Smjerovna ovisnost izdvajanja antimona na površinama legura FeSi

The antimony surface segregation was investigated on surfaces of a polycrystalline Fe-Si alloy with 0.05 wt. % Sb, under UHV conditions, in the temperature range from 450 to 950 °C. The grain boundary segregation in experimental alloys was negligible. It was concluded that the texture formation results from orientation-dependent effects of antimony on the surface energy and through them on grain boundaries. Controlled surface segregation promotes the selective grain growth.Proučavano je površinsko izdvajanje antimona na površinama polikristalne legure FeSi sa 0.05 tež.%, u ultravakuumu i na temperaturama od 450 do 950 ◦C. Izdvajanje na granicama zrna je zanemarivo. Ustanovljeno je da je nastajanje teksture posljedica smjerovno–ovisnih učinaka antimona na površinsku energiju pa stoga i na granice zrna. Upravljavano površinsko izdvajanje potiče poseban rast zrna

Kinetics of Arsenic Surface Segregation in Scrap-Based Silicon Electrical Steel

The segregation kinetics of surface-active, residual elements are investigated in an in situ study of annealing scrap-based silicon electrical steel sheet where the arsenic (As) surface segregation is highlighted. During annealing in the temperature range of 300–950 °C, different kinds of interactions between the segregated residual elements were observed. Attractive interactions between the segregands produced co-segregation, e.g., between Sn and Sb, whereas repulsive interactions resulted in site competition, e.g., between Sn and As. These competing interactions are strongly time dependent. In spite of there being twice as much Sn compared to As in the bulk material, the As prevailed in the surface enrichments of the polycrystalline silicon steel at 950 °C. The intensity of the As surface segregation in the temperature range 800–950 °C is proportional to the calculated amount of γ-austenite phase in the (α + γ) steel matrix. The detected phenomenon of the As versus Sn site competition could be valuable for the texture design and surface engineering of silicon steels with a thermodynamically stable two-phase (α + γ) region

Vpliv bakra na razogljičenje in rekristaizacijo zlitin Fe-Si-Al

The decarburization and recrystallization of Fe-Si-Al alloys containing copper was investigated. The decarburization annealing of non-oriented electrical steel sheets produced from Fe-Si-Al alloys depends on the chemical reactions between the gas mixture and the carbon at the steel\u27s surface. The carbon diffusion, the temperature of decarburization annealing, the composition of the gas mixture and the chemical composition of the steel are the influencing parameters that determine the kinetics and the mechanism of decarburization. The decarburization of Fe-Si-Al alloy with the mass fraction of 0.24% and 0.43% of copper was compared with the decarburization of an Fe-Si-Al alloy with a very small amount of copper (0.01%). The decarburization annealing was performed in a H2-H2O gas mixture at 840 °C. The residual carbon content was determined by analytical chemical method. The alloys were also recrystallized in hydrogen at 980 °C. Microstructure of samples after decarburization and recrystallization annealing was investigated with optical microscopy.Preučevali smo razogljičenje in rekristalizacijo modelnih zlitin Fe-Si-Al z različno vsebnostjo bakra. Razogljičenje neorientiranih elektropločevin, ki jih lahko izdelujemo iz zlitin Fe-Si-Al, je odvisno od kemijskih reakcij med ogljikom, ki difundira na površino jekla, ter plinsko mešanico. Vplivni parametri, ki določajo kinetiko in mehanizem razogljičenja, so: površinska segregacija ogljika, temperatura razogljičevalnega žarjenja, sestava plinske mešanice in kemijska sestava jekla. Razogljičenje smo merili v zlitinah Fe-Si-Al z vsebnostjo masnega deleža bakra 0,24 % in 0,43 % ter ga primerjali s tistim v zlitini z zelo nizko vsebnostjo bakra, 0,01 %. Zlitine smo razogljičili pri temperaturi 840 °C v plinski mešanici H2-H2O. Preostali delež ogljika po razogljičenju smo določili s kemijsko analizo vzorcev. Zlitine smo tudi rekristalizacijsko žarili v suhem vodiku pri 980 °C. Mikrostrukturo vzorcev po žarjenju za razogljičenje in rekristalizacijo smo analizirali s svetlobno mikroskopijo

Surface Stoichiometry and Roughness of a Degraded A380 Alloy after Casting, Technical Cleaning and Packaging

The surface stoichiometry of the degraded surface of a commercial Al–Si casting was investigated. The die-cast component was previously stored in a sealed plastic envelope. After that, surface stains in the form of white layers were observed. X-ray photoelectron spectroscopy (XPS) was used to study these layers. For comparison, a seemingly unaffected area as well as a freshly cut surface of the casting were also analysed. In order to additionally assess the surface condition, surface roughnesses were measured. Based on the binding energies (BEs) of the Al and O in the XPS spectra, and the stoichiometric results, it was concluded that the surface layers of the degraded and undegraded samples consist mostly of aluminium oxide and aluminium hydroxide. Furthermore, sodium phosphate from the leftover detergent and silicon oxide were detected in both analysed areas. Analyses of the Al KLL Auger transition were used to corroborate this. The relative shares of Al oxide vs. hydroxide based on the elemental concentrations were determined. The chemical compositions and chemical states of the elements in the top layers were thus obtained. The combination of surface-sensitive analytical techniques was found to be a suitable tool for the ex-post identification of the source of defects

Classification of hot-rolled plates using the Mahalanobis distance of NMIs in Ti-stabilized austenitic stainless-steel produced by secondary metallurgy

Three charges of scrap-based, Ti-stabilized, Cr-Ni-Mo austenitic stainless steel in the form of hot-rolled steel plates were characterized. Based on automated metallographic analyses of representative microstructures, a quality characterization in terms of cleanliness of the hot-rolled steel plates was performed. Elevated contents of impurities, especially Pb, Bi, and oxygen, which affect the hot workability of stainless steels, were detected. The recycled FeTi-cored wire was the main source of the elevated levels of impurities detected in the hot-rolled, Ti-stabilized, stainless-steel plates. Related to this, elevated levels of nonmetallic inclusions (NMIs) and segregations were formed. The three charges were classified based on calculations of the Mahalanobis distance (MD) between the inclusions. The charge with the smallest number of nonmetallic inclusions was set as the reference class. The selection of outlier inclusions based on their MDs and their back-representation into ternary diagrams gave relevant metallurgical information about the abnormalities. The advantage of this technique is that the calculations of the MD and the threshold can be fully automated

Differential scanning calorimetry study of the solidification sequence of austenitic stainless steel

peer reviewedRecent researches have stated the fast deployment of IPv6. It has been demonstrated that IPv6 grows much faster, being so more and more adopted by both Internet service providers but also by servers and end-hosts. In parallel, researches have been conducted to discover and assess the usage of MPLS tunnels. Indeed, recent developments in the ICMP protocol make certain categories of MPLS tunnels transparent to traceroute probing. However, these studies focus only on IPv4, where MPLS is strongly deployed. In this paper, we provide a first look at how MPLS is used under IPv6 networks using traceroute data collected by CAIDA. At first glance, we observe that the MPLS deployment and usage seem to greatly differ between IPv4 and IPv6, in particular in the way MPLS label stacks are used. While label stacks with at least two labels are marginal in IPv4 (and mostly correspond to a VPN usage), they are prevalent in IPv6. After a deeper analysis of the label stack typical content in IPv6, we show that such tunnels result from the use of 6PE. This is not really surprising since this mechanism was specifically designed to forward IPv6 traffic using MPLS tunnels through networks that are not fully IPv6 compliant. However, we show that it does not result from non dual-stack routers but rather from the absence of native IPv6 MPLS signaling protocols. Finally, we investigate a large Tier-1 network, Cogent, that stands out with an original set-up

Microstructural anisotropy of magnetocaloric gadolinium cylinders

The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces

Microstructural Anisotropy of Magnetocaloric Gadolinium Cylinders: Effect on the Mechanical Properties of the Material

The development of advanced materials and technologies based on magnetocaloric Gd and its compounds requires an understanding of the dependency of mechanical properties on their underlying microstructure. Therefore, the aim of the study was to characterize microstructural inhomogeneities in the gadolinium that can be used in magnetocaloric refrigeration systems. Microstructures of magnetocaloric gadolinium cylinders were investigated by light microscopy and FE-SEM (Field Emission Scanning Electron Microscopy), EDS (Energy-dispersive X-ray Spectroscopy), and BSE (Back-scattered Electrons) in both the extrusion and the extrusion-transversal directions. XRD (X-ray Diffraction) analyses were performed to reveal the presence of calcium- and fluorine-based compounds. Metallographic characterization showed an oxidized and inhomogeneous microstructure of the cross-sections. The edges and the outer parts of the cylinders were oxidized more intensively on the surfaces directly exposed to the processing tools. Moreover, a significant morphological anisotropy of the non-metallic inclusions was observed. CaF inclusions act as active nucleation sites for internal oxidation. The non-metallic, Ca- and F-containing inclusions can be classified as complex calciumoxyfluorides. The solubility of Er and Yb in the CaF was negligible compared to the Gd matrix and/or the oxide phase. Lower mechanical properties of the material are a consequence of the lower structural integrity due to selective oxidation of surfaces and interfaces

Solidification Behavior of Fe-6.5Si Alloy Powder for AM-SLM Processing, as Assessed by Differential Scanning Calorimetry

Lab-scale investigations on the processing of small powder volumes are of special importance for applications in additive manufacturing (AM) techniques. Due to the technological importance of high-silicon electrical steel, and the increasing need for optimal near-net-shape AM processing, the aim of this study was to investigate the thermal behavior of a high-alloy Fe-Si powder for AM. An Fe-6.5wt%Si spherical powder was characterized using chemical, metallographic, and thermal analyses. Before thermal processing, the surface oxidation of the as-received powder particles was observed by metallography and confirmed by microanalysis (FE-SEM/EDS). The melting, as well as the solidification behavior of the powder, was evaluated using differential scanning calorimetry (DSC). Due to the remelting of the powder, a significant loss of silicon occurred. The morphology and microstructure analyses of the solidified Fe-6.5wt%Si revealed the formation of needle-shaped eutectics in a ferrite matrix. The presence of a high-temperature phase of silica was confirmed by the Scheil–Gulliver solidification model for the ternary model Fe-6.5wt%Si-1.0wt%O alloy. In contrast, for the binary model Fe-6.5wt%Si alloy, thermodynamic calculations predict the solidification exclusively with the precipitation of b.c.c. ferrite. The presence of high-temperature eutectics of silica in the microstructure is a significant weakness for the efficiency of the magnetization processes of soft magnetic materials from the Fe-Si alloy system