scholarly journals On the interplay of microstructure and residual stress in LPBF IN718

2020 ◽  
Vol 56 (9) ◽  
pp. 5845-5867
Author(s):  
Itziar Serrano-Munoz ◽  
Tobias Fritsch ◽  
Tatiana Mishurova ◽  
Anton Trofimov ◽  
Daniel Apel ◽  
...  
Keyword(s):  
Residual Stress ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characterization ◽  
Theoretical Models ◽  
Near Surface ◽  
Powder Bed ◽  
Rs Analysis ◽  
Scanning Strategies ◽  
Backscatter Diffraction

AbstractThe relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90° XY-scan, and 67° Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the near-surface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuß model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kröner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys.

scholarly journals Recent Advances in EBSD Characterization of Metals

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1097
Author(s):  
Íris Carneiro ◽  
Sónia Simões
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characterization ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Character ◽  
Recent Advances ◽  
Wide Range ◽  
Plane Distribution ◽  
Backscatter Diffraction

Electron backscatter diffraction (EBSD) has been attracting enormous interest in the microstructural characterization of metals in recent years. This characterization technique has several advantages over conventional ones, since it allows obtaining a wide range of characterization possibilities in a single method, which is not possible in others. The grain size, crystallographic orientation, texture, and grain boundary character distribution can be obtained by EBSD analysis. Despite the limited resolution of this technique (20–50 nm), EBSD is powerful, even for nanostructured materials. Through this technique, the microstructure can be characterized at different scales and levels with a high number of microstructural characteristics. It is known that the mechanical properties are strongly related to several microstructural aspects such as the size, shape, and distribution of grains, the presence of texture, grain boundaries character, and also the grain boundary plane distribution. In this context, this work aims to describe and discuss the possibilities of microstructural characterization, recent advances, the challenges in sample preparation, and the application of the EBSD in the characterization of metals.

scholarly journals Characterization of Ni–CNTs Nanocomposites Produced by Ball-Milling

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 2 ◽  
Author(s):  
Íris Carneiro ◽  
Filomena Viana ◽  
Manuel F. Vieira ◽  
José Valdemar Fernandes ◽  
Sónia Simões
Keyword(s):  
Ball Milling ◽  
Milling Time ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characterization ◽  
Ni Powder ◽  
Metal Matrix Nanocomposite ◽  
Cold Pressed ◽  
Backscatter Diffraction ◽  
Matrix Nanocomposite

This research focuses on the characterization of a metal matrix nanocomposite (MMNC) comprised of a nickel matrix reinforced by carbon nanotubes (CNTs). The aim of this study was to characterize Ni–CNTs nanocomposites produced by powder metallurgy using ball-milling. CNTs were initially untangled using ultrasonication followed by mixture/dispersion with Ni powder by ball-milling for 60, 180, or 300 min. The mixtures were cold-pressed and then pressureless sintered at 950 °C for 120 min under vacuum. Their microstructural characterization was mainly performed by optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were evaluated by Vickers microhardness. The results indicate that combining ultrasonication and ball-milling can successfully produce Ni–CNTs nanocomposites. The ball-milling time has a significant effect on both the CNT dispersion and the final nanocomposite microstructure.

Microstructural Characterization of Hydrogen Induced Cracking in TRIP Steels by EBSD

2014 ◽  
Vol 922 ◽  
pp. 412-417 ◽  
Author(s):  
A. Laureys ◽  
Tom Depover ◽  
Roumen H. Petrov ◽  
Kim Verbeken
Keyword(s):  
Retained Austenite ◽  
Electron Backscatter Diffraction ◽  
Mechanical Load ◽  
High Strength ◽  
Microstructural Characterization ◽  
Trip Steels ◽  
Multiphase Microstructure ◽  
Hydrogen Induced Cracking ◽  
Backscatter Diffraction

The present work evaluates hydrogen induced cracking in a high strength TRIP steel with a complex multiphase microstructure, containing ferrite, bainite, retained austenite, and some martensite. Each structural constituent demonstrates a different behavior in the presence of hydrogen and when deformed, the retained austenite transforms to martensite. The goal of this work is to understand the response of the hydrogen saturated multiphase structure to a mechanical load. A tensile test on notched samples combined with in-situ electrochemical hydrogen charging was carried out. The test was interrupted at certain specific points, before the macroscopic failure of the material. Hydrogen induced crack initiation and propagation were examined by studying several intermediate elongations. The microstructure of the samples was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The EBSD measurements allowed both microstructural and crystallographic characterization of the hydrogen induced crack surroundings. A correlation was found between the occurrence of martensite, which is known to be very susceptible to hydrogen embrittlement, and the initiation of hydrogen induced cracks. These cracks were located at the surface in specific high stressed regions. Finite element simulations indicated that these regions were induced due to the presence of the notch.

Application of Electron Backscatter Diffraction for Crystallographic Characterization of Tin Whiskers

2012 ◽  
Vol 18 (4) ◽  
pp. 876-884 ◽  
Author(s):  
Joseph R. Michael ◽  
Bonnie B. McKenzie ◽  
Donald F. Susan
Keyword(s):  
Electron Backscatter Diffraction ◽  
Growth Direction ◽  
Tin Whiskers ◽  
Physical Growth ◽  
Final Choice ◽  
Advantages And Disadvantages ◽  
Electron Backscatter ◽  
Backscatter Diffraction

AbstractUnderstanding the growth of whiskers or high aspect ratio features on substrates can be aided when the crystallography of the feature is known. This study has evaluated three methods that utilize electron backscatter diffraction (EBSD) for the determination of the crystallographic growth direction of an individual whisker. EBSD has traditionally been a technique applied to planar, polished samples, and thus the use of EBSD for out-of-surface features is somewhat more difficult and requires additional steps. One of the methods requires the whiskers to be removed from the substrate resulting in the loss of valuable physical growth relationships between the whisker and the substrate. The other two techniques do not suffer this disadvantage and provide the physical growth information as well as the crystallographic growth directions. The final choice of method depends on the information required. The accuracy and the advantages and disadvantages of each method are discussed.

scholarly journals Application of Electron Backscatter Diffraction (EBSD) for Crystallographic Characterization of Aluminum-Doped Zinc Oxide Sputtered Films

2013 ◽  
Vol 19 (S4) ◽  
pp. 103-104
Author(s):  
C.B. Garcia ◽  
E. Ariza ◽  
C.J. Tavares
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Zinc Oxide ◽  
Electron Backscatter Diffraction ◽  
Wide Range ◽  
Electron Backscatter ◽  
Aluminum Doped Zinc Oxide ◽  
Ebsd Technique ◽  
Backscatter Diffraction

Zinc Oxide is a wide band-gap compound semiconductor that has been used in optoelectronic and photovoltaic applications due to its good electrical and optical properties. Aluminium has been an efficient n-type dopant for ZnO to produce low resistivity films and high transparency to visible light. In addition, the improvement of these properties also depends on the morphology, crystalline structure and deposition parameters. In this work, ZnO:Al films were produced by d.c. pulsed magnetron sputtering deposition from a ZnO ceramic target (2.0 wt% Al2O3) on glass substrates, at a temperature of 250 ºC.The crystallographic orientation of aluminum doped zinc oxide (ZnO:Al) thin films has been studied by Electron Backscatter Diffraction (EBSD) technique. EBSD coupled with Scanning Electron Microscopy (SEM) is a powerful tool for the microstructural and crystallographic characterization of a wide range of materials.The investigation by EBSD technique of such films presents some challenges since this analysis requires a flat and smooth surface. This is a necessary condition to avoid any shadow effects during the experiments performed with high tilting conditions (70º). This is also essential to ensure a good control of the three dimensional projection of the crystalline axes on the geometrical references related to the sample.Crystalline texture is described by the inverse pole figure (IPF) maps (Figure 1). Through EBSD analysis it was observed that the external surface of the film presents a strong texture on the basal plane orientation (grains highlighted in red colour). Furthermore it was possible to verify that the grain size strongly depends on the deposition time (Figure 1 (a) and (b)). The electrical and optical film properties improve with increasing of the grain size, which can be mainly, attributed to the decrease in scattering grain boundaries which leads to an increasing in carrier mobility (Figure 2).The authors kindly acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) scientific program for the National Network of Electron Microscopy (RNME) EDE/1511/RME/2005.

scholarly journals Diffracting-grain identification from electron backscatter diffraction maps during residual stress measurements: a comparison between the sin2ψ and cosα methods

2019 ◽  
Vol 52 (4) ◽  
pp. 828-843 ◽  
Author(s):  
Dorian Delbergue ◽  
Damien Texier ◽  
Martin Lévesque ◽  
Philippe Bocher
Keyword(s):  
Residual Stress ◽  
Grain Size ◽  
Tilt Angle ◽  
Measurement Errors ◽  
Electron Backscatter Diffraction ◽  
Measurement Techniques ◽  
Single Exposure ◽  
X Ray ◽  
Electron Backscatter ◽  
Backscatter Diffraction

X-ray diffraction (XRD) is a widely used technique to evaluate residual stresses in crystalline materials. Several XRD measurement methods are available. (i) The sin2ψ method, a multiple-exposure technique, uses linear detectors to capture intercepts of the Debye–Scherrer rings, losing the major portion of the diffracting signal. (ii) The cosα method, thanks to the development of compact 2D detectors allowing the entire Debye–Scherrer ring to be captured in a single exposure, is an alternative method for residual stress measurement. The present article compares the two calculation methods in a new manner, by looking at the possible measurement errors related to each method. To this end, sets of grains in diffraction condition were first identified from electron backscatter diffraction (EBSD) mapping of Inconel 718 samples for each XRD calculation method and its associated detector, as each method provides different sets owing to the detector geometry or to the method specificities (such as tilt-angle number or Debye–Scherrer ring division). The X-ray elastic constant (XEC) ½S 2, calculated from EBSD maps for the {311} lattice planes, was determined and compared for the different sets of diffracting grains. It was observed that the 2D detector captures 1.5 times more grains in a single exposure (one tilt angle) than the linear detectors for nine tilt angles. Different XEC mean values were found for the sets of grains from the two XRD techniques/detectors. Grain-size effects were simulated, as well as detector oscillations to overcome them. A bimodal grain-size distribution effect and `artificial' textures introduced by XRD measurement techniques are also discussed.

scholarly journals Visualization of the Bainite Fine Structure Using EBSD and Euler Angles

2019 ◽  
Vol 1 (1) ◽  
pp. 11
Author(s):  
Yu.V. Yudin ◽  
A.A. Kuklina ◽  
M.V. Maisuradze ◽  
M.S. Karabanalov
Keyword(s):  
Fine Structure ◽  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
Diffraction Method ◽  
Bainitic Steel ◽  
Near Surface ◽  
Steel Microstructure ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Ebsd Method

The electron backscatter diffraction method (EBSD) is widely used to studycrystallographic orientational relationships of the steel microstructure constituentsincluding bainite. Nevertheless the fine structure of bainite (subunits, plates) is notinvestigated by this method. In this paper we propose a technique for visualizing ofthe structure of a bainitic steel near-surface layer using the values of Euler anglesobtained by EBSD method. A three-dimensional picture of the bainite fine structure ofthe HY-TUF steel obtained by the proposed technique is in

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