Electron backscatter diffraction

About: Electron backscatter diffraction is a research topic. Over the lifetime, 15184 publications have been published within this topic receiving 317847 citations. The topic is also known as: EBSD.

XRDUA: crystalline phase distribution maps by two‐dimensional scanning and tomographic (micro) X‐ray powder diffraction

Abstract: Imaging of crystalline phase distributions in heterogeneous materials, either plane projected or in virtual cross sections of the object under investigation, can be achieved by scanning X-ray powder diffraction employing X-ray micro beams and X-ray-sensitive area detectors. Software exists to convert the two-dimensional powder diffraction patterns that are recorded by these detectors to one-dimensional diffractograms, which may be analysed by the broad variety of powder diffraction software developed by the crystallography community. However, employing these tools for the construction of crystalline phase distribution maps proves to be very difficult, especially when employing micro-focused X-ray beams, as most diffraction software tools have mainly been developed having structure solution in mind and are not suitable for phase imaging purposes. XRDUA has been developed to facilitate the execution of the complete sequence of data reduction and interpretation steps required to convert large sequences of powder diffraction patterns into a limited set of crystalline phase maps in an integrated fashion.

Molybdenum and tungsten manufactured by selective laser melting: Analysis of defect structure and solidification mechanisms

Abstract: In this work, processing of molybdenum and tungsten by Selective Laser Melting (SLM) is analyzed. The study reveals the impact of the oxygen content of the powder, the process atmosphere and the temperature of the substrate plate on the structural and mechanical properties of the processed material. For clarifying the causes and mechanisms for the formation of defects in molybdenum and tungsten processed by SLM, the samples were examined by x-ray, scanning and transmission electron microscopy including elemental distribution maps and crystallographic analyses by electron backscatter diffraction. Impurities, mainly oxygen, were identified as cause for the predominant defect structure comprising cracks and residual porosity. During processing, oxygen in the form of molybdenum/tungsten oxide, segregates at the grain boundaries, thereby inducing hot cracking. This is due to the lower melting point of the eutectic compared to the matrix phase. Moreover, the oxygen impurities were found to weaken the grain boundaries and thus increasing the risk for cold cracking and leading to a higher Ductile-to-Brittle Transition Temperature (DBTT). Subsequently, the combination of cracks through hot cracking at planar solidified grain boundaries and cold cracking along weakened grain boundaries during rapid cooling from the melting point creates the crack network generally found in molybdenum and tungsten processed by SLM. Also a substrate plate temperature of 1000 °C does not prevent the formation of cracks in tungsten caused by oxygen segregations.

Microstructural characterization of AISI 431 martensitic stainless steel laser-deposited coatings

Abstract: High cooling rates during laser cladding of stainless steels may alter the microstructure and phase constitution of the claddings and consequently change their functional properties. In this research, solidification structures and solid state phase transformation products in single and multi layer AISI 431 martensitic stainless steel coatings deposited by laser cladding at different processing speeds are investigated by optical microscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), orientation imaging microscopy (OIM), ternary phase diagram, Schaeffler and TTT diagrams. The results of this study show how partitionless solidification and higher solidification rates alter the microstructure and phase constitution of martensitic stainless steel laser deposited coatings. In addition, it is shown that while different cladding speeds have no effect on austenite–martensite orientation relationship in the coatings, increasing the cladding speed has resulted in a reduction of hardness in deposited coatings which is in contrast to the common idea about obtaining higher hardness values at higher cladding speeds.