Dislocation avalanches are like earthquakes on the micron scale.

Compression experiments on micron-scale specimens and acoustic emission (AE) measurements on bulk samples revealed that the dislocation motion resembles a stick-slip process - a series of unpredictable local strain bursts with a scale-free size distribution. Here we present a unique experimental set-up, which detects weak AE waves of dislocation slip during the compression of Zn micropillars. Profound correlation is observed between the energies of deformation events and the emitted AE signals that, as we conclude, are induced by the collective dissipative motion of dislocations. The AE data also reveal a two-level structure of plastic events, which otherwise appear as a single stress drop. Hence, our experiments and simulations unravel the missing relationship between the properties of acoustic signals and the corresponding local deformation events. We further show by statistical analyses that despite fundamental differences in deformation mechanism and involved length- and time-scales, dislocation avalanches and earthquakes are essentially alike.

A Sequence of Phase Transformations and Phases in NiCoFeCrGa High Entropy Alloy.

The present investigation is directed to phase transitions in the equimolar NiCoFeCrGa high entropy alloy, which is a mixture of face-centered cubic (FCC) and body-centered cubic (BCC) crystalline phases. The microstructure of the samples was investigated by using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), transmission electron microscopy-based energy-dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS), as well as X-ray diffraction (XRD) measurements. Based on the phases observed in different temperature ranges, a sequence of the phase transitions can be established, showing that in a realistic process, when freely cooling the sample with the furnace from high to room temperature, a microstructure having spinodal-like decomposition can also be expected. The elemental mapping and magnetic behaviors of this decomposed structure are also studied.

In Situ Atomic Force Microscopy Depth-Corrected Three-Dimensional Focused Ion Beam Based Time-of-Flight Secondary Ion Mass Spectroscopy: Spatial Resolution, Surface Roughness, Oxidation.

Atomic force microscopy (AFM) is a well-known tool for studying surface roughness and to collect depth information about features on the top atomic layers of samples. By combining secondary ion mass spectroscopy (SIMS) with focused ion beam (FIB) milling in a scanning electron microscope (SEM), chemical information of sputtered structures can be visualized and located with high lateral and depth resolution. In this paper, a high vacuum (HV) compatible AFM was installed in a TESCAN FIB-SEM instrument that was equipped with a time-of-flight SIMS (ToF-SIMS) detector. To calibrate the sputtering rate and measure the induced roughness caused by the ToF-SIMS analysis, subsequent AFM measurements were performed on an inorganic multilayer vertical cavity surface-emitting laser sample. Normalized sputtering rates were used to aid the accurate three-dimensional reconstruction of the sputtered volume's chemical composition. Achievable resolution, surface roughness during sputtering, and surface oxidation issues were analyzed. The integration of complementary detectors opens up the ability to determine the sample properties as well as to understand the influence of the Ga+ ion sputtering method on the sample surface during the analysis.