Melt Pool Changes Characterization in Laser-Processed H11 Hot Work Tool Steel Using Point-by-Point Scanning Mode towards LPBF Process Optimization.

Additive manufacturing techniques employing laser-based metal melting have garnered significant attention within the scientific community. Despite a decade of comprehensive research on the fundamentals of these techniques, there still remain unexplored facets related to heat flux impact on metallic alloys' properties. Particularly, the effects of point-by-point laser operation on melt pool formation in metallic materials still remain unclear.

EBSD and TKD analyses using inverted contrast Kikuchi diffraction patterns and alternative measurement geometries.

Electron backscatter diffraction (EBSD) patterns can exhibit Kikuchi bands with inverted contrast due to anomalous absorption. This can be observed, for example, on samples with nanoscale topography, in case of a low tilt backscattering geometry, or for transmission Kikuchi diffraction (TKD) on thicker samples. Three examples are discussed where contrast-inverted physics-based simulated master patterns have been applied to find the correct crystal orientation.

Synthesis and Characterization of Boron Carbide Nanoparticles as Potential Boron-Rich Therapeutic Carriers.

Boron carbide is one of the hardest materials in the world which can be synthesized by various methods. The most common one is a carbothermic or magnesiothermic reduction of BO performed at high temperatures, where the obtained powder still requires grinding and purification. The goal of this research is to present the possibility of synthesizing BC nanoparticles from elements via vapor deposition and modifying the morphology of the obtained powders, particularly those synthesized at high temperatures.

Mapping of lattice distortion in martensitic steel-Comparison of different evaluation methods of EBSD patterns.

To visualize the varying tetragonal distortions in high carbon martensitic steels by EBSD, two different approaches have been applied on backscattered Kikuchi diffraction (BKD) patterns. A band-edge refinement technique called Refined Accuracy (RA) (Oxford Instruments) is compared with a technique called Pattern Matching (PM), which optimizes the fit to a simulated BKD signal. RA distinguishes between hypothetical phases of different fixed c/a, while PM determines a best fitting continuous c/a by projective transformation of a master pattern.

Influence of polyvinylpyrrolidone (PVP) in the synthesis of luminescent NaYF:Yb,Er upconversion nanoparticles.

Polyvinylpyrrolidone (PVP) can be used to produce upconversion nanoparticles (UCNPs) in an advantageous manner, i.e. at modest temperatures in open-to-air conditions with simple hotplate and flask apparatus.

Aerogels based on cationically modified chitosan and poly(vinyl alcohol) for efficient capturing of viruses.

In this study, we developed a new filtering bioaerogel based on linear polyvinyl alcohol (PVA) and the cationic derivative of chitosan (N-[(2-hydroxy-3-trimethylamine) propyl] chitosan chloride, HTCC) with a potential antiviral application. A strong intermolecular network architecture was formed thanks to the introduction of linear PVA chains, which can efficiently interpenetrate the glutaraldehyde(GA)-crosslinked HTCC chains. The morphology of the obtained structures was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Correlative Analysis of the Dimensional Properties of Bipyramidal Titania Nanoparticles by Complementing Electron Microscopy with Other Methods.

In this paper, the accurate determination of the size and size distribution of bipyramidal anatase nanoparticles (NPs) after deposition as single particles on a silicon substrate by correlative Scanning Electron Microscopy (SEM) with Atomic Force Microscopy (AFM) analysis is described as a new measurement procedure for metrological purposes. The knowledge of the exact orientation of the NPs is a crucial step in extracting the real 3D dimensions of the particles. Two approaches are proposed to determine the geometrical orientation of individual nano-bipyramides: (i) AFM profiling along the long bipyramid axis and (ii) stage tilting followed by SEM imaging.

Application of Nanosilicon to the Sintering of Mg-MgSi Interpenetrating Phases Composite.

The new in situ fabrication process for Mg-MgSi composites composed of interpenetrating metal/intermetallic phases via powder metallurgy was characterized. To obtain the designed composite microstructure, variable nanosilicon ((n)Si) (i.e.

Transmission Kikuchi diffraction: The impact of the signal-to-noise ratio.

Signal optimization for transmission Kikuchi diffraction (TKD) measurements in the scanning electron microscope is investigated by a comparison of different sample holder designs. An optimized design is presented, which uses a metal shield to efficiently trap the electron beam after transmission through the sample. For comparison, a second holder configuration allows a significant number of the transmitted electrons to scatter back from the surface of the sample holder onto the diffraction camera screen.

Kikuchi pattern simulations of backscattered and transmitted electrons.

We discuss a refined simulation approach which treats Kikuchi diffraction patterns in electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). The model considers the result of two combined mechanisms: (a) the dynamical diffraction of electrons emitted coherently from point sources in a crystal and (b) diffraction effects on incoherent diffuse intensity distributions. Using suitable parameter settings, the refined simulation model allows to reproduce various thickness- and energy-dependent features which are observed in experimental Kikuchi diffraction patterns.

Effect of a Sulfur Precursor on the Hydrothermal Synthesis of CuMnSnS.

CuMnSnS (CMTS) is acknowledged as an alternative to traditional semiconductors. The structure and microstructure of synthetic CMTS depend on, among other things, the types of sulfur sources used. Traditionally obtained CMTS mostly has a tetragonal structure.

Crystallographic analysis of the lattice metric () from single electron backscatter diffraction or transmission Kikuchi diffraction patterns.

A new software is presented for the determination of crystal lattice parameters from the positions and widths of Kikuchi bands in a diffraction pattern. Starting with a single wide-angle Kikuchi pattern of arbitrary resolution and unknown phase, the traces of all visibly diffracting lattice planes are manually derived from four initial Kikuchi band traces via an intuitive graphical user interface. A single Kikuchi bandwidth is then used as reference to scale all reciprocal lattice point distances.

Assignment of enantiomorphs for the chiral allotrope β-Mn by diffraction methods.

The assignment of enantiomorphs by diffraction methods shows fundamental differences for x-rays and electrons. This is particularly evident for the chiral allotrope of β-Mn. While it is not possible to determine the sense of chirality of β-Mn with established x-ray diffraction methods, Kikuchi pattern simulation of the enantiomorphs reveals differences, if dynamical electron diffraction is considered.

Omega Phase Formation in Ti-3wt.%Nb Alloy Induced by High-Pressure Torsion.

It is well known that severe plastic deformation not only leads to strong grain refinement and material strengthening but also can drive phase transformations. A study of the fundamentals of α → ω phase transformations induced by high-pressure torsion (HPT) in Ti-Nb-based alloys is presented in the current work. Before HPT, a Ti-3wt.

Numerical Study on the Dependency of Microstructure Morphologies of Pulsed Laser Deposited TiN Thin Films and the Strain Heterogeneities during Mechanical Testing.

Numerical study of the influence of pulsed laser deposited TiN thin films' microstructure morphologies on strain heterogeneities during loading was the goal of this research. The investigation was based on the digital material representation (DMR) concept applied to replicate an investigated thin film's microstructure morphology. The physically based pulsed laser deposited model was implemented to recreate characteristic features of a thin film microstructure.

Synthesis and Characterization of CuFeSnS-CuMnSnS Solid Solution Microspheres.

In this study, we used a hydrothermal method to synthesize microspheres of Cu(MnFe)SnS solid solution (X = 1, 0.8, 0.6, 0.

Approximant-based orientation determination of quasicrystals using electron backscatter diffraction.

Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of electron backscatter diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations.

Refined Calibration Model for Improving the Orientation Precision of Electron Backscatter Diffraction Maps.

For the precise determination of orientations in polycrystalline materials, electron backscatter diffraction (EBSD) requires a consistent calibration of the diffraction geometry in the scanning electron microscope (SEM). In the present paper, the variation of the projection center for the Kikuchi diffraction patterns which are measured by EBSD is calibrated using a projective transformation model for the SEM beam scan positions on the sample. Based on a full pattern matching approach between simulated and experimental Kikuchi patterns, individual projection center estimates are determined on a subgrid of the EBSD map, from which least-square fits to affine and projective transformations can be obtained.

Manual measurement of angles in backscattered and transmission Kikuchi diffraction patterns.

A historical tool for crystallographic analysis is provided by the Hilton net, which can be used for manually surveying the crystal lattice as it is manifested by the Kikuchi bands in a gnomonic projection. For a quantitative analysis using the Hilton net, the projection centre as the relative position of the signal source with respect to the detector plane needs to be known. Interplanar angles are accessible with a precision and accuracy which is estimated to be ≤0.

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals.

FeNiCoAlTa single crystals oriented along the [001] direction were investigated in order to establish the influence of two-step aging conditions on superelastic properties. The homogenized and quenched single crystalline material was subjected to a combination of high-temperature and low-temperature heat treatment at 973 K for 0.5 h and at 723 K for various aging times, respectively.

Dissolution of Ag Precipitates in the Cu⁻8wt.%Ag Alloy Deformed by High Pressure Torsion.

The aim of this work was to study the influence of severe plastic deformation (SPD) on the dissolution of silver particles in Cu⁻8wt.%Ag alloys. In order to obtain different morphologies of silver particles, samples were annealed at 400, 500 and 600 °C.