Effect Of Grain Size Research Articles

Mechanical and electrical responses of natural-cooled high-temperature granite of different grain sizes

In order to understand the effect of grain size on the mechanical and electrical responses of natural-cooled high-temperature granite, uniaxial compression tests were carried out on natural cooled coarse- and fine-grained granite samples subjected to thermal treatment at room temperature, 200 °C, 400 °C, and 600 °C respectively. The resistivity and acoustic emission (AE) during the compression were monitored and changes in physical and mechanical properties, the AE and resistivity characteristics in the loading process were analyzed. Results show that high temperature exerts a more significant effect on deteriorating the coarse-grained granite. Changes in resistivity can reflect the development of rock damage. Corresponding to the compaction stage, crack initiation and stable propagation stage, and crack rapid propagation stage of rock under compressive load, changes in resistivity can be divided into three stages accordingly, including the initial rapid descent stage, the gentle descent stage, and the secondary rapid descent stage for the thermal-treated rock at 25–400 °C. The secondary rapid descent stage of resistivity can be used as a precursor for rock entering into the failure stage. The resistivity change is more sensitive to the damage development in coarse-grained granite.

The Effect of Grain Size of Reinforcing Material (Corn Cob) on Some Mechanical Properties of the Composite Material.

The Effect of Grain Size of Reinforcing Material (Corn Cob) on Some Mechanical Properties of the Composite Material.

Effect of Grain Size and Layer Thickness on Hardened State Properties in Selective Cement Activation

AbstractThis article demonstrates the effect of varying the maximum grain size and the layer thickness of the particle bed on hardened state properties in Selective Cement Activation (SCA). The compressive strength and geometry (deviation from nominal geometry, surface roughness) are analyzed. Supplementary investigations (μCT, μRFA) are performed to explain the causes of the observed effects. It is found that the compressive strength of the manufactured specimens increases with decreasing layer thickness. This is attributed to reduced process‐induced segregation of the particle bed and fewer process‐induced voids. The geometric precision as well as the surface roughness of the printed test specimens do not differ significantly. As the grain size increases, the amount of compaction required to achieve the target packing density decreases. The compressive strength was found to increase when the grain size in the specimen is reduced. As the finer particle mixtures tend to have less void formation as a result of water application, an increased density of the specimen can be observed. The lower porosity as well as the smaller pores also have a favorable effect on geometric precision, which tends to increase with reduced grain size. At the same time, a lower surface roughness is also present.

Empirical Study on the Effect of Tungsten Carbide Grain Size on Wear Resistance, Cutting Temperature, Cutting Forces and Surface Finish in the Milling Process of 316L Stainless Steel

Empirical Study on the Effect of Tungsten Carbide Grain Size on Wear Resistance, Cutting Temperature, Cutting Forces and Surface Finish in the Milling Process of 316L Stainless Steel

Microstructural effects in rate-dependent responses of smooth and notched magnesium bars

We perform three-dimensional crystal plasticity simulations of smooth and notched bar geometries made of polycrystalline hexagonal close-packed material representing a magnesium alloy. The polycrystalline microstructure is explicitly resolved to investigate the combined effect of initial texture and grain size on the rate-dependent macroscopic responses and their micromechanical underpinnings under uniaxial and multiaxial stress states. The simulations reveal that in addition to the textural effect recently investigated by Ravaji et al. (2021), grain size plays an important role in the anisotropy of macroscopic responses. For a given texture, the lateral deformation anisotropy increases with grain size refinement for all strain rates considered here. The load-deformation responses exhibit a synergistic strengthening effect in microstructures with stronger initial textures and finer grain sizes, which is enhanced with increasing notch acuity. A transition from a conventional power-law type load-deformation response to a sigmoidal load-deformation response may occur, which depends on the imposed strain rate. It is a result of the interaction between textural weakening and grain size refinement that influence extension twinning together with an equitable landscape of the different slip mechanisms. We discuss possible implications of the net material plastic anisotropy due to texture and grain size on macroscopic failure using a micromechanical basis.

The effect of grain size on the relationship between urbanization and bird diversity

The intensifying urbanization markedly influences bird diversity, frequently with negative repercussions but also yielding mixed outcomes. Our hypothesis posits that the variability in results often arises from methodological choices in measuring both bird diversity and urbanization. We investigated whether the effects of urbanization on bird diversity are influenced by the grain size of the measurements. Selected urban areas in China from 2000 to 2020 were analyzed, and bird diversity distributions were derived from citizen science data. Urbanization levels rose by approximately 30%, resulting in the loss of around 17 urban bird species. Panel data analyses at different grain sizes showed that urbanization negatively affected bird diversity, while taxonomic diversity was more resilient at the grain size (1–10 km). Furthermore, our findings indicate a grain effect on the urbanization-bird diversity relationship, revealing instability at various measurement grains. Functional diversity requires finer grains (1 km), reflecting feature redundancy. Our analytical approach enhances understanding of the mechanisms and cross-grain relationships through which urbanization impacts bird communities, and underscores the significance of grain in urban ecology.

Constrained viscous sintering of melting grains

Viscous sintering of food grains can occur spontaneously and cause undesired caking or be induced to drive a change in food product structure. The dynamics of this phenomenon are still poorly understood, particularly when the sintering is coupled with heat or mass transfer. The aim of this work is to investigate experimentally the effects of heat transfer and grain size on the sintering dynamics of partially melting fat-based food products, i.e., dark chocolate. Two spherical particles were heated through forced convection using an air stream at different temperatures and velocities. Optical and IR thermal cameras were employed to capture the bridge growth and surface temperature evolution. Subsequently, the optical images were analysed to extract the evolution of the size of the bridge between the grains and a first order kinetics model was used to describe the sintering dynamics. The experimental observation showed that the viscous sintering is faster for smaller spheres, and at higher air flow temperature and velocity. When the spheres are heated from ambient conditions, a lag time is observed, which was found to be related to the time required by the material to reach a temperature at which its viscosity decreases to about 54 Pa·s allowing flow. Therefore, the lag time is temperature-dependent and decreases with decreasing particle size and increasing air temperature and velocity. Moreover, a semiempirical model involving a temperature dependent viscosity was proposed to describe the viscous coalescence. It is shown that considering some correction parameters accounting for the experimental conditions leads to an accurate prediction of the bridge growth. The model could be incorporated into the discrete element method to simulate the viscous sintering of a bulk of chocolate grains.

Effect of grain size and precipitates on hydrogen embrittlement susceptibility of nickel alloy 718

The present work reports on the effect of grain size and its combined effect with precipitation on hydrogen uptake and hydrogen embrittlement (HE) susceptibility of alloy 718. HE susceptibility of fine-grained microstructure obtained by friction-stir processing (FSP) is compared with standard heat-treated conditions. Melt extraction measurements on hydrogen pre-charged samples reveal that fine-grained FSP condition compared to solution-treated (ST) condition contains increased hydrogen content, indicating that higher vol% of grain boundaries and density of dislocations promote trapping. The presence of γ’ and γ” phases reduces hydrogen uptake in both fine-grained and aged (FSP-A) and peak-aged (PA) conditions, indicating a lack of affinity of these phases to hydrogen. Under tensile loading, for identical pre-charging conditions, the FSP (with fine grains) and ST (with coarse grains) conditions display similar susceptibility to HE. However, the FSP-A condition with refined grains and precipitates showed substantially reduced HE susceptibility than coarse grained PA condition, measured through % reduction in area. The finding that fine-grained microstructures absorb more hydrogen than larger grained microstructures yet have similar or reduced susceptibility to HE, demonstrates the inherent HE resistant character of fine-grained microstructures.

Numerical study of the influence of grain size and heterogeneity on thermal cracking and damage of granite

In the process of geothermal or deep energy resource exploitation, rock damage and failure due to thermal cracking pose a great challenge to construction safety. To investigate the effects of grain size on thermal damage of the typical hot dry rock, granite, a grain-based numerical model study was conducted. The result shows that, with temperature increasing, the thermal crack pattern changes from mainly tensile crack along grain boundaries to mainly shear crack within intra-grain. When intra-grain cracking occurs, more strength damage can be induced in coarse-grained or homogeneous granite. The quartz particle grains contained in those samples were larger, contributing to a higher thermal expansion coefficient and thereby causing a more significant strength reduction. Thermal damage was calculated and plotted against volumetric thermal strain. The same curve pattern was observed in samples with different sizes and heterogeneity, indicating that the damage variation depends on the volumetric thermal strain. The relational model for the curves was further fitted. In fine-grain or heterogeneous granite, the rate of damage increasing along with volumetric thermal strain is higher. This is mainly due to larger amounts of grain boundaries in the samples, which act as weak bonding and are easier to break at a certain thermal strain. Confining pressure around the specimen can significantly suppress thermal strain and inhibit thermal damage, which corresponds to less value of model parameter related to peak damage and a higher value of that related to curve shape. Our work clarified the major factor determining thermal damage of granite with different sizes and proposed a relation model, which can offer as an instruction for the development of the high temperature geological repository.

Exploring the dependence of creep behavior on the grain size of a peak-aged Mg-10.5Y alloy

In this work, the effects of grain size on the compressive creep behavior of a peak-aged Mg-10.5 wt%Y alloy were studied. Compressive creep tests were conducted at 523 K using three group samples, each having an average grain size of d = 25 µm, d = 50 µm and d = 90 µm along the rolling direction. An inverse Hall-Petch relationship for mechanical strength could be used to evaluate the dependence of creep behavior on the grain size, and the creep resistance was continuously deteriorated with decreasing grain size. The dominant creep mechanisms were pyramidal <c+a> slip, cross-slip and prismatic slip in the d = 25 µm sample whilst pyramidal <c+a> slip, cross-slip and basal slip controlled the creep process in both the d = 50 µm and d = 90 µm samples. In addition, precipitate-free zones (PFZs) decorated randomly the grain boundaries during creep. Both the PFZs width and PFZs amounts were increased as the average grain size decreased, and the softening effects from the frequent activated prismatic slip and profuse PFZs induced the worst creep resistance in the d = 25 µm sample. Thus, the creep resistance of the fine-grained samples was always unsatisfactory even though grain boundary sliding was absent at creep duration. It hopes that this work can enrich the understanding of creep theories and offer important reference to the microstructure design of heat-resistant Mg-RE alloys.

Effects of initial Cu grain size and impurity residues on the liquid phase reactions between molten solder and electroplated Cu

Copper (Cu) electroplating is a cost-effective and scalable technology used to fabricate interconnects/metallizations in microelectronic products. Liquid-phase soldering reactions between electroplated Cu and Sn-based alloys are essential for constructing heterogeneous joints for mechanical support and electrical conduction applications. In this study, three Cu electroplated layers with different grain sizes and impurity contents are fabricated by formulating additives in the plating solution. The Cu electroplated layers are reacted with molten Sn-3.5 wt% Ag alloy at 260 °C for 20–60 min to investigate the liquid phase reactions. Microstructural characterizations of the electroplated Cu layers and the Cu/solder/Cu joints are carried out using electron microscopy and X-ray diffraction processes. A time-of-flight secondary ion mass spectrometer is used to analyze the impurity contents in the Cu electroplated layers. The Cu/solder/Cu joints after liquid phase reactions are mechanically analyzed to measure the shear strength. The results show that the additive formulas affect the microstructural features and the impurity contents in the Cu electroplated layers. Electroplating of Cu with an ultrafine grain texture accompanies a high impurity content, and the solder joint constructed by the ultrafine-grained Cu exhibits a rapid liquid phase reaction and interfacial voiding propensity, leading to a low shear strength.

Effect of Grain Size on the Heat-Affected Zone (HAZ) Cracking Susceptibility in Ni Base XH67 Superalloy

Effect of Grain Size on the Heat-Affected Zone (HAZ) Cracking Susceptibility in Ni Base XH67 Superalloy

Finite Element Analysis of Tyre Contact Interaction Considering Simplified Pavement with Different Aggregate Sizes

This study considered the effect of pavement aggregate grain size on tyre–pavement contact interaction during the late stages of pavement skid resistance. First, hemispherical shells 7, 9, and 13 mm in diameter were used to simulate coarse pavement aggregates. Subsequently, a three-dimensional finite element tyre–pavement contact model developed using ABAQUS was employed to analyse the contact interaction between each simplified pavement type and the tyre under steady–state rolling and braking conditions. Finally, the concept of occlusal depth was proposed and applied to characterise pavement skid resistance. The results showed that under steady–state rolling conditions, the peak contact stress of the simplified pavement increased with the pavement mean texture depth, whereas the contact area decreased. Under steady–state braking conditions, the effect of the contact interaction between the tyre and simplified pavement aggregates was ranked in order of superiority as aggregate grain sizes of 9, 7, and 13 mm, indicating that aggregate grain size did not exhibit any correlation with tyre–pavement contact interaction. Additionally, the squares of linear correlation coefficients between the pavement cumulative occlusal depth and horizontal braking force reached 0.921, 0.941, 0.889, and 0.894 for vehicle speeds of 30, 60, 90, and 120 km/h, respectively, indicating that they could be used to assess pavement skid resistance.

Effect of grain size on gas bubble evolution in nuclear fuel: Phase-field investigations

Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO2 and U3Si2 according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra- and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO2 and U3Si2 have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U3Si2 is evaluated.

Effect of grain size and temperature on deformation mechanism of commercially pure titanium

To investigate the effects of grain size and processing temperature on the deformation behaviors of commercially pure titanium (CP-Ti), the tensile tests were conducted at room temperature (RT) and liquid nitrogen temperature (LNT) on the samples with the average grain size of 2, 9, 23, and 51 μm, respectively. The experimental results based on EBSD and TEM characterizations showed that dislocation slip was the main deformation mechanism at RT, while abundant deformation twins including {102} extension twins, {11} compression twins and some {11}−{102} secondary twins were observed under LNT condition. The transition of deformation modes from dislocation slip to dynamic twinning contributes to the outstanding mechanical properties of the samples with a larger grain size at LNT. Additionally, a modified Hall−Petch relationship was proposed to study the quantitative contribution of average grain size and deformation twins on yield stresses of CP-Ti under LNT condition.

Investigation into effect of grain sizes on deformation behavior of AZ31 alloys in different loading conditions

The AZ31 magnesium alloy with different grain sizes was prepared by adjusting the heat treatment process, and then the tension and compression tests were carried out to explore the effect of grain sizes and loading conditions on the microstructures and properties of the magnesium alloy. The Hall-Petch slope presented dramatic anisotropy under tension (181 Mpa· μm1∕2) and compression (115 Mpa· μm1∕2), the geometric compatibility factor (m′) and the difference in activation stress between the initiated deformation modes of two neighboring grains (σd) were calculated to analyze the anisotropy quantitatively. In compression, it was found that the elongation increased with further grain coarsening, which was attributed to the fact that more twins were initiated in the coarse grains and the preferred initiation of twinning to inhibit competitive crack initiation.

The Effect of Shear Stress on Armor Layer Thickness Under Steady Uniform Flow

The armor layer is essential for maintaining stability on riverbed surfaces. This layer forms when bedload sediment moves until the bed's surface erodes, resulting in a stable layer that reaches an equilibrium state where no further sediment transport occurs. Therefore, the objective of this study is to investigate the effect of grain size and shear stress on armor layer thickness using evenly mixed sand and gravel with five different grain size variations. The research methodology consists of laboratory experiments and optimization analysis. The main instrument used is a sediment-recirculating flume constructed from plexiglass, measuring 10, 0.60, and 0.45 m in length, width, and height, respectively. Bed slope varies across gradients of 1%, 1.4%, 1.8%, 2.2%, and 2.6%. The constant flow rate is set at capacities of 25 l/s, 30 l/s, 40 l/s, and 45 l/s. The results show the consistent behavior of the channel bed surface under different flow rate variations. Meanwhile, the variables affecting armor layer thickness are the uniformity coefficient (Cu), the difference in shear stress on the bed surface (τo-τc)/τc), beds shear stress, and the critical shear stress of the sediment grain. The primary novelty of this research is a formula to determine armor layer thickness. It showed that both shear stress and the proportion of sand-to-gravel materials play significant roles in the armoring process and subsequent changes in the riverbed. Doi: 10.28991/CEJ-2023-09-11-012 Full Text: PDF

Study on the effect of grain size on the microstructure evolution of Q345 steel plate under high-speed impact

This study used a two-stage light gas gun to launch reactive fragments at high speeds into steel plates with different grain sizes (large and small). In addition, utilizing material characterization technologies like SEM, EBSD, and TEM, the microstructure evolution of steel plates with varying grain sizes was measured and analyzed both before and after impact. The results indicate that small-grain steel plates are more prone to intergranular or transgranular crack propagation, and they produce more macroscopic and microscopic cracks on the perforated surface under high-speed impact than large-grain steel plates. At the grain boundaries of both large and small grains of steel plate, as well as high-density dislocations, the impact process produces a significant number of minor angles with local misorientation ranging from 2 to 10°. A small-grain steel plate has an obvious grain boundary-strengthening effect. Small grains are more likely than large grains to cause changes in the crystal structure of BCC-HCP close to the perforation, and some grains form a lot of nanoscale elongated structures with the same crystal structure as the matrix. The interaction between dislocations or the emission of a large number of dislocation cells from grain boundaries may occur within some of the larger grains. The study's findings, which are illustrated in this article, can be used as a reference to understand how grain size influences the steel plates' microstructure changes after impacts.

Investigation of dissimilar metal (stainless steel and copper) joining and the effect of offsetting and other welding parameters

Dissimilar metal joining without additional preparation like preheating and grooving using conventional arc welding processes. The challenges related to dissimilar joints are overcome by using proper heat distribution according to the heat requirement of different plates. In the present study, GTAW is used to join SS and Cu, mode of joining is welding-brazing mode on the SS side. The heat distribution is done by offsetting the arc towards the Cu side because of the high thermal diffusivity of Cu compared to stainless steel (SS). For the complete joining, the 2nd pass is done without offset. A “beach” of unmixed Cu metal along the Cu fusion line and “peninsula” of an unmixed SS in the weld metal is observed in the microstructure. The grain size variation is observed in the different zones of the weldment due to the segregation of SS particles in weldment. The joint integrity is analyzed with an optical microscope image of the bead, and the detailed analysis of weldment is done using FESEM images in BSD mode. From the microstructure porosity and Cu, penetration is observed in the SS side mushy zone. The microhardness of the weld bead is utilized to see the effect of grain size and amount of SS particles on the mechanical property of weldment in the different zone of the weld bead. The tensile test is conducted to study the joint property of the test coupon. The joint strength of Joint-7 is 225 MPa and percentage elongation is 17 percent, efficiency obtained is around 85 per cent of the Cu plate.

Grain-size effect on Cr3+ and F-centres photoluminescence in nanophase MgAl2O4 ceramics

Photoluminescence (PL) spectroscopy of transparent MgAl2O4 spinel ceramics with grain size between 100 and 300 nm was studied at 7 K temperature in the near-IR-VUV range of spectrum with synchrotron radiation excitation. The PL spectra were composed of optical transitions from spatially different regions of the ceramics, which analysis evidenced grain size effect on the emission line-shapes and intensities. In particular, emission of impurity Cr3+ ions, being structured in the crystalline bulk, became broad-band in the grain boundary regions, which was associated with respectively strong and weak local crystalline fields. It was observed that (i) excitons and F centres transfer energy to Cr3+ and (ii) Cr(2Eg)/Cr(4T2g) and F-centres/Cr3+ PL intensity ratios underwent a linear dependence on the grain size.