Solid State Phenomena Vols. 203-204

Abstract: A new method for analysis of powder diffraction intensity data recently developed by the author has been modified to include the effects of possible statistical errors in the goniometer angle 2Θ. The analytical method is based on the maximum-likelihood estimation. Structure parameters refined by the method for fluorapatite Ca₅(PO₄)₃F, anglesite PbSO₄ and barite BaSO4 have become closer to those obtained by single-crystal structure analyses than the results obtained by applications of a conventional Rietveld refinement to the same powder diffraction data, similarly to the previous analyses, where the errors in 2Θ are not included. The statistical errors about 2Θ are estimated at Δ2Θ = 0.0030º, 0.00099º and 0.0036º from the powder diffraction data sets of fluoroapatite, anglesite and barite, respectively.

Abstract: In this work the feasibility of depositing magnesium coatings, on copper substrates is investigated. The deposition was accomplished by pack cementation process and the experiments were undertaken at 500°C, 550°C and 600°C for different deposition times. The purpose of these experiments was also to investigate the effect of deposition temperature on the morphology and the structure of the as-formed coatings. The characterization was performed with a SEM microscopy and XRD analysis. It was revealed that the as formed coatings mainly contain two phases corresponding to CuMg₂ and MgCu₂. Furthermore, the coating thickness and morphology was significantly affected by temperature and time.

Abstract: The presented paper describes X-ray diffraction study of Ni-Mn-Ga modulated martensite single crystal. A standard powder laboratory diffractometer equipped with texture cradle and monocapillary was found to be suitable and sufficient tool for this type of studies. Three different scans were performed to unambiguously identify the martensitic twin variants at selected place. From this identification and with the help of theoretical calculation full description of martensitic microstructure can be determined. In addition the effect of sample displacement on beam position on sample was derived.

Abstract: There is an ongoing interest in nanoparticles for the unique properties that have applications in a range of fields including catalysis, semi-conductors, gas storage amongst many others. In this study a variety of distinct techniques were applied on the same in-house X-Ray diffractometer. In particular, SAXS, conventional XRD and Total Scattering of nano-sized TiO2 powders were performed, together with in-situ heating experiments. The combination of the results from each technique proves to be a powerful tool for a more complete description of the material.

Abstract: Single crystal inclusions in natural single crystals bear a lot of information on the genesis and phase stabilities between host and guest crystals. Not only parameters of the natural environment of crystallization may be elucidated, also the history of up-rise within the earth to the surface and the development during procedures, eventually applied by mankind to enhance the physical properties of crystals, may be detectable. Structural reactions resulting in phase separation due to chemical stress during change of physical parameters shed light on the borders of solid solution and exsolution domains. Natural crystals of proper quality allow us to evaluate a time factor in phase stabilities.Crystal structures are able to react by epitaxial growth, by chemical induced twinning, by miscibility reactions, exsolution, and by solid solutions. Some of the phenomena we are meanwhile able to detect by means of (sub-) micro analytical methods. But many problems are left undiscovered between chemical analysis and phase detection due to the local behavior of atoms or ions within a given architecture, which locally provides stable and/or stabilizing crystallization.

Abstract: Defects recognition in GaN epilayers was performed using HRTEM and LACBED images. Edge type dislocations, basal plane and prismatic stacking faults were determined from HRTEM analysis. Stacking mismatch boundaries on zigzag steps were found and examined using LACBED patterns in bright and dark field. For stacking faults Bragg lines split into a main and a subsidiary line. The fault plane and displacement vector can be identified from trace analysis performed on LACBED patterns.

Abstract: The present research is a part of project dealing with structural aspects of ferrite and austenite co-deformation in duplex stainless steels. The examination concerned a development of ferrite and austenite microstructures, major deformation mechanisms operating in both phases and texture formation upon cold-rolling of a model duplex type steel. The investigations showed that the band-like morphology of two-phase structure formed upon processing together with specific starting textures obtained after a preliminary thermo-mechanical treatment exerted significant influence on texture and microstructure development in both constituent phases. Microstructure and texture evolution in examined duplex steel significantly differed from those in one-phase steels. These differences resulted first of all from the role of the phase boundaries acting as the barriers for dislocation movement and affecting the processes of strain localization at higher deformations.

Abstract: The work focuses on the analysis of microstructural features of retained austenite in a thermomechanically processed Si-Al TRIP-type steel microalloyed with Nb and Ti. Austenite amount was determined using XRD and EBSD. Combined methods of LM, SEM and EBSD were applied to reveal the morphology, grain size and distribution of structural constituents. It is possible to retain 14% of  phase enriched in C to about 1.14 wt.%. Retained austenite is uniformly located as blocky grains with a diameter up to 4.5 m in a fine-grained ferritic matrix or between bainitic ferrite laths as thin layers. Special crystallographic relationships between bainitic ferrite and retained austenite were identified on the basis of the analysis of misorientation angles and image quality values.

Abstract: The effect of cold rolling and annealing treatments in two temperatures, 800°C and 900°C on texture formation in duplex steel (X60MnAl30-9) was examined. Texture measurements were carried out using X-ray diffraction and Schulz reflection technique. The mechanical properties i. e. 0.2% proof stress, ultimate tensile strength and elongation were measured for each experimental conditions. It was found that ferrite was characterized by the orientations of a fibre which could be found in cold rolling state and also after the annealing in both temperatures. The weak orientations close to g fibre were observed after the annealing. The cold rolling texture of austenite was a typical texture of cold rolled fcc metals. No significant changes in texture of austenite after the annealing treatments were found.