Initial Grain Research Articles

The Study of Genetic Divergence in Rice (Oryza Sativa L.) Genotypes with Grain Yield and Different Morpho-Physiological Traits using Mahalanobis’ D2 Analysis

The current study attempted to study genetic divergence in rice (Oryza sativa L.) genotypes with grain yield and different morpho-physiological traits among 18 rice varieties using Mahalanobis' D2 analysis. Keeping this in mind, the performance of the studied genotypes, as well as the association between various morpho-physiological and yield contributing traits among the genotypes, were evaluated in the field. The experiments were conducted from July to December 2018 at the Agronomy Field, Department of Agronomy and Agricultural Extension, Faculty of Agriculture, Rajshahi University. In terms of grain yield and other morpho-physiological traits, the genotypes differed significantly. The genotypes were classified into five clusters using Mahalonobis' D2 statistics and Tocher's method (Table 3). Cluster IV was the smallest of the clusters. Cluster l is the largest, with six genotypes. Clusters II and lV each contained three and two genotypes. The pattern of genotype distribution among various clusters reflected the significant genetic variability present in the genotypes, which may be due to adaptation of these genotypes to specific environmental conditions. Genotypes from different clusters are expected (inter-cluster). The intra (bold) and inter-cluster distances from D2 analysis (Table 4). Cluster I has the greatest intra cluster distance (0.956), while Cluster IV has the smallest (0.3583). The greatest inter-cluster distance is observed between cluster IV and (8.190), while the smallest inter-cluster distance is observed between cluster II and IV (2.924). In both vectors, the average inter-cluster distances were greater than the average intra-cluster distances, indicating the presence of greater genetic diversity among genotypes from different clusters than those from the same cluster. These findings indicated that these five traits contributed the most to the divergence among the eighteen rice genotypes. The results revealed that the clusters were remarkably distinct for the majority of the traits, indicating proper clustering. The most effective tiller, grain panicle, effective grain panicle, and days to maturity were found in Cluster V. The intra-cluster mean for grain yield was the lowest in this cluster. Cluster III had the lowest grain yield per acre. This was the cluster with the lowest initial grain yield. The intra-cluster mean for effective tiller and days to maturity was highest in this cluster. Cluster II had the smallest grain yield and the second smallest thousand grain weight. Cluster V had the shortest panicle length intra-cluster.

Deformation-restricted forging of Mg-8Al alloy under high pressure

Magnesium AZ80 alloy disks were forged under conditions of extremely high pressures beyond their fracture strength in a die which eliminated plastic deformation. With increasing forging stress, mechanical twins were formed more frequently which subdivided the coarse initial grains, and the evolved (0001) basal texture became sharper. The mechanical properties tended to be notably improved with increasing forging stress; their modifications were rapid in the forging stress region just under 400 MPa, but became gradual above 400 MPa. The achieved Vickers hardness, yield stress, and ultimate tensile strength were 950 MPa, 280 MPa, and 436 MPa at best, respectively. The improvement of mechanical properties was reasonably understood from grain refinement due to dense mechanical twinning and texture strengthening, as well as strain hardening.

Grain refinement of Mg-14Li alloy by Sn addition and large strain rolling

Mg-Li alloy is the lowest density structural metal, which has great potential for various industrial applications. Although Mg-Li alloy has excellent plasticity, it has low strength and requires further strengthening. In this study, the grain size of Mg-14 wt% Li alloy was refined to 15.7 μm by the addition of 6 wt% Sn, the initial grain size of as-cast Mg-14Li alloy was 180 μm. Furthermore, the grain size of Mg-14Li-6Sn was further refined to 400 nm by the subsequent large strain rolling (LSR). The yield strength of the ultra-fine grained Mg-14Li-6Sn reached 160 MPa, and the elongation was not sacrificed but increased to 30% compared with the as-cast alloy (14%). The microstructural evolution was characterized by optical microscopy (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The high ductility of the ultra-fine grained Mg-14Li-6Sn is attributed primarily to the dynamic recovery, and the increase in strength is mainly due to the grain refinement.

Influence of high-current pulsed electron beam irradiation on elemental diffusion and mechanical properties of copper/316L stainless-steel bonded joints

In this paper, Cu and 316L stainless steel with abundant crystal defects are constructed on bonding surfaces using high-current pulsed electron beam (HCPEB), and direct bonding is carried out in vacuum. The bonding temperature was varied as 800 °C and 850 °C, while the bonding pressure of 5 MPa and the bonding time of 40 min was maintained. Microstructure observations revealed that the initial coarse grains of the 316L was significantly changed to fine grains with abundant crystal defects after HCPEB irradiation. After diffusion bonding, the bonded area of the initial joint is not completely joined. Comparatively, the joints pretreated by HCPEB displayed a well-bonded interface. The diffusion coefficient of Cu at interface is significantly increased as well, which is attributed to the acceleration of atomic diffusion. Bonding strength indicates that the shear strength of the joints prepared via HCPEB pretreatment is much higher than the initial joints.

Formation of η-oriented shear bands and its significant impact on recrystallization texture in strip-cast electrical steel

The evolution of shear band (SB) and texture in strip-cast electrical steel was studied in order to investigate the crystallographic character of SB and its influence on recrystallization texture. Shear deformation in the form of SB played an effective role in tailoring the local lattice rotation to accommodate heavy deformation in the case of inhomogeneous deformation under conditions of initial coarse grain in strip-cast electrical steel. During rolling process, η-oriented SBs appeared at different stages of deformation as a result of geometric softening. Cube-oriented SB was mainly retained from initial exact Cube grain at early stage of shear deformation and Goss-oriented SB was newly developed during the formation of γ-fiber matrix after heavy deformation. {210}<001> SB formed as a transition form among different SBs. Crystal rotation inside SB, SB dimension and SB boundary misorientation progressed in proportion to cold rolling reduction. It is demonstrated that crystallographic direction of SBs tended to be parallel to <001> under the driving force of reduction in stored energy to maintain relatively quasi-stable state. Low orientation gradient as well as relatively low density of dislocations was developed within SB region, while high orientation gradient formed between SB region and surrounding matrix. Interestingly, the η-oriented cell blocks inside SBs provided preferential nucleation sites for Goss and Cube texture at early stage of recrystallization, which significantly contributed to beneficial recrystallization texture in a manner of texture inheritance and superior magnetic properties (B50 was as high as 1.81 T, and P1.5/50 was as low as 4.0 W/kg).

Thermo-kinetic orientation study on interface behavior of polycrystalline Cu-Nb composite by crystal plasticity finite element method

In this work, a 3-dimensional (3D) crystal plastic finite element method (CPFEM) combined with the qualitative analysis of slip thermodynamics and kinetics is applied to study the co-deformation behavior of heterophase interface and its relationships with the initial grain orientation or misorientation upon compression of FCC/BCC Cu-Nb polycrystalline metal matrix composites (MMCs). The present simulations well predict the interface instability of the 5-layered polycrystalline Cu-Nb composites arising from the onset and aggregation of the non-crystallographic bandlike concentrated strain. Meanwhile, by changing the grain orientation, the suppression or promotion of plastic shear localization can be realized, where the occurrence of interface instability depends not only on inhomogeneous stress fields, i.e., a single thermodynamic factor, but also on an implicit kinetic factor, i.e., misorientation. On this basis, a so-called artificial “coding” strategy by translating orientation-inhibited strain localization into implicit thermodynamic and kinetic information is presented to tailor the Cu-Nb MMCs, i.e., triggering as much plastic slip as possible from a thermodynamic perspective, while narrowing the misorientation as much as possible from a kinetic selection.

Microstructure and crystallographic texture of martensitic stainless steels after cold rolling and subsequent recrystallization

Martensitic transformation occurs after the final conformation in the quenching process of martensitic stainless steels. Ferrite grains and Cr-rich carbides are observed in the microstructure during the hot rolling, cold rolling and annealing industrial processes. In this context, this study investigated the microstructures and textures of AISI 410, AISI 420 and EN 1.4116 stainless steels with different carbide fractions, initial grain sizes and initial textures after 50% cold rolling reduction and recrystallization. The experimental results showed that the stored energy after cold rolling and grain growth during the annealing were mainly influenced by the (Cr,Fe) 23 C 6 carbide fraction, which was identified as Cr 15.58 Fe 7.42 C 6 carbide type. Reducing initial grain size caused a larger grain boundary constraints, weakening the {110}〈001〉 Goss component in recrystallized texture. The initial texture and pinning effect of (Cr,Fe) 23 C 6 carbides favored α-fiber retention and texture gradient after recrystallization in AISI 410 steel. The recrystallized microstructures of AISI 420 and EN 1.4116 steels were heterogeneous owing to the (Cr,Fe) 23 C 6 carbide bands in the as-received condition. In addition, the selective particle drag caused the γ-fiber development with a shift toward (334)[4 8 ¯ 3] component in AISI 420 and EN 1.4116 steels. • Transition between deformation heterogeneities to larger grain boundary constraints with the reduction of initial grain size was observed after cold rolling. • The initial texture and the pinning effect of (Cr,Fe) 23 C 6 carbides favored α-fiber retention and texture gradient after recrystallization in AISI 410 steel. • The selective particle drag caused the γ-fiber development with a shift toward (334)[4 8 ¯ 3] component in AISI 420 and EN 1.4116 steels.

Effects of hot-rolling on secondary electron yield properties of Cu-2.7Be alloy

The effects of hot-rolling on the secondary electron property evolution of activated Cu-2.7Be sheets were investigated in this study. The microstructures of both pristine and activated Cu-2.7Be alloys subjected to different hot-rolling temperatures were characterized. Their phase compositions were found to comprise an α matrix and eutectoid phases ( α + γ ). Using electron back-scattered diffraction, the initial average grain size ( d 0 ) was found to vary from 6.45 μ m to 15.63 μ m as the hot-rolling temperature increased from 680 °C to 830 °C. Scanning electron microscopy and X-ray photoelectron spectroscopy studies of the activated Cu-2.7Be sheets revealed that the amount of BeO increased with a decrease in the average grain size, resulting in the enhancement of the peak secondary electron emission yield. Scanning Kelvin probe force microscopy measurements confirmed that the main contributor to the BeO enhancement was the α matrix, while transmission electron microscopy analysis showed that BeO formed preferentially from sub-grain boundaries, indicating the importance of grain boundaries for BeO formation. Moreover, the peak secondary electron yield ( δ m ) exhibited a linear relationship with d 0 −0.5 similar to the Hall-Petch relation. The results in this study will be important for enhancing the secondary electron yield of Cu-Be dynodes used in photomultiplier tubes and electron multipliers. • The peak secondary electron yield (SEY)of Cu-2.7Be alloys after activation are inversely proportional to the rolling temperature. • The lower the deformation temperature is, the more BeO content is after activation. • The matrix contributes more to the increase of SEY than eutectoid structure.

Modeling of Austenite Grain Growth Behavior for AISI 302 Stainless Steel

Background: Among the metals used in foundry, we find the austenitic stainless steels, which are used in several fields because of their mechanical properties, which can change during the heat treatments; for that, it is important to understand and control the growth of the austenite grains Objective: Modeling austenite grain growth by considering the effects of heating temperature, holding time, and initial austenite grain size on austenite grain growth. Methods: In this paper, the austenite grain growth process of AISI 302 steel was studied in a temperature range of 900 to 1000 °C and a holding time of up to 360 minutes. Based on the experimental results and a combination of Arrhenius and Sellars type equations, a mathematical model of austenite grain growth was developed Results: From the experimental part, it was found that the increase in heating temperature caused the dissolution of carbides; therefore, the size of austenite grains grew faster, implying a higher growth rate. The prolongation of the holding time also led to the increase in the size of the austenite grains. Conclusion: Based on statistical indicators and a comparison between experimental and predicted results, the ability of the model to predict austenite grain growth was confirmed.

Effect of LPSO orientation on the compression behavior and workability of the Mg-5Gd-3Y–1Zn-0.5Zr alloy

To investigate the effect of LPSO orientation on the compression behavior and workability of Mg alloys, a Mg-5.3Gd-3.3Y-1.1Zn-0.5Zr (wt%) alloy was extruded to obtain the bimodal microstructure with a certain amount of directionally arranged LPSO phases. The subsequent compression tests indicate that the values of activation energy of deformation (Q) are approaching (180–194 kJ/mol) along different orientations (ED, 45°, and TD), which are much lower compared with the as-homogenized Mg-Gd-Y-Zn-Zr alloys due to the sufficient initial grain boundaries (I-GBs). Enhanced kinking and DRX at kink bands at the higher Zener-Hollomon (Z) parameters result in the slight decrease of Q and the movement of optimal processing domains for the ED orientation. The I-GBs overshadow the effect of LPSO orientation via kinking deformation on the DRX ratio and workability. The increase of Z parameter tends to reduce the DRXed grain size and the homogeneity of both the microstructure and hardness. Different α-Mg and LPSO orientations of the extruded alloy induce the anisotropy of peak flow stress (σp) during compression and the extraordinary elliptical shape of the compressed TD specimens. This work provides useful information for the industrial production of wrought LPSO-containing Mg alloys.

Application of Transformation Treatment to Commercial Low-Grade Electrical Steels under Different Processing Conditions

In this paper, two low-grade electrical steels are used to inspect the effect of initial columnar grains and final transformation treatment on the microstructure and textures. Results show that the Al and P elements, besides causing the surface oxidation or segregation, increase the critical transformation temperatures of steels, thus restricting the formation of strong {100} texture. Two-layer grain structure of typical surface-effect-induced transformation is developed in the steels without Al. The transformation textures in both steels are nearly random, which are much better than the {111} recrystallization texture or the memory type of transformation texture. The steel with initial columnar grained structure produces more {110}-oriented grains in finally transformed sheets, whereas the initial hot-rolled structure induces more {100}-oriented grains. In addition, high cold rolling reduction produces a one-layer grain structure in the final transformed sheets. It is confirmed again that the increase in final heating temperature leads to a transition from the memory type of transformation texture to surface-effect-induced transformation texture. For commercial steels containing harmful Al and P, the change in processing parameters during transformation treatment does not influence transformed structure and texture. Finally, the combined control of three stages of transformation during casting, hot rolling and final annealing is discussed.

DEM-FEM based numerical analysis on mechanical responses of sandy soil and pipeline to seepage erosion

Seepage erosion around the underground pipelines will produce various adverse influences on the stratum stability and the structural safety. It involves behaviours at three scales, that is, particle-scale, cell-scale and engineering-scale. The problem relies on the fact that finding general equations for the granular media is difficult due to the changing nature of how solids flow, so that the continuous approach is unavailable to directly describe the phenomenon. Hence, DEM simulations are firstly conducted in this study to quantify the relationship between the fine particle loss (ΔFC = 0, 5%, 10%, 15%, 20%, 25%, 30%) and the mechanical properties of soil elements, upscaling particle to cell. Considering two initial fine grain contents (S6:4, S3:7), the empirical equations of soil mechanical parameters εve, E0, φ and c changing with the fine particle loss ΔFC are obtained by regression analysis. Then, based on the corresponding constitutive parameters of different erosional stages, FEM simulations at the engineering scale are conducted to analyse the structural mechanical response to the seepage erosion, upscaling cell to engineering. This study reveals the multiscale response of the seepage erosion in the sandy strata, and helps in providing the practical guidance for engineering application and the reference for the next multiscale parallel computation on this issue.

Assessment of the Purdue Improved Crop Storage (PICS) bag for maize storage in Ghana

Despite the recent introduction of improved grain storage methods and technologies, many smallholder maize farmers in Ghana still use traditional storage practices and structures for storing their maize grains after harvest. This practice contributes to the high post-harvest losses in maize grain at the smallholder level largely due to insect pest infestation. Hermetic bag storage is a proven technology effective in reducing grain damage and losses from insect pests. In this study, the efficacy of the Purdue Improved Crop Storage (PICS) bag was compared with a polypropylene (PP) bag stored with maize treated with Betallic Super EC chemical and PP bag stored with maize without Betallic treatment (Control) during a 6-month storage period. Data on grain moisture content (MC), number of live insects, insect damaged kernels (IDK) and maize weight loss were collected monthly for analysis. Grain viability and nutrient analysis were also conducted before and after storage. The results showed initial grain moisture content of 11.4% was not significantly affected in the PICS bags but increased by 1-2% in the PP bags. Purdue Improved Crop Storage (PICS) bags and Betallic treatment significantly reduced insect damage grains with mean weight loss of &lt; 5% and 6.35 % respectively compared to the control (PP bag without Betallic) treatment with mean weight loss of 21 % over the 6-month storage period. Germination rate of sampled seeds after storage in the PICS bags (75 %) was not significantly different to the initial germination rate (78 %) compared to the control (PP bag without Betallic) treatment of 56 %. Overall, maize grains stored in the PICS bags showed no signs of deterioration as compared to grains in the PP bags. The PICS bags were superior to the PP bags in terms of other grain quality metrics assessed and the nutrient characterization such as protein and carbohydrate which had no significant difference (p&lt;0.05) between the initial and the three treatments. The results showed that PICS bags can be effective in protecting maize grains during storage. Smallholder farmers are therefore encouraged to consider this technology especially for controlling insect pests of stored maize. Key words: Insect pests, Polypropylene, Smallholder farmers, Purdue Improved Crop Storage bag

Shear-induced amorphization in nanocrystalline NiTi micropillars under large plastic deformation

Shear-induced amorphization is a phenomenon observed in polycrystalline NiTi shape memory alloys under severe plastic deformation, but the underlying mechanism of such a microstructural change remains elusive. To study the isothermal large-strain plastic deformation behavior and the associated mechanisms, uniaxial compression is performed on nanocrystalline NiTi cuboidal micropillars with initial grain sizes of 35 and 110 nm. It is found that the micropillars demonstrate high deformability with plastic strains up to 110% via shear-induced amorphization. It is shown that plastic strain localization in shear bands of the 35 nm-grain-size sample prompts notable amorphization up to an area fraction of 90% and crystal refinement down to 5 nm. High-resolution transmission electron microscope and molecular dynamics simulations reveal that the shear-induced amorphization starts from the local martensite phase near grain boundaries through accumulation of crystalline defects. The amorphization can lead to a reduction in the crystal size and an increase in the plastic flow stress. The large plastic deformation of the nanocrystalline NiTi micropillars via shear-induced amorphization is enabled by the suppression of crack nucleation through dynamic recovery of nanovoids. Our work provides new perspectives for producing crystalline-amorphous nanostructures in shape memory alloys at small scale.

Effect of Initial Grain Temperature on Combustion Response of Composite Solid Propellants in T-burner

ABSTRACT The effect of initial grain temperature on the combustion response of composite solid propellants (AP/HTPB/RDX/Al) is experimentally investigated using a T-burner. Tests were conducted at different frequencies ranging from 200–400 Hz and at different pressures of 1–8 MPa at different initial propellant temperatures using a novel method (303 K, 243 K and 343 K) for two industrial-grade propellants, propellant-A and propellant-B. The test results revealed that the hot and cold temperatures increase the response. The combustion responses of the propellant-B are lower than propellant-A. Pulsed tests are conducted when the propellant showed low or negative response. This work highlights that the initial grain temperature is a crucial factor in determining the stability of solid rocket motors. The negative response compels us to further investigate toward a better understanding about the unsteady combustion behavior since there is no model available which could predict negative responses as of today.

Modeling of temperature- and strain-driven intermetallic compound evolution in an Al–Mg system via a multiphase-field approach with application to refill friction stir spot welding

The prospect of joining dissimilar materials via solid-state processes presents an opportunity to obtain multi-material structures having a synergy of desirable properties of the joined materials. However, the issue of the formation of intermetallic compounds at the weld interface of dissimilar materials arises with that, depending upon the temperature and pressure conditions as per phase diagram. As the thickness of the intermetallic compounds may determine the mechanical properties of the joint, understanding the driving mechanisms and evolution of these intermetallic compounds in solid-state joining processes, such as refill friction stir spot welding (refill FSSW), is crucial. In this contribution, we account for the effect of different driving forces in a multiphase-field approach and investigate the evolution of the intermetallic compounds driven by chemical and mechanical forces. A finite-element simulation of the refill FSSW is pursued to obtain the peak temperature and strain at different locations of the weld interface. The microstructure simulations obtained via the multiphase-field model give insight into the morphology and kinetics evolution of the intermetallic compounds for both, the absence of strain (purely chemically-driven model) as well as presence of strain (chemo-mechanically-driven model). The consideration of strain proves to result in thicker intermetallic compound layer. Furthermore, the impact of interface energy and initial grain configuration is found to be significant on the overall intermetallic compounds evolution.

In situ radiographic study of the grain refining behavior of Al3Sc during the solidification of Al-10Cu alloy

Grain refinement of Al alloys inoculated by rare earth elements, such as Sc, has been extensively acknowledged, while the practical behavior of how inoculant Al3Sc particles affect the refinement in solidification has not been clarified due to the non-transparency of the solidification process. Here, the microstructural evolution of primary Al3Sc particles and α-Al grains in Al-10 wt.% Cu alloy solidifications with 0.2 wt.%, 0.6 wt.%, and 1.0 wt.% Sc additions was investigated by in situ synchrotron X-ray radiography. The detailed mechanisms of curve motion of grains (CMG) and melt convection were revealed. The efficient grains nucleation, uniformly scattered small initial grains, and long duration of melt convection contributed to the best refinement in the 0.6 wt.% Sc addition sample. This work provides a deep insight into grain refinement in solidification with Sc addition, which will enlighten the composition design and casting process of Al alloys inoculated by rare earth elements.

Hot deformation behavior and constitutive modeling of a cost-effective Al8Cr12Mn25Ni20Fe35 high-entropy alloy

In this study, a new non-equiatomic and cost-effective high-entropy alloy (HEA), Al8Cr12Mn25Fe35Ni20, was designed using thermodynamic parameters and prepared by arc melting. The alloy was subjected to homogenization at 1200 °C and a hot-rolling reduction of 50%. The hot deformation behavior and deformation mechanism were studied at varying strain rates ranging from 0.01 to 10 s−1 and temperatures ranging from 900° to 1100°C via plane strain compression tests using a Gleeble 3800 thermo-mechanical simulator. The phase structure of the rolled alloy was studied using electron backscattered diffraction (EBSD), X-ray diffraction, and differential thermal analysis to detect phase transformation. The constitutive model was implemented to predict the high-temperature flow stress using the Zener-Holloman parameter (Z), which correlated well with the experimental values. The studied HEA exhibited a relatively high activation energy for hot deformation of 389.5 kJ.mol−1, i.e., comparable to those of equiatomic HEAs in the literature. The hot-deformed microstructural features and deformation mechanism were studied using EBSD, which revealed discontinuous dynamic recrystallization as the main softening mechanism. Dynamic recrystallization (DRX) showed the formation of fine grains along the initial grain boundaries, accompanied by Al-Ni-rich B2 precipitates at the recrystallized grain boundaries.

Effect of initial grain structure on the concurrent precipitation and recrystallization of Co37Cr20Ni37Ti3Al3 high-entropy alloy

High performance precipitation strengthened high-entropy alloys (HEAs) can be prepared by concurrent recrystallization and precipitation in the process of aging at intermediate temperatures after rolling. Generally, the homogenized samples are subjected to rolling before aging, where the effects of initial grain structure before rolling on the concurrent recrystallization and precipitation are overlooked. In this study, we revealed the inherited effect of initial grain on the concurrent recrystallization and precipitation in Co37Cr20Ni37Ti3Al3 HEA. The heredity of grain homogeneity to the initial grain structure was revealed, where the initial grain structure influences the homogeneity of strain distribution during rolling and influences the recrystallization in the subsequent aging. Moreover, the inherited effect of the initial grain structure also influences the precipitation behavior. TEM characterization confirmed that the lamellar precipitation decreases, while spherical precipitation increases with the increase of the initial grain size. By tailoring the initial grain size, the strength and ductility of Co37Cr20Ni37Ti3Al3 alloy were simultaneously improved. The present study provides a good understanding of the concurrent recrystallization and precipitation in HEAs.

Metallurgical Factors Affecting the Tensile Properties of Weld Heat-Affected Zone in Medium Mn Transformation-Induced Plasticity Steel

The role of retained austenite in the mechanical property changes in the medium Mn transformation-induced plasticity (TRIP) steel heat-affected zone (HAZ) was elucidated throug a comparison with conventional TRIP steel. The two steel grades had similar microstructures consisting of ferritic phases with a high fraction of retained austenite in the as-received state; however, the difference in properties after welding was significant. The microstructures of both steels were dramatically changed to a martensitic matrix in the coarse-grained HAZ region. The medium Mn TRIP steel HAZ can have a higher retained austenite fraction than the conventional one; hence, an excellent combination of tensile strength and elongation can be obtained. The decisive difference between the two steels was determined in terms of austenite stability and the initial grain size.