Advanced High-Strength Steels (AHSSs) are one of the most rapidly developing group of Fe-based metallic materials. Their excellent combination of high strength, ductility and formability is due to their complex microstructure and strain-induced martensitic transformation of metastable retained austenite (RA), which favors extra ductility of the sheet steels. A deformation temperature is one of the most important factors affecting the phase transformation behavior in these Fe–C–Mn–Al–Si systems. Therefore, the present study aimed at understanding the temperature-dependent phase transformations and structural phenomena in an advanced medium-Mn–Al-alloyed steel. The 3Mn steel was thermomechanically processed and subjected to tensile testing in a temperature range from 20°C to 200°C. The different extent of the strain-induced martensitic transformation and some softening phenomena of bainitic ferrite matrix were revealed using transmission electron microscopy and electron backscatter diffraction techniques. It was found that the thermal stability of RA is strongly dependent on the deformation temperature. Moreover, the dynamic recovery and carbide precipitation play a key role when the deformation temperature is increased to 140°C and higher temperatures.

4D-STEM, in which the 2D diffraction plane is captured for each 2D scan position in the scanning transmission electron microscope (STEM) using a pixelated detector, is complementing, and increasingly replacing existing imaging approaches. However, at present the speed of those detectors, although having drastically improved in the recent years, is still 100 to 1,000 times slower than the current PMT technology operators are used to. Regrettably, this means environmental scanning-distortion often limits the overall performance of the recorded 4D data. Here, we present an extension of existing STEM distortion correction techniques for the treatment of 4D data series. Although applicable to 4D data in general, we use electron ptychography and electric-field mapping as model cases and demonstrate an improvement in spatial fidelity, signal-to-noise ratio (SNR), phase precision, and spatial resolution.

In the scanning transmission electron microscope, fast-scanning and frame-averaging are two widely used approaches for reducing electron-beam damage and increasing image signal noise ratio which require no additional specialized hardware. Unfortunately, for scans with short pixel dwell-times (less than 5 μs), line flyback time represents an increasingly wasteful overhead. Although beam exposure during flyback causes damage while yielding no useful information, scan coil hysteresis means that eliminating it entirely leads to unacceptably distorted images. In this work, we reduce this flyback to an absolute minimum by calibrating and correcting for this hysteresis in postprocessing. Substantial improvements in dose efficiency can be realized (up to 20%), while crystallographic and spatial fidelity is maintained for displacement/strain measurement.

The interaction of NCC-A (no cement content, with tabular corundum) refractory castable with corrosive refining steel slag CaO–Al2O3–SiO2–MgO–(FeO, MnO) was studied with static crucible corrosion tests. The corrosion process was evaluated using chemical and phase analyses, and the macro- and microstructures on the corrosion boundary of slag–refractory materials were investigated. We describe the corrosion progress and explain the NCC-A corrosion mechanism by oxide metallurgical slags. The alumina refractory material surface was wetted with molten oxide slag (contact angle θ1390°C from 10° to 20°). The slag penetrated through dissolution of the matrix (fine alumina cement), and the Ca–Si–Al slag, enriched with alumina, attacked the corundum grog. Marked changes in the chemical composition of the slag had an impact on the primary crystallization temperature. As the concentration of Al–O complexes increased in the slag, the binding parameters in Si–O complexes changed and complex tetrahedral units (Al–O–Si) and (Al–O–Mg) were created. Analyses of the corrosion interface grog show that calcium ions diffuse through structural defects in the corundum but Mg2+ diffusion was not observed. A sharp interface is observed between the slag and the corroded corundum layer. Differences in the chemical composition of the slag in the corrosion zone affected the convention stream, and formed the concave corrosion profile of the crucible.

Low-voltage transmission electron microscopy (≤80 kV) has many applications in imaging beam-sensitive samples, such as metallic nanoparticles, which may become damaged at higher voltages. To improve resolution, spherical aberration can be corrected for in a scanning transmission electron microscope (STEM); however, chromatic aberration may then dominate, limiting the ultimate resolution of the microscope. Using image simulations, we examine how a chromatic aberration corrector, different objective lenses, and different beam energy spreads each affect the image quality of a gold nanoparticle imaged at low voltages in a spherical aberration-corrected STEM. A quantitative analysis of the simulated examples can inform the choice of instrumentation for low-voltage imaging. We here demonstrate a methodology whereby the optimum energy spread to operate a specific STEM can be deduced. This methodology can then be adapted to the specific sample and instrument of the reader, enabling them to make an informed economical choice as to what would be most beneficial for their STEM in the cost-conscious landscape of scientific infrastructure.

The exotic internal structure of polar topologies in multiferroic materials offers a rich landscape for materials science research. As the spatial scale of these entities is often subatomic in nature, aberration-corrected transmission electron microscopy (TEM) is the ideal characterization technique. Software to quantify and visualize the slight shifts in atomic placement within unit cells is of paramount importance due to the now routine acquisition of images at such resolution. In the previous ~decade since the commercialization of aberration-corrected TEM, many research groups have written their own code to visualize these polar entities. More recently, open-access Python packages have been developed for the purpose of TEM atomic position quantification. Building on these packages, we introduce the TEMUL Toolkit: a Python package for analysis and visualization of atomic resolution images. Here, we focus specifically on the TopoTEM module of the toolkit where we show an easy to follow, streamlined version of calculating the atomic displacements relative to the surrounding lattice and thus plotting polarization. We hope this toolkit will benefit the rapidly expanding field of topology-based nano-electronic and quantum materials research, and we invite the electron microscopy community to contribute to this open-access project.