Grain Size Variation Research Articles

Identification of natural allelic variation in TTL1 controlling thermotolerance and grain size by a rice super pan-genome.

Continuously increasing global temperatures present great challenges to food security. Grain size, one of the critical components determining grain yield in rice (Oryza sativa L.), is a prime target for genetic breeding. Thus, there is an immediate need for genetic improvement in rice to maintain grain yield under heat stress. However, quantitative trait loci (QTLs) endowing heat stress tolerance and grain size in rice are extremely rare. Here, we identified a novel negative regulator with pleiotropic effects, Thermo-Tolerance and grain Length 1 (TTL1), from the super pan-genomic and transcriptomic data. Loss-of-function mutations in TTL1 enhanced heat tolerance, and caused an increase in grain size by coordinating cell expansion and proliferation. TTL1 was shown to function as a transcriptional regulator and localized to the nucleus and cell membrane. Furthermore, haplotype analysis showed that hapL and hapS of TTL1 were obviously correlated with variations of thermotolerance and grain size in a core collection of cultivars. Genome evolution analysis of available rice germplasms suggested that TTL1 was selected during domestication of the indica and japonica rice subspecies, but still had much breeding potential for increasing grain length and thermotolerance. These findings provide insights into TTL1 as a novel potential target for the development of high-yield and thermotolerant rice varieties.

Possibilities of Reprocessing Solid Waste with Tritium from Fusion Using High-Temperature Heating

This study evaluates the types of waste generated by tritium during nuclear fusion. Some methods of reprocessing and decontaminating solid waste using thermal processes are evaluated, and the advantages and disadvantages of different methods are compared. The high-temperature technology selected for this study is intended for use in the EU DEMO project in the area where waste from nuclear fusion reactions is processed. Safety and environmental concerns around the technology are evaluated. The potential for detritiation of solid wastes of various sizes are investigated. The study’s focus is on wastes comprising mostly tungsten dust grains of various sizes. The possibilities and rationale for the use of high-temperature technologies are investigated. Tests conducted focus primarily on tungsten waste in powder form in various atmospheres. Problems related to the induction heating and melting of metals and nonmetals are addressed.

Reservoir Characteristics and Controlling Factors of Large-Scale Mono-Block Gas Field Developed in Delta-Front Sandstone—A Case Study from Zhongqiu 1 Gas Field in the Tarim Basin

Taking the Zhongqiu 1 Gas Field in the Tarim Basin as an example, the heterogeneity of large-scale mono-block gas fields and their primary controlling factors have been analyzed. Based on drilling core data, well log data, scanning electron microscopy, thin-section analysis, and mercury injection experiments, combining sedimentological interpretation, research on the reservoir characteristics and variability was carried out. The results showed that: (1) The lithologic characteristics showed obvious variations among wells in the Zhongqiu 1 gas field. Specifically, the main lithology developed in the Zhongqiu 1 well is feldspar lithic sandstone, while the remaining wells predominantly consist of lithic feldspar sandstone. These differences in rock composition maturity reveal that a higher proportion of stable mineral components leads to poorer reservoir properties; (2) the main factors controlling oil and gas productivity include the variations in petrology, mineralogy, and diagenetic process characteristics. The high content of unstable mineral components and constructive diagenesis could increase reservoir porosity together. (3) Sedimentary facies of the Bashijiqike Formation in the Zhongqiu 1 Gas Field played a dominant role in the reservoir distribution. The division of sedimentary facies zones reflects variations in material composition and grain size, serving as the main material basis for reservoirs. Differences in mineral composition reflect the sedimentary environment of the reservoir. Additionally, mineral composition indicates the relationship between diagenetic processes and reservoir evolution. The high feldspar content in well ZQ1 corresponded to relatively favorable reservoir properties. The dominant feldspar type was plagioclase, suggesting that early-stage chemical weathering had undergone significant alteration. The above conclusions provided a microscopic perspective to explain the differences in oil and gas production capacity of large delta-front gas fields, serving as a geological basis for the exploration and exploitation of similar fields.

Does the evolution of micromorphology accompany chromosomal changes on dysploid and polyploid levels in the Barnardia japonica complex (Hyacinthaceae)?

BackgroundChromosome number and genome size changes via dysploidy and polyploidy accompany plant diversification and speciation. Such changes often impact also morphological characters. An excellent system to address the questions of how extensive and structured chromosomal changes within one species complex affect the phenotype is the monocot species complex of Barnardia japonica. This taxon contains two well established and distinct diploid cytotypes differing in base chromosome numbers (AA: x = 8, BB: x = 9) and their allopolyploid derivatives on several ploidy levels (from 3x to 6x). This extensive and structured genomic variation, however, is not mirrored by gross morphological differentiation.ResultsThe current study aims to analyze the correlations between the changes of chromosome numbers and genome sizes with palynological and leaf micromorphological characters in diploids and selected allopolyploids of the B. japonica complex. The chromosome numbers varied from 2n = 16 and 18 (2n = 25 with the presence of supernumerary B chromosomes), and from 2n = 26 to 51 in polyploids on four different ploidy levels (3x, 4x, 5x, and 6x). Despite additive chromosome numbers compared to diploid parental cytotypes, all polyploid cytotypes have experienced genome downsizing. Analyses of leaf micromorphological characters did not reveal any diagnostic traits that could be specifically assigned to individual cytotypes. The variation of pollen grain sizes correlated positively with ploidy levels.ConclusionsThis study clearly demonstrates that karyotype and genome size differentiation does not have to be correlated with morphological differentiation of cytotypes.

Interplay between microstructure, micromechanical, and tensile properties in wire arc additive manufactured nickel-aluminum bronze: As-built and heat treated

The generalized hardness-strength relationship in additively manufactured materials may differ from that observed in cast/wrought materials. To investigate this, the present study focuses on wire-arc additive manufactured (WAAM) Nickel-Aluminum Bronze (NAB) in both its as-built state and three distinct heat-treated conditions. Tensile tests and nanoindentation hardness tests were conducted simultaneously to establish a correlation between hardness and strength. Additionally, a comparison is made between the cast-NAB material and WAAM-NAB in this article. By considering the variations in grain size (coarse vs. fine) and intermetallic compounds in the cast and WAAM-NAB materials (in their as-built and post-heat treated forms), the correlation factor is found to differ based on the specific manufacturing processes and heat treatments employed. This paper aims to develop empirical equations that account for the various influencing factors, including rigid plasticity and uniform plastic work hardening conditions. Moreover, the study reports several indentation-based quantitative variables, such as the plasticity index, elastic recovery, recovery resistance, and wear resistance index of the WAAM-NAB material. By providing a comprehensive analysis of these factors, this research contributes to a better understanding of the hardness-strength relationship and the associated material properties in WAAM-NAB.

Paleoenvironmental changes on the central Tibetan Plateau over the last two millennia inferred from sedimentological proxies and brGDGTs in Bamu Co

Understanding multi-centennial climate variations and their impact on lake catchment productivity over the last 2000 years (the Common Era), is crucial for assessing the role of natural climatic factors in driving productivity changes, and for predicting productivity changes under recent global warming scenarios. However, the climate patterns on the Tibetan Plateau (TP), including temperature and hydrological variations, during the Common Era, and their possible links with productivity, are poorly understood. We present a quantitative reconstruction of mean annual air temperature (MAAT), together with grain size and other sedimentary records, from a non-glacial lake sediment archive on the central TP, with the objective of tracking changes in climate and lake catchment productivity over the past two millennia. Our results reveal an overall cooling trend in temperature reconstructed from branched glycerol dialkyl glycerol tetraethers (brGDGTs), with multi-centennial-scale fluctuations superimposed. These fluctuations include relatively warm periods during 200 BCE–400 CE and the Medieval Climate Anomaly (1050–1400 CE), and cold periods centered on ∼500–1000 CE and the Little Ice Age (∼1500–1900 CE). A rapid warming trend since 1900 CE corresponds to the Current Warm Period. The variations in sedimentary grain size reflect lake level changes associated with changes in the summer monsoon. Paleoproductivity inferred from total organic carbon (TOC) shows a similar pattern to the paleoclimate records, suggesting that millennial-scale productivity was influenced by both temperature and the catchment hydrology. In recent decades, human activities exerted a more substantial influence on lake productivity. Additionally, we suggest that the use of brGDGTs for temperature reconstruction necessitates the investigation of the temperature relationship of various fractions of brGDGTs, specifically tetramethyl-brGDGTs; and that careful selection of the temperature calibration equation is needed to minimize inaccuracies in paleotemperature reconstruction.

Influence of Microstructure on the Material Properties of LLZO Ceramics Derived by Impedance Spectroscopy and Brick Layer Model Analysis.

Variants of garnet-type Li7La3Zr2O12 are being intensively studied as separator materials in solid-state battery research. The material-specific transport properties, such as bulk and grain boundary conductivity, are of prime interest and are mostly investigated by impedance spectroscopy. Data evaluation is usually based on the one-dimensional (1D) brick layer model, which assumes a homogeneous microstructure of identical grains. Real samples show microstructural inhomogeneities in grain size and porosity due to the complex behavior of grain growth in garnets that is very sensitive to the sintering protocol. However, the true microstructure is often omitted in impedance data analysis, hindering the interlaboratory reproducibility and comparability of results reported in the literature. Here, we use a combinatorial approach of structural analysis and three-dimensional (3D) transport modeling to explore the effects of microstructure on the derived material-specific properties of garnet-type ceramics. For this purpose, Al-doped Li7La3Zr2O12 pellets with different microstructures are fabricated and electrochemically characterized. A machine learning-assisted image segmentation approach is used for statistical analysis and quantification of the microstructural changes during sintering. A detailed analysis of transport through statistically modeled twin microstructures demonstrates that the transport parameters derived from a 1D brick layer model approach show uncertainties up to 150%, only due to variations in grain size. These uncertainties can be even larger in the presence of porosity. This study helps to better understand the role of the microstructure of polycrystalline electroceramics and its influence on experimental results.

Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream

SUMMARYIce streams are major contributors to ice sheet mass loss and sea level rise. Effects of their dynamic behaviour are imprinted into seismic properties, such as wave speeds and anisotropy. Here, we present results from a distributed acoustic sensing (DAS) experiment in a deep ice-core borehole in the onset region of the Northeast Greenland Ice Stream, with focus on phenomenological and methodological aspects. A series of active seismic surface sources produced clear recordings of the P and S wavefield, including internal reflections, along a 1500 m long fibre-optic cable that was placed into the borehole. The combination of nonlinear traveltime tomography with a firn model constrained by multimode surface wave data, allows us to invert for P and S wave speeds with depth-dependent uncertainties on the order of only 10 m s−1, and vertical resolution of 20–70 m. The wave speed model in conjunction with the regularly spaced DAS data enable a straightforward separation of internal upward reflections followed by a reverse-time migration that provides a detailed reflectivity image of the ice. While the differences between P and S wave speeds hint at anisotropy related to crystal orientation fabric, the reflectivity image seems to carry a pronounced climatic imprint caused by rapid variations in grain size. Further improvements in resolution do not seem to be limited by the DAS channel spacing. Instead, the maximum frequency of body waves below ∼200 Hz, low signal-to-noise ratio caused by poor coupling, and systematic errors produced by the ray approximation, appear to be the leading-order issues. Among these, only the latter has a simple existing solution in the form of full-waveform inversion. Improving signal bandwidth and quality, however, will likely require a significantly larger effort in terms of both sensing equipment and logistics.

A 3-D-printed precision sediment feed

Abstract Reproducible and regulated sediment feed rates are necessary for many flume experiments. A sediment feed mechanism capable of precisely providing a wide range of feed rates was developed for this purpose. It was constructed using wood, aluminum, and 3-D-printed components. It is powered by a stepper motor and controlled by an Arduino, and is easily programmable. Commercially available sediment feeds use augers or vibrating trays to move sediment; in contrast, this feed employs the novel design of a slotted wheel. While some commercially available sediment feeds can handle a wider variety of grain sizes, the error of their output (vol/t) tends to be slightly higher than the error of this feed's output, and this feed can deliver sediment over a much wider range of delivery rates. The most notable advantage of this sediment feed is that the cost of materials is only about $300 U.S.

Geochemical Characterization of Sediments from the Bibione Coastal Area (Northeast Italy): Details on Bulk Composition and Particle Size Distribution

The aim of this study is to characterize the sediments of the coastal area of Bibione and the Baseleghe Lagoon (Province of Venice, Italy). The characterization includes the assessment of particle size distribution, carbonate content, composition of major oxides, and heavy metal concentrations. The results indicated that the sediments primarily consisted of carbonate but showed significant heterogeneity in both composition and grain size within the different environments of the Bibione coastal area. Carbonate content decreased from the beach to the seabed, which does not appear to be solely influenced by variations in sediment grain size. This finding has potential implications for the Bibione area’s coastal erosion processes and sediment quality. Significant differences in grain size and composition were observed between the mouth and the inner region in the lagoon area. The textural characteristics of the sediments in the inner part of the lagoon make it particularly vulnerable to pollution, with potential environmental and economic consequences. Different pollution indices have indicated the presence of heavy metal contamination in both the coastal and, especially, the lagoon area. The source of these metals appears to be predominantly natural, although there may be some contribution from anthropogenic sources for certain metals. However, the comparison of the metal concentrations in the samples with the limits set by the Italian legislation showed that the sediments were still of good quality.

Enhanced strength-ductility synergy in high-entropy alloys via architecting three-level gradient hierarchical nanostructure

Gradient microstructural design represents a new strategy for enhancing strength-ductility synergy of high/medium entropy alloys (H/MEAs). However, most of the reported gradient H/MEAs have only one type of gradient microstructure, which has limited ability to realize the full potential of gradient structure. Here, we report a three-level gradient hierarchical nanostructure (GHN) in a Al0.3CoCrFeNi HEA by ultrasonic surface rolling processing (USRP) followed by aging treatment that can result in a six-fold enhancement in yield strength with almost no loss in ductility compared to the coarse structured counterpart. The proposed three-level GHN is characterized with gradient variations in grain size, nano-twin and dislocation density, B2 and σ precipitates content. Systematic experiments indicate that strong hetero-deformation-induced (HDI) hardening associated with the activation of deformation twinning, are responsible for this exceptional strength-ductility synergy. This three-level GHN engineering strategy in this work can also be feasibly applied to many other H/MEAs, and offers an available pathway to develop high strong and ductile metallic materials.

On the Processability and Microstructural Evolution of CuCrZr in Multilayer Laser-Directed Energy Deposition Additive Manufacturing via Statistical and Experimental Methods

Laser-directed energy deposition (LDED) is a promising technology for coating, repairing, and building near-net-shape 3D structures. However, the processing of copper alloys, specifically, has presented a significant challenge due to their low laser absorptivity at the 1060 nm laser wavelength and high thermal conductivity. This study undertook a methodical examination by employing a 2 kW disk laser, operating at a wavelength of 1064 nm, and a coaxial nozzle head to comprehensively examine the processability of the highly conductive CuCrZr alloy for expanding the range of materials that can be successfully processed using LDED. The investigation focuses not only on optimizing the input process parameters that are the laser power, scanning speed, powder feed rate, and overlap ratio, but also on planning the toolpath trajectory, as these factors were found to exert a substantial influence on processability, geometrical accuracy, and the occurrence of defects such as lack of fusion. The optimal toolpath trajectory discovered involved implementing a zigzag strategy combined with a 90° rotation of the scanning direction. Additionally, a start point rotation was considered between each layer to even out the deposition of the layers. Moreover, a contour with a radial path at the corners was introduced to enhance the overall trajectory. Based on the hierarchal experimental study, the appropriate ranges for the key process parameters that leads to 99.99% relative density have been identified. They were found to be from 1100 up to 2000 W for the laser power (P), and from 0.003 up to 0.016 g/mm for the amount of powder that is fed to the melt pool distance (F/V). Regarding the influence of process parameters on the microstructure of the samples with equal deposition height, it was observed that varying combinations of process parameters within the optimal processing window resulted in variations in grain size ranging from 105 to 215 µm.

Retained austenite grain size as a strength-plasticity relationship indicator in Al-alloyed medium-Mn steel processed by intercritical annealing

Although most studies focus on the impact of the fraction of retained austenite (RA) on the relationship between strength and plasticity, this research explores the influence of the mechanical stability of RA, which is primarily affected by its grain size. To investigate this, samples of 5% Mn steel with varying fractions of RA, as well as different sizes and concentrations of carbon (C) and manganese (Mn), were produced by adjusting the soaking time during intercritical annealing (IA) between 1 and 300 min at a temperature of 680 °C. The mechanical properties of the samples were evaluated using static tensile tests. Detailed microstructural analyses were conducted before and after deformation through hardness tests, X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) images, TEM-EDS microanalysis, and electron backscatter diffraction (EBSD) phase and orientation maps. Additionally, thermodynamic calculations were used to supplement the experimental findings. The results suggest that both chemical enrichment and grain size reduction have comparable effects on stabilizing the RA. The wide variation of RA grain sizes from 0.02 to 0.15 μm3 promotes a gradual and continuous martensitic transformation under strain throughout the entire strain range, leading to a uniform elongation exceeding 19% in the steel analyzed. However, the presence of an appropriate average size of RA (from ∼0.07 to ∼0.11 μm3) is crucial because grains smaller than ∼0.02 μm3 impede martensitic transformation, while coarse grains characterized by a volume greater than ∼0.13 μm3 result in significant transformation in an early stage of deformation.

Molecular dynamics simulation of the effect of supersonic fine particle bombardment on the mechanical behaviour of γ-TiAl alloy: The effect of grain size

Due to the nanoscale inverse Hall-Petch (H-P) effect, the grain size exerts a significant influence on the mechanical behaviour of the material. The impact of supersonic fine particle bombardment (SFPB) on the mechanical response of γ-TiAl alloy with varying grain sizes was investigated using molecular dynamics simulations. The dislocation density and stress state of the material surface were analyzed before and after SFPB treatment. The results indicate that the degree of grain refinement in the matrix varies depending on the grain size following SFPB treatment. In contrast, the critical average grain size for observing the H-P effect is determined to be 9.96 nm. The hardness of the material increases as the average grain size decreases, but it decreases below the critical average grain size. Moreover, monocrystalline samples exhibit the highest hardness and demonstrate greater sensitivity to elastic recovery in both depth and width directions compared to polycrystalline samples. The variation in grain size following SFPB impact influences the distribution of von Mises stress and hydrostatic stress. The present study investigates the grain refinement and mechanical behaviour of polycrystalline γ-TiAl alloys at the atomic scale, thereby offering valuable insights into the SFPB process.

Contamination of the marine environment by Antarctic research stations: Monitoring marine pollution at Casey station from 1997 to 2015.

The contamination of the marine environment surrounding coastal Antarctic research stations remains insufficiently understood in terms of its extent, persistence, and characteristics. We investigated the presence of contaminants in marine sediments near Casey Station, located in the Windmill Islands of East Antarctica, during the period spanning from 1997 to 2015. Metals, hydrocarbons, PBDEs, PCBs, and nutrients were measured in sediments at anthropogenically disturbed sites, including the wastewater outfall, the wharf area, two former waste disposal sites, and various control locations. Sampling was carried out at three spatial scales: Locations, which were generally kilometres apart and formed the primary scale for comparison; Sites, which were 100 meters apart within each location; and Plots, which were 10 meters apart within each site. Consistently higher concentrations of most contaminants, and in some cases nutrients, were observed at disturbed locations. Some locations also exhibited an increase in contaminant concentrations over time. The spatial distribution of sediment properties (such as grain size and organic matter) and contaminants displayed intricate patterns of variation. Variation in grain size depended on the size category, with fine grains (e.g., <63 μm) showing the greatest variation at the Location scale, while coarse grains exhibited minimal variation at this scale. Contaminant levels demonstrated significant differences between Locations, accounting for approximately 55% of the overall variation for metals, while the variation within the 10-meter scale generally exceeded that within the 100-meter scale. Residual variation among replicate samples was also very high, demonstrating the need for adequate replication in studies of sediments and contaminants around stations. Some contaminants exceeded international guidelines for sediment quality, including metals, hydrocarbons, and PCBs. We conclude that Antarctic research stations such as Casey are likely to pose a moderate level of long-term ecological risk to local marine ecosystems through marine pollution. However, contamination is expected to be confined to areas in close proximity to the stations, although its extent and concentration are anticipated to increase with time. Raising awareness of the contamination risks associated with Antarctic stations and implementing monitoring programs for marine environments adjacent to these stations can contribute to informed decision-making and the improvement of environmental management practices in Antarctica.

Old core, new tricks: a comparative study of old and new mudstone cores for applications in the energy transition

Repurposing depleted oil and gas reservoirs for secondary storage may play an important role in the transition to low-carbon energy. The integrity of the cap rocks overlying the reservoirs is an important factor for gas storage and needs to be understood prior to repurposing. In some cases, old cap-rock cores collected during exploration and development of oil and gas fields may be available for characterization using modern techniques but after being stored for decades these cores are likely to have experienced many changes in moisture, which can lead to physical changes. A comparative study of samples taken from old, unpreserved mudstone core and samples from a recently acquired and preserved core taken from the same formation shows that the mineralogy, porosity and permeability results are relatively similar between the two cores. The differences in the porosity measurements between the old and new core samples are primarily due to natural variations in grain size, rather than the preservation status of the cores. Geomechanical data, however, show significant and non-systematic differences between the old samples and the new samples, suggesting that old core samples are not suitable for geomechanical characterization. In the absence of new, well-preserved core, old core samples may provide suitable porosity, permeability and mineralogical data, whereas the old, unpreserved core is unlikely to provide reliable geomechanical data. Supplementary material: Individual BIB-SEM porosity measurements for each sample are available at https://doi.org/10.6084/m9.figshare.c.6725765 Thematic collection: This article is part of the Fault and top seals 2022 collection available at: https://www.lyellcollection.org/topic/collections/fault-and-top-seals-2022

The Effect of Rolling Texture on the Plastic Deformation of Nano-Gradient Aluminum.

Creating alloys with a gradient microstructure in grain size has been shown to be a potential method to resolve the trade-off dilemma between strength and ductility. However, different textures developed with various processing methods cannot be fully eliminated, which can significantly affect the mechanical behavior of alloys. In this study, we use a multiscale framework based on dislocation theory to investigate how the combination of rolling texture and gradient in grain size affects the plastic deformation of nano-gradient aluminum during a tensile test. We found that specific rolling textures, such as {110} texture, can significantly enhance the strength and ductility of nano-gradient aluminum. This improvement is the result of the grain being reoriented and the redistribution of stress and strain, which are caused by the combined influence of texture and variation in grain size. These results provide new insights into developing high-performance aluminum by mediating texture and grain size gradient.

Critical Assessment 43: Microstructural and mechanical properties of friction stir additively fabricated SiC-Reinforced AA6061 build

Friction stir additive manufacturing was employed to fabricate a SiC-reinforced AA6061 composite. The tool with a pin length of 4.5 mm (plunge depth of 50% into the lower layer thickness) was used for the experiment. The stir zone consisted of fine, equiaxed grains due to dynamic recrystallisation. Variations in grain size, as well as changes in precipitate distribution, size, and morphology, were detected along the build direction. Hardness and tensile strength varied across layers, with the top slice having the greatest values of 104.2 HV and 268.4 MPa, respectively. Notably, the FSAM build demonstrated improved ductility with a maximum of 58.98%, mostly ascribed to fragmentation and partial loss of grain-boundary phases, as well as strong interfaces that delayed necking.

Effect of tin concentration on the morphological & crystal structure, and optical properties of chemical vapor deposited MAPb1−xSnxI3 perovskite films for 0 ≤ x < 0.5

In this article, we evaluate the impact of Sn proportion on the morphology and crystal structure, and its influence on the optical properties of MAPb1−xSnxI3 (0 ≤ x < 0.5) perovskite films. The uniform and compact Sn-Pb halide films with a variety of grain sizes were deposited using a low-pressure chemical vapor deposition (LP-CVD) system and were sequentially converted into perovskite films. Rutherford backscattering spectrometry (RBS) measurements were performed to determine the depth profile of elements and the simulated spectra suggested multilayered films. The x-ray diffraction (XRD) patterns confirmed the formation of the perovskite phase, i.e. tetragonal structure with I4cm space group. The energy bandgap (Eg) and the Urbach energy (Eu) approximation insinuate a tradeoff between the attainment of low bandgap Sn-Pb halide perovskites and defect-disorder tolerant films.

Evolution of microstructure and mechanical properties in the molten pool of γ-TiAl alloy synthesized in situ by dual-wire-fed electron beam directed energy deposition

Dual-wire-fed electron beam directed energy deposition (EB-DED) is a highly efficient technique for additive manufacturing (AM) of TiAl alloys, but research into the evolution of microstructure and mechanical properties within the melt pool is limited. Experimental and numerical simulations are used together to study the evolution along the vertical direction within the TiAl alloy melt pool. The chemical composition, microstructure and microhardness in the top region (TR), middle region (MR) and bottom region (BR) within the melt pool were characterized and comparatively analysed. The results showed that the Al content decreased from 52 at. % to 49 at. % from the top to the bottom, the grain size increased and then decreased, and the grain aspect ratio increased from 1 to over 3. The decreasing size factor and increasing shape factor result in variations in grain size and shape. The improvement in microhardness from 226 HV0.5 to 280 HV0.5 was quantitatively analysed as being mainly due to the reduction in Al content. The results of this study are of paramount importance in facilitating the use of the dual-wire-fed EB-DED technique for the production of high performance TiAl alloy components.