scholarly journals Base Plate Preheating Effect on Microstructure of 316L Stainless Steel Single Track Deposition by Directed Energy Deposition

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5129
Author(s):  
Abhilash Kiran ◽  
Martina Koukolíková ◽  
Jaroslav Vavřík ◽  
Miroslav Urbánek ◽  
Jan Džugan
Keyword(s):  
Process Parameters ◽  
Significant Influence ◽  
Rapid Heating ◽  
Grain Morphology ◽  
Base Plate ◽  
High Energy ◽  
Grain Structure ◽  
Single Track ◽  
Boundary Misorientation ◽  
Electron Backscattered Diffraction

The microstructural morphology in additive manufacturing (AM) has a significant influence on the building structure. High-energy concentric heat source scanning leads to rapid heating and cooling during material deposition. This results in a unique microstructure. The size and morphology of the microstructure have a strong directionality, which depends on laser power, scanning rate, melt pool fluid dynamics, and material thermal properties, etc. The grain structure significantly affects its resistance to solidification cracking and mechanical properties. Microstructure control is challenging for AM considering multiple process parameters. A preheating base plate has a significant influence on residual stress, defect-free AM structure, and it also minimizes thermal mismatch during the deposition. In the present work, a simple single track deposition experiment was designed to analyze base plate preheating on microstructure. The microstructural evolution at different preheating temperatures was studied in detail, keeping process parameters constant. The base plate was heated uniformly from an external heating source and set the stable desired temperature on the surface of the base plate before deposition. A single track was deposited on the base plate at room temperature and preheating temperatures of 200 °C, 300 °C, 400 °C, and 500 °C. Subsequently, the resulting microstructural morphologies were analyzed and compared. The microstructure was evaluated using electron backscattered diffraction (EBSD) imaging in the transverse and longitudinal sections. An increase in grain size area fraction was observed as the preheating temperature increased. Base plate preheating did not show influence on grain boundary misorientation. An increase in the deposition depth was noticed for higher base plate preheating temperatures. The results were convincing that grain morphology and columnar grain orientation can be tailored by base plate preheating.

scholarly journals QUANTITATIVE CHARACTERIZATION OF MICROSTRUCTURE OF PURE COPPER PROCESSED BY ECAP

2013 ◽  
Vol 32 (2) ◽  
pp. 65 ◽  
Author(s):  
Ondřej Šedivý ◽  
Viktor Beneš ◽  
Petr Ponížil ◽  
Petr Král ◽  
Václav Sklenička
Keyword(s):  
Structural Parameters ◽  
Pure Copper ◽  
Orientation Imaging Microscopy ◽  
Grain Morphology ◽  
Grain Structure ◽  
Boundary Structure ◽  
Electron Backscattered Diffraction ◽  
Quantitative Characterization ◽  
Grain Boundary Structure

Orientation imaging microscopy (OIM) allows to measure crystallic orientations at the surface of the material. Digitalized data representing the orientations are processed to recognize the grain structure and they are visualized in crystal orientation maps. Analysis of the data firstly consists in recognition of grain boundaries followed by identification of grains themselves. Knowing the grain morphology it is possible to characterize the homogeneity of the structure and estimate structural parameters related to the physical properties of the material. The paper describes methods of imaging and quantitative characterization of the grain boundary structure in metals based on data from electron backscattered diffraction (EBSD).

Multiscale Modeling of SPD Processes for Grain Refinement

2008 ◽  
Vol 584-586 ◽  
pp. 1069-1076
Author(s):  
Igor V. Alexandrov
Keyword(s):  
Multiscale Modeling ◽  
Structure Refinement ◽  
Grain Morphology ◽  
Grain Structure ◽  
Boundary Misorientation ◽  
Active Deformation ◽  
Structure Sensitive ◽  
Successful Prediction ◽  
Grain Boundary Misorientation ◽  
Complex Influence

The results of a recent multiscale computer modeling are presented in this report. The conducted investigations are devoted to the processes, which take place in different metallic materials subjected to severe plastic deformation (SPD). It is presented that the developed models and approaches can be useful in the successful prediction and comprehensive analysis of the peculiarities of material flow and the ways of its homogenization, the understanding of principles of grain structure refinement, the achievement of given grain morphology, grain boundary misorientation spectrum and crystallographic texture, as well as in the evaluation of the active deformation mechanisms, estimating the level of structure-sensitive properties, etc. It is shown that multiscale modeling is a very promising approach which could supply the researchers with the possibility to take into account the complex influence of the different parameters, related to SPD processing and material in order to refine the grain size and obtain homogeneous bulk nanostructured materials.

Demonstration of near Field High Energy X-Ray Diffraction Microscopy on High-Z Ceramic Nuclear Fuel Material

2014 ◽  
Vol 777 ◽  
pp. 112-117 ◽  
Author(s):  
Donald W. Brown ◽  
Levente Balogh ◽  
Darrin Byler ◽  
Chris M. Hefferan ◽  
James F. Hunter ◽  
...  
Keyword(s):  
Nuclear Fuel ◽  
Near Field ◽  
Grain Morphology ◽  
High Energy ◽  
X Ray Diffraction ◽  
Boundary Misorientation ◽  
Sintered Ceramic ◽  
X Ray ◽  
Diffraction Microscopy ◽  
Fuel Material

Near-field high energy x-ray diffraction microscopy (nf-HEDM) and high energy x-ray micro-tomography (μT) have been utilized to characterize the pore structure and grain morphology in sintered ceramic UO2nuclear fuel material. μT successfully images pores to 2-3μm diameters and is analyzed to produce a pore size distribution. It is apparent that the largest number of pores and pore volume in the sintered ceramic are below the current resolution of the technique, which might be more appropriate to image cracks in the same ceramics. Grain orientation maps of slices determined by nf-HEDM at 25 μm intervals are presented and analyzed in terms of grain boundary misorientation angle. The benefit of these two techniques is that they are non-destructive and thus could be performed before and after processes (such as time at temperature or in-reactor) or even in-situ.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

Influence of Nd:YAG Laser Irradiation on an Adhesive Restorative Procedure

2006 ◽  
Vol 31 (5) ◽  
pp. 604-609 ◽  
Author(s):  
M. Franke ◽  
A. W. Taylor ◽  
A. Lago ◽  
M. C. Fredel
Keyword(s):  
Statistical Analysis ◽  
Bond Strength ◽  
Laser Irradiation ◽  
Significant Influence ◽  
Nd:Yag Laser ◽  
Deleterious Effect ◽  
Adhesive System ◽  
High Energy ◽  
Low Energy ◽  
Adhesive Penetration

Clinical Relevance Statistical analysis of the results obtained in this study shows that Nd:YAG laser irradiation on the adhesive system has a significant influence on bond strength to dentin. Bond strength is improved by better adhesive penetration when low energy is applied; whereas, high energy densities have a deleterious effect on the procedure.

scholarly journals EBSD Investigation of the Microtexture of Weld Metal and Base Metal in Laser Welded Al–Li Alloys

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2357 ◽  
Author(s):  
Li Cui ◽  
Zhibo Peng ◽  
Xiaokun Yuan ◽  
Dingyong He ◽  
Li Chen
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Transverse Section ◽  
Grain Morphology ◽  
Structural Features ◽  
Butt Joint ◽  
Horizontal Surface ◽  
Boundary Misorientation ◽  
Texture Intensity ◽  
Highly Correlated

Autogenous laser welding of 5A90 Al–Li alloy sheets in a butt-joint configuration was carried out in this study. The microstructure characteristics of the weld metal and base metal in the horizontal surface and the transverse section of the welded joints were examined quantitatively using electron back scattered diffraction (EBSD) technique. The results show that the weld metal in the horizontal surface and the transverse section exhibits similar grain structural features including the grain orientations, grain shapes, and grain sizes, whereas distinct differences in the texture intensity and misorientation distributions are observed. However, the base metal in the horizontal surface and the transverse section of the joints reveals the obvious different texture characteristics in terms of the grain orientation, grain morphology, predominate texture ingredients, distribution intensities of textures, and grain boundary misorientation distribution, resulting in the diversity of the microhardness in the base metal and the softening of the weld metal. However, the degree of the drop in the hardness of the weld metal is highly correlated to the microtexture developed in the base metal.

scholarly journals Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 159
Author(s):  
Nicholas Olynik ◽  
Bin Cheng ◽  
David J. Sprouster ◽  
Chad M. Parish ◽  
Jason R. Trelewicz
Keyword(s):  
Extreme Environments ◽  
High Energy ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Grain Boundary Engineering ◽  
Carbon Impurities ◽  
Grain Structures ◽  
Metallurgical Processing ◽  
Size Population

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders.

scholarly journals Space-Selective Control of Functional Crystals by Femtosecond Laser: A Comparison between SrO-TiO2-SiO2 and Li2O-Nb2O5-SiO2 Glasses

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 979
Author(s):  
Xuan He ◽  
Qiming Liu ◽  
Matthieu Lancry ◽  
François Brisset ◽  
Bertrand Poumellec
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic ◽  
Scanning Speed ◽  
High Energy ◽  
Femtosecond Laser Irradiation ◽  
Laser Polarization ◽  
Electron Backscattered Diffraction ◽  
Sio2 Glass ◽  
Significant Difference ◽  
Induced Crystallization

We report on space-selective crystallization of congruent and polar Sr2TiSi2O8 crystals in a stoichiometric SrO-TiO2-SiO2 glass induced by (1030 nm, 300 fs) femtosecond laser irradiation. This allows us to compare with non-congruent laser-induced crystallization of polar LiNbO3 in non-stoichiometric Li2O-Nb2O5-SiO2 glass and gain information on the mechanism of nanocrystals orientation with the laser polarization that we pointed out previously. Using scanning electron microscopy (SEM), second harmonic generation (SHG), and electron backscattered diffraction (EBSD), we studied the laser-induced crystallization according to the laser processing parameters (pulse energy, pulse repetition rate, scanning speed). We found (1) a domain where the laser track is filled with crystals not perfectly textured (low energy), (2) a domain where an amorphous volume remains surrounded by a crystallized shell (high energy). This arises from Sr out-diffusion and may give rise to the crystallization of both SrTiO3 and Sr2TiSi2O8 phases at low speed. In the one-phase domain (at higher speed), the possibility to elaborate a tube with a perfect Fresnoite texture is found. A significant difference in size and morphology whereas the crystallization threshold remains similar is discussed based on glass thermal properties. Contrarily to Li2O-Nb2O5-SiO2 (LNS) glass, no domain of oriented nanocrystallization controlled by the laser polarization has been found in SrO-TiO2-SiO2 (STS) glass, which is attributed to the larger crystallization speed in STS glass. No nanogratings have also been found that is likely due to the congruency of the glass.

Numerical and Experimental Analysis of Laser Surface Remelting of Al 9wt% Si Alloy Samples

2008 ◽  
Vol 587-588 ◽  
pp. 721-725
Author(s):  
Noé Cheung ◽  
Kleber A.S. Cruz ◽  
Noman H. Khan ◽  
Amauri Garcia
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Rapid Heating ◽  
Thermal Action ◽  
High Energy ◽  
Laser Surface ◽  
High Energy Density ◽  
Temperature Fields ◽  
Laser Materials ◽  
Laser Surface Remelting

Laser materials processing has been widely applied in industrial processes due to unique precision and very localized thermal action furnished by the laser’s high energy density and power controllability. With the inherent rapid heating and cooling rates to which this surface layer is subjected, this process provides an opportunity to produce different microstructures from that of the bulk metal leading to useful properties. The aim of this work is to develop a heat transfer mathematical model based on the finite difference method in order to simulate temperature fields in the laser surface remelting process. Convective heat transfer in the remelted pool is taken into account by using the effective thermal conductivity approach. Theoretical predictions furnished by previous models from the literature were used for validation of numerical simulations performed with the proposed model. Experiments of laser surface remelting of Al-9 wt pct Si samples was carried out in the present investigation, and numerical simulations was applied for the laser machine operating parameters. The work also encompasses the analysis of microstructural and microhardness variations throughout the resulting treated and unmolten zones.

scholarly journals Optimization of the Cutting Process Parameters to Ensure High Efficiency of Drilling Tunnels and Use the Technical Potential of the Boom-Type Roadheader

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6597
Author(s):  
Piotr Cheluszka
Keyword(s):  
Control System ◽  
Energy Consumption ◽  
Automatic Control ◽  
Automatic Control System ◽  
Process Parameters ◽  
High Efficiency ◽  
Rock Cutting ◽  
High Energy ◽  
Cutting Process ◽  
Underground Mines

This paper deals with the automation of the rock cutting process with roadheaders used widely in civil engineering for drilling roadways in underground mines and tunnels. Although there has been intensive technical development, roadheaders are still manually controlled. Manual control does not allow optimizing the values of the cutting process parameters, which often results in low mining efficiency, especially in the case of hard rocks, as well as high energy consumption and significant dynamic overloading of the roadheader. As part of theoretical and experimental research, an automatic control system was designed for the boom-type roadheader and an algorithm was developed for the optimal control of the cutting process parameters. Control criteria have been formulated, based on which the current values of the cutting process parameters are worked out using the information on the dynamic load state of the roadheader. The paper presents selected results of numerical tests conducted on roadheader dynamics, which simulated the automatic control system operation of the heading face cutting process of drilled roadway or tunnel. These tests were intended to analyze the behavior of the investigated object during simulated rock cutting in automatic mode. The results confirmed the possibility of a significant reduction in mining energy consumption.

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