Fatigue cracks were found in water-filter housings made of styrene-acrylonitrile. These cracks initiated on the external surface, along the sharp corner between the wall of the housing and the ...vertical external ribs or at a pre-existing crack in the base of the water-filter housing. The reason for the crack was the high stress concentration due to an inappropriate design or the poor quality of the filter housing in combination with water-pressure impacts during the operation of an electromagnetic water valve and taps.
•Fatigue cracks exist in a water-filter housing made of styrene-acrylonitrile.•Quality of the styrene-acrylonitrile is good.•Cracks initiated due to water-pressure impacts in areas of high stress concentration.•Failure is due to improper design or a pre-existing crack in the base of the filter housing.
In the present work, free-cutting aluminum alloy AA6026 with 1.1 wt.% bismuth addition was fabricated by different melt preparation methods in order to investigate whether the melt preparation route ...affects the solidification sequence and thus has an influence on the machinability of the alloy. All experiments were designed to simulate variable industrial conditions: addition of bismuth in an induction melting furnace, addition of bismuth in an electric resistance holding furnace, addition of bismuth together with grain refiner, effect of holding time and melt temperature before casting. Detailed thermodynamic analyses (DSC, Thermo-Calc) and microstructural characterization (SEM-EDS, XRD) have been performed to explain the solidification sequence, microstructure development and especially formation of the intermetallic Mg3Bi2 phase.
In the present work, TiC/TiB2/Al composite coatings were synthesized onto a precipitation hardened AlSi1MgMn alloy by laser surface alloying (LSA), using 13.3 J/mm2 and 20 J/mm2 laser energy ...densities. Microstructure evaluation, microhardness, wear and corrosion performance were investigated and compared with the untreated/substrate Al alloy sample. The results confirmed sound, compact, crackles composite coating of low porosity, with a proper surface/substrate interface. Microstructural analyses revealed the formation of extremely fine nano-precipitates, ranging from of 50–250 nm in the laser melted (LMZ) and large precipitates, accompanied with grain coarsening in the heat-affected zone (HAZ), due to the substrate overheating during the LSA process. Nonetheless, both coatings achieved higher microhardness, with almost 7-times higher wear resistance than the untreated sample as a consequence of high fraction volume of hard, wear resistant TiB2 and TiC phases inside the composite coatings. Further, cyclic polarization results in 0.5 M NaCl aqueous solution confirmed general improvement of corrosion resistance after LSA processed samples, with reduced corrosion current by more than a factor of 9, enhanced passivation/repassivation ability and complete prohibition of crystallographic pitting, which was detected with the untreated Al alloy.
•The presence of sulphate ions does not significantly affect the dissolution mechanism of the alloy.•Corrosion products mostly contain oxides and chlorides of Al, Mn and Cu.•The Cualmn alloy ...undergoes general corrosion in the studied solutions.•The growth dynamic of the spontaneous surface film in the tested solutions is different.•The stability of the surface film increases with the immersion time and the presence of sulphate ions.
The electrochemical behaviour of a CuAlMn alloy in a 0.5 M NaCl solution with the addition of different concentrations of Na2SO4 (0.1, 0.3, and 0.5 M) was investigated by observing the change in open circuit potential (EOC) with time, applying polarization methods and electrochemical impedance spectroscopy (EIS). The damage to the metal surface was determined by optical microscopy and SEM/EDS analysis.
Although the increase in the content of sulphate ions in the NaCl solution reduces the corrosion current and increases the polarization resistance, their presence does not affect the CuAlMn dissolution mechanism. The anodic reaction of Cu dissolution is controlled by the diffusion of soluble CuCl2− species from the electrode surface into the bulk solution. Surface analysis showed a uniform dissolution of the investigated alloy.
The corrosion resistance of CuAlMn at EOC is a consequence of forming a natural surface film. The experimental conditions (immersion time and presence of sulphate ions) increase the stability of the surface layer (the resistance, compactness, and thickness of the surface layer increase). Moreover, in the presence of sulphate ions, a subsequent ordering of the structure of the surface layer takes place during stabilization at the open circuit potential which is a consequence attributed to the formation of adsorbed species such as Cu(SO4)ads and/or Cu(OH)ads on the electrode surface.
When extruding the casted rods from EN AW 2011 aluminium alloys, not only their homogenized structure, but also their extrudable properties were significantly influenced by the hardness of the alloy. ...In this study, the object of investigations was the EN AW 2011 aluminium alloy, and the effect of homogenisation time on hardness was investigated. First, homogenisation was carried out at 520 °C for different times, imitating industrial conditions. After homogenisation, the samples were analysed by hardness measurements and further characterised by microscopy and image analysis to verify the influence of homogenisation on the resulting microstructural constituents. In addition, non-equilibrium solidification was simulated using the program Thermo-Calc and phase formation during solidification was investigated. The homogenisation process enabled more rounded shape of the Al2Cu eutectic phase, equilibrium formation of the phases, and the precipitation in the matrix, leading to a significant increase in the hardness of the EN AW 2011 aluminium alloy. The experimental data revealed a suitable homogenisation time of 4–6 h at a temperature of 520 °C, enabling optimal extrusion properties.
Cerkvena glasba 19. in 20. stoletja je bila do sedaj v glasbenem zgodovinopisju opazovana le s pomočjo umeščanja v »velike pripovedi«. Ta metoda nujno zabrisuje ali celo potvarja velik del ...podrobnosti o tem zgodovinskem pojavu. Zdi se, da je edina pot za odkritje primernejše interpretacije uporaba metod mikro-zgodovinskega raziskovanja.
Sol–gel boehmite coatings were produced on the polished surfaces of hypo-eutectoid C45carbon steel by dip coating. After the deposition the coatings were heat treated by drying at RT, 150 and 200 °C. ...It was found that for crack-free coatings, the drying temperature needs to be ≥150 °C. Properly heat-treated boehmite coatings then improve the corrosion resistance of steel, while proposed alumina coatings derived from the boehmite coatings during annealing of the steel affect the decarburization. The coated steel samples were annealed at temperatures that are typical for the heat-treatment and thermomechanical process of C45 steel, i.e., <A
C1
(tempering, sphereoidization) and >A
C3
(austenitization, thermomechanical process). The sol–gel alumina coating decreased the decarburization rate of the quenched steel during the tempering (≤600 °C), which meant that the hardness reduction on the steel surface was smaller. Alumina coatings have a smaller effect on the decarburization at higher temperatures; however, the metallographic analyses indicate that the coatings can retard the oxidation rate in comparison to the decarburization rate and thus, somewhat increase the visual level of the decarburization. Under annealing conditions (
T
= 950 °C,
t
= 0.5–2 h) at which the oxidation rate is higher than the decarburization rate the decarburization process is not important since the decarburized layer is peeled off the steel surface together with the scale. No visual decarburization is then observed.
Differential scanning calorimetry, thermodynamic calculations, and metallographic analyses were used for a determination of the solidification sequence in a Fe–2.42 %Si–0.5 %Al–0.94 %Mn alloy. For ...the prediction of the solidification process of the Fe–Si–Al–Mn alloy also a modified Scheil–Gulliver solidification model was used. According to the thermodynamic calculations the two-phase region in the selected Fe–Si–Al–Mn alloy is stable between 1,303 and 913 °C. The highest mass-fraction of the γ-phase is reached at 1,150 °C. With decreasing temperature the austenite retransforms into ferrite. In the temperature range where the thermodynamic calculations predict the existence of the two-phase region in the DSC curves, weak thermal events were observed. A post-exposure metallographic analysis revealed that the substructures in the ferrite microstructure indicate the γ → α phase transformation. This suggests consistency between the differential scanning calorimetry, the thermodynamic calculations, and the metallographic analyses.
The article outlines the reception of Gregorian chant in Slovenia in the nineteenth century. Using the scarce sources, it describes the situation in the first half of the century and the impact of ...the first sporadic attempts at a historicist reform. It traces in detail the growth of the Cecilian movement after 1877 and uses sources to analyse the means, content and success of its reform efforts.
•Cleavage fracture in thick steel plate occurred due to tensile stresses in the “Z” axis.•Rolled banded ferrite–pearlite microstructure and phosphorus segregations are characteristic.•Steel plate has ...a very good contraction in the “Z” axis.•Steel plate has a very low toughness in the central part.•After normalizing the toughness of the central part of the plate was highly improved.
Due to residual tensile stresses acting through the material’s thickness a cleavage fracture occurred in the central part of a thick steel plate during the cooling of a welded T-joint. Steel in the normalized rolled state, without non-metallic inclusions and with a very good contraction in the “Z” axis, is brittle because of its banded, ferrite–pearlite microstructure, which is dependent on phosphorus segregation. A normalizing heat treatment greatly improved the toughness of the central part of the thick plate and prevented its cracking during the cooling of the welded T-joint.
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