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.

Effect of martensitic morphology on mechanical properties of an as-quenched and tempered 25CrMo48V steel

Abstract: The microstructures of 25CrMo48V martensitic steel quenched at the different temperatures of 800–1200 °C and tempered at 650 °C were characterized by optical microscope (OM), field emission scanning electron microscopy (FESEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The tensile and impact properties were evaluated from the as-quenched and tempered specimens. The results show that the refinement of the prior austenite grains due to the decrease of quenching temperature could induce the refinement of packets and blocks, while the lath width remained stable. The yield strength and the 50% fraction appearance transition temperature (50% FATT) varied linearly with the reciprocal square root of the prior austenite grain size, packet size and block width. Their relationships followed the classical formula of Hall–Petch and FATT = A − B d − 1 / 2 , respectively. The prior austenite grain size has a remarkable effect on the strength and toughness, while the block is the minimum structure unit controlling strength and toughness.

Electron Diffraction Based Analysis of Phase Fractions and Texture in Nanocrystalline Thin Films, Part I: Principles

Abstract: A method for phase analysis, similar to the Rietveld method in X-ray diffraction, was not developed for electron diffraction (ED) in the transmission electron microscope (TEM), mainly due to the dynamic nature of ED. Nowadays, TEM laboratories encounter many thin samples with grain size in the 1–30 nm range, not too far from the kinematic ED conditions. This article describes a method that performs (semi)quantitative phase analysis for nanocrystalline samples from selected area electron diffraction (SAED) patterns. Fractions of the different nanocrystalline components are determined from rotationally symmetric ring patters. Both randomly oriented nanopowders and textured nanopowders, observed from the direction of the texture axis produce such SAED patterns. The textured fraction is determined as a separate component by fitting the spectral components, calculated for the previously identified phases with a priori known structures, to the measured distribution. The Blackman correction is applied to the set of kinematic diffraction lines to take into account dynamic effects for medium grain size. Parameters of the peak shapes and the other experimental parameters are refined by exploring the parameter space with the help of the Downhill-SIMPLEX. Part I presents the principles, while future publication of Parts II and III will elaborate on current implementation and will demonstrate its usage by examples, respectively.

Morphology-property studies of amorphous polycarbonate

Abstract: The relationship between morphology and several physical properties (tensile, thermal, dielectric, and dynamic mechanical properties) of amorphous poly-bisphenol-A-carbonate was examined as a function of annealingtime at temperatures below the glass transition temperature (Tg). The change in structure of the amorphous films was studied by means of X-ray diffraction and with electron diffraction using a rotating sector in an electron microscope as well as by electron micrographs of replicas of surfaces prepared by etching with dilute aqueous NaOH solutions. The changes in morphology and physical properties caused by annealing below Tg are, in general, closely related. The relationship cannot be explained only by changes in free volume; it is proposed that changes in the degree and type of order (nodular structure) also play a role. The design and application of the rotating sector is described in an Appendix.

Microstructure characterization of SLM-processed Al-Mg-Sc-Zr alloy in the heat treated and HIPed condition

Abstract: Sc- Zr-modified Al-Mg alloy, processed by selective laser melting, offers excellent properties in the as processed condition, due to the formation of a desirable microstructure. As in conventional processing, such alloys are age hardenable, thereby precipitating a high fraction of finely dispersed coherent Al3(Scx Zr1-x) intermetallics, which serve for the improvement of the mechanical strength. Electron backscatter diffraction measurements and transmission electron microscopy were used to determine the effects of heat treatment and HIP on the microstructures of SLM processed specimens. In addition, the chemistry and number density of Al3Sc particles was analysed by atom probe tomography. The results show that the bi-modal grain size distribution observed in the as-processed condition can be maintained even after a heat treatment, due to a high density of intragranular Al3(ScxZr1-x) precipitates, and various other particles pinning the grain boundaries. A HIP post-processing can lead to grain growth in certain coarser grained areas, probably due to a local imbalance between driving and dragging forces, hence higher defect density and fewer pinning precipitates. Applying a heat treatment results in an increase of the density of ≤5 nm sized intragranular Al3(Scx Zr1-x) particles by a factor of 4–6, reaching 3·1023 m−3 to 5·1023 m−3.