Preferred Grain Research Articles

Intracrystalline vorticity record of flow kinematics during shear zone reactivation

The vorticity axis of deformation of a shear zone is a rotational axis controlled by the relative movement of its boundaries. When characterized, it is a reliable tool to determine the ductile flow geometry (monoclinic general, monoclinic transpressive, or triclinic) and an asset to identify the kinematics of complex oblique collisions. Advancements in analysis of electron backscattered diffraction (EBSD) maps now permit inference of vorticity axes – known as crystallographic vorticity axes (CVAs) – from the intragranular lattice orientation dispersion of strain-bearing minerals. However, natural shear zones may preserve a record of multiple shear events with contrasting kinematics and it is not understood to which extent the quartz lattice may preserve a kinematic record through multiple deformation events. Herein, we characterize the finite flow kinematic record produced during reactivation of the Eastern Highlands shear zone (EHSZ), in an oblique collision within the Canadian Appalachians. We integrate field and thin section observations, quartz lattice preferred orientations, EBSD maps, and grain classification, leading to a new method to determine and compare CVA within relict and recrystallized quartz grains. Using this method, we were able to conclude that the EHSZ was reactivated in an heterogenous monoclinic flow environment.

Microstructural control during laser powder fusion to create graded microstructure Ni-superalloy components

This work explores the feasibility of additively manufacturing tailored microstructures through varying process parameters, to eventually control the mechanical properties and performance. The investigation focuses on controlling the heat input and thermal history during laser-powder bed fusion of IN718 through process parameter manipulation; notably the heat input parameters (power, scan speed, and hatch spacing) and island scanning parameters (island size, shift, and island overlap). The changes in preferred orientation, morphology and grain size were characterised in both the transverse and build cross-sections using scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD), while the texture development was comparatively characterised using X-ray diffraction (XRD). The solidification cell size was quantified to estimate the influence of the process parameters on the cooling rates. This was also rationalised using a thermal model resolving the scan characteristics to provide the transient temperature distribution to a numerical grain growth model. Based on the obtained microstructures, graded microstructures were generated using the island strategy and identical laser parameters throughout but changing subtle features such as the island size and shift. A suitable post-process heat treatment was applied to retain the tailored microstructures, while obtaining the required hardness.

Nanoparticle Alignment: Quantized Grain Boundary States Promote Nanoparticle Alignment During Imperfect Oriented Attachment (Small 29/2020)

In article number 2001423, Selim Elhadj and co-workers offer new insights into the crystallographic alignment of nanoparticles during self-assembly and aggregation. The salient details reveal that grain boundaries between small particles (0–10 nm) rapidly disintegrate via deformation processes due to the quantization of energetically preferred grain boundary structures and the existence of small barriers associated with the motion of grain boundary dislocations to nearby surfaces.

Effects of lattice mismatches in In2O3/substrate structures on the structural, morphological and electrical properties of In2O3 films

Indium oxide thin films were deposited by ultrasonic spray technique on ITO coated glass and single crystalline Si (400) substrates at 400 °C. Lattice mismatch effect on the crystalline structure, surface morphology and electrical properties of these samples is then studied. X-ray diffraction (XRD) and Raman spectroscopy patterns suggest that the films deposited on ITO coated glass substrate are polycrystalline in nature having a cubic crystal structure with a preferred grain orientation along the (222) plane. However, films deposited on Si wafer substrate, exhibit randomly oriented growth. The crystallite size varies from 18 to 66.5 nm. AFM topographical images revealed that the In2O3/ITO films follow 2D or layer-by-layer-growth. But in the case of In2O3/Si films, 3D or island growth becomes dominant. The In2O3/ITO films is found to exhibit a higher value of conductivity (σ = 5 × 102 Ω−1 cm−1) than the In2O3/Si films, and the low value of the RMS roughness (9.83 nm).

Microstructure and mechanical properties of friction stir welded joint of TRIP steel

Friction stir welding (FSW), as a new type of solid-solid welding method, was utilized to join transformation-induced plasticity (TRIP) steel. This method can avoid the solidification structural defects caused by fusion welding technology and improve the welding quality. In this study, the microstructural transformation and deformation behavior of TRIP steel during FSW were evaluated by optical microscopy, electron backscatter diffraction, and room-temperature tensile test. The results show that after FSW, martensite transformation occurred in the stir zone (SZ) and thermomechanically affected zone (TMAZ), and the retained austenite content decreased. The grain refinement and ratio of low-angle boundaries (LABs) increased. In heat-affected zone (HAZ), the retained austenite was thermally spheroidized and decomposed, the grains were coarsened, and the ratio of LABs decreased. No obvious preferred grain orientation was observed in each region of joint, and the texture strength decreased by phase transformation and grain rotation. After the tensile deformation of FSW joint, the retained austenite disappeared, the grains were refined, and the proportion of LABs increased in the base metal (BM) and HAZ. The content of retained austenite in SZ remained unchanged, but decreased in TMAZ. The grains were refined, and the ratio of LABs did not change significantly in SZ and TMAZ. FSW increased the microhardness of SZ and TMAZ by 218 HV and 93 HV, respectively, while the microhardness of HAZ decreased by 4 HV. The yield strength, tensile strength, and elongation of joint were 563 MPa, 942 MPa, and 12.8 %, respectively, reaching 96%, 104%, and 59%of BM, respectively. The tensile fracture exhibited ductile fracture characteristics. In addition, the joint exhibited strain nonuniformity during the tensile deformation, and the order of deformation degree was as follows: HAZ > TMAZ > SZ. Therefore, HAZ became a weak zone of joint mechanical properties. Continuous dynamic recrystallization and discontinuous dynamic recrystallization were the main mechanisms of grain refinement, and the martensite transformation conformed to the Kurdjumov-Sachs orientation relationship.

Marker Assisted Forward Breeding to Combine Multiple Biotic-Abiotic Stress Resistance/Tolerance in Rice

BackgroundUnfavorable climatic changes have led to an increased threat of several biotic and abiotic stresses over the past few years. Looking at the massive damage caused by these stresses, we undertook a study to develop high yielding climate-resilient rice, using genes conferring resistance against blast (Pi9), bacterial leaf blight (BLB) (Xa4, xa5, xa13, Xa21), brown planthopper (BPH) (Bph3, Bph17), gall midge (GM) (Gm4, Gm8) and QTLs for drought tolerance (qDTY1.1 and qDTY3.1) through marker-assisted forward breeding (MAFB) approach.ResultSeven introgression lines (ILs) possessing a combination of seven to ten genes/QTLs for different biotic and abiotic stresses have been developed using marker-assisted selection (MAS) breeding method in the background of Swarna with drought QTLs. These ILs were superior to the respective recurrent parent in agronomic performance and also possess preferred grain quality with intermediate to high amylose content (AC) (23–26%). Out of these, three ILs viz., IL1 (Pi9+ Xa4+ xa5+ Xa21+ Bph17+ Gm8+ qDTY1.1+ qDTY3.1), IL6 (Pi9+ Xa4+ xa5+ Xa21+ Bph3+ Bph17+ Gm4+ Gm8+ qDTY1.1+ qDTY3.1) and IL7 (Pi9+ Xa4+ xa5+ Bph3+ Gm4+ qDTY1.1+ qDTY3.1) had shown resistance\\tolerance for multiple biotic and abiotic stresses both in the field and glasshouse conditions. Overall, the ILs were high yielding under various stresses and importantly they also performed well in non-stress conditions without any yield penalty.ConclusionThe current study clearly illustrated the success of MAS in combining tolerance to multiple biotic and abiotic stresses while maintaining higher yield potential and preferred grain quality. Developed ILs with seven to ten genes in the current study showed superiority to recurrent parent Swarna+drought for multiple-biotic stresses (blast, BLB, BPH and GM) together with yield advantages of 1.0 t ha− 1 under drought condition, without adverse effect on grain quality traits under non-stress.

Directed energy deposition of Al 5xxx alloy using Laser Engineered Net Shaping (LENS®)

Here, we present directed energy deposition (DED) of wrought-like Al 5xxx AlMg alloy by Laser Engineered Net Shaping (LENS®). A transition from an Al 5083 gas atomized powder feedstock to Al 5754 characteristics of the as-deposited material due to selective evaporation of Mg was observed. Density values obtained by X-ray micro-computed tomography (μ-CT) were compared to those obtained by the Archimedes method. The latter indicated a relative density as high as 99.26%. Possible origins of porosity are discussed. The as-deposited material was comprised of both equiaxed and columnar grains with no preferred crystallographic orientation and mean grain size of 36 μm. The Young's modulus, yield stress, ultimate tensile strength, fracture strain, Poisson's ratio, and total ultimate strain energy (toughness) were determined by uniaxial tensile tests combined with digital image correlation (DIC). Fractography complemented the mechanical testing. A pulse-echo ultrasonic non-destructive test was used to obtain more accurate values of the Young's and shear moduli and to adjust the value of the yield strength accordingly. The measured mechanical properties meet the requirements of international standards for wrought Al 5754 in its annealed condition.

Evolution of microstructure and performance of n-type BiTeSe thermoelectric materials fabricated by multi-path equal channel angular extrusion

Poor repeatable thermoelectric properties and inevitable contamination are introduced in n-type polycrystalline Bi2Te3 based alloys prepared by conventional powder metallurgy technology. In the present work, equal channel angular extrusion (ECAE) method was used to extrude the cast ingot directly via various routes (A, BA, BC, C) to obtain the BiTeSe polycrystalline bulk alloys with uniform microstructure and free contamination. All extruded bulks boasted the much stronger mechanical properties due to the grain refinement, and the much higher thermoelectric properties due to the simultaneous improvement of electrical and thermal transport performances, compared with that (22.06 HV0.05 and 0.009) of the initial cast ingot. Among all extruded bulks, the one extruded via route BC achieved the maximum Vickers hardness of 59.8 HV0.05 due to the most preferable grain refinement, and that via route A achieved the maximum dimensionless figure of merit (ZT) of 0.724 due to the strongly developed texture.

Graphene oxide coated flower-shaped ZnO nanorods: Optoelectronic properties

Abstract In this paper, the influence of graphene oxide coating on optical and photoluminescence properties of zinc oxide nanorods (ZnO NRs) has been investigated. ZnO NRs were prepared using a hydrothermal route (from zinc nitrate hexahydrate and hexamethylenetetramine), graphene oxide (GO) was fabricated by Hummer’s method, while for synthesis of ZnO nanorods:graphene oxide nanocomposite (ZnO NRs:GO) on Si (100) substrate, a facile technique (drop coating) was proposed. The structural, morphological, optical and luminescence properties of the films were investigated using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), together with Fourier transform infrared (FT-IR), Raman, ultraviolet–visible–near-infrared (UV/VIS/NIR) and photoluminescence (PL) spectroscopies. As revealed by XRD analysis, composites display a hexagonal wurtzite type structure with a (101) preferred grain orientation. The average crystallite sizes decrease from 45 to 40 nm after GO coating. The SEM study confirms successful coating of GO layers on flower-like ZnO nanostructures. The FTIR and Raman analyses validated the hybridization of nanocomposite and the strong interaction between ZnO NRs and GO. The band gap of the ZnO NRs:GO nanocomposite is lower (2.95eV) compared to that of ZnO NRs (3.11 eV), as determined from the analysis of UV absorbance spectra. The ZnO NRs:GO nanocomposite exhibits a broad PL band, from ∼450 nm to ∼750 nm, with a nearly white-light integrated emission and a chromaticity coordinate of (0.25, 0.34). Gaussian deconvoluted broad PL band exhibits three distinct sub-bands, associated with radiative recombinations in ZnO and GO.

Effect of Microstructure and Texture Evolution on the Electrochemical Corrosion Behavior of Warm-Rolled API 5L X70 Pipeline Steel

Thermomechanical treatments were used to improve the corrosion resistance of API 5L X70 pipeline steel materials. Successive warm rolling was performed at consistently reduced temperatures; 700 °C, 600 °C, and 500 °C. Steel plates comprised of different ferrite grain sizes were produced. However, the finest grain distribution was achieved at 700 °C rolling temperature. A combination of electron backscattered diffraction and X-ray diffraction (XRD) techniques were used to determine weak texture (i.e., preferred grain orientation) across all specimens. Grain orientation showed deviation toward the 〈111〉 direction at the surface of 700 °C rolled steel. After deformation at 600 °C, mostly 〈110〉 grains oriented parallel to the normal direction were obtained. Rolling at 500 °C resulted in random orientation of grains. Corrosion results show that anodic dissolution increased as the rolling temperature decreased in the order 700 °C > 600 °C > 500 °C for hydrogen-producing and non-hydrogen-producing test media. Also, molecular dynamics (MD) simulation confirmed that the adsorption energy of corrosive species interacting with the iron (Fe) surface increased in the order of Einteraction (111) < Einteraction (110) < Einteraction (100) for the two types of electrolytes. The relationships between the molecular species interacting in each corrosive media and selected crystal planes (i.e., (111), (110), and (100)) were established. X-ray photoelectron spectroscopy (XPS) confirmed that the adsorbed corrosion film on all tested steels are Fe2O3 (Fe2+) and hydrated ferric oxides such as FeOOH.

Structure and property modulation of primary CoSn and peritectic CoSn2 intermetallic compounds through ultrasonicating liquid Sn–10%Co alloy

The effects of power ultrasound on the peritectic solidification of binary Sn–10%Co peritectic type alloy were investigated. If introducing ultrasound in the whole solidification process, primary CoSn intermetallic compound which grew as coarse strips with a preferred grain orientation under static condition was considerably refined and exhibited a random orientation distribution. Moreover, the significant increase in thickness ratio of peritectic CoSn2 to primary CoSn compounds indicated that the peritectic transformation was remarkably enhanced. To further reveal the underlying mechanism, power ultrasound was respectively applied to primary phase growth and peritectic transformation stages. As compared with the latter one, the former procedure led to a finer primary CoSn phase and a higher peritectic transformation extent. The results showed that ultrasound induced refinement of primary CoSn phase played the dominant role, while ultrasound accelerated atomic diffusion between primary and peritectic solid phases may also contributed to the enhancement of peritectic transformation. Both the yield strength and ultimate compressive strength of Sn–10%Co alloy were improved after ultrasonic solidification.

Structural, optical and electrical properties of SnxSy thin films deposited by spray pyrolysis technique

ABSTRACT In the present work, SnxSy thin films have been deposited into heated glass substrates at 350°C from different molar concentrations (x = 0.05M, y = 0; 0.03; 0.05; 0.07; 0.1M) by means of a spray pyrolysis technique. Firstly, it was found that optimum molar concentration of the precursor to obtain device quality SnS thin film is x = 0.05 M and y = 0.05 M. Moreover, the findings detected by X-ray diffraction (XRD) analysis show that the film crystallized in the orthorhombic crystal structure with a preferred grain orientation along (111) plane. Furthermore, the optical characterization revealed that the average optical transmission had been significantly reduced and the band gap value is 1.8 eV as well as a very high absorption coefficient (105/cm). Besides, the electrical properties study exhibited that the sample is p-type and the value of the electrical resistivity of SnS film is 2.75 × 10−2 (Ω.cm).

Effect of ceramic particle size on densification behavior, microstructure formation, and performance of TiB2-reinforced Al-based composites prepared by selective laser melting

Abstract

Cover Picture: Materials and Corrosion. 1/2020

Cover:Friction stir processing (FSP) and subsequent aging heat treatment were used to modify the microstructure of AZ80 magnesium alloy. EBSD images (left) and pole figures (right) of (a, b) base material (BM), (c, d) FSP, (e, f) FSP‐with aging treatment (5 h at 180°C) and (g, h) FSP‐with aging treatment (24 h at 180°C) samples. The average grain size of FSP sample was refined from (a) to (c) due to dynamic recrystallization through FSP. After aging heat treatment, the average grain size of FSP‐5 and FSP‐24 samples was slightly larger (e, g) than that of the FSP sample. The pole figures clearly demonstrate that BM sample possessed an obvious preferred grain orientation.More detailed information can be found in: Liying Huang, Kuaishe Wang, Wen Wang, Pai Peng, Ke Qiao, Qiang Liu, Microstructural evolution and corrosion behavior of friction stir processed fine‐grained AZ80 Mg Alloy, Materials and Corrosion 2020, 71, 93.

Effect of multi-allele combination on rice grain size based on prediction of regression equation model.

Rice yield potential is partially affected by grain size and weight, which associates with a great number of genes and QTLs. However, it is still unclear that how multiple alleles in different genes take a combined effect on grain shape/size. Here, we investigated seven core grain size-related functional genes (GL7, GS3, GW8, GS5, TGW6, WTG1, and An-1) and observed a wide phenotypic variation for five agronomic traits (grain length, grain width, grain length-width ratio, grain thickness and thousand-grain weight) in 521 rice germplasm. The correlation analysis showed a strong association among these grain traits which have distinct impacts on determining the final rice grain size. Genotyping analysis demonstrated that a relatively small number of allele combinations were preserved in the diverse population and these allele combinations were significantly associated with differences in grain size. Furthermore, alleles were regarded as individual variables to develop the multiple regression equation. We found that B and C allelic types of GS3 and conventional type of WTG1 played relevant roles in grain size and thousand-grain weight, separately. The models would conduceto devise instructive approaches by selecting appropriate candidate alleles, which could fuel further research for breeding preferred grain shape and high-yielding crop.

Hydroxyapatite-based cements induce different apatite formation in radicular dentin

ObjectiveTo investigate crystallinity and ultrastructure of the formed hydroxyapatite at radicular cervical and apical dentin after being treated with three different canal sealers. MethodsCervical and apical root dentin surfaces were treated with two experimental hydroxyapatite-based sealers, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite) and an epoxy resin-based canal sealer (AH Plus); gutta-percha without sealer was included as control. Dentin surfaces were studied by X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging after 24h and 12m of storage. ResultsRoot cervical dentin treated with calcypatite and oxipatite produced poor crystallinity of new minerals, wide amorphous phase and non-stoichiometry. Reflections at the 002 plane and the corresponding diffraction rings attained lower values in the Scherrer equation and the Scherrer-Wilson equation in samples treated with both HAp-based sealers than in specimens without sealer or with AH Plus. At root cervical dentin treated with calcypatite, shorter and wider crystallite size formations and lower crystals grain size were found, if compared to those encountered at oxipatite treated dentin. Oxipatite attained improved crystallographic atomic order and less structural variation in both distances and angles. Apical dentin treated with oxipatite attained preferred grain orientation with polycrystalline lattices. SignificanceThe immature crystallites formed in dentin treated with calcypatite and oxipatite will account for high hydroxyapatite solubility and remineralizing activity. New polycrystalline formations encountered in apical dentin treated with oxipatite may also produce high mechanical performance.

Effect of two-dimensional ultrasonic rolling on grain size and micro-hardness of 7075 aluminum alloy

Two-dimensional ultrasonic surface rolling process (TDUSR) is an effective method to improve fatigue, wear, and corrosion resistance of materials by producing strain hardening and changing stress state and microstructure. In this paper, the experiment and finite element simulation of two-dimensional ultrasonic surface rolling 7075 aluminum alloy were carried out to study the evolution of the microstructure and the relationship between the surface grain size and micro-hardness. Deform was redeveloped on the basis of grain refinement model to simulate the change of grain size of 7075 aluminum alloy after TDUSR treatment. The micro-hardness and grain size obtained by TDUSR were analyzed using micro-hardness tester and XRD diffractometer. The relationship between the grain size and micro-hardness was established based on the experimental results. The simulation and experimental results showed that the grain size in the rolled region decreased greatly after TDUSR treatment. And the grain size refined from micron to nanometer, forming a gradient nanocrystalline structure along the radial direction. The grain refinement might be caused by the comprehensive influence of the surface equivalent stress and the equivalent strain rate when the static load was less than 150 N. When the static load exceeded 150 N, the plastic deformation temperature also had a certain effect on the grain refinement. TDUSR treatment can promote the preferred grain orientation and change the microstructure in the rolled surface layer. The inverse Hall-Petch phenomenon existed in the nanostructured surface layer, and the surface micro-hardness increased with the increment of the grain size.

Effects of post-deposition annealing and copper inclusion in superstrate Sb2Se3 based solar cells by thermal evaporation

Earth-abundancy, nontoxic constituent, along with excellent stability and optoelectronic properties make antimony selenide (Sb2Se3) one of the potential candidate for low cost photovoltaics. In this work, antimony selenide (Sb2Se3) thin films were prepared by low temperature thermal evaporation method and characterized. Solar cells were fabricated in the superstrate configuration of Glass/ITO/ZnO/CdS/Sb2Se3/Au. It was found that annealing in vacuum after Sb2Se3 deposition played a significant role in the device performance. One-dimensional crystal structure of Sb2Se3 with a preferred grain orientation was found to be beneficial for the higher performance of the solar cells with vacuum annealing at 300 °C. Furthermore, Cu addition after the deposition of Sb2Se3 was introduced to improve the back contact and the device performance. In particular, Cu addition as a back contact leads to a significant increase in the Voc and the fill factor (FF). Moreover, aging of the finished cells during accelerated stability tests revealed a light soaking effect without degradation even in case of copper insertion. Our best solar cell showed a conversion efficiency of 3.5% without selenization.

Electric field induced splitting of the preferred orientation in PMN‐PT textured ceramics

AbstractWe have performed studies of the orientation distribution in &lt;001&gt;C textured, 0.03(Na1/2Bi1/2)TiO3 ‐ 0.97[0.715Pb(Mg1/3Nb2/3)TiO3 ‐ 0.285PbTiO3] (0.03NBT‐0.97[PMN‐28.5PT]) ceramics by a pole figure method, comparing the results to those for PMN‐PT single crystal and polycrystal samples. The pole figures about the (001) zone are found to have monoclinic, Ma, phase for textured ceramics in the annealed condition and were similar to those for electrically poled single crystals. However, electrical poling of the textured ceramics resulted in a doublet splitting of the orientation distribution about the direction that defined the original grain texturing. Studies of pole figures about other high‐symmetry zones also revealed the development of some degree of preferred orientation along the in‐plane directions after poling. Our findings demonstrate that E‐field induced phase transformation and domain textures superimpose with that of preferred grain orientations, giving rise to a unique texture symmetry for PMN‐PT. The texture symmetry changes are driven by minimization of the elastic strain energy, and have an important effect upon the piezoelectric properties.

Build Orientation Effects on Texture and Mechanical Properties of Selective Laser Melting Inconel 718

The production of components via selective laser melting (SLM) metal additive manufacturing results in microstructures unique to the process that are highly dependent on laser processing parameters and orientation of part geometry relative to the build direction. This study investigates the variation in tensile properties of SLM Inconel 718 at varying angles with respect to build direction. ASTM E8 tensile specimens were built in XY, Z, and B+45 from Z orientations to near-net shape, HIP and heat treated, and tensile tested at room temperature. Orientation dependence of mechanical properties was observed; Z samples had the lowest strength and highest elongation, while XY samples had the highest strength and lowest elongation. Optical, SEM, and EBSD analysis were conducted to probe for microstructure variation that could be the cause of the difference in mechanical properties. Analysis of pole figures and grain maps suggests a preferred grain texture and twinning orientation that aligns with the build direction, which may contribute to the anisotropic enhancement in ductility.