Journal articles: 'Melt Pools'

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Schmid, Simon, Johannes Krabusch, Thomas Schromm, Shi Jieqing, Stefan Ziegelmeier, Christian Ulrich Grosse, and Johannes Henrich Schleifenbaum. "A new approach for automated measuring of the melt pool geometry in laser-powder bed fusion." Progress in Additive Manufacturing 6, no. 2 (March 12, 2021): 269–79. http://dx.doi.org/10.1007/s40964-021-00173-7.

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AbstractAdditive manufacturing (AM) offers unique possibilities in comparison to conventional manufacturing processes. For example, complex parts can be manufactured without tools. For metals, the most commonly used AM process is laser-powder bed fusion (L-PBF). The L-PBF process is prone to process disturbances, hence maintaining a consistent part quality remains an important subject within current research. An established indicator for quantifying process changes is the dimension of melt pools, which depends on the energy input and the cooling conditions. The melt pool geometry is normally measured manually in cross sections of solidified welding seams. This paper introduces a new approach for the automated visual measuring of melt pools in cross-sections of parts manufactured by L-PBF. The melt pools are first segmented in the images and are then measured. Since the melt pools have a heterogeneous appearance, segmentation with common digital image processing is difficult, deep learning was applied in this project. With the presented approach, the melt pools can be measured over the whole cross section of the specimen. Furthermore, remelted melt pools, which are only partly visible, are evaluated. With this automated approach, a high number of melt pools in each cross-section can be measured, which allows the examination of trends over the build direction in a specimen and results in better statistics. Furthermore, deviations in the energy input can be estimated via the measured melt pool dimensions.

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Kube, Christopher M. "Acoustics for in-process melt pool monitoring during metal additive manufacturing." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A188. http://dx.doi.org/10.1121/10.0015980.

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Intrinsic to most metal additive manufacturing (AM) processes are melt pools generated from directed energy sources like lasers. Melt pools are critical as they function to join powder layers to previous layers during the process. Their criticality extends deeper as most porosity in AM parts stems from melt pool behavior while melt pool solidification dictates the parts’ microstructure. Significant breakthroughs in metal AM are severely hindered by the lack of access to experimental tools to study melt pools and modeling that do not fully capture the complex physics. Thus, melt pool related defects are often difficult to predict in occurrence and location while determining optimal process parameters to eliminate defects is extremely challenging and costly. Furthermore, the many exciting opportunities such as realizing new AM alloys, developing gradient materials/structure, and tailoring microstructure to intended applications are possible only with further understanding of melt pool behavior. With these clear needs, in-process acoustics have been proposed as plausible experimental tools for studying melt pool behavior. This presentation will provide an overview of the current activity in this area in addition to the specific needs the acoustics community can potentially address.

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Schwerz, Claudia, and Lars Nyborg. "Linking In Situ Melt Pool Monitoring to Melt Pool Size Distributions and Internal Flaws in Laser Powder Bed Fusion." Metals 11, no. 11 (November 18, 2021): 1856. http://dx.doi.org/10.3390/met11111856.

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In situ monitoring of the melt pools in laser powder bed fusion (LPBF) has enabled the elucidation of process phenomena. There has been an increasing interest in also using melt pool monitoring to identify process anomalies and control the quality of the manufactured parts. However, a better understanding of the variability of melt pools and the relation to the incidence of internal flaws are necessary to achieve this goal. This study aims to link distributions of melt pool dimensions to internal flaws and signal characteristics obtained from melt pool monitoring. A process mapping approach is employed in the manufacturing of Hastelloy X, comprising a vast portion of the process space. Ex situ measurements of melt pool dimensions and analysis of internal flaws are correlated to the signal obtained through in situ melt pool monitoring in the visible and near-infrared spectra. It is found that the variability in melt pool dimensions is related to the presence of internal flaws, but scatter in melt pool dimensions is not detectable by the monitoring system employed in this study. The signal intensities are proportional to melt pool dimensions, and the signal is increasingly dynamic following process conditions that increase the generation of spatter.

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Guo, Kai, Yunping Ji, Yiming Li, Xueliang Kang, Huiyi Bai, and Huiping Ren. "Numerical Simulation of Temperature Field and Melt Pool Characteristics of CP-Ti Manufactured by Laser Powder Bed Fusion." Metals 13, no. 1 (December 20, 2022): 11. http://dx.doi.org/10.3390/met13010011.

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A coupled heat source model that combined a Gauss surface heat source with a Gauss cylindrical volumetric heat source was introduced to simulate temperature field distribution and melt pool characteristics using a finite element simulation (FEM) method for the deep and narrow melt pools formed in laser powder bed fusion (L-PBF) aiming at commercial pure titanium (CP-Ti). For comparison, the same simulations using the Gauss surface heat source model and the double ellipsoid heat source model were also performed. The simulated melt pool geometries using the coupled heat source model match well with the measurements, with an average error of 1% for the melt pool depth and 7% for the width. Based on the single-track experimental results, it was found by comparing the simulated results from the three heat source models that the coupled heat source model had better accuracy than the other two. Then, the temperature field and the melt pool geometries of CP-Ti fabricated at different laser power levels from 300 W to 500 W and scanning speeds from 600 mm/s to 4000 mm/s were simulated. According to the simulated maximum temperature and geometries of the melt pool, a suitable process parameters map for CP-Ti was obtained. The reported experimental results agree well with the simulated map. The coupled heat source model is more accurate and applicable for the deep and narrow melt pools formed during L-PBF.

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Tranter, Martyn, Andrew G. Fountain, W. Berry Lyons, Thomas H. Nylen, and Kathy A. Welch. "The chemical composition of runoff from Canada Glacier, Antarctica: implications for glacier hydrology duringa cool summer." Annals of Glaciology 40 (2005): 15–19. http://dx.doi.org/10.3189/172756405781813753.

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AbstractVariations in the chemical composition of subsurface runoff within Canada Glacier, Antarctica, are used to identify the main source waters, which are vertical surfaces, and melt from solar-heated debris within channels, cryoconite holes and pools. The main flow paths are subsurface connections between cryoconite holes, pools and riffles. The latter may become partially disconnected during hard freeze. The chemical composition of runoff at the outlet of Canada Glacier during January 2000 was dominated by Ca2+, HCO3– and sea salt (Na+ and Cl–), and became depleted in sea-salt and non-sea-salt (*) SO42– as the subsurface drainage system in a frozen pool-and-riffle system was flushed and the melting ice surface became depleted of overwinter dry deposited salts. Only during 2 days of hard freeze did sea salt and *SO42– increase in concentration together. Otherwise, sea salt and *SO42– declined while *Ca2+ and HCO3– increased. The latter ions are derived from the chemical weathering of sediment in frozen-topped pools, channels and cryoconite holes. It is inferred that the hydrochemical processes which occur in the vestigial, subsurface drainage system are the elution of ions from ice melt, dilution of these ions downstream by ice melt from vertical surfaces and the dissolution of dust, in subsurface pools, channels and/or cryoconite holes.

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Fotovvati, Behzad, Steven F. Wayne, Gladius Lewis, and Ebrahim Asadi. "A Review on Melt-Pool Characteristics in Laser Welding of Metals." Advances in Materials Science and Engineering 2018 (2018): 1–18. http://dx.doi.org/10.1155/2018/4920718.

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Laser welding of metals involves with formation of a melt-pool and subsequent rapid solidification, resulting in alteration of properties and the microstructure of the welded metal. Understanding and predicting relationships between laser welding process parameters, such as laser speed and welding power, and melt-pool characteristics have been the subjects of many studies in literature because this knowledge is critical to controlling and improving laser welding. Recent advances in metal additive manufacturing processes have renewed interest in the melt-pool studies because in many of these processes, part fabrication involves small moving melt-pools. The present work is a critical review of the literature on experimental and modeling studies on laser welding, with the focus being on the influence of process parameters on geometry, thermodynamics, fluid dynamics, microstructure, and porosity characteristics of the melt-pool. These data may inform future experimental laser welding studies and may be used for verification and validation of results obtained in future melt-pool modeling studies.

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Wang, Xiang, Jinwu Kang, Tianjiao Wang, Pengyue Wu, Tao Feng, and Lele Zheng. "Effect of Layer-Wise Varying Parameters on the Microstructure and Soundness of Selective Laser Melted INCONEL 718 Alloy." Materials 12, no. 13 (July 5, 2019): 2165. http://dx.doi.org/10.3390/ma12132165.

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Selective laser melting (SLM) is a promising powder bed fusion additive manufacturing technique for metal part fabrication. In this paper, varying scanning speed in the range of 500 mm/s to 1900 mm/s, and laser power in the range of 100 W to 200 W, were realized from layer to layer in a cycle of 56 layers in a single cuboid Inconel 718 alloy specimen through SLM. Layer-wise variation of microstructure and porosity were acquired, showing the layer-wise controlling capability of microstructural soundness. The melt pool size and soundness are closely linked with the energy input. High energy density led to sound regions with larger, orderly stacked melt pools and columnar grains, while low energy density resulted in porous regions with smaller, mismatched melt pools, un-melted powder, and equiaxed grains with finer dendrites. With the increase of laser energy density, the specimen shifts from porous region to sound region within several layers.

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Tan, M. J., D. H. Cho, and F. B. Cheung. "Thermal Analysis of Heat-Generating Pools Bounded From Below by Curved Surfaces." Journal of Heat Transfer 116, no. 1 (February 1, 1994): 127–35. http://dx.doi.org/10.1115/1.2910846.

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A computer code that features the use of a directional effective thermal conductivity in modeling natural convection in heat-generating pools has been developed to analyze heat transfer in such pools, which are bounded from below by curved surfaces. Illustrative calculations pertaining to two published experimental studies on convective heat transfer in water pools with uniformly distributed volumetric energy sources are carried out using the code. The water pools used in the two studies under consideration were cooled either from the top or from the bottom, but not from both. The utility as well as the limitations of the effective thermal conductivity approach in the context of addressing the issue of melt-pool coolability is demonstrated by comparisons of calculated results with the experimental data.

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Shi, Wanyuan, and Nobuyuki Imaishi. "Hydrothermal waves in rotating annular pools of silicon melt." Microgravity Science and Technology 19, no. 3-4 (October 2007): 159–60. http://dx.doi.org/10.1007/bf02915785.

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Tam, A. S., and D. E. Hardt. "Weld Pool Impedance for Pool Geometry Measurement: Stationary and Nonstationary Pools." Journal of Dynamic Systems, Measurement, and Control 111, no. 4 (December 1, 1989): 545–53. http://dx.doi.org/10.1115/1.3153090.

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The most elusive quantity in describing weld pool geometry is the depth, since it cannot be directly observed; yet it is the most important quantity to be regulated during welding. This paper addresses the problem of depth feedback measurement for full penetration welds, where the objective is to completely melt the cross section. It has been demonstrated that the existence and size of a full penetration weld can be detected by measuring the mechanical impedance of the resulting weld pool. Previous work in modeling this phenomenon has been limited to stationary welds, and experiments have either used impractical measurement methods or have not provided conclusive results. In this paper, a model of pool motion is developed that applies to both the stationary and moving weld case, and the pool motion is detected directly from changes in the arc voltage. A description of pool motion is derived from an elliptical membrane model, and the total system transfer function, including arc and pool dynamics is derived. A series of experiments demonstrates that the pool motion can indeed be detected for the moving pool case. However, the exact determination of pool oscillation frequencies requires knowledge of the pool perimeter geometry, since the elliptical system has many closely spaced eigenvalues arising from both symmetric and antisymmetric mode shapes.

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Jeffries, Martin O., William M. Sackinger, and Harold V. Serson. "Remote Sensing of Sea-Ice Growth and Melt-Pool Evolution, Milne Ice Shelf, Ellesmere Island, Canada." Annals of Glaciology 9 (1987): 145–50. http://dx.doi.org/10.3189/s0260305500000525.

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Periodically since 1950, air photographs and SLAR images have been taken of the Arctic ice shelves. The study of air photographs and SLAR images of the outer part of Milne Ice Shelf had three aims: (1) to map losses and ice re-growth at the shelf front, (2) to map the evolution of melt pools on shelf ice and multi-year land-fast sea ice, and (3) to assess the usefulness of air photographs and SLAR for these purposes. For mapping of ice calvings and subsequent sea-ice growth, both air photographs and radar images have been used sucessfully. However, air photographs are better than radar for mapping ice-surface features. The ridge-and-trough systems that characterize the surface of the ice shelf and old sea ice are clearly visible on each type of imagery but, because of their larger scale, air photographs proved to be most useful for a study of melt-pool evolution. The orientation of the melt pools is parallel to the prevailing winds which drive water along the troughs. The drainage system evolves by a process of elongation and coalesence.

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Jeffries, Martin O., William M. Sackinger, and Harold V. Serson. "Remote Sensing of Sea-Ice Growth and Melt-Pool Evolution, Milne Ice Shelf, Ellesmere Island, Canada." Annals of Glaciology 9 (1987): 145–50. http://dx.doi.org/10.1017/s0260305500000525.

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Periodically since 1950, air photographs and SLAR images have been taken of the Arctic ice shelves. The study of air photographs and SLAR images of the outer part of Milne Ice Shelf had three aims: (1) to map losses and ice re-growth at the shelf front, (2) to map the evolution of melt pools on shelf ice and multi-year land-fast sea ice, and (3) to assess the usefulness of air photographs and SLAR for these purposes. For mapping of ice calvings and subsequent sea-ice growth, both air photographs and radar images have been used sucessfully. However, air photographs are better than radar for mapping ice-surface features. The ridge-and-trough systems that characterize the surface of the ice shelf and old sea ice are clearly visible on each type of imagery but, because of their larger scale, air photographs proved to be most useful for a study of melt-pool evolution. The orientation of the melt pools is parallel to the prevailing winds which drive water along the troughs. The drainage system evolves by a process of elongation and coalesence.

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Qi, Xing, Naoki Takata, Asuka Suzuki, Makoto Kobashi, and Masaki Kato. "Microstructure of Al-2.5Fe Binary Alloy Fabricated by Laser Powder Bed Fusion." Materials Science Forum 1016 (January 2021): 1175–80. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1175.

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In the present study, microstructural and crystallographic features of an Al-Fe binary alloy with a near eutectic composition (Al-2.5wt%Fe) fabricated by laser powder bed fusion (LPBF) process were examined. The LPBF processing for the Al-Fe alloy powder was conducted at room temperature using a 3D Systems ProX 200 operating at a laser power of 204 W and a laser scan speed of 0.6 m/s and 0.8 m/s to fabricate cube samples with high relative density above 99 %. The fabricated sample exhibited characteristic microstructure consisting of a number of melt pools in which the regions had locally melted and rapidly solidified by laser irradiation during the LPBF process. Numerous fine particles of Al-Fe intermetallics with a mean size below 100 nm were found within the α-Al matrix in the observed melt pools, whereas relatively coarsened particles were localized around melt pool boundaries. Electron backscatter diffraction (EBSD) analyses revealed a number of columnar a-Al grains with a mean size of approximately 10 μm. The LPBF-fabricated Al-Fe alloy exhibits a high hardness of approximately 90 HV, which is more than twice higher than the conventionally casted Al-Fe alloy.

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Jähnig, Theresa, Cornelius Demuth, and Andrés Fabián Lasagni. "Influence of Sulphur Content on Structuring Dynamics during Nanosecond Pulsed Direct Laser Interference Patterning." Nanomaterials 11, no. 4 (March 27, 2021): 855. http://dx.doi.org/10.3390/nano11040855.

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The formation of melt and its spread in materials is the focus of many high temperature processes, for example, in laser welding and cutting. Surface active elements alter the surface tension gradient and therefore influence melt penetration depth and pool width. This study describes the application of direct laser interference patterning (DLIP) for structuring steel surfaces with diverse contents of the surface active element sulphur, which affects the melt convection pattern and the pool shape during the process. The laser fluence used is varied to analyse the different topographic features that can be produced depending on the absorbed laser intensity and the sulphur concentration. The results show that single peak geometries can be produced on substrates with sulphur contents lower than 300 ppm, while structures with split peaks form on higher sulphur content steels. The peak formation is explained using related conceptions of thermocapillary convection in weld pools. Numerical simulations based on a smoothed particle hydrodynamics (SPH) model are employed to further investigate the influence of the sulphur content in steel on the melt pool convection during nanosecond single-pulsed DLIP.

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Ebrahimi, Amin, Aravind Babu, Chris R. Kleijn, Marcel J. M. Hermans, and Ian M. Richardson. "The Effect of Groove Shape on Molten Metal Flow Behaviour in Gas Metal Arc Welding." Materials 14, no. 23 (December 4, 2021): 7444. http://dx.doi.org/10.3390/ma14237444.

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One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a computational model to describe the melt-pool behaviour in root-pass gas metal arc welding (GMAW). Three-dimensional numerical simulations have been performed using an enhanced physics-based computational model to unravel the effect of groove shape on complex unsteady heat and fluid flow in GMAW. The influence of surface deformations on the magnitude and distribution of the heat input and the forces applied to the molten material were taken into account. Utilising this model, the complex thermal and fluid flow fields in melt pools were visualised and described for different groove shapes. Additionally, experiments were performed to validate the numerical predictions and the robustness of the present computational model is demonstrated. The model can be used to explore the physical effects of governing fluid flow and melt-pool stability during gas metal arc root welding.

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Paraschiv, Alexandru, Gheorghe Matache, Mihaela Raluca Condruz, Tiberius Florian Frigioescu, and Ion Ionică. "The Influence of Laser Defocusing in Selective Laser Melted IN 625." Materials 14, no. 13 (June 22, 2021): 3447. http://dx.doi.org/10.3390/ma14133447.

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Laser defocusing was investigated to assess the influence on the surface quality, melt pool shape, tensile properties, and densification of selective laser melted (SLMed) IN 625. Negative (−0.5 mm, −0.3 mm), positive (+0.3 mm, +0.5 mm), and 0 mm defocusing distances were used to produce specimens, while the other process parameters remained unchanged. The scanning electron microscopy (SEM) images of the melt pools generated by different defocusing amounts were used to assess the influence on the morphology and melt pool size. The mechanical properties were evaluated by tensile testing, and the bulk density of the parts was measured by Archimedes’ method. It was observed that the melt pool morphology and melting mode are directly related to the defocusing distances. The melting height increases while the melting depth decreases from positive to negative defocusing. The use of negative defocusing distances generates the conduction melting mode of the SLMed IN 625, and the alloy (as-built) has the maximum density and ultimate tensile strength. Conversely, the use of positive distances generates keyhole mode melting accompanied by a decrease of density and mechanical strength due to the increase in porosity and is therefore not suitable for the SLM process.

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Mridha, S., A. N. Md Idriss, and T. N. Baker. "Incorporation of TiC Particulates on AISI 4340 Low Alloy Steel Surfaces via Tungsten Inert Gas Arc Melting." Advanced Materials Research 445 (January 2012): 655–60. http://dx.doi.org/10.4028/www.scientific.net/amr.445.655.

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Surface cladding utilizes a high energy input to deposit a layer on substrate surfaces providing protection against wear and corrosion. In this work, TiC particulates were incorporated by meltingsingle tracksin powder preplaced onto AISI 4340 low alloy steel surfaces using a Tungsten Inert Gas (TIG) torch with a range of processing conditions. The effects of energy input and powder content on the melt geometry, microstructure and hardness were investigated. The highest energy input (1680 J/mm) under theTIG torchproduced deeper (1.0 mm) and wider melt pools, associated with increased dilution, compared to that processed at the lowest energy (1008 J/mm). The melt microstructure contained partially meltedTiC particulatesassociated with dendritic, cubic and globular typecarbidesprecipitated upon solidification of TiC dissolved in the melt; TiC accumulated more near to the melt-matrix interface and at the track edges. Addition of 0.4, 0.5 and 1.0 mg/mm2TiC gave hardness values in the resolidified melt pools between 750 to over 1100Hv, against a base hardness of 300 Hv; hardness values are higher in tracks processed with a greater TiC addition and reduced energy input.

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Bruni, C., D. Ciccarelli, T. Mancia, M. Pieralisi, and L. Greco. "Analytical modeling of surface roughness of metal manufactured components based on building history." IOP Conference Series: Materials Science and Engineering 1270, no. 1 (December 1, 2022): 012021. http://dx.doi.org/10.1088/1757-899x/1270/1/012021.

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The realization of metal physical objects by localized laser fusion techniques requires the building under specified and predictable conditions in order to reduce errors in that phase. The stratification and the dimension got by solidified melt bath pools determine the geometry and the surface micro-characteristics appearing on the manufactured component. The relationship between internal microstructure and external characteristics are proposed by a analytical modeling in which internal variables such as the melt pool surfaces detected in the sectioned part of the specimen are given as input to describe the surface roughness at given positions of the surface of the object. The proposed method is based on the use of melt pool areas directly as obtained by the building history and on the use of an interpolating equation able to approximate their trend in order to reduce the variability got by real process. The obtained analytical models are able not only to correlate but to describe in detail the surface roughness as a function of internal bath areas. The modeling approach proposed is based on the regression analysis in which different variables affecting the geometry and the surface roughness are considered and their significance evaluated. An improvement in the predictive ability of the model using the interpolated melt pool areas is obtained.

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Slodczyk, Marcel, Alexander Ilin, Thomas Kiedrowski, Jens Schmiemann, and Vasily Ploshikhin. "Simulation Aided Process Development with Multi-Spot Strategies in Laser Powder-Bed Fusion." Advanced Materials Research 1161 (March 2021): 75–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1161.75.

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A challenge in laser powder-bed fusion is to achieve high process speed while maintaining quality level of the melting tracks. One approach to increase productivity is to distribute available laser power over several laser spots, resulting in higher melting rate. Using multiple laser spots opens up new parameter spaces in comparison to the conventional single-spot exposure. In addition to classical process parameters, e.g. total laser power and scanning speed, the distribution of power to the specific spots and the respective spatial arrangement have an impact on resulting process quality and speed. Within the scope of this research work, a physically based model is presented to define multi-spot process strategies for the generation of desired melt pool dimensions. Diffractive optical elements are used in order to adjust power or spatial arrangement of multiple laser spots. Resulting melt pool has more width and less depth compared to single-spot generated melt pools. Simulations and experiments show an optimum in applied spot distance between laser spots to obtain higher melting rates.

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Luo, Simin, Yapei Zhang, Dalin Zhang, Guanghui Su, and Suizheng Qiu. "SIMULATIONS ON NATURAL CONVECTION OF STRATIFIED MELT POOLS WITH VOLUMETRIC HEAT GENERATION." Proceedings of the International Conference on Nuclear Engineering (ICONE) 2019.27 (2019): 1948. http://dx.doi.org/10.1299/jsmeicone.2019.27.1948.

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Brinkmeyer, Robin, Frank-Oliver Glöckner, Elisabeth Helmke, and Rudolf Amann. "Predominance of β-proteobacteria in summer melt pools on Arctic pack ice." Limnology and Oceanography 49, no. 4 (July 2004): 1013–21. http://dx.doi.org/10.4319/lo.2004.49.4.1013.

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Adeleke, S. A., and M. A. Maleque. "Tungsten Inert Gas Surface Alloying of Commercial Purity Titanium (CP-Ti) with Fe-C-Si Ternary Mixtures." Advanced Materials Research 1024 (August 2014): 207–10. http://dx.doi.org/10.4028/www.scientific.net/amr.1024.207.

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Surface modification by means of alloying is a vital process to improve the performance of a material surface which is subjected to wear and corrosion environments without altering the bulk properties. In this study, the surface of commercial purity-titanium (CP-Ti) material was alloyed using pre-placed powder mixture of iron, silicon and carbon at different weight ratios under TIG torch melting technique. The effects of energy input (1080 and 1350 J/mm) in TIG torch on the melt geometry, topography, microstructure and hardness were examined. The results showed that the TIG torch produced melt pools geometry with hemispherical in shape and different geometrical dimensions. Pores were seen to be concentrated at the edges where low melting energies are prominent to entrapped escaped gases upon fast melt solidification. The melt layers with the 1350 J/mm consisted of armed typed of TiC precipitation in the presence of longer solidification time. The sizes of dendrites observed at energy inputs of 1350 J/mm was found to be greater in population and larger in the middle of the melt pool compared to the energy input of 1080 J/mm. The alloyed layer exhibited a maximum hardness of ~ 810 HV which is about 4 times greater than the base hardness of 200 HV. The high hardness observed at particular areas is attributed to the higher population and larger sizes of dendritic microstructure produced using 1350 J/mm TIG arc source compared to 1080 J/mm which was dominated by lesser precipitated TiC resulting lower hardness values in the melt pool. Keywords: Surface modification; TiC; TIG; dendrites; microhardness

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Vahedi Nemani, Alireza, Mahya Ghaffari, and Ali Nasiri. "On the Post-Printing Heat Treatment of a Wire Arc Additively Manufactured ER70S Part." Materials 13, no. 12 (June 21, 2020): 2795. http://dx.doi.org/10.3390/ma13122795.

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Wire arc additive manufacturing (WAAM) is known to induce a considerable microstructural inhomogeneity and anisotropy in mechanical properties, which can potentially be minimized by adopting appropriate post-printing heat treatment. In this paper, the effects of two heat treatment cycles, including hardening and normalizing on the microstructure and mechanical properties of a WAAM-fabricated low-carbon low-alloy steel (ER70S-6) are studied. The microstructure in the melt pools of the as-printed sample was found to contain a low volume fraction of lamellar pearlite formed along the grain boundaries of polygonal ferrite as the predominant micro-constituents. The grain coarsening in the heat affected zone (HAZ) was also detected at the periphery of each melt pool boundary, leading to a noticeable microstructural inhomogeneity in the as-fabricated sample. In order to modify the nonuniformity of the microstructure, a normalizing treatment was employed to promote a homogenous microstructure with uniform grain size throughout the melt pools and HAZs. Differently, the hardening treatment contributed to the formation of two non-equilibrium micro-constituents, i.e., acicular ferrite and bainite, primarily adjacent to the lamellar pearlite phase. The results of microhardness testing revealed that the normalizing treatment slightly decreases the microhardness of the sample; however, the formation of non-equilibrium phases during hardening process significantly increased the microhardness of the component. Tensile testing of the as-printed part in the building and deposition directions revealed an anisotropic ductility. Although normalizing treatment did not contribute to the tensile strength improvement of the component, it suppressed the observed anisotropy in ductility. On the contrary, the hardening treatment raised the tensile strength, but further intensified the anisotropic behavior of the component.

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Venkateshwaran, Akash, Mahendhar Kumar, Shyam Kumar M.B., Davidson Jebaseelan D., Sivakumar R., Aniket Joshi, and Christopher Pain. "Numerical study of the effect of geometry on the behaviour of internally heated melt pools for in-vessel melt retention." Progress in Nuclear Energy 156 (February 2023): 104555. http://dx.doi.org/10.1016/j.pnucene.2022.104555.

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Diaz Vallejo, Nathalia, Cameron Lucas, Nicolas Ayers, Kevin Graydon, Holden Hyer, and Yongho Sohn. "Process Optimization and Microstructure Analysis to Understand Laser Powder Bed Fusion of 316L Stainless Steel." Metals 11, no. 5 (May 19, 2021): 832. http://dx.doi.org/10.3390/met11050832.

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The microstructural development of 316L stainless steel (SS) was investigated over a wide range of systematically varied laser powder bed fusion (LPBF) parameters, such as laser power, scan speed, hatch spacing and volumetric energy density. Relative density, melt pool width and depth, and the size of sub-grain cellular structure were quantified and related to the temperature field estimated by Rosenthal solution. Use of volumetric energy density between 46 and 127 J/mm3 produced nearly fully dense (≥99.8%) samples, and this included the best parameter set: power = 200 W; scan speed = 800 mm/s; hatch spacing = 0.12 mm; slice thickness = 0.03; energy density = 69 J/mm3). Cooling rate of 105 to 107 K/s was estimated base on the size of cellular structure within melt pools. Using the optimized LPBF parameters, the as-built 316L SS had, on average, yield strength of 563 MPa, Young’s modulus of 179 GPa, tensile strength of 710 MPa, and 48% strain at failure.

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Sharma, Avadhesh Kumar, Marco Pellegrini, Koji Okamoto, Masahiro Furuya, and Shinya Mizokami. "Validation and application of numerical modeling for in-vessel melt retention in corium pools." International Journal of Heat and Mass Transfer 196 (November 2022): 123313. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2022.123313.

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Cabrini, Marina, Sergio Lorenzi, Cristian Testa, Diego Manfredi, Mariangela Lombardi, Alberta Aversa, Francesco Andreatta, et al. "Effect of Heat Treatment on Microstructure and Selective Corrosion of LPBF-AlSi10Mg by Means of SKPFM and Exo-Electron Emission." Materials 14, no. 19 (September 27, 2021): 5602. http://dx.doi.org/10.3390/ma14195602.

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The paper deals with the evolution of the microstructure of AlSi10Mg alloy obtained by laser powder bed fusion (LPBF), as a function of the post-processing heat treatment temperature. This was approached by complementary methods including FE-scanning electron microscopy, scanning Kelvin probe force microscopy and exo-electron emission techniques. The fast cooling rate of the LPBF process as compared to traditional casting produces a very fine microstructure with high mechanical properties and corrosion resistance. However, the LPBF-AlSi10Mg alloy can be susceptible to selective corrosion at the edge of the melt pools generated by the laser scan tracks. Post-process thermal treatments of the Al alloy induce a marked modification of the silicon network at melt pool edges, in particular at high temperature such as 400 °C. It was found that this is associated to a more homogeneous distribution of Volta potential. Analysis of exo-electron emission confirms the silicon diffusion during thermal treatment. The modification of the silicon network structure of the LPBF-AlSi10Mg during thermal treatment reduces the susceptibility to selective corrosion.

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Macatangay, D. A., S. Thomas, N. Birbilis, and R. G. Kelly. "Unexpected Interface Corrosion and Sensitization Susceptibility in Additively Manufactured Austenitic Stainless Steel." Corrosion 74, no. 2 (December 19, 2017): 153–57. http://dx.doi.org/10.5006/2723.

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This communication describes observations of unexpected microstructural interface susceptibility to accelerated dissolution in additively manufactured (AM) Type 316L stainless steel prepared by selective laser melting. Observations include accelerated microstructural interface dissolution in the as-built condition, as well as more rapid sensitization of grain boundaries upon exposure to elevated temperature. Electrolytic etching in persulfate solution was used to evaluate the susceptibility of microstructural interfaces to accelerated dissolution in both wrought and AM 316L. Post-test optical microscopy and profilometry on AM 316L revealed that the melt pool boundaries in the as-built condition were susceptible to accelerated attack, although the small grains within the prior melt pools were not. Furthermore, short, elevated temperature exposure (1 h at 675°C) also induced sensitization of the grain boundaries. Identical testing on as-manufactured wrought 316L confirmed that no microstructural interfaces showed susceptibility to accelerated dissolution, and grain boundaries could be sensitized only by extended periods (24 h) at elevated temperature (675°C). Annealing was capable of removing sensitization in wrought 316L, but activated the surface of the AM 316L, leading to widespread, uniform dissolution.

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Liu, Hao, Zhong Zeng, Linmao Yin, Zhouhua Qiu, and Long Qiao. "Volume effect on the instabilities of thermocapillary flow in annular pools filled with silicon melt." International Communications in Heat and Mass Transfer 121 (February 2021): 105099. http://dx.doi.org/10.1016/j.icheatmasstransfer.2020.105099.

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Xing, Wei, Xin Chu, Tianyi Lyu, Chi-Guhn Lee, Yu Zou, and Yiming Rong. "Using convolutional neural networks to classify melt pools in a pulsed selective laser melting process." Journal of Manufacturing Processes 74 (February 2022): 486–99. http://dx.doi.org/10.1016/j.jmapro.2021.12.030.

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31

Pohlner, Georg, Zoran Vujic, Manfred Bürger, and Günter Lohnert. "Simulation of melt jet breakup and debris bed formation in water pools with IKEJET/IKEMIX." Nuclear Engineering and Design 236, no. 19-21 (October 2006): 2026–48. http://dx.doi.org/10.1016/j.nucengdes.2006.03.037.

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Liu, Hao, Zhong Zeng, Linmao Yin, Zhouhua Qiu, and Long Qiao. "Volume effect on the instabilities of thermocapillary flow in annular pools filled with silicon melt." International Communications in Heat and Mass Transfer 121 (February 2021): 105099. http://dx.doi.org/10.1016/j.icheatmasstransfer.2020.105099.

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33

He, Yining, Ming Zhong, Nick Jones, Jack Beuth, and Bryan Webler. "The Columnar-to-Equiaxed Transition in Melt Pools During Laser Powder Bed Fusion of M2 Steel." Metallurgical and Materials Transactions A 52, no. 9 (July 18, 2021): 4206–21. http://dx.doi.org/10.1007/s11661-021-06380-9.

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34

Kamenetsky, Vadim S., Bernard Charlier, Liudmila Zhitova, Victor Sharygin, Paul Davidson, and Sandrin Feig. "Magma chamber–scale liquid immiscibility in the Siberian Traps represented by melt pools in native iron." Geology 41, no. 10 (October 2013): 1091–94. http://dx.doi.org/10.1130/g34638.1.

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35

Shi, Wanyuan, Guoyuan Li, Xi Liu, You-Rong Li, Lan Peng, and Nobuyuki Imaishi. "Thermocapillary Convection and Buoyant-Thermocapillary Convection in the Annular Pools of Silicon Melt and Silicone Oil." Journal of Superconductivity and Novel Magnetism 23, no. 6 (January 23, 2010): 1169–72. http://dx.doi.org/10.1007/s10948-010-0662-7.

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36

Safdar, Shakeel, Andrew J. Pinkerton, Lin Li, Mohammed A. Sheikh, and Philip J. Withers. "An anisotropic enhanced thermal conductivity approach for modelling laser melt pools for Ni-base super alloys." Applied Mathematical Modelling 37, no. 3 (February 2013): 1187–95. http://dx.doi.org/10.1016/j.apm.2012.03.028.

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37

von Fricken, Michael E., Matthew A. Voorhees, Jeffrey W. Koehler, Carmen Asbun, Brandon Lam, Barbara Qurollo, Kathryn M. Hogan, Uyanga Baasandagva, Battsetseg Jigjav, and Randal J. Schoepp. "Molecular Characteristics of Rickettsia in Ticks Collected along the Southern Border of Mongolia." Pathogens 9, no. 11 (November 13, 2020): 943. http://dx.doi.org/10.3390/pathogens9110943.

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Tick-borne infections are a significant threat to public health, particularly in regions where individuals frequently enter tick habitats. Roughly 26% of the population in Mongolia practice nomadic pastoralism and are considered at high risk of exposure to ticks and the diseases they carry. This study tested ticks from Mongolia’s southern border for Rickettsia spp. to better understand the epidemiology of tick-borne diseases in the region. Dermacentor nuttalli and Hyalomma asiaticum ticks (n = 4022) were pooled and tested for Rickettsia spp. by real-time PCR. Melt-curve analyses and Sanger sequencing were used to identify Rickettsia species. Approximately 64% of the 786 tick pools tested positive for Rickettsia bacteria. Melt curve analyses identified four different Rickettsia species circulating in these tick pools. Amplicon sequencing of the ompA gene identified Rickettsia spp. that closely resembled R. raoultii and R. sibirica. Dermacentor nuttalli ticks from Govi-Altai had the highest maximum likelihood estimation infection rate 48.4% (95% CI: 41.7–56.5%), while Hyalommaasiaticum collected in Omnogovi had a rate of 7.6% (95% CI: 6.2–9.2%). The high detection of Rickettsia suggests a substantial risk of infection in southern Mongolia. Further studies are necessary to investigate the clinical burden of tick-borne diseases in Mongolia.

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Calandri, Michele, Shuo Yin, Barry Aldwell, Flaviana Calignano, Rocco Lupoi, and Daniele Ugues. "Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting." Materials 12, no. 8 (April 19, 2019): 1293. http://dx.doi.org/10.3390/ma12081293.

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Nickel-based Inconel 718 is a very good candidate for selective laser melting (SLM). During the SLM process, Inconel 718 develops a complex and heterogeneous microstructure. A deep understanding of the microstructural features of the as-built SLM material is essential for the design of a proper post-process heat treatment. In this study, the microstructure of as-built SLM Inconel 718 was investigated at different length scales using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electron backscatter diffraction (EBSD) was also used to analyze the grain morphology and crystallographic texture. Grains elongated in the build direction and crossing several deposited layers were observed. The grains are not constrained by the laser tracks or by the melt pools, which indicates epitaxial growth controls the solidification. Each grain is composed of fine columnar dendrites that develop along one of their <100> axes oriented in the direction of the local thermal gradient. Consequently, prominent <100> crystallographic texture was observed and the dendrites tend to grow to the build direction or with occasional change of 90° at the edge of the melt pools. At the dendrite length scale, the microsegregation of the alloying elements, interdendritic precipitates, and dislocations was also detected.

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Gourdal, Margaux, Martine Lizotte, Guillaume Massé, Michel Gosselin, Michel Poulin, Michael Scarratt, Joannie Charette, and Maurice Levasseur. "Dimethyl sulfide dynamics in first-year sea ice melt ponds in the Canadian Arctic Archipelago." Biogeosciences 15, no. 10 (May 29, 2018): 3169–88. http://dx.doi.org/10.5194/bg-15-3169-2018.

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Abstract. Melt pond formation is a seasonal pan-Arctic process. During the thawing season, melt ponds may cover up to 90 % of the Arctic first-year sea ice (FYI) and 15 to 25 % of the multi-year sea ice (MYI). These pools of water lying at the surface of the sea ice cover are habitats for microorganisms and represent a potential source of the biogenic gas dimethyl sulfide (DMS) for the atmosphere. Here we report on the concentrations and dynamics of DMS in nine melt ponds sampled in July 2014 in the Canadian Arctic Archipelago. DMS concentrations were under the detection limit (< 0.01 nmol L−1) in freshwater melt ponds and increased linearly with salinity (rs = 0.84, p ≤ 0.05) from ∼ 3 up to ∼ 6 nmol L−1 (avg. 3.7 ± 1.6 nmol L−1) in brackish melt ponds. This relationship suggests that the intrusion of seawater in melt ponds is a key physical mechanism responsible for the presence of DMS. Experiments were conducted with water from three melt ponds incubated for 24 h with and without the addition of two stable isotope-labelled precursors of DMS (dimethylsulfoniopropionate), (D6-DMSP) and dimethylsulfoxide (13C-DMSO). Results show that de novo biological production of DMS can take place within brackish melt ponds through bacterial DMSP uptake and cleavage. Our data suggest that FYI melt ponds could represent a reservoir of DMS available for potential flux to the atmosphere. The importance of this ice-related source of DMS for the Arctic atmosphere is expected to increase as a response to the thinning of sea ice and the areal and temporal expansion of melt ponds on Arctic FYI.

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Liu, Mulin, Takafumi Wada, Asuka Suzuki, Naoki Takata, Makoto Kobashi, and Masaki Kato. "Effect of Annealing on Anisotropic Tensile Properties of Al–12%Si Alloy Fabricated by Laser Powder Bed Fusion." Crystals 10, no. 11 (November 5, 2020): 1007. http://dx.doi.org/10.3390/cryst10111007.

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In this study, we systematically investigated microstructures and tensile properties of an Al–12mass%Si alloy additive-manufactured by laser powder bed fusion (LPBF) process and subsequently annealed at various temperatures. Microstructure of the as-fabricated sample was characterized by a number of melt pools consisting of α-Al phases surrounded by Si eutectic phases. Fine Si precipitates were observed in the α-Al phase in the sample annealed at 200 °C. The eutectic Si phase appears to agglutinate, resulting in a coarsened Si phase formed at high temperatures above 300 °C. The initial cellular microstructure completely disappears and a number of coarsened Si phases and plate-shaped intermetallic phases (β-AlFeSi) were formed in the sample annealed at 530 °C. However, the grain morphology of the α-Al matrix slightly changed after the annealing at high temperatures. The as-fabricated specimen showed a high strength above 400 MPa and a low ductility of below 10% in total elongation. The tensile ductility varied depending on the tensile direction. The annealed specimens exhibited a lower tensile strength and larger elongation, whereas the direction dependence of the tensile properties was less pronounced in the specimens annealed at higher temperatures. The anisotropic tensile ductility can be rationalized by preferential fractures occurred around melt pool boundaries.

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41

Goldney, D. "The Distribution and Abundance of Platypuses in The Thredbo River-Lake Jindabyne System." Australian Mammalogy 20, no. 2 (1998): 303. http://dx.doi.org/10.1071/am98307.

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The Thredbo River is an upland alpine stream, with a steep gradient over its 50 km length contained within a 251 km2 catchment in the Australian Alps. The altitude gradient from its source to Lake Jindabyne is 850 metres. The distribution and abundance of platypuses were determined over a two year period using volunteer sightings, disciplined transect walking and pool observation, gill-netting in selected pools and fyke-netting in riffle areas. Under low flow conditions, 93 pools were identified downstream of Dead Horse Gap, 85% of which were judged to be in the medium to small category. Under snow melt conditions, as river flow increases and smaller pool 'disappear' in the torrent, the carrying capacity of the river is significantly reduced. Some base-line data were available from the 1980s. Platypuses were uncommon or absent in the upland and common, but not abundant, in the mid and lowland segments of the river. Small numbers of platypuses were located in two larger tributaries, but none in the remainder, which had very steep gradients and narrow channels. Low recruitment rates, an overall decline in numbers, as judged by catch effort compared to base-line data, a probable increase in transience suggesting a non-stable population, are all signs that the population is under considerable stress. Episodic flood events, habitat degradation and the dam wall barrier preventing reinvasion from downstream segments of the population after flood-induced population losses, when considered together with population data, suggest that the platypus population is vulnerable.

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Peng, Jin, Jigao Liu, Xiaohong Yang, Jianya Ge, Peng Han, Xingxing Wang, Shuai Li, and Zhibin Yang. "Numerical Simulation of Droplet Filling Mode on Molten Pool and Keyhole during Double-Sided Laser Beam Welding of T-Joints." Crystals 12, no. 9 (September 6, 2022): 1268. http://dx.doi.org/10.3390/cryst12091268.

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The effects of droplets filling the molten pools during the double-sided laser beam welding (DSLBW) of T-joints was established. The dynamic behavior of the keyhole and the molten pool under different droplet filling modes were analyzed. The results indicated that compared with the contact transition, the stability of metal flow on the keyhole wall was reduced by free transition and slight contact transition. At the later stage of the droplet entering the molten pool via free transition, slight contact transition, and contact transition, the maximum flow velocity of the keyhole wall was 5.33 m/s, 4.57 m/s, and 2.99 m/s, respectively. When the filling mode was free transition or slight contact transition, the keyhole collapsed at the later stage of the droplet entering the molten pool. However, when the filling mode was contact transition, the middle-upper part of the interconnected keyholes became thinner at the later stage of the droplet entering the molten pool. At the later stage of the droplet entering the molten pool via free transition, the flow vortex at the bottom of the keyhole disappeared and the melt at the bottom of the keyhole flowed to the rear of the molten pool, however, the vortex remained during slight contact transition and contact transition.

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Erdmann, Martin, and Jürgen Koepke. "Experimental temperature cycling as a powerful tool to enlarge melt pools and crystals at magma storage conditions." American Mineralogist 101, no. 4 (April 2016): 960–69. http://dx.doi.org/10.2138/am-2016-5398.

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44

Shi, Wanyuan, Michael K. Ermakov, You-Rong Li, Lan Peng, and Nobuyuki Imaishi. "Influence of Buoyancy Force on Thermocapillary Convection Instability in the Differentially Heated Annular Pools of Silicon Melt." Microgravity Science and Technology 21, S1 (May 27, 2009): 289–97. http://dx.doi.org/10.1007/s12217-009-9118-8.

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45

Zhao, Junhao, Binbin Wang, Tong Liu, Liangshun Luo, Yanan Wang, Xiaonan Zheng, Liang Wang, et al. "A study on overlapping effect of melt pools in powder bed fusion based on a novel prediction method." Additive Manufacturing 59 (November 2022): 103151. http://dx.doi.org/10.1016/j.addma.2022.103151.

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46

Aripin, Mohammad Azlan, Zainuddin Sajuri, Nashrah Hani Jamadon, Amir Hossein Baghdadi, Junaidi Syarif, Intan Fadhlina Mohamed, and Ahmad Muhammad Aziz. "Effects of Build Orientations on Microstructure Evolution, Porosity Formation, and Mechanical Performance of Selective Laser Melted 17-4 PH Stainless Steel." Metals 12, no. 11 (November 17, 2022): 1968. http://dx.doi.org/10.3390/met12111968.

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In this study, the effect of phase, microstructure, and porosity in Selective Laser Melting (SLM) on hardness, tensile, and fracture behavior of 17-4 PH was investigated. The increasing interest in SLM in producing complex parts has encouraged the industry to produce performance parts, such as martensitic 17-4 PH stainless steel. However, the microstructure and mechanical behavior of SLM 17-4PH is not fully understood by researchers. Understanding the microstructure profile is complex because it is driven by thermal history and porosity. Both elements vary, based on the build directions, further hindering researchers from fully understanding the mechanical properties. To fabricate specimens in three different building orientations (0°, 45°, and 90°), 17-4 powder was used. Two phases, namely, austenite and martensite, with 90° build direction, retained more austenite, due to the reheating process on a smaller base area. The optical microstructure revealed several elements that were distinct for SLM processing, including circular, columnar lath, wave melt pool, and porosity. Columnar lath was found to grow continuously across different melt pools. Hardness was found to be higher for 0° than for 90°, due to higher martensite content. Tensile strength was highest for 0°, at 958 MPa, higher than at 45° and 90° at 743 and 614 MPa, respectively. Porosity analysis validated that 90° had all three types of porosities and, specifically, the crescent type, which held un-melted powders. All types of porosities were found in fractography analysis.

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Gillespie, Jared, Wei Yi Yeoh, Cang Zhao, Niranjan D. Parab, Tao Sun, Anthony D. Rollett, Bo Lan, and Christopher M. Kube. "In situ characterization of laser-generated melt pools using synchronized ultrasound and high-speed X-ray imaging." Journal of the Acoustical Society of America 150, no. 4 (October 2021): 2409–20. http://dx.doi.org/10.1121/10.0006386.

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Kim, Jaewoong, Seulbi Lee, Jae-Keun Hong, Namhyun Kang, and Yoon Suk Choi. "Calibration of Laser Penetration Depth and Absorptivity in Finite Element Method Based Modeling of Powder Bed Fusion Melt Pools." Metals and Materials International 26, no. 6 (January 10, 2020): 891–902. http://dx.doi.org/10.1007/s12540-019-00599-3.

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49

Corre, Y., A. Grosjean, J. P. Gunn, K. Krieger, S. Ratynskaia, O. Skalli-Fettachi, C. Bourdelle, et al. "Sustained W-melting experiments on actively cooled ITER-like plasma facing unit in WEST." Physica Scripta 96, no. 12 (November 8, 2021): 124057. http://dx.doi.org/10.1088/1402-4896/ac326a.

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Abstract The consequences of tungsten (W) melting on divertor lifetime and plasma operation are high priority issues for ITER. Sustained and controlled W-melting experiment has been achieved for the first time in WEST on a poloidal sharp leading edge of an actively cooled ITER-like plasma facing unit (PFU). A series of dedicated high power steady state plasma discharges were performed to reach the melting point of tungsten. The leading edge was exposed to a parallel heat flux of about 100 MW.m−2 for up to 5 s providing a melt phase of about 2 s without noticeable impact of melting on plasma operation (radiated power and tungsten impurity content remained stable at constant input power) and no melt ejection were observed. The surface temperature of the MB was monitored by a high spatial resolution (0.1 mm/pixel) infrared camera viewing the melt zone from the top of the machine. The melting discharge was repeated three times resulting in about 6 s accumulated melting duration leading to material displacement from three similar pools. Cumulated on the overall sustained melting periods, this leads to excavation depth of about 230 μm followed by a re-solidified tungsten bump of 200 μm in the JxB direction.

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Everitt, Nicola M. "Nanoindentation Shows Uniform Local Mechanical Properties Across Melt Pools And Layers Produced By Selective Laser Melting Of AlSi 10Mg Alloy." Advanced Materials Letters 7, no. 1 (January 1, 2016): 13–16. http://dx.doi.org/10.5185/amlett.2016.6171.

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Journal articles on the topic 'Melt Pools'

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