Effect of Mg on the Formation of Periodic Layered Structure during Double Batch Hot Dip Process in Zn-Al Bath

The article presents the results of studies on the influence of Mg on the formation of the periodic layered structure of the Zn-AlMg coatings. These coatings were produced by the double batch hot dip method in a Zn bath and then in a Zn-Al(Mg) bath with a content of 15, 23, 31 wt.% Al and 3, 6 wt.% Mg. The microstructure of the coatings (OM, SEM) was revealed and the phase composition (XRD) obtained in two-component Zn-Al baths and Zn-AlMg baths were determined. The periodic layered structure was found to consist of alternating FeAl3 phase layers and a bath alloy (Zn + Al + Mg). Moreover, it was observed that the addition of 3 wt.% Mg reduces the thickness of the coating in baths containing 23 and 31 wt.% Al. However, the addition of 6 wt.% Mg causes complete disappearance of periodic layered structure in a bath with 23 wt.% Al. In a bath with a content of 31 wt.% Al the addition of 6 wt.% Mg creates a compact layer consisting of the FeAl3 phase containing the precipitation of the MgZn2 phase and Fe2Al5 phase. Such a structure of the coating transition layer limits the growth of the periodic layered structure in the coating.

Dry Adhesive Friction Process Regularities during Frictional Contact of Heterogeneous “Copper-Aluminum” System Materials

By means of optical and scanning electron microscopy the surface layer structure of aluminum alloy AMg5 samples with introduced copper part after adhesive frictional contact with AISI 420 steel counterbody was studied. It is revealed that under plastic deformation and material fragmentation in the frictional contact zone a complex mixture of different phase layers is formed due to the formation of different flows of aluminum alloy and copper during friction. Mechanical mixing of a material occurs on all length of a friction path with different intensity depending on distance to copper fragment. Both laminar and turbulent flows of material are formed in the surface layer, as well as a wide range of solid solutions, intermetallic phases and mechanical mixtures.

EFFECT OF Mg AND TEMPERATURE ON Fe–Al ALLOY LAYER IN Fe/(Zn–6%Al–x%Mg) SOLID–LIQUID DIFFUSION COUPLES

Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe–Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe–Al alloy layer. It was found that the Fe2Al5Znxphase layer forms close to the iron sheet and the FeAl3Znxphase layer forms near the side of the melted Zn–6%Al–3%Mg in diffusion couples. When the Fe/(Zn–6%Al–3%Mg) diffusion couple is kept at 510[Formula: see text]C for more than 15[Formula: see text]min, a continuous Fe–Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples, the Fe–Al alloy layer on the interface of the Fe/(Zn–6% Al–3% Mg) diffusion couple is the thinnest. The Fe–Al alloy layer forms only when the diffusion temperature is above 475[Formula: see text]. These results show that the Fe–Al alloy layer in Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples is composed of Fe2Al5Znxand FeAl3Znxphase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe–Al alloy layer. When the Mg content in the Fe/(Zn–6%Al–[Formula: see text]%Mg) diffusion couples is 3%, the growth of the Fe–Al alloy layer is inhibited. These results may explain why there is no obvious Fe–Al alloy layer formed on the interface of steel with a Zn–6%Al–3%Mg coating.

Statistics of vertical velocities in supercooled cloud layers over Leipzig and Praia measured with Doppler lidar

This study presents statistics of vertical air velocity at the bases of supercooled shallow cloud layers separately for mixed-phase and liquid-only clouds. For the first time, this statistics is compared for clouds observed over a sub-tropical site at Cape Verde (14.9° N, 26° W) and a mid-latitudinal site at Leipzig, Germany (51.3° N, 12.4° E). Phase properties and spatio-temporal extent of the cloud layers were obtained from combined observations with Doppler lidar, Raman polarization lidar, and cloud radar. The statistical properties of the vertical-velocity distributions in both mixed-phase and pure-liquid cloud layers are found to be similar at both measurement sites. Standard deviation of the vertical velocities at both sites was found to be 0.4 m s−1 and was also the same in pure-liquid and mixed-phase layers. Skewness groups around −0.4 for both sites, pointing to radiative cooling as the driver for the cloud turbulence. Occasionally, positive skewness in some cloud layers indicated external drivers, e.g., gravity waves, for the turbulence. From the observed similarity in the vertical-velocity statistics derived at the base of supercooled liquid cloud layers at Praia and Leipzig it can be concluded that other factors besides cloud dynamics are responsible for the differences in ice formation efficiency reported previously for both sites.

Investigation of Surface Phase Layers on GaAs after Selective Chemical Etching

Normal 0 false false false RU X-NONE X-NONE The combination of methods of voltammetry, Raman spectroscopy, and X-ray reflectometry for the first time has been applied for the more comprehensive investigation of interfacial boundaries of GaAs, i.e. determination of phase distribution and thickness of the phase layers. The conditions for the formation of elemental arsenic on a GaAs surface in the process of selective dissolution are discussed. The stability of interfacial boundaries in air has also been studied. The investigations have shown that air storage lead to the oxidation of formed As0 and reorganization of GaAs interfacial boundary accompanied by the formation of Ga2O3 and As0 as a result of a reaction between As2O3 and GaAs. The results on interfacial boundaries composition were found to be correlated with the theoretical data. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Обычная таблица"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-fareast-language:EN-US;}

Microstructure and Mechanical Properties of Tough Phase Layers of a NiCoCrAl/YSZ Multiscalar Microlaminate

One multiscalar microlaminate comprising 66 thin strong layer stacks of NiCoCrAl / ZrO2-8wt.%Y2O3 (YSZ) and 5 thick tough phase layers of NiCoCrAl whose thicknesses ranged from 5μm to 25μm was fabricated by Electron Beam Physical Vapor Deposition (EB-PVD) and followed by hot pressing treatment. Scanning electron microscopy was used to characterize the microstructures and failure mode of the tough phase layers. Tensile tests and nanoindentation tests were performed to evaluate the mechanical properties of the tough phase layers. The influence of thicknesses of tough phase layers on their microstructure and mechanical properties was investigated. It was found that with the increasing thicknesses of the tough phase layers, their hardness decreased, but their plasticity increased. There was a critical thickness for the tough phase layers between 13μm and 20μm. The tough phase layers with thickness less than the critical value displayed the different microstructure and failure mode from those with thickness more than the critical value.

A Morphology of Diffusion Zone from Entropy Production Calculations

Interdiffusion plays a significant role in the formation and stability of metallic joints and coatings. It is also of critical importance in designing advanced materials. Because commercial alloys are usually multicomponent, the key target is prediction of a complex morphology of the diffusion zone which grows between the alloys, alloy-coating, etc. In a two-component system, the diffusion zone can be composed of single-phase layers of the intermetallic compounds and solid solutions. The evolution of the composition and thicknesses of such layers are fairly well understood and consistent with the phase diagrams. The situation is qualitatively different in multicomponent systems. For example, the diffusion zone in a ternary system can be composed of single-and two-phase sublayers. Their number and thicknesses depend on the initial conditions, i.e. composition, component diffusivities and geometry of the system. The usual way of presenting the sequence of the layers and their compositions is by drawingadiffusionpathwhich is, by definition,a mapping of thestationary concentrations onto the isothermal section of the equilibrium phase diagram. The diffusion path connects initial compositions of the diffusion couple and can go across the single-, two-and three-phase fields. It starts at the composition of one alloy and ends at the other. The possibility of mapping the concentration profiles onto the ternary isotherm has been postulated in one from the seventeen theorems by Kirkaldy and Brown [] for the diffusion path. The detailed presentation of all theorems was recently done by Morral []. Here we remind the reader only of the chosen ones (shown in italics).