Effect Of Grain Size Research Articles

Effect of WC particle size on the microstructure and mechanical properties of Ni–Co coarse grain cemented carbide

AbstractThe effect of different WC grain size additions on the microstructure and grain distribution of Ni–Co coarse crystalline cemented carbide was studied. And then the effect of grain distribution on the mechanical properties of cemented carbide was discussed. The effect of WC grain size on the grain size and coherency of cemented carbide was analyzed by microstructure. And the distribution of grains in the microstructure was investigated by the truncation method. The addition of fine (1.1–1.4 μm), medium (2.3–2.7 μm), and coarse WC (5.6–6.0 μm) particles can increase the nucleation rate of WC grains in the bonded phase. And the higher grain growth driving force can produce the theoretical limitation of nucleation and inhibit the coarsening of WC grains to a certain extent. The WC grain size has an insignificant effect on the frequency of the occurrence of super‐coarse grains in coarse crystalline cemented carbide. The average grain size and super coarse grains in microstructure gradually decrease, which promotes the improvement of transverse rupture strength. The increase of the adjacent degree and the decrease of the mean free path reduce which is beneficial to the improvement of the corrosion resistance of the alloy. The best overall performance of the alloy is achieved when fine‐grained WC is added.

Effect of Austenite Grain Size on Phase Transformation and Q&P Design for a Commercial CMnSi Steel

Effect of Austenite Grain Size on Phase Transformation and Q&P Design for a Commercial CMnSi Steel

Effect of Initial Grain Size on Microstructure and Mechanical Properties of In Situ Hybrid Aluminium Nanocomposites Fabricated by Friction Stir Processing

Friction stir processing (FSP) offers a unique opportunity to tailor the microstructure and improve the mechanical properties due to the combination of extensive strains, high temperatures, and high-strain rates inherent to the process. Reactive friction stir processing was carried out in order to produce in situ Al/(Al13Fe4 + Al2O3) hybrid nanocomposites on wrought/as-annealed (673 K) AA1050 substrate. The active mixture of pre-ball milled Fe2O3 + Al powder was introduced into the stir zone by pre-placing it on the substrate. Microstructural characterisation showed that the Al13Fe4 and Al2O3 formed as the reaction products in a matrix of the dynamically restored aluminium matrix. The aluminium matrix means grain size was found to decrease markedly to 3.4 and 2 μm from ~55 μm and 40–50 μm after FSP using wrought and as-annealed substrates employing electron backscattered diffraction detectors, respectively. In addition, tensile testing results were indicative that the fabricated surface nanocomposite on the as-annealed substrate offered a greater ultimate tensile strength (~160 MPa) and hardness (73 HV) than those (146 MPa, and 60 HV) of the nanocomposite formed on the wrought substrate.

Role of grain size and shape on undrained monotonic shear, liquefaction, and post-liquefaction behaviour of granular ensembles

This paper presents a fundamental study to explore the independent effects of grain size and shape on the pre-liquefaction, liquefaction, and post-liquefaction shearing behaviour of granular ensembles through a series of multi-stage constant volume simple shear tests. Three different granular materials (glass ballotini, river sand, and manufactured sand) of three different sizes (fine, medium, and coarse) with distinct shape descriptors were chosen for the study. Shape parameters of the granular materials, including roundness, sphericity, regularity, and angularity, and their grain level kinematic behaviour were determined from the microscopic images using image analysis algorithms. Experiments were carried out on reconstituted specimens prepared at different relative densities of 15, 30, and 45%, and the results were interpreted in the light of the critical state framework. Undrained monotonic shear tests showed that ensembles with similar grain shapes exhibit a unique critical state line (CSL) and also exhibit a unique phase transformation line (PTL), irrespective of the grain size. However, ensembles with different grain shapes exhibited different CSLs and different PTLs. Irrespective of grain shape, an increase in grain size increased the liquefaction resistance because of an increase in the tendency for dilation. Irrespective of grain size, an increase in particle angularity and irregularity increased the liquefaction resistance due to an increase in the interlocking tendency at grain contacts. Grain size and shape significantly affected the post-liquefaction shear strength of the granular ensembles. The post-liquefaction initial and secondary shear moduli were found to be highly dependent on the grain size and shape.

How grain size influences hydrocarbon generation and expulsion of shale based on Rock-Eval pyrolysis and kinetics?

The differences between the Rock-Eval pyrolysis results of powder and grain samples have attracted wide attentions. Grain samples show lower hydrocarbon yield and different composition of the products. However, the effect of grain size on hydrocarbon generation and expulsion has not yet been quantitatively evaluated. In this study, we prepared each grain into a regular column with precise geometric parameters such as diameter, height, surface area, and volume, which is defined as an independent unit of hydrocarbon generation and expulsion. For comparison, a powder sample corresponding to each grain sample is collected simultaneously during the preparation process. The grain samples are used to simulate the mass of hydrocarbons expelled, while the powder samples are used to simulate the total mass of hydrocarbon generated. Our results show significant differences between the grain samples and the powder samples. All powder samples have a higher expulsion of free hydrocarbons (S1) than grain samples, and almost all grain samples have a higher expulsion of pyrolysis hydrocarbons (S2) than powder samples when the diameter of the grains is smaller than 3 mm. Temperature controls hydrocarbon generation, but grain size retards hydrocarbon expulsion. The influences of the “carry-over” phenomenon, oil adsorption and nanopore confinement are enhanced by grain size, which retards and inhibits hydrocarbon expulsion. Some free hydrocarbons (S1) cannot be expelled from the grain samples at 300 °C. Parts of the retained free hydrocarbons (S1) further cracked into small molecules, which can be expelled and detected as pyrolysis hydrocarbons (S2) at 300–650 °C. Four new parameters were proposed to quantify these influences, namely the S1retained, the S2extra expulsion, the HI difference parameter, and the TOC difference parameter. Diameter is more closely related to hydrocarbon expulsion rather than height. For grain samples, HI increases and TOC decreases with increasing diameter. Activation energies for hydrocarbon generation ranges from 43 to 67 kcal/mol for powder samples, while activation energies for grain samples are almost concentrated in 54–55 kcal/mol, indicating a high expulsion threshold for grain samples. As the grain diameter increases from 1.74 to 5.24 mm, the transformation ratio decreases and the generation rate increases, indicating that the grain size delays the expulsion of hydrocarbon. This laboratory simulation provides some new results to better understand the hydrocarbon generation and expulsion of shale rock under natural conditions.

Hydrogen Embrittlement Mechanism of Ultrafine-grained Iron with Different Grain Sizes

To investigate the effect of grain sizes on hydrogen embrittlement of 4N-purity iron, miniature tensile tests were conducted after hydrogen charging for the ultrafine-grained specimens produced by high-pressure torsion and subsequent annealing. Hydrogen embrittlement indexes defined from reduction of area were increased with decreasing grain size, and shear-type fracture occurred with fine dimples on the fracture surface of the diagonally raptured tensile specimen with a smaller grain size. The formation and growth of microvoids at triple junctions of grain boundaries ahead of propagated cracks were responsible for such earlier shear-type fracture because necking between adjacent microvoids more likely and extensively occurred. In the specimens with larger grain sizes or without hydrogen charging, on the other hand, local coalescence and growth of microvoids were predominant due to longer distances between triple junctions, resulting in void coalescence-type fracture with coarser dimple patterns. Therefore, hydrogen atoms introduced by hydrogen charging are considered to enhance the formation of deformation-induced vacancies in ultrafine-grained iron, resulting in shear-type fracture with finer dimple patterns.

Influence of hydrogen on the hydraulic fracture behavior of a 42CrMo4 steel welds: Effect of the prior austenite grain size

The influence of hydrogen on the mechanical behavior of a quenched and tempered 42CrMo4 steel has been evaluated by means of high internal pressure fracture tests carried out on hydrogen precharged notched cylindrical specimens. The notched cylindrical specimens were precharged in a 1 M H2SO4 + 0.25 g/l As2O3 solution for 3 h with 1.2 mA/cm2. Hydraulic fracture tests were performed at different loading rates. Hydrogen embrittlement resistance increased with grain size refinement although the fine grained specimen had a higher hydrogen content than the coarse grained one. Fractographic analysis showed hydrogen enhanced decohesion fracturewas less pronounced with decreasing grain size. Hydrogen embrittlement susceptibility is discussed in terms of the prior austenite grain size (PAGS) and the operative fracture mechanisms.

Pine-to-Bioenergy: Potential of pine sap as adhesive and pine flower biomass waste in the production of biobriquettes

Pine-flower biomass waste is abundant, but its utilization is still lacking. This research converts pine-flower waste into biobriquettes by using pine resin adhesive. This study aims to identify the effect of pine resin adhesive concentration and the effect of grain size on the quality of the resulting biobriquettes. The production of biobriquettes begins by processing pine flower waste into biochar using the pyrolysis method at 400 °C. Biochar from pinecones was ground and sieved into sizes (250, 500, and 750 µm). Then proximate analysis (moisture content, ash content, volatile matter, fixed carbon), and heating value were performed. Making biobriquettes using pine resin adhesive with different concentrations (5, 10, and 15%) of the total mixture According to the results, the ideal grain size was 750 m, the adhesive concentration was 15%, and the moisture content, ash content, volatile matter content, fixed carbon content, and heating value were all respectively 2.23%, 4.51%, 30.23%, 70.04%, and 23.34 MJ/kg, and the longest flame was also determined to be 0.0250 g/sec. All of them comply with universally accepted biobriquette standards (Indonesian National Standard 01–6235–2000), Japanese, English, and ISO 17225. Biobriquettes have potential applications in bioenergy products. Investigation of the economic feasibility of biobriquette production seen from Profit on Sales is 26.43%, Rate on Investment is 34.00%, Pay Out Time is 2.47 years, and Break Event Point is 49.22%.

Effect of rotation speed on microstructure and mechanical properties of bobbin tool friction stir welded T2 copper

In this study, the effects of different rotation speeds (600, 800, 1000 and 1200 rpm) on the microstructure, mechanical properties, electrochemical corrosion properties and resistivity of T2 pure copper bobbin tool-friction stir welded joint at a fixed welding speed of 50 mm/min were investigated. The results show that the grain size of the microstructure of welded joints with different rotational speeds has a large difference, and the recrystallization mode are continuous dynamic recrystallization, discontinuous dynamic recrystallization and geometric dynamic recrystallization. The fracture location is at the thermo-mechanically affected zone of the retreating side with the largest difference in microstructure gradient and grain size. Due to the combined effect of grain size and low angle grain boundaries distribution, the welded joints at 1000 rpm have higher tensile strength, elongation, microhardness values, and electrical conductivity, and the welded joints at 600 rpm have higher yield strength. The impedance curve and polarization curve fitting results in electrochemical corrosion are consistent, and the corrosion is mainly intergranular corrosion and full-scale corrosion, and has good corrosion resistance at 600 rpm and 1000 rpm rotational speed.

Grain-size effects of TiC on mechanical properties in diamond/TiC combinations: A molecular dynamics exploration

Epitaxial growth of titanium carbide (TiC) layer is vital for single-crystalline diamond (SCD) to ensure wettability when brazed with metals, however, how TiC grain size affects the mechanical behavior of SCD/TiC interfaces remains unclear. Herein, molecular dynamics simulations were performed to investigate the tensile properties of SCD/TiC combinations with different TiC in-plane grain sizes (d). The results show that d influenced both the elastic and plastic deformation, ascribing to the specific grain boundaries (GBs) network. The Young's modulus of the combinations was found to increase with the increase of d. After yielding, TiC{111} partial dislocations emitting from both the GBs and interfaces were observed to cross GBs or pile-up at GBs, among which d had a negligible effect on the planar-slip induced relaxation. Furthermore, it was found the interaction of dislocation-GB and dislocation-dislocation made a great contribution to strain-hardening. For the combinations with d < 8 nm, it was strengthened by piling-up dislocation at GBs, whereas for the larger d, it was dominated by intragranular dislocation entanglement. Overall, strain localization and micro crack took place at the interfaces due to the absence of plastic mechanism to accommodate strain gradient. This work provided an atomistic insight into the mechanical behaviors in SCD/TiC combinations, offering guidance for interfacial design to improve the mechanical performances in diamond devices.

The microstructure evolution and the effect of grain size, temperature, and TiBw on the deformation mechanism of TiBw/TA15 composites during high temperature deformation

In this paper, the deformation mechanism and microstructure evolution of TiB whisker (TiBw)/TA15 composites during high temperature (HT) rolling and tensile were investigated. The effects of grain size and temperature on the HT mechanical properties, deformation mechanism, and strengthening/softening effects were studied. The influence of temperature on the TiBw fracture mode was analyzed within the range of 600–750 °C. The results show that grain boundary slip (GBS) and dislocation motion were more prone to promote the occurrence of discontinuous dynamic recrystallization (DRX) and continuous DRX, respectively. TiBw could withstand higher forces and fractured when the orientation was consistent with the loading direction and at a lower temperature, while it was easier to debond with temperature increasing. TiBw/TA15 composites had Hall-Petch (H–P) and inverse H–P (I–H–P) regions in the range of 4.5–7.0 μm with a critical grain size of 5.8 μm under HT tensile at 600 °C and 0.001 s−1. The grain boundary strength decreased with the temperature increased, which caused the transformation of the deformation mechanism and the H–P/I–H–P regions at different temperatures. The deformation was dominated by GBS when the strength of grain boundary was lower than that of intracrystalline. The deformation mechanism transformation temperature of TiBw/TA15 composites was 700 °C under HT deformation at 0.001 s−1.

Effects of grain size, texture and grain growth capacity gradients on the deformation mechanisms and mechanical properties of gradient nanostructured nickel

Effects of grain size, texture and grain growth capacity gradients on the deformation mechanisms and mechanical properties of gradient nanostructured nickel

Effect of grain size on critical twinning stress and work hardening behavior in the equiatomic CrMnFeCoNi high-entropy alloy

While the impact of grain boundary strengthening on dislocation slip is particularly effective in the equiatomic CrMnFeCoNi high-entropy alloy (HEA), its effect on deformation twinning remains unclear. To better understand how a grain size reduction affects the onset of deformation twinning and the work hardening behavior of the CrMnFeCoNi HEA, chemically homogeneous, nearly untextured, and single-phase face-centered cubic alloys with different grain sizes were investigated. Tensile tests were performed at 293 and 77 K and interrupted at different strains followed by systematic transmission electron microscopy observations. In all cases, deformation twinning occurs above a critical stress that is independent of temperature. This uniaxial twinning stress decreases from ∼785 to ∼615 MPa when the grain size increases from 6 to 242 µm, respectively, following the Hall-Petch equation. The resistance of the grain boundaries against slip and twinning is found to be nearly identical (Hall-Petch slope: ∼500 MPa·µm1/2) but the twinning stress extrapolated to infinite grain size (592 ± 30 MPa) is larger than the uniaxial friction stress against dislocation glide at 293 and 77 K (130 and 320 MPa, respectively). Deformation twinning at 77 K is found to sustain a high work hardening rate when it is triggered in a plastic regime dominated by planar glide of dislocations. In contrast, it does not significantly contribute to the work hardening rate at 293 K when dislocation cells have already formed and the dislocation mean free path is smaller than the mean twin spacing.

Influence of nanoparticles on the compressive rate-sensitivity of magnesium alloys

A numerical model to describe the onset of tension twining in magnesium alloys, which incorporates the influence of nanoparticles and strain rate, is proposed. This model is employed in conjunction with crystal plasticity, to study the compressive flow stress of magnesium alloys at strain rates from 10−3/s to 103/s. The results show negative strain rate sensitivity (SRS) for the flow stress during the initial phase of plastic deformation, which is consistent with experimental results. The influence of nanoparticles on restraining twinning is demonstrated to diminish with strain rate, and regarded as the underlying mechanism for the negative SRS. The combined effects of nanoparticle presence, strain rate, grain size and initial texture on the compressive flow stress of nanoparticle-reinforced magnesium alloys, are investigated using the proposed model. Grain size and texture are shown to affect the SRS significantly, and a critical grain size (i.e., ∼2 µm) is identified from the simulations. When grains are smaller than this critical value, a negative SRS is observed. When the initial texture is changed, the numerical results show a transition from a negative SRS to a positive one.

A study of high cycle fatigue life and its correlation with microstructural parameters in IN713C nickel-based superalloy

IN713C nickel-based superalloy is widely used in the form of turbine blades in the automobile industry. High cycle fatigue (HCF) or very-HCF is one of the major failure modes for the alloy. The significant grain structure/size variations produced during the casting process are supposed to affect its fatigue life. In the present study, IN713C cast bars with different grain structures and grain size were HCF tested under similar stress level (∼300 MPa) at 650 °C. The fatigue life, varying from ∼87,000 to 10 × 106 cycles, mainly determined by the size of porosity and faceting grain. Size of porosity determines the time of initiation of faceting and crack, i.e., the crack initiation stage, which occupies the major part of fatigue life. Smaller pore size leads to delay of faceting and higher fatigue life. Whilst size of facet has profound effects in the crack propagation stage. Smaller facet (grain) size leads to lower crack propagation rate and longer loading cycles, and finally contributes to higher fatigue life. This research revealed the beneficial effect of smaller grain size on fatigue property from the perspective of reducing initial crack propagation rate, which has rarely been reported before.

Grain size distribution does not affect the residual shear strength of granular materials: An experimental proof.

Granular materials are used in several fields and in a wide variety of processes. An important feature of these materials is the diversity of grain sizes, commonly referred to as polydispersity. When granular materials are sheared, they exhibit a predominant small elastic range. Then, the material yields, with or without a peak shear strength depending on the initial density. Finally, the material reaches a stationary state, in which it deforms at a constant shear stress, which can be linked to the residual friction angle ϕ_{r}. However, the role of polydispersity on the shear strength of granular materials is still a matter of debate. In particular, a series of investigations have proved, using numerical simulations, that ϕ_{r} is independent of polydispersity. This counterintuitive observation remains elusive to experimentalists, and especially for some technical communities that use ϕ_{r} as a design parameter (e.g., the soil mechanics community). In this Letter, we studied experimentally the effects of polydispersity on ϕ_{r}. In order to do so, we built samples of ceramic beads and then sheared these samples in a triaxial apparatus. We varied polydispersity, building monodisperse, bidisperse, and polydisperse granular samples; this allowed us to study the effects of grain size, size span, and grain size distribution on ϕ_{r}. We find that ϕ_{r} is indeed independent of polydispersity, confirming the previous findings achieved through numerical simulations. Our work fairly closes the gap of knowledge between experiments and simulations.

A microscale constitutive model for thin stainless steel sheets considering size effect

This research is focused on the modeling of the deformation behavior of thin austenitic stainless steel sheets to consider size effect in microscale. First, the material with two different thicknesses is heat treated to obtain different grain sizes, and then they are characterized by the uniaxial tensile tests. The experimental results show that flow stress decreases with the reduction of the sheet thickness and the increase of the grain size. The decline of the flow stress curve is associated with the decrease of the strength coefficient and increase of the hardening exponent as the plastic deformation is scaled down to the microscale. To better model the behavior of the material in the microscale, a new constitutive model is proposed based on the Swift equation to take into account the geometry and grain size effect. This model is also defined in the finite element model of the uniaxial tensile test. It is found that the flow stress curve predicted by the proposed constitutive model shifts down by the decrease of the number of grains across the thickness, which are consistent with the experimental results. In addition, the finite element model with the proposed constitutive model predicts accurately the deformation load in the uniaxial tensile tests. It can be concluded that the proposed constitutive model can provide a good description of the flow stress by considering the interactive effect of specimen and grain sizes and can be used in the modeling of material behavior in microforming processes.

Grain size effect on near-threshold fatigue crack propagation in CrMnFeCoNi high-entropy alloy fabricated by spark plasma sintering

High-entropy alloys (HEAs), which comprise five or more elements and have an equiatomic composition, are known to exhibit superior static strength and ductility. The present study evaluated the effect of grain size on fatigue crack propagation in a CrMnFeCoNi alloy comprising a single-phase solid solution with a face-centered-cubic structure and fabricated by spark plasma sintering. Stress intensity factor-K decreasing tests were conducted with force ratios from 0.1 to 0.8, and no noticeable differences in fatigue threshold were observed between specimens having fine-grained and coarse-grained structures at relatively low force ratios. This result was attributed to fatigue crack reflection inside coarse grains. The magnitude of crack closure was high even in the fine-grained specimens and exceeded that of austenitic stainless steel having the same fine grains. Thus, the effect of grain size on the threshold stress intensity factor range was not significant in the present CrMnFeCoNi alloy, in contrast to the behavior of austenitic stainless steels.

Effect of Grain Size on the Dynamic Flexural Tensile Strength of Granite: Insight from GBM3D-PFC Simulations

For reproducing the heterogeneous structure of granites, a novel three-dimensional grain-based model based on particle flow code (GBM3D-PFC) was proposed in this paper. Then, dynamic semicircular bending tests under different impact velocities were conducted on the numerical samples with different grain sizes by the coupled split Hopkinson pressure bar system. On the one hand, with increasing grain size, the dynamic flexural tensile strength and proportion of transgranular cracks increase, while the total crack number decreases. On the other hand, as the loading rate increases, the dynamic flexural tensile strength and transgranular crack proportion increase. Based on the GBM3D-PFC, the evolution of the load applied to the sample can be reasonably described. The relationship between the contact force network and the sample’s strength can be established. The microcracking behavior obtained by numerical simulations can be used to explain the variation of the macroscopic mechanical parameters.

Grain size effect on direct conversion low-dose X-ray sensing nature of nanocrystalline silver bismuth sulfide

Nanocrystalline materials have garnered significant recognition in the scientific and research community for developing X-ray sensors. The applicability of bismuth-based binary and ternary compounds has been extensively studied in X-ray imaging and cancer therapy applications owing to their high attenuation. Among the binary and ternary compounds of bismuth, the n-type semiconductor silver bismuth sulfide (AgBiS2) was studied for the detection of X-rays at lower doses, based on its total attenuation (μ = 3.07 cm2 g−1 at 70 keV), density (ρ = 7.02 g cm−3), and bandgap (Eg = 1.21 eV). The effect of grain size on X-ray sensing performance was examined to validate the effective size required for maximum attenuation of X-rays and successful extraction of induced mobility carriers. X-ray sensors with four different AgBiS2 grain sizes were cast on interdigitated electrodes (IDEs) and subjected to different doses of X-rays at 2 V bias to study its dose-dependent X-ray sensing nature using an intra-oral (70 kVp-AC) X-ray machine. AgBiS2-based X-ray sensor exhibited the highest sensitivity of 20.13 μC mGy−1 cm−3 with the lowest Noise-equivalent dose ratio (NED) of 0.08 μGy Hz−0.5, 0.20 mGy detection limit and a response time of 0.12 s. This outcome validates that AgBiS2 can be applied as a potential replacement for perovskites in direct X-ray detection.