Solid State Phenomena Vols. 203-204

Abstract: Electrolytic Zn-Ni alloy coatings were obtained on the steel substrate under galvanostatic conditions, and then, subjected to thermal treatment in argon atmosphere. The influence of thermal treatment on the surface morphology, phase composition and corrosion resistance of the electrodeposited coatings has been studied. Surface morphology was examined using a scanning electron microscopy. Chemical composition was determined by a X-ray fluorescence spectroscopy. Structural studies were carried out using a X-ray diffraction method. Corrosion resistance tests were carried out in 3% NaCl solution using open circuit potential method and potentiodynamic measurements. It was found that after thermal treatment, the value of polarization resistance increases, the value of the corrosion current decreases, and the value of corrosion potential is shifted towards anodic potentials. This suggests a positive effect of thermal treatment of the Zn-Ni alloy coatings on their corrosion resistance.

Abstract: The work presents the results on the microstructure of CrAlSiN+DLC coating deposited onto X40CrMoV5-1 hot work tool steel. The films were produced using a two-step method. In the first phase the physical vapour deposition (PVD) method was applied, whereas in the second Chemical Vapour Deposition (CVD) method was used. The microstructure and morphology of the CrAlSiN+DLC coating were analyzed by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. It was found that tested coatings have nanostructural character with fine crystallites, while their average size is between 11-25 nm. The TEM investigation showed a sharp interface between the coting and steel substrate. The AFM studies showed that the topography of the CrAlSiN and DLC layers were similar on the macroscopic scale

Abstract: The influence of Al substitution for Sn in Ni₄₄Mn_43.5Al_xSn_12.5-x (x= 0, 1, 2, 3) ferromagnetic shape memory alloy ribbons on phase transformation and microstructure evolution is outlined in this paper. Ribbons produced by melt spinning technique showed fully crystalline structure, however non uniform. Energy dispersive spectroscopy microanalysis (EDS) confirmed the average composition of ribbons in accord with the initial alloys. The higher symmetry parent phase was identified with the aid of X-ray diffraction (XRD) as bcc L2₁ Heusler type structure. The unit cell parameters were determined applying the XRD profile fitting method. It was observed that with increase of Al content unit cell parameters and in turn unit cell volume decrease. This may be attributed to the fact that Al has a smaller radius compared to Sn, which it was substituted for. Differential scanning calorimetry (DSC) measurements did not allow to detect the martensitic transformation above -150°C.

Abstract: In this study, the electrosynthesis method of the zinc oxide films on NiTi shape memory alloy substrate from zinc acetate solution, has been studied. The optimum conditions for production of the ZnO thin films were found at a voltage of 20 V for 60 s. Experimental data were presented on the deposition process, structure and composition of the ZnO thin films. It was found that depending on the deposition parameters, the structure of the obtained zinc oxide films varies from amorphous to coarse-grained. It was ascertained that the examined electrosynthesis of the ZnO films appears as a useful method for the surface modification of the NiTi alloy towards biomedical applications.

Abstract: In the present study the series of the Ni46.2Co5.0Mn36.1In12.6, Ni48.7Co5.2Mn34.4In11.6 and Ni45.6Co4.8Mn36.4In13.2 alloys (at. %) were studied. The influence of the indium addition on structure and phase transitions was studied. All alloys were annealed at 900°C for 24 hours and then slowly cooled in the furnace. After annealing all of the studied alloys showed the macrostructure of radially oriented columnar grains, which lied in the direction perpendicular to the casting axis. For the alloy containing about 13 at. % of indium the monoclinic 14M modulated martensite was stated at room temperature. Apart from the modulated martensite in a1_133 alloy the gamma phase was also observed. For alloy with higher indium content the mixture of cubic L21 parent phase and cubic gamma phase was identified. All studied alloys showed one-step martensitic transformation.

Abstract: The paper presents results of microstructural investigations of Mg-5Al-3Ca-0.7Sr-0.2Mn (ACJM53) magnesium alloys in the as-cast condition and after heat treatment at 450°C for 4.5 hours. Two kinds of transformation were observed in ACJM53 alloy after heat treatment: (Mg,Al)2Ca (C36) → Al2Ca (C15) and Al3Mg13(Sr,Ca) → Mg17(Sr,Ca)2 transformations without the change in morphology of output compounds. Morphology of Mg2Ca (C14) have been changed from fine lamellar to globular and precipitation process of Al2Ca (C15) phase inside the grains of solid solution was found.

Abstract: Results of studies on the modification of Al-7%SiMg alloy with an exothermic modifier on base Na2B4O7 are presented in the paper. The alloy was modified in a casting mold. Its structure, tensile strength and percentage elongation were determined. The results of the study indicate that in addition to modifier quantity and the type of reducing agent applied to produce an exothermic reaction, the reaction's thermal effect influences the quality of the modification process, leading to changes in the microstructure and mechanical properties of the alloy.

Abstract: Two morphological types of mechanical twins occur in the microstructure of cold rolled Ni-Mo-Cr alloy: long – passing over whole grains and micro-twins – confined to individual long range ordered domains. Long mechanical twins were only formed in the disordered alloy. Such twins are typical for metals with the face centered cubic structure with relatively low stacking fault energy. They do not form in the grains with twinning prohibited crystallographic orientations, e.g. {110}. Both types of twins were found in an alloy subjected to prolong annealing at 650 °C. The annealing induces long range ordering reaction leading to the formation of ordered domains with the body centered orthorombic crystal structure (oI8). The twins were of type I, type II, compound twins or pseudo-twins, depending on the crystallographic orientation of the ordered phase in relation to the matrix. It was found that twins of such types were formed even in grains with the {110} orientation and result from the anti-twinning deformation. However, in this orientation they were confined to ordered domains rather than developed into the long form crossing entire grains. On the other hand, the long twins of various types were formed in grains with other twinning favoring crystallographic orientations.

Abstract: This research addresses the EBSD analysis of friction stir welded 7136-T76 aluminum alloy. The objectives of this study were to evaluate the grain size and their shape, character of grain boundaries in the stirred and thermo-mechanically affected zones, both on the advancing and retreating side as well as to investigate changes in the crystallographic texture. Results of texture analysis indicate the complexity of the FSW process. The texture gradually weakens on moving from the thermo-mechanically affected zone toward the weld center. The stirred zone is characterized by very weak texture and is dominated by high angle boundaries. On the other hand, the thermo-mechanically affected zone exhibits a high frequency of low angle boundaries.

Abstract: Crystal structure of two spinel single crystals CdCr₂Se₄ and ZnCr_2-xV_xSe₄ have been reinvestigated using automated electron diffraction tomography method with beam precession. 3D reciprocal space have been reconstructed base on recorded tilt series. For both samples crystal structure was refined and the cubic symmetry with space group Fd-3m was confirmed. No additional electron potential has been located beside occupied atom sites.