compared to bcc single metal samples, the HP maximum of this HEA appears at a lower grain size, and this could be related to the chemical complexity facilitating dislocation nucleation. We use machine learning to help understand deformation regimes. We also compare our results to a single crystal (SC) HfNbTaZr HEA deformed along [001] and find that the single crystal is weaker than the nanocrystalline samples. The single crystal deforms initially by twinning and then rapidly by dislocation multiplication, leading to strong hardening. It has been proposed that edge dislocations play a major role in bcc HEA plasticity, and we also analyze the relative contributions of edge versus screw dislocations during deformation for both single crystal and nanocrystalline samples.

Effect of Microstructural Evolution on the Mechanical Properties of Ni-Cr-Mo Ultra-Heavy Steel Plate

In this study, microstructural evolution and its effects on mechanical properties across the thickness of a 120 mm Ni-Cr-Mo industrial ultra-heavy steel plate were quantitatively investigated by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron back-scatter diffraction (EBSD). The results show that the martensite fraction is 65% at 10 mm and disappears at 40 mm, while granular bainite appears at 35 mm and climbs up to as high as 32% at 60 mm, with M-A constituents significantly coarsened. The strength drops with the gradual coarsening of the laths as well as decreased martensite fraction from the surface to the centre. The toughness is mainly affected by the block size and the morphology and quantity of M-A constituents. This study established a multivariate function between the microstructure and toughness (50% fibre area transition temperature, FATT50) with careful consideration of the influence of effective grain size (EGS) and M-A constituent size distribution.

Mechanisms of the preferential cleavage of Ti2AlNb-based alloy: The influence of grain size and local plasticity

An in-depth understanding on the preferential cleavage of the matrix B2 phase, with an ordered body-centered cubic (BCC) structure, is pivotal to improve the processability of Ti2AlNb-based alloys. This research employed in-situ micro tensile tests, multiscale microstructure characterizations, and crystal plasticity simulations to study the grain-size dependent cleavage of the alloy with a full B2 phase. The material was intentionally prepared with two grain sizes differing by order of magnitude, i.e., the millimeter-level coarse grain (CG) and the micron-level fine grain (FG). The experimental results showed that the cleavage of CGs always occurred on the {100} planes, even when the loading direction was much less favorable for the cleavage of these planes, whereas the cleavage of FGs took place on both {100} and {110} planes. The investigation demonstrated that the plastic deformation takes a critical role in selecting cleavage planes. Full-field crystal plasticity simulations demonstrated that, for the CGs, the plastic deformation associated with cleavage on {100} planes is less than that associated with cleavage on {110} planes, indicating a less plastic deformation-induced blunting effect with cleavage on {100} planes. For the FG material, however, the existence of plentiful grain boundaries (GBs) leads to significantly heterogeneous plastic deformation, local stress distribution deviating from the imposed global stress, and hot spots of stress and strain concentration at GB triple junctions. These local plasticity heterogeneities enable the possibility for cleavage on both the {100} and {110} planes.

Experimental investigations of influence on grain size and cold deformational behavior of AL6063 during the microforming process

Miniature products are requisite to make micro creation widely in electronics and micromechanical products. The microfabrication process is identified to satisfy the production of such miniature products rather than an ordinary manufacturing process. Microextrusion is one of the microforming processes in micromanufacturing. In this present work, an attempt has been made to investigate the influence of grain size and deformation behavior of Al6063 microstepped pin with annealed billets for the cold extrusion process. The methodology on the characterization of the microextrusion of Al6063 includes, annealing of the billet, extrusion testing, microhardness examination and surface roughness analysis. The billet with three different sizes of grains is extruded. The experimental result shows that the deformation load and average microhardness of the AA96 (annealed Al6063 with an obtained grain size of 96 μm) are high compared to AA208 (annealed Al6063 with an obtained grain size of 208 μm). The surface finish has improved using diamond-like carbon (DLC) coated die compared to uncoated and lubricated dies. DLC coating with AA208 billet achieved a maximum pin length of 13.1 mm, and uncoated die with AA96 billet achieved a minimum pin length of 5.5 mm. Thus, the findings of this study contribute to the fundamental understanding of cold microextrusion of aluminium 6063 alloy.

Nanoindentation characteristics of nanocrystalline tungsten via atomistic simulation

ABSTRACT Molecular dynamics simulations are performed to explore nanoindentation characteristics of tungsten, and the influences of grain size, indenter velocity, indenter size, and temperature are discussed. The results illustrate that the hardness reduces as the grain size (5.00 ∼ 24.62 nm) decreases. There is no phase change observed during the whole deformation process. For monocrystalline W, the dislocation nucleation and propagation dominate the deformation mechanisms. Differently, the primary deformation mode of nanocrystalline W is the grain split and motion of GBs. Dislocations primarily nucleate below the contact surface of the indenter and substrate and then glide in the grain core. The monocrystalline W has better pattern-forming ability than nanocrystalline. Besides, the pattern-forming ability of nanocrystalline W is negatively correlated with the average grain size (5.00 ∼ 24.62 nm). The von Mises stress is mainly concentrated in the interface between the indenter and substrate, the dislocation area for monocrystalline, and grain boundaries for nanocrystalline. The indentation force and hardness are positively correlated with indenter radius size (30 ∼ 80 Å), negatively correlated with temperature (10 ∼ 1500 K), and insensitive to the indenter velocity when velocity is lower than 3.0 Å /ps (300 m/s).

Manufacturing Methods Induced Property Variations in Ti6Al4V Using High-Speed Machining and Additive Manufacturing (AM)

Additive manufacturing techniques are replacing conventional subtractive machining processes; however, the surface quality and defects have been a key roadblock to expanding AM’s uses. This paper describes experimental investigations in the high-speed dry machining and additive manufacturing (AM) of titanium alloy (Ti6Al4V), discussing the effect of machining and AM conditions on the surface characteristics due to the micro-deformation layer. Analysis of the machined surfaces shows the deposition of microparticles at a high cutting speed of 170 m/min at moderate feed rates. The predominant thermal softening effect at a high cutting speed causes restructuring of the micro-deformation layer. Thus, the machined surface shows fewer alterations and a correspondingly lower surface roughness. A high cutting speed also favors the induction of high residual stresses that are compressive. Shallow grooves are seen throughout the surface along the feed spacing with a higher depth of cut of 0.8 mm. An increase in the cutting speed from 170 m/min to 190 m/min leads to a 61% increase in the surface finish owing to a rise in machining temperature leading to thermal softening, and subsequent restructuring of the machined surface layer occurs. For the feed rate, the surface finish values decrease gradually as the feed rate increases, and the worst finish of 1.37 µm is attained at a feed rate of 0.875 mm/rev. This study also compares different AM processes for Ti6Al4V based on the defects and their effects on mechanical properties, such as tensile and fatigue strength. It was observed that the ultimate tensile strength and the yield strength were approximately 20% more in SLM and direct energy deposition as compared to electron beam melting. The mechanism of these effects is also explained by elaborating on the influence of grain size, phase, and other microstructural behaviors on the final mechanical properties of the produced part.

Refinement Mechanism and Influence of Grain Size in Sintered Nd-Fe-B

Refinement Mechanism and Influence of Grain Size in Sintered Nd-Fe-B

Mid-Infrared (MIR) Spectroscopy of Silicate Glasses as Analogs for Mercury’s Surface: The Influence of Grain Size

Volcanic products are widely present on Mercury: they occur as low-viscosity lava flows, but traces of ash deriving from explosive volcanism are also observed. Silicate glasses represent a major component in volcanic products, and it is likely that the fine-powdered regolith on Mercury contains a non-negligible fraction of glassy material. In the laboratory, we have reproduced a Mercury-like silicate glass, from which we have obtained 14 powdered samples with different granulometric characteristics: 8 samples are extremely sorted with grain sizes ranging from 25 to 425 µm, and 6 samples consist of less sorted powders with normal distributions, varying mean values (30, 95, and 160 µm) and standard deviation (40 and 80 µm). The reflectance of samples was investigated in the mid-infrared (MIR) region: we observe how the reflectance intensity increases with grain size, and the presence of extremely fine material defines the emergence of the transparency feature (TF). We provide reference data with qualitative observations and quantitative parameterization of spectral characteristics; in particular, we observe how a small fraction of fine material can greatly influence the spectral response of coarser powders. Results of this work will be crucial for the interpretation of data collected by the BepiColombo mission, but need to be integrated with other possible Mercurian compositions.