Grain Growth Rate Research Articles

Corn Grain Weight: Dependence upon Nitrogen Supply and Source-Sink Relations

From a yield component perspective, final grain yield in corn (Zea mays L.) is the result of the number of grains per unit area and their final grain weight. The understanding of grain weight parameters, the rate and duration of grain growth, is critical to improve our rational design of management practices and breeding strategies. In this study, we attempted to determine the effect on grain weight and grain-filling parameters of source-sink modifications (i.e. the amount of assimilates available per grain) during linear grain fill under contrasting levels of nitrogen (N) fertilization in two commercially available US corn hybrids. Two hybrids (3394 and P1197) were evaluated under zero-N and two fertilized strategies at a N rate of 194 lb/a. Four levels of source-sink manipulations were implemented: 1) control; 2) reduced sink, with partially restricted pollination; 3) reduced source, with partial defoliation; and 4) both reduced sink and source. Final grain weight was significantly affected by N management and by modifications of the source-sink ratio during grain-filling. In addition, variations in grain filling rate were responsible for the major changes in grain weight. Results from this study suggest that grain weight is very responsive to reductions in the source capacity during grain-filling, but only marginally responsive to increments in the assimilate availability per seed during grain-filling.

ЖҰМСАҚ БИДАЙ СОРТТАРЫНАН АЛЫНҒАН МУТАНТТЫ ЛИНИЯЛАРДЫҢ ДАМУ ТИПІНЕ ГЕНЕТИКАЛЫҚ ТАЛДАУ

Among cereals, a special place is occupied by wheat as the main food of humanity and in improving the country's economy. The main task of breeding is to produce valuable wheat varieties that are stable to the unfavorable external environment of various natural climatic zones of Kazakhstan, consisting of a combination of valuable features. The prospects for the use of mutants in the process of hybridization are reflected in the achievements of world and domestic selection. The effect of various solutions of chemical compounds on the plant was observed from the first days during the growth of wheat sprouts. The growth of the first sprout of seeds treated with a certain solution of cadmium chloride and zinc chloride - 0.01%, the activity of cell division and structural disorders of chromosomes were manifested by variability in the varieties Kazakhstani3, Shagala, Zhenis and Lutescens 32. When treating dry wheat grain with a concentration of 0.1% cadmium chloride, it brought the growth of the Sprout to a lethal state, 0.01% inhibited the growth of the Sprout for 4 days, and in a 0.001% solution, the growth rate of the control grains was the same. On the contrary, a 0.1% vertical solution of zinc chloride inhibited the growth of the Sprout for 1 Week, 0.01% for three days. Among the studied concentrations, a 0.01% solution of cadmium chloride inhibited the growth of sprouts, causing chromosomal aberrations and morphological variability in cell division. Therefore, a concentration of 0.01% of cadmium salt was obtained as an optimal concentration to expand the limits of variability in wheat. In this regard, in our study, it was found that a 0.01% solution of cadmium chloride is an effective concentration that expands the limits of variability in wheat. The effect of this amount of solution leads to morphological changes in the plant (Binding of the stem, elongation of the earlobe, increase in the number and weight of grains in the headlobe, increase in the weight of 1000 grains, etc.), and changes in the characteristics of the M1 - M4 offspring are constantly inherited. Mutant lines L1, L2 and L3 differ in valuable breeding characteristics under the influence of a 0.01 percent solution of cadmium salt were obtained for the Kazakhstanskaya 3 and Shagala varieties. A genetic analysis of the type of development of these altered lines was carried out, as a result of which a long (16 cm) dense ear (0.80) changed from the Gull variety to a prismatic plant of the control variety (0.50), as a result of hybridization, its summer type (from the vrn gene) to the autumn type (Vrn gene). As a result of the study, Kazakhstanskaya 3, Kazakhstanskaya mutant 3 varieties contain the genes Vrn 1, Vrn 3. Well, it was found that Shagala varieties consist of the genes Vrnl, Vrn2. Varieties containing the genes Vrn1, Vrn3 show rapid maturation. However, they differed from each other in the period of intoxication.

Improved strength and ductility of AZ31B Mg alloy sheets processed by accumulated extrusion bonding with artificial cooling

In this study, accumulated extrusion bonding (AEB) process with application of artificial water cooling was successfully performed to fabricate fined-grains AZ31B Mg alloy sheets at 150°C, 200°C and 250°C. The resultant microstructure and mechanical properties are systematically investigated. It reveals that the processing temperature has an important effect on the microstructural evolution during extrusion. During AEB process at 150°C and 200°C, {10–12} tensile twinning was activated at early stage of extrusion, and subsequently continuous dynamic recrystallization (CDRX) occurred and dominated the further deformation. However, for the sample extruded at 250°C, hardly any twins can be observed, and new fined dynamic recrystallized grains were found along grain boundaries. Artificial cooling was utilized to reduce the rate of grain growth out of the extrusion die, resulting the grains significantly refined from 11 µm to 2.5 µm. Local high dislocation density region was also observed in the microstructure of sample processed at 150°C in artificial cooling condition, and the degree decreased with the processing temperature increase. The results summarized from tensile tests indicated that due to the grain refinement the strength and ductility was significantly enhanced (YS of 186 MPa vs. 145 MPa, UTS of 391 MPa vs. 336 MPa and FE of 31.5% vs. 24.5% compared with the as-received sample). Subsequently, annealing treatment at different temperatures was applied to eliminate the high dislocation density. The sample annealed at 200°C exhibited the best comprehensive mechanical property with YS of 179 MPa, UTS of 390 MPa and FE of 33.0%. As the annealing temperature increasing, the dislocation density was reduced by static recrystallization (SRX) and grain growth, leading to a decreased strength and ductility.

Dust Growth by Accretion of Molecules in Supersonic Interstellar Turbulence

Abstract We show that the growth rate of dust grains in cold molecular clouds is enhanced by the high degree of compressibility of a turbulent, dilute gas. By means of high-resolution (10243) numerical simulations, we confirm the theory that the spatial mean growth rate is proportional to the gas-density variance. This also results in broadening of the grain-size distribution (GSD) due to turbulence-induced variation of the grain-growth rate. We show, for the first time in a detailed numerical simulation of hydrodynamic turbulence, that the GSD evolves toward a shape that is a reflection of the gas-density distribution, regardless of the initial distribution. That is, in case of isothermal, rotationally forced turbulence, the GSD tends to be a lognormal distribution. We also show that in hypersonic turbulence, decoupling of gas and dust becomes important and that this leads to an even further accelerated grain growth.

Rates of Olivine Grain Growth During Dynamic Recrystallization and Postdeformation Annealing

AbstractWe performed deformation and grain growth experiments on natural olivine aggregates with olivine water contents (COH = 600 ± 300 H/106 Si) similar to upper mantle olivine, at 1000–1200°C and 1,400 ± 100 MPa confining pressure. Our experiments differ from published grain growth studies in that most were (1) conducted on natural olivine cores rather than hot‐pressed aggregates and (2) dynamically recrystallized prior to or during grain growth. We combine our results with similar experiments performed at 1200–1300°C and fit the data to a grain growth relationship, yielding a growth exponent (p) of 3.2, activation energy (EG) 620 ± 145 kJ mol−1 (570 ± 145 kJ mol−1 when accounting for the role of temperature on water content), activation volume (VG) ~5 × 10−6 m3 mol−1, and rate constant (k0) 1.8 × 103 mp s−1. Our EG is within uncertainty of that predicted for dislocation creep of wet olivine (E* = 480 ± 40 kJ mol−1). Grain size in strain rate‐stepping samples adjusted to the olivine piezometer within 1.3–7.9% strain. The active grain boundary migration processes during deformation and dynamic recrystallization affect the kinetics of postdeformation grain growth, as grain boundary migration driven by strain energy density (ρGBM) may delay the onset of grain growth driven by interfacial energy (γGBM). We compared our postdeformation grain growth rates with data from previously published hydrostatic annealing experiments on synthetic olivine. At geologic timescales, the growth rates are much slower than predicted by the existing wet olivine grain growth law.

Tracing the recrystallization of warm temper-rolled Fe–6.5 wt% Si non-oriented electrical steel using a quasi in situ EBSD technique

Fe–6.5 wt% Si non-oriented electrical steel is an excellent soft magnetic material due to the low core losses at high frequencies and near-zero magnetostriction. In this study, an Fe–6.5 wt% Si non-oriented electrical steel was processed by hot rolling, warm cross rolling, intermediate annealing, warm temper rolling and final annealing. The evolution of microstructure and microtexture during final annealing was investigated using a quasi in situ EBSD (electron backscatter diffraction) technique. After warm temper rolling, an area on the ND–RD (normal direction–rolling direction) cross section was marked by micro-hardness indents, and the recrystallization of individual grains in this area was traced under EBSD when the annealing time was increased. Due to the differences in the microstructure, texture and stored energy after warm temper rolling, the surface and center regions showed different recrystallization behaviors. The recrystallization of the surface region was essentially initiated by the growth of existing crystallites having lower stored energy than their neighboring areas (essentially no nucleation), while the center region showed both nucleation and grain growth during annealing. The growth rates of individual grains were evaluated with respect to the number of neighboring grains, and they approximately followed the von Neumann–Mullins law of grain growth. The surface region showed a much faster growth rate than the center region. The final texture was dominated by //ND and //ND in both the surface and center regions, due to the preferred growth of these grains.

Influence of Manganese on the Recrystallization Characteristics and Texture Development of Cu-29Zn Alloys

Studies regarding the recrystallization texture of brass alloys are quite complex. Previous experiments showed that the addition of the alloying elements on brass alloys affect the deformation mechanism and texture development. Alloying elements promoted the inhomogeneous deformation and resulted in a heterogeneous microstructure. During annealing, the new grains form around the shear band area and develop the random texture. This research studied the effect of Mn addition on the recrystallization characteristics and texture development of Cu-29Zn alloys. The Cu-Zn-xMn alloys were produced by gravity casting with a dimension of 110x110x6 mm3. The feeding material includes pure Cu, Zn, and Mn. The as-homogenized samples were then cold-rolled with the level of deformation of 70 % and followed by an annealing process at temperatures of 400, 500, and 600°C. Samples characterization includes chemical composition analysis, microstructure observation, hardness testing, and texture measurement. The results showed that the addition of Mn tended to reduce the rate of recrystallization and grain growth. At 70% deformation, Mn addition promoted the formation of brass and Goss texture. The presence of Mn also influenced the formation of recrystallization and annealing texture.

Understanding of adiabatic shear band evolution during high-strain-rate deformation in high-strength armor steel

The microstructural evolution and formation mechanism of adiabatic shear band (ASB) in a high-strength armor steel were investigated using a laboratory-scale split Hopkinson pressure bar, and the results were correlated with the actual ballistic impact behavior. The interrupted dynamic compressive test results reveal that a deformed ASB (dASB) starts to form right after the stress collapse and it develops into a transformed ASB (tASB). In the ballistic impact, wide tASBs form mostly at the perforated surface, and narrower tASBs are branched from the tASB. Very fine equiaxed grains of ∼190 nm in the tASB developed during the dynamic compression indicates that the dynamic recrystallization occurs even in 86.5 μs, and then the grains grow up to 260 nm in 9.5 μs. Rotational dynamic recrystallization mechanism and grain-growth rate model were proposed based on the calculation of temperature rise from a thermo-elasto-plastic finite element method, which provide a reasonable explanation for the formation and growth of fine equiaxed grains during both the dynamic compression and ballistic impact. A linkage of equiaxed subgrains and elongated parent subgrains demonstrates that the equiaxed subgrains did not evolve from nucleation and growth processes but from the sub-boundary rotation. Based on the underlying formation mechanisms and kinetics of ASBs, this study would suggest a reliable method to interpret the ASB formation and associated fracture mechanism during the ballistic impact.

Comparison of Spectra of Grain Boundaries Spontaneously Formed in Cu-Ag and Cu-In Systems

Spectra of grain boundaries existing in the polycrystalline copper-silver system (positive enthalpy of mixing) have been studied in comparison with those of the copper-indium system (negative enthalpy of mixing). Spectra of grain boundaries are formed spontaneously upon an increase in the temperature, occurrence of eutectic and peritectic reactions, and subsequent relaxation of structures in the two-phase solid/liquid region of phase diagrams. It has been shown that the rate of grain growth and the relation between different grain boundary types in the total spectrum depend on the enthalpy of mixing.

Grain Growth Behavior of 0.95(Na0.5Bi0.5)TiO3–0.05BaTiO3 Controlled by Grain Shape and Second Phase

The grain growth behavior of 0.95(Na0.5Bi0.5)TiO3 –0.05BaTiO3 (mole fraction, NBT–5BT) grains was investigated with excess Bi2O3 addition. The powder compacts of NBT–5BT were sintered at 1200 °C for various sintering times and with various amounts of Bi2O3 (0.1, 1.5, 4.0 and 10.0 mol%). When Bi2O3 was added to round-edged cubic NBT–5BT, the grain shape changed to a more faceted cube and the amount of liquid phase increased during sintering. A more faceted cubic grain shape indicates an increase in the critical driving force for appreciable growth of grains. However, obvious abnormal grain growth did not appear in any of the NBT–5BT samples with excess Bi2O3. The amount of liquid phase increased as the amount of Bi2O3 increased. Therefore, the rate of grain growth could be decreased by the increasing the distance for the diffusion of atoms. These observations allowed us to conclude that the growth of Bi2O3-excess NBT–5BT grains is governed by the growth of facet planes via the two-dimensional nucleation grain growth mechanism during changing grain shape and amount of liquid.

Effect of oscillatory pressure on the sintering behavior of ZrO2 ceramic

Zirconia ceramics were prepared by oscillatory pressure sintering (OPS) and hot pressing (HP). The result revealed that OPS could enhance densification compared to HP when sintering temperature was higher than a critical value. The onset temperature for rapid grain growth was found to be same for both techniques. However, rate of grain growth in OPS was lower than that in HP. Furthermore, the result also showed that samples prepared by OPS exhibited higher hardness than those prepared by HP when sintering temperature was higher than the critical value. The improved hardness was solely due to the higher density of the samples prepared by OPS.

Characterization and Grouping of All Primary Branches at Various Positions on a Rice Panicle Based on Grain Growth Dynamics

Grain filling can directly influence rice yield. However, there is limited information on the growth relationship among grains at different positions on the entire panicle during grain filling. In this study, field experiments were conducted in 2014–2015 to compare the growth dynamics of grains at various positions for two rice cultivars (Nongle 1 and Guifeng 2). The results showed that a high similarity and a slow–fast–slow trend of dry-matter accumulation occurred in all primary branches. However, the maximum grain growth rates of the top primary branches were 86% and 44% higher than basal primary branches of Nongle 1 and Guifeng 2, respectively. Similarly, the maximum final grain weights were 32% and 18% greater in the top primary branches than in the basal primary branches of Nongle 1 and Guifeng 2, respectively. In contrast, the active grain filling duration was 1.5 and 1.3 times longer in the basal primary branches than the top primary branches of Nongle 1 and Guifeng 2, respectively. The time to reach the maximum rate of grain growth of the basal primary branches for Nongle 1 and Guifeng 2 was 2.2 and 2.5 times longer than those of the top primary branches, respectively. Based on cluster analysis of growth characteristics of all primary branches, Group I (superior primary-branches) was considered to be the fastest for grain filling and greatest for dry matter weight, followed by Group II (medium primary-branches). The poorest growth occurred in Group III (inferior primary-branches). Therefore, the yield of poor-filling grains at the basal panicle could be achieved primarily by improving the growth of Group III.

Mechanism of Improving Heat-Affected Zone Toughness of Steel Plate with Mg Deoxidation after High-Heat-Input Welding

In the present study, the mechanism of improving HAZ toughness of steel plate with Mg deoxidation after the simulated welding with the heat input of 400 kJ/cm was investigated through in situ observation, characterization with SEM-EDS and TEM-EDS, and thermodynamic calculation. It was found that intragranular acicular ferrite (IAF) and polygonal ferrite (PF) contributed to the improvements of HAZ toughness in steels with Mg deoxidation. With the increase of Mg content in steel, the oxide in micron size inclusion was firstly changed to MgO-Ti2O3, then to MgO with the further increase of Mg content in steel. The formation of nanoscale TiN particles was promoted more obviously with the higher Mg content in the steel. The growth rates of austenite grains at the high-temperature stage (1400~1250 °C) during the HAZ thermal cycle of steels with conventional Al deoxidation and Mg deoxidation containing 0.0027 and 0.0099 wt% Mg were 10.55, 0.89, 0.01 μm/s, respectively. It was indicated that nanoscale TiN particles formed in steel with Mg deoxidation were effective to inhibit the growth of austenite grain. The excellent HAZ toughness of steel plates after welding with a heat input of 400 kJ/cm could be obtained by control of the Mg content in steel to selectively promote the formation of IAF or retard the growth of austenite grain.

Multiphase-field modelling of concurrent grain growth and coarsening in complex multicomponent systems

Phase-field modelling of microstructural evolution in polycrystalline systems with phase-associated grains has largely been confined to continuum-field models. In this study, a multiphase-field approach, with a provision for introducing grain boundary and interphase diffusion, is extended to analyse concurrent grain growth and coarsening in multicomponent polycrystalline microstructures with chemically-distinct grains. The effect of the number of phases and components on the kinetics of evolution is investigated by considering binary and ternary systems of duplex and triplex microstructures, along with a single phase system. It is realised that the mere increase in the number of phases minimises the rate of concurrent grain growth and coarsening. However, the effect of components is substantially dependent on the respective kinetic coefficients. This work unravels that the disparity in the influence of phases and components is primarily due to the corresponding change introduced in the transformation mechanism. While the raise in number of phases convolutes the diffusion paths, the increase in number of component effects the rate of evolution through the interdiffusion, which introduces interdependency in the diffusing chemical-species. Additionally, the role of phase-fractions on the transformation rate of triplex microstructure is studied, and correspondingly, the interplay of interface- and diffusion-governed evolution is elucidated. A representative evolution of three-dimensional triplex microstructure with equal phase-fraction is comparatively analysed with the evolution of corresponding two-dimensional setup.

Integral mean curvature analysis of 3D grain growth: Linearity of dV/dt and grain volume

The volumetric growth rate of individual grains has been found to be directly proportional to the individual grain volume V as dV/dt = β(Vo-V). This simple result is explained through the DeHoff relationship dV/dt = −kMs between growth rate and the integral mean curvature of individual grains, Ms, combined with the experimentally observed relationship between Ms and grain volume, Ms = α(Vo-V). These relationships have now been observed consistently in both 3D grain growth simulations and experiments. This paper describes the relationships among these kinetic and geometric grain characteristics that provide this simple description of 3D grain growth.

Kinetic Monte Carlo simulation of sintering behavior of additively manufactured stainless steel powder particles using reconstructed microstructures from synchrotron X-ray microtomography

Abstract In this study, the sintering behavior of additively manufactured stainless steel powder particles is simulated using a three-dimensional kinetic Monte Carlo (kMC) model. The initial microstructure of powder particles is reconstructed using micro-CT images from the Argonne National Laboratory’s synchrotron X-ray microtomography facility. Using the model, the sintering characteristics of the powder, including its relative density, neck growth, and grain coarsening, are quantitatively analyzed. Sintering temperature directly affects the rate of densification and grain growth and coarsening. Higher temperature results in faster densification and grain growth. Additionally, the relationship between grain coarsening and densification is analyzed. It is observed that when the relative density is below 0.70, the powder particles undergo densification; whereas when the relative density is higher than 0.70, grain coarsening is the main mechanism.

Phase field modeling of stressed grain growth: Effect of inclination and misorientation dependence of grain boundary energy

The effect of anisotropic grain boundary energy on the kinetics of stressed grain growth is investigated by two-dimensional phase field simulations. The simulations are performed for a two-dimensional representative volume element of polycrystalline copper with elastic cubic symmetry under both uniaxial elongation and shear loading with elastic strains in the order of a few thousandths. The Read-Shockley relation for the misorientation–dependence and the cubic symmetry for the inclination–dependence of grain boundary energy are assumed. The simulation results have generally shown that the misorientation–dependent anisotropy, compared to the inclination–dependent anisotropy, significantly affects the evolution of microstructure and texture during stressed grain growth. Particularly, the misorientation–dependent anisotropy of grain boundary energy results in (i) the elongated morphology of grains in the evolved microstructure; (ii) the aggregation of grains with similar orientations in the evolved microstructure; (iii) the strengthening of lower–misorientation angle grain boundary segments; and hence (iv) decelerating the overall rate of stressed grain growth and texture evolution and (v) decelerating stress relaxation under constant–strain loading. These results are based on the assumption that the isotropic grain boundary energy is equal to the high angle grain boundary energy of the misorientation–dependent grain boundary energy and the inclination–dependent grain boundary energy varies sinusoidally around the isotropic grain boundary energy.

Grain boundary curvature based 2D cellular automata simulation of grain coarsening

2D grain coarsening CA models based on the grain boundary curvature models of Kremeyer and Mason were established. The parameters needed in the two models were obtained via different methods. Then, the grain growth kinetics, grain size distribution, topological aspects and individual grain growth kinetics were deeply studied with these two curvature based CA models. The grain growth exponents of both models were close to 2 which was a constant derived from theory and verified experimentally. The Weibull function has a better fitting for the simulation results than the other analytical distributions proposed by Hillert and Rios. The topological aspect of both models was analyzed with the Aboav-Weaire relation. Excellent agreements between the simulation results and the Aboav-Weaire relation were obtained. At last, a new relationship was proposed to calculate the growth rate of individual grains.

A comparison study of dislocation density, recrystallization and grain growth among nickel, FeNiCo ternary alloy and FeNiCoCrMn high entropy alloy

The microstructural evolutions in terms of dislocation density, annealing twin density as well as with respect to microstructural changes due to recrystallization and grain growth were investigated in pure Ni, equiatomic FeNiCo alloy, and FeNiCoCrMn high entropy alloy (HEA) during the thermomechanical process. All samples were single phase and showed a face-centered cubic (FCC) lattice structure. This was maintained during thermomechanical processing comprising of cold swaging by 85% reduction of cross-sectional area and subsequent annealing at 800 °C. The level of dislocation accumulation during cold swaging increased with the number of constituent elements. The FeNiCoCrMn HEA obtained the highest dislocation density, followed by the FeNiCo and Ni, respectively. After the annealing at 800 °C for 0.5 h, all samples achieved the large fraction of recrystallized grains with minor fraction of substructured grains and no deformed grain. The FeNiCoCrMn HEA obtained the smallest recrystallized grain size (∼5 μm) after the annealing at 800 °C for 0.5 h. This could be a result of the highest dislocation density generated during cold swaging prior to the annealing. The prolonged annealing at 800 °C for up to 24 h led to a grain growth for all the samples, however, at different growth rates. The FeNiCoCrMn HEA revealed the lowest rate of grain growth, but the microstructural changes during the annealing were not significantly different between the FeNiCo and Ni samples. Besides the effect of the number of constituent elements, the type and the combination of constituent elements have an effect on the microstructural evolution during the annealing.

Size effect on interface reaction of Sn–xCu/Cu solder joints during multiple reflows

At present, electronic products are developing in the direction of miniaturization and integration, which leads to the downsizing of solder bump in the packaging process. Moreover, micro solder bumps often require undergoing multiple reflow processes due to the improvement of packaging technology, which has a great influence on interface reaction. Hence, it is necessary to study the effects of solder composition, bump size and reflow cycle on interfacial reaction between solder alloys and Cu substrates. In this experiment, Sn–xCu (x = 0, 0.7, 2.0 wt%) alloys with diameter of 200 µm, 500 µm, and 800 µm were soldered to Cu substrates at 250 °C for 1 min, and then reflowed 20 cycles totally. The size effect of micro solder joints on the growth of IMC after multiple reflows was analyzed. At the same time, the impact of Cu concentration inside the bulk solder on the interfacial reaction during multiple reflows was explored. This experiment finds that the diameter of IMC grains increases with the decrease of solder ball diameter after one reflow cycle, and a significant size effect occurs in Sn/Cu solder bump. As the number of reflow cycle increases, the size effect on interface reaction is more pronounced. The most direct kinetic factor of this phenomenon is that the average Cu concentration in the small-sized solder ball rises faster than the others. When the number of reflow cycle reach to nine times, the lateral growth rate of IMC grains begins to surpass the longitudinal growth rate, and the morphology of IMC grains becomes flat. This phenomenon is especially evident in the small-sized solder ball. Moreover, the addition of Cu element in solder promotes ripening reaction resulting in the lateral growth of IMC. Cu6Sn5 micro particles appearing at the Sn/Cu, Sn–0.7Cu/Cu interface hinder the grain boundary motion and inhibit the lateral annexation of IMC grains, thereby suppressing the lateral growth of IMC.