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The article investigates the potential for producing hydrogen by combining the methods of water splitting under cavitation and the chemical activation of aluminum in a high-speed cavitation–jet flow generated by a specialized hydrodynamic reactor. The process of cavitation and water spraying causes the liquid heating itself until it reaches saturated vapor pressure, resulting in the creation of vapor–gaseous products from the splitting of water molecules. The producing of vapor–gaseous products can be explained through the theory of non-equilibrium low-temperature plasma formation within a high-speed cavitation–jet flow of fluid. Special focus is also given to the interactions occurring at the interface boundary phase of aluminum and liquid under cavitation condition. The primary solid products formed on aluminum surfaces are bayerite, copper oxides (I and II), iron carbide, and a compound of magnesium oxides and aluminum hydroxide. A high hydrogen yield of 60% was achieved when using a 0.1% sodium hydroxide solution as a working liquid compared to demineralized water. Moreover, hydrogen methane was also detected in the volume of the vapor–gas mixture, which could be utilized to address the challenges of decarbonization and the recycling of aluminum-containing solid industrial and domestic waste. This work provides a contribution to the study of the mechanism of hydrogen generation by cavitation–jet processing of water and aqueous alkali solutions, in which conditions are created for double cavitation in the cavitation–jet chamber of the hydrodynamic reactor. [ABSTRACT FROM AUTHOR]

Majority of anthropogenic air pollutants enter the atmosphere as a result of material combustion, industrial production and transport. Fires not only cause air pollution, but also disrupt ecosystems. Knowledge of the flammability parameters and proper flame-retardant modification of materials hinders the origin and spread of a fire, while also protecting against air pollution. The aim of this study was to obtain fire-retardant modifications of the epoxy resin, and then to analyse the effect of the introduced additives on the rate of heat release, the thermokinetic properties and the toxicity of volatile combustible products. The modifiers of the epoxy resin were organophosphorus compounds and aluminium and magnesium hydroxides, with a grain size of 10 nm. The introduced additives were found to be effective flame retardants as they reduced the rate of heat release and the amounts of toxic products of thermal decomposition and combustion. The HRRmax and HRRav values of all fire-retardant modifications were lower compared to the corresponding HRR values of the unmodified epoxy material. [ABSTRACT FROM AUTHOR]

This paper presents the influence of selected flame retardant additives on heat release rate and thermokinetics properties of epoxy materials made of epoxy resin—Epidian 5. The epoxy resin underwent flame retardant modification with the use of organophosphorus compounds (Roflam F5, Roflam B7) and Al(OH)3, Mg(OH)2. The fire characteristics of the analysed epoxy resin were determined using the cone calorimeter method, and thermal analysis of epoxy resin and the surface morphology of the analysed epoxy materials was with the use of an SEM microscope with an EDS attachment. The lowest value of the heat release rate was recorded for hardened epoxy resin containing one component additive 5% by weight of Mg(OH)2, as well as two component additive 10% by weight of Roflam F5 and 5% by weight of Al(OH)3. Moreover, the initial temperature of thermal decomposition of phase I of the modified epoxy resin samples with Mg(OH)2 (sample 5M) or organophosphorus compounds and Mg(OH)2 (samples 5B + 10M and 5F + 10M) were higher compared to the unmodified epoxy resin for these samples. Considering the surface morphology of the samples with Mg(OH)2, it can be concluded that the additives cause a homogeneous charred layer. [ABSTRACT FROM AUTHOR]

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Detoxification of aflatoxin M1 from solution and milk using layered double hydroxides was investigated. The Aluminum‐Magnesium layered double hydroxide (Al‐Mg LDH) and Iron‐Magnesium layered double hydroxide (Fe‐Mg LDH) were selected in their calcined and non‐calcined forms to evaluate the effect of the calcination on detoxification. These materials were produced using the co‐precipitation method. Preliminary adsorption tests confirmed use of Al‐Mg LDH as the selected adsorbent. Characteristics of the adopted adsorbent were studied and confirmed by XRD, FTIR, SEM, and BET methods. Effects of the initial content of aflatoxin, amount of the adsorbents and detoxification time were investigated. Influence of the adsorbents on the nutritional aspects of milk were also studied. The study showed that while the non‐calcined forms of LDH were not able to adsorb aflatoxin M1 more than 23%, the calcined form of Al‐Mg LDH exhibited 100% adsorption in the solutions and about 70–100% in the contaminated milk samples. The reason is pointed to the fact that calcination of Al‐Mg LDH considerably increased the surface area, the total pore volume, and the pore size of the material. Multivariate regression analysis and calculation of the Pearson correlation factor showed that the remained aflatoxin at each time was more strongly correlated with the initial amount of aflatoxin and the elapsed time and less strongly with the amount of the adsorbent. It was found that the adsorption isotherms fitted to the Freundlich equation with a high adsorption capacity of 555.5 mg g−1. Practical Application: This study is focused on examining ability of layered double hydroxides (LDH) for adsorbing AFM1. LDHs are promising layered materials due to some of their interesting characteristics, such as ease of synthesis and uniqueness of structure. In practice, results of this study can be used for detoxification of aflatoxin, especially in milk, at high efficiency in shorter time durations. [ABSTRACT FROM AUTHOR]

To characterize the thermal activation process of dislocation motion in the creep region, thermal activation parameters must be determined. However, the activation volume has never been used to directly understand dislocation motion in this region. In this study, the effective stress and activation volume during creep in AlMg solid-solution alloys were determined using indentation techniques. The obtained effective stress and activation volume corresponded to the results obtained from the uniaxial test. At the tested creep rate of ε = 1 × 10-54 × 10-3 s-1, the obtained activation volume decreased with increasing solute concentration, a trend opposite to that of the effective stress. Using this activation volume and previously reported computer simulation results of the interactions between dislocations and solute atoms, the thermal activation process of dislocation motion during creep in several AlMg solid-solution alloys was investigated. The thermally activated dislocation length decreased with increasing stress and was smaller than that between the forest dislocations. The results indicated that dislocations during creep could overcome thermal obstacles when the corresponding effective stress was interpolated against the increase/decrease in thermally activated dislocation length, and each dislocation fragment on the length between forest dislocations moved individually through each thermal activation process. [ABSTRACT FROM AUTHOR]

High atomic diffusivity in metals enables substantial tuneability of their structure and properties by tailoring the diffusional processes, but this causes their customized properties to be unstable at elevated temperatures. Eliminating diffusive interfaces by fabricating single crystals or heavily alloying helps to address this issue but does not inhibit atomic diffusion at high homologous temperatures. We discovered that the Schwarz crystal structure was effective at suppressing atomic diffusion in a supersaturated aluminumÐmagnesium alloy with extremely fine grains. By forming these stable structures, diffusion-controlled intermetallic precipitation from the nanosized grains and their coarsening were inhibited up to the equilibrium melting temperature, around which the apparent across-boundary diffusivity was reduced by about seven orders of magnitude. Developing advanced engineering alloys using the Schwarz crystal structure may lead to useful properties for high-temperature applications. [ABSTRACT FROM AUTHOR]

Al10SiMg alloy have been used for die casting and additive manufacturing. In this study, solution-treated Al10SiMg and Al10Si alloys (mass%) were heat-treated at several temperatures and the linear dimensional changes arising from the heat-treatments were investigated. A theoretical model for calculating the linear dimensional change in AlSiMg ternary alloys was proposed, and the theoretically and the experimentally determined linear dimensional changes were compared. It was found that the linear dimensional changes of Al10SiMg and Al10Si alloys were almost the same. In both alloys, the linear dimensional changes increased with the decrease of the heat-treatment temperature. The linear dimensional changes of Al10SiMg and Al10Si alloys agreed well with the values estimated by the proposed theoretical model. [ABSTRACT FROM AUTHOR]

Ultrafine-grained AlMgSc alloys were fabricated by multi-directional forging (MDF) with different number of forging passes of 3, 9 and 15, i.e., to cumulative strains of ΣΔε = 1.2, 3.6 and 6.0, at room temperature. The achieved average grain sizes were 950, 680 and 360nm at 3, 9 and 15 passes, respectively. Peak-aging treatments at 473K for 172.8 ks were adopted for a portion of specimens after MDF in order to obtain finely dispersed Al3Sc precipitates. Grain coarsening did not take place in all the specimens during the aging. The activation volume for plastic deformation was estimated from the strain-rate jump tensile tests before and after the aging. Aging-free 3- and 9-pass specimens showed positive temperature dependence of the activation volume, while that of the aging-free 15-pass one bearing the smallest grain size exhibited a negative temperature dependence. Contrary to these results, values of the activation volume in the peak-aged specimens were approximately identical regardless of grain size or deformation temperature. These results strongly suggested that, due to the precipitation of Al3Sc, the rate-controlling process of deformation was changed from interaction between forest dislocations and mobile dislocations for the aging-free 3- and 9-pass specimens to interaction between mobile dislocations and Al3Sc precipitates, or from bowing-out of dislocations from grain boundaries for the aging-free 15-pass specimen to the interaction between the mobile dislocations and precipitates. [ABSTRACT FROM AUTHOR]

Physicochemical changes occurring in an oxide shell of boron particles during heating are extremely important for the oxidation and combustion of boron, including those in solid propellant compositions. The Al2O3, MgO, MgF2, Al, and Mg impurities were experimentally discovered in an oxide layer on boron particles obtained by various methods. The goal of this work is to determine the effect of these impurities on the thermal behavior of boron oxide, with particular attention paid to evaporation of B2O3. The temperature and thermal effects of reactions between the components are thermoanalytically determined, and the processes of dehydration, melting, and evaporation of boron oxide are analyzed in detail. The enthalpy of evaporation of boron oxide, starting at a temperature above 1300°C is experimentally determined, and is equal to 347 ± 3 kJ/mol. An interaction is observed between magnesium fluoride and boron oxide at a temperature of about 1000°C with a mass loss corresponding to the content of magnesium fluoride and the formation of gas-phase boron fluoride. It is established that boron dissolved in oxide has virtually no effect on the evaporation of the boron oxide melt, while the addition of Al2O3or MgO significantly increases its thermal stability. Based on the analysis of the results obtained, an assumption is made about the effect of impurities on boron activity in the processes of boron ignition and combustion. [ABSTRACT FROM AUTHOR]

After chewing the tablets, the active components of the tablets can be released quickly, and the layered network lattice structure can be generated on the surface of gastric mucosa, which can protect the wounds. At the same time, the active ingredient aluminum can promote ulcer healing. The purpose of this paper is to study the micro mechanism and nursing observation of the treatment of gastric ulcer combined with gastric hemorrhage. This paper introduces the pathogenesis of gastric ulcer and the treatment of gastric ulcer with aluminum and magnesium carbonate, and then summarizes the application of large nursing observation and image processing technology of optical microscope. The experimental results showed that the ulcer area of the control group was large, covered with white moss, the ulcer bottom was dirty, the surrounding mucosa was swollen and swollen; the ulcer surface of the low dose and high dose groups was shallow, the swelling and swelling of the surrounding mucosa was small, the ulcer index was also lower than that of the control group, and the inhibition rate of the low dose group was 15% The inhibition rate of high dose ulcer was 75%. It may be related to the expression of EGF and PGE2. [ABSTRACT FROM AUTHOR]

Based on the preparation of magnesium (AZ31B) – aluminium (1060) composite materials by friction stir processing, a study of the formation and transformation of Al–Fe phases in the aluminium solid solution near the Al–Mg interface was performed by transmission electron microscopy. The results show that there are many Al6Fe particles with the size span range of 100–300 nm in the aluminium solid solution, and the morphology of Al6Fe centre phase encapsulated by Al3Fe thin-layer phase was observed. Meanwhile, the interface types of Al–Al3Fe and Al3Fe–Al6Fe are both coherent interfaces, and there are crystallographic orientation relationships between them, namely: The crystallographic orientation relationships have not been reported yet. [ABSTRACT FROM AUTHOR]

Hydrotalcite or Mg-Al LDHs were synthesized by co-precipitation method. The Mg-Al mixed oxide was then derived by calcination of hydrotalcite at 450°C. The metal modified catalysts (Mo/Mg-Al and V/Mg-Al) were prepared by incipient wetness impregnation method. The obtained catalysts were characterized by several useful techniques and tested the reactivity for dehydrogenation and oxidative dehydrogenation of ethanol (gas-phase) to produce acetaldehyde. The catalytic reactions were performed at temperature range from 200 to 400°C for both non-oxidative and oxidative atmospheres. The results showed that the vanadium-modified hydrotalcite (V/Mg-Al) exhibited the highest ethanol conversion (34.3%) and acetaldehyde yield (15.5%) at 400°C in the non-oxidative atmosphere. For the oxidative dehydrogenation of ethanol, the V/Mg-Al catalyst showed the highest activity at 400°C giving the ethanol conversion and acetaldehyde yield of 73.7% and 29.5%, respectively. This result probably related to the highest base density of V/Mg-Al catalyst (6.13 µmol CO2/m2) measured by CO2-TPD. The catalytic activity of Mg-Al catalyst and metal modified catalyst slightly decreased upon time-on-stream test for 10 h on oxidative dehydrogenation of ethanol due to carbon deposition. [ABSTRACT FROM AUTHOR]

Abstract Diffusion bonding, due to improving the dispersion of brittle intermetallic compounds, reducing the process energy and increasing the bonding strength of aluminum-magnesium joints, is widely used. In the present study, the commercially pure aluminum and magnesium bulks were successfully diffusion bonded at different strain values (0, 30 and 60%) at 480 °C and different holding times in two cases of without interlayer and with cold rolled copper interlayers. The results of the microstructural study using scanning electron microscopy (SEM) showed that, in interlayer-used bonding, the increase in the strain value of copper interlayer led to a wider joint diffusion layer. The results of the micro hardness test indicated that the hardness of the bonding interface in interlayer-used bonding, decreased in comparison with the non-interlayer bonding state. Moreover, the shear strength test showed that, as the holding time in the non-interlayer state increased, the strength decreased and in the case of interlayer-used bonding, increased time and strain resulted in increased strength of the Al-Mg bond. By rolling the interlayer to different values, the structural and mechanical properties of the Al-Mg diffusion bonding can be adjusted. Graphical abstract Image 1 Highlights • The shear strength of diffusion bonded Al-Mg increased by using Cu interlayer. • Cold working on Cu interlayer, improved the diffusion depth at Al-Cu and Cu-Mg interfaces. • The shear strength of diffusion bonded Al-Mg increased by increasing the strain value of Cu interlayer. [ABSTRACT FROM AUTHOR]

Abstract Microstructure of deformed DMLS-AlSi10Mg under quasi-static loading was studied using TEM to elaborate the strengthening mechanisms. In addition to Orowan (due to presence of Si precipitates), Hall-Petch (due to eutectic Si walls), and dislocation hardening (due to pre-existing entangled dislocations) mechanisms, Mg 2 Si precipitates (colonies) contributed to the strength of alloy by impeding dislocation motion. The level of this contribution was evaluated as ~13 MPa by comparing the modeled and measured yield strength. [ABSTRACT FROM AUTHOR]

In this work, the tribological behaviors of the bulk AlMgB 14 (BAM) were investigated under different counterface materials in deionized water. As the results show, the tribological behaviors of BAM are closely related to the counterface materials. When 316 L ball is used as the slider, the contact pair exhibits no self-lubricity proved by the higher friction coefficient (COF), about 0.33, and the adhesive wear prevails. While when Si 3 N 4 and Al 2 O 3 balls are used as the sliders, the contact pairs shows better self-lubricity with a COF as low as 0.03, due to the tribo-chemistry products—hydrated SiO 2 and Al(OH) 3 gel, respectively. In addition, BAM/Al 2 O 3 tribo-pair presents the polishing wear, indicating a more significant self-lubricity compared with that of BAM/Si 3 N 4 tribo-pair. [ABSTRACT FROM AUTHOR]

Abstract The deformation behavior of MgAl/Mg nanoscale amorphous/crystalline multilayers (NACMs) with equal layer thicknesses of amorphous and crystalline phases under tension loading is investigated by molecular dynamics simulation method. The results show that the plastic deformation mode of NACMs changes from cross generalized shear bands dominated deformation to finally single shear band plastic deformation with the increase of layer thickness, and the plastic deformation of NACMs with medium layer thickness is realized through cooperative interactions among crystalline layer, amorphous layer and amorphous/crystalline interfaces (ACIs), which could be treated as a transition progress. The results indicate that the peak stresses of the NACMs are greater than that of monolithic amorphous regardless of layer thickness, which is likely to result from the increase of the strong crystalline phase and the strengthening effect of the ACIs. The results also reveal that the ductility and strength of NACMs could be improved effectively by choosing the appropriate layer thickness. In addition, the deformation behavior of NACMs is also quantificationally disclosed and analyzed in current study. Graphical abstract Unlabelled Image Highlights • The deformation mechanisms of NACMs change with the increase of layer thickness. • The peak stresses of NACMs are greater than that of monolithic amorphous. • The ductility and strength of NACMs could be improved by adjusting thickness. [ABSTRACT FROM AUTHOR]

The composite β ′/ β ″ precipitates rather than well-defined β ′ phase form in trace-Sn containing Al-Mg-Si alloy peak-aged at 250 °C, leading to considerable morphological refinement. The preferential occupation of 2~6 adjacent Si sites of the tiny β ′ phase by Sn and typical β ″ substructure units covering the precipitates are frequently observed. The substructures grow upon further ageing into differently oriented β ″ with 2~3 complete structural unit cells. It is inferred that the β ′ (Mg 9 Si 5-x Sn x ) forms initially on the Sn/vacancy complexes and then acts as heterogeneous nucleus for β ″. These findings demonstrate Sn could fundamentally alter the pre−/precipitation behaviors in Al-Mg-Si alloys. [ABSTRACT FROM AUTHOR]

The main objective of this work is to produce a composite consisting of (a) a cast heat-treatable Al-Mg-Si alloy with high contents of Mg for corrosion resistance and Si to offset the Mg-due poor castability (in situ hypoeutectic Mg2Si/Al composite) and (b) TiC particles at high enough volume fractions (≤ 15%), in order to achieve a satisfactory combination of wear and corrosion performance. TiCp/Al-7Mg-5Si (wt.%) composites were produced by flux-assisted casting followed by solution and aging heat treatment. Solution treatment led to a relatively uniform dispersion and shape rounding of Mg2Si precipitates and Si particles. TiC particle addition resulted in refinement of primary Al, modification of the Mg2Si Chinese script morphology and refinement/spheroidization of primary Mg2Si. Heat treatment combined with TiC addition notably improved the sliding wear resistance of Al-7Mg-5Si. A wear mechanism has been proposed. The TiC/Al interfaces remained intact of corrosion during potentiodynamic polarization of the heat-treated materials in 3.5 wt.% NaCl. Different main forms of localized corrosion in 3.5 wt.% NaCl were identified for each TiC content (0, 5, 15 vol.%), depending on specific degradation favoring microstructural features (topology/size/interface wetting) at each composition. [ABSTRACT FROM AUTHOR]

Metallized propellants typically produce large agglomerates that result in two-phase flow losses. Tailoring composite metal fuel particles can improve ignition and combustion characteristics while reducing product droplet sizes. In this work, mechanically activated (MA) aluminum (Al) and magnesium (Mg) powders are synthesized, characterized and compared to magnalium (Mag) alloy, neat Al, neat Mg and their physical mixtures (PM) at the same 1:1 mass ratio as MA and Mag powders. CO 2 laser ignition tests showed that the MA powders are more reactive than those of Mag and exhibit particle fragmentation upon ignition. Mag powders only show fragmentation and microexplosions at high heating rates. The burning rates of the ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants containing MA powders were the highest, compared to Mag, neat Al, PM and neat Mg in decreasing order. High-speed imaging of the propellants and product collection showed that MA, Mg and Mag powders produce much smaller agglomerates than neat Al or PM at lower pressures due to fragmentation and Mg vaporization. However, the microexplosion tendency of the MA and Mag particles in the propellants was reduced at higher pressures due to reduced vapor bubble growth. Out of all the materials investigated, MA particles provide the best combination of burning rate and product sizes. [ABSTRACT FROM AUTHOR]

Ablation rates of Al-Mg alloy were studied as a function of laser fluences in air and vacuum. The central wavelength was 800 nm and the pulse duration was 35 fs. Three distinct ablation regimes were identified from the ablation rate curves. Ablation thresholds of 0.16 J/cm 2 , and 0.73 J/cm 2 were obtained in the low and moderate laser fluence regimes, respectively. In the case of the third ablation regime, the ablation rate in vacuum is much higher than that in air, which may be due to the oxidation effects and strong defocusing effects associated with the non-equilibrium ionization of air. The damage threshold decreased with the increase of the pulse number, showing an accumulation effect. The fs laser ablated craters showed smooth edges, and laser-induced periodic surface structures (LIPSS) were observed around craters. [ABSTRACT FROM AUTHOR]

Hypoeutectic Al–xSi–0.45Mg (x = 6.5, 7.5, 8.5, 9.5) alloys were refined by Al5Ti1B containing TiB2 and Al3Ti3B containing TiB2 and AlB2, respectively. With increasing Si, Si poisoning on TiB2 results in the obvious coarsening of primary α-Al in Al5Ti1B-refined alloys from 350 ± 40 to 400 ± 50, 475 ± 50 and 560 ± 80 μm, and the competition between Si promotion on AlB2 and Si poisoning on TiB2 leads to the slight coarsening of primary α-Al in Al3Ti3B-refined alloys from 215 ± 30 to 265 ± 35, 265 ± 30 and 315 ± 25 μm. After T6 heat treatment, with increasing Si, the yield strength (YS) of Al5Ti1B-refined alloys increases from 294 ± 2 to 299 ± 2, 304 ± 1 and 309 ± 2 MPa, and the elongation first increases from 3.5 ± 0.8 to 4.5 ± 1.0 and 7.8 ± 1.4%, after decreases to 5.5 ± 1.2%, while the YS of the Al3Ti3B-refined alloys increases from 300 ± 1 to 305 ± 2, 312 ± 1 and 317 ± 2 MPa, and the elongation increases from 6.1 ± 1.1 to 8.5 ± 1.2, 11.8 ± 1.5 and 12.1 ± 1.6%. The increase in the secondary phase and precipitation strengthening results in the increase in strength with increasing Si. With increasing Si, the decrease in porosity formation by decreasing solidification interval and increasing fluidity is superior to the increase in porosity formation by slightly coarsening grain size, which leads to the increase in ductility in the Al3Ti3B-refined alloys, while the competition between porosity decreasing and increasing factors leads to the inverted ‘V’-shaped evolution of ductility in the Al5Ti1B-refined alloys. [ABSTRACT FROM AUTHOR]

In order to better understand how future candidate solid propellants may affect combustion characteristics in ramjet motor, the aluminum–magnesium fuel-rich propellant was tested on a sealed high-pressure laser ignition platform. The laser ignition experimental device was designed and built, then the ignition and combustion characteristics of aluminum–magnesium fuel-rich propellant under different pressures and oxygen concentrations in environment gas were studied. The comprehensive impacts of pressure and oxygen concentration on ignition delay time and burning rate were appraised. The results displayed that the ignition delay time was decreased with the increase of pressure and oxygen concentration. The effect of pressure on ignition delay time was weaker than oxygen concentration. The impact of oxygen concentration on ignition was very complex. When the oxygen concentration of environment gas was less than that of the oxidizing gas from the propellant pyrolysis products, the ignition gas phase reaction occurred in the dispersion region of the solid propellant pyrolysis product, the initial flame was close to the propellant surface. In contrast, when the oxygen concentration was larger than the pyrolysis oxidizing gas, the ignition gas phase reaction occurred in the diffusion zone of the propellant pyrolysis products and the environment gas, the initial flame appeared far from the propellant surface. The burning rate of aluminum–magnesium fuel-rich propellant increased with the increase of pressure and oxygen concentration, where their effect on burning rate is accord with B-number theory. Comparing the experimental measurements with an analytical model, the results showed good consistency. The function of oxygen concentration and pressure could explain the effect on burning rate and ignition delay time, because pressure and oxygen concentration were favorable for the heat transfer, radiation and convection from the flame. The function of the combined influences of pressure and oxygen concentration on burning rate was established by a power law fitting. The good fitting is consistent with the experimental measurements, and shows that the scaling is valid for a full range of pressure and oxygen concentration tests to predict burning rate. [ABSTRACT FROM AUTHOR]

A 3D multi-scale and multi-physics numerical model has been developed and validated to predict the occurrence of hot cracking during fusion welding of Al-Mg-Si alloys. The new model consists of four modules: (I) a welding solidification module that creates the desired weld microstructure consisting of both columnar and equiaxed grains and varies as a function of welding conditions; (II) a thermo-mechanical analysis module that predicts the deformation of the weld mushy zone due to solidification contraction and the response of the base metal; (III) a fluid flow module that calculates the variation in fluid velocity and pressure within the micro liquid channels of the semisolid; and (IV) a crack initiation module that applies Kou's hot cracking criterion [ 1 ] to identify cracked liquid channels based on inputs from the solidification, thermo-mechanical and fluid-flow modules. The results identify the underlying mechanisms by which welding process parameters (current and travel speed) and external restraining conditions influence hot cracking susceptibility during Gas Tungsten Arc welding. Interestingly, micro hot cracks seem to initiate near the fusion zone but then localize and form a macroscopic hot crack at the core of the weld. [ABSTRACT FROM AUTHOR]

The in-situ electrical resistivity monitors the isothermal annealing history of Al-Mg-Mn aluminum alloy sheet. The resistivity-time and the yield stress-time curves well fitted with each other helps mill engineers in optimizing both the annealing time and temperature for the mill product. The resistivity-time curves are revealed as an exponential decay and interpreted by Avrami equation with R-squared values higher than 0.98. From the extended Avrami equations, the activation energy of the recrystallization is found to be 261 kJ/mol which is a reference for the future annealing experiment. This pioneering in-situ electrical resistivity system well quantitatively correlates the resistivity with the yield stress, and therefore is a potential candidate of the commercial instrument to clarify the annealing process. [ABSTRACT FROM AUTHOR]

In this study, magnesium and aluminum ion was firstly inhaled into the silica sphere by low-vacuum impregnation technique, and subsequently hydrotalcite (Mg-Al-LDH) was synthesized inside the silica-based mesoporous material using in-hole precipitation method. Metal composite oxide (Mg-Al-LDO) was the calcined product by calcining Mg-Al-LDH at 450   °C and the composite material Mg-Al-LDO/SiO 2 was the main absorbent for absorbing iodine ion (I − ) in this study. The characteristics of SEM inner-morphology, FT-IR spectroscopy and X-ray diffraction strongly demonstrated hydrotalcite admirably grew in the channel of silica matrix. The influence of composite material dosage, pH values of aqueous solution, and initial concentration of I − on adsorption capacity was investigated in detail. The batch experiment results showed that Mg-Al-LDO/SiO 2 had an excellent adsorption performance on I − and the removal efficiency reached 99.81% from a 30 mg/L I − solution in 5 min, with a dosage of 0.05 g/100 ml. The adsorption kinetics was fitted well by pseudo -second-order model. The column experiment data demonstrated that the application of Mg-Al-LDO/SiO 2 in a column model for the continuous treatment of iodine ion effluents exhibited optimum breakthrough curves by adjusting the bed heights. The experimental breakthrough curves were correlated with Thomas, Adams–Bohart and Yoon–Nelson models. [ABSTRACT FROM AUTHOR]

We successfully prepared aluminum(Al)-magnesium(Mg) composite materials using a spark plasma sintering (SPS) process with pure Al and Mg powders as the raw materials. Composite materials containing 20, 50, or 80 vol% Mg (Al-20 vol% Mg, Al-50 vol% Mg, and Al-80 vol% Mg, respectively) were sintered at 410 °C and 50 MPa for 5 min. Using X-ray diffraction, intermetallic compounds such as Al 3 Mg 2 and Al 12 Mg 17 were detected, which were formed in the Al-Mg composite materials owing to the reaction between Al and Mg during SPS. The results of scanning electron microscopy with energy-dispersive spectroscopy and elemental mapping also confirmed the existence of the intermetallic compounds. The mechanical properties of the composite materials, analyzed using a Vickers hardness tester, showed that the Al-50 vol% Mg composite material exhibited the highest hardness value of approximately 189 HV. In conclusion, the composite materials manufactured with SPS may act as lightweight and high-efficiency materials, applicable in various fields, such as the aerospace and automobile industries. [ABSTRACT FROM AUTHOR]

The precipitation hardening behavior of Al-5.1Mg-0.15Cu alloy with 3.0Zn (wt%) addition at various temperatures has been systematically investigated in this study. The Al-5.1Mg-0.15Cu-3.0Zn alloy possesses the higher strength compared with traditional Zn-free alloy, when the alloy is treated at 363 K for 24 h and subsequently aged at 413 K for 25 h. The precipitation sequence of the hardening phase T-Mg(AlZn) is investigated by differential scanning calorimetry tests, transmission electron microscopy and high-resolution electron microscopy. The different effects of natural aging and pre-aging on the precipitation hardening behavior are detailed. The formation of relatively stable Guinier-Preston zones of T-Mg(AlZn) phase during pre-aging rather than natural aging results in higher mechanical strength during subsequent artificial aging at relatively high temperatures. When the Al-5.1Mg-0.15Cu-3.0Zn alloy is aged at 453 K, the peak hardness is from synergetic effect of hardening of S-AlCuMg phase and coarsening of T phase. However, during two-step artificial aging treatment, the peak hardness results from fine, spherical and homogeneously distributed T phase in the absence of the S phase. [ABSTRACT FROM AUTHOR]

AlSi10Mg inclined struts with angle of 45° were fabricated by selective laser melting (SLM) using different scanning speed and hatch spacing to gain insight into the evolution of the molten pool morphology, surface roughness, and dimensional accuracy. The results show that the average width and depth of the molten pool, the lower surface roughness and dimensional deviation decrease with the increase of scanning speed and hatch spacing. The upper surface roughness is found to be almost constant under different processing parameters. The width and depth of the molten pool on powder-supported zone are larger than that of the molten pool on the solid-supported zone, while the width changes more significantly than that of depth. However, if the scanning speed is high enough, the width and depth of the molten pool and the lower surface roughness almost keep constant as the density is still high. Therefore, high dimensional accuracy and density as well as good surface quality can be achieved simultaneously by using high scanning speed during SLMed cellular lattice strut. [ABSTRACT FROM AUTHOR]

Due to the higher demand for energy efficient products, light-weight constructions have become more important in recent years. An innovative, hydrostatic extruded Al-Mg-compound used here combines the corrosion resistance of aluminium with the outstanding lightweight properties of magnesium. During the production process, a thin boundary layer is built between the two basic materials. Investigations on further hot forming processing revealed a good formability of these compounds despite the fact that the boundary layer splits into fragments during forging and a new secondary boundary layer is built when the basic materials between the fragments come into contact again during the continuous deformation. The aim of the research is now to investigate fragmentation depending on the deformation rate and boundary layer thickness, which increases during the heat-up process in preparation of forging. For this purpose, a channel compression test is used in conjunction with a special newly developed specimen shape. The metallographic evaluation of the boundary layer reveals a strong dependency of fragmentation on the deformation rate and the boundary layer thickness. With the aid of a numerical simulation, an individual critical stretch could be determined at which fragmentation starts, and provide guidance for an optimal forging process design. [ABSTRACT FROM AUTHOR]

The effect of Cu addition on dispersoid precipitation, mechanical properties and creep resistance was investigated in an Al-Mn-Mg 3004 alloy. The addition of Cu promoted dispersoid precipitation by increasing the number density and decreasing the size of dispersoids. Metastable β0-Mg2Si and Q-AlCuMgSi precipitates were observed during the heating process and both could provide favorable nucleation sites for dispersoid precipitation. The addition of Cu improved the thermal stability of dispersoids during a long-term thermal holding at 350 °C for 500 h. Results of mechanical testing show that the addition of Cu remarkably improved the hardness at room temperature, as well as the yield strength and creep resistance at 300 °C, which was mainly attributed to dispersoid strengthening and Cu solid solution strengthening. The yield strength contribution at 300 °C was quantitatively evaluated based on the dispersoid, solid solution and matrix contributions. It was confirmed that dispersoid strengthening is the main strengthening mechanism in the experimental alloys. [ABSTRACT FROM AUTHOR]

The aim of this research is to characterize the unique microstructural features of Al-matrix nanocomposites reinforced by graphene nano-platelets (GNPs), fabricated by multi-pass friction-stir processing (FSP). During this process, secondary phase GNPs were dispersed within the stir zone (SZ) of an AA5052 alloy matrix, with a homogenous distribution achieved after five cumulative passes. The microstructural characteristics and crystallographic textures of different regions in the FSPed nanocomposite, i.e., base metal (BM), heat affected zone (HAZ), thermo-mechanical affected zone (TMAZ), and SZ, were evaluated using electron back scattering diffraction (EBSD) and transmission electron microscopy (TEM) analyses. The annealed BM consisted of a nearly random crystal orientation distribution with an average grain size of 10.7 μm. The SZ exhibited equiaxed recrystallized grains with a mean size of 2 μm and a high fraction of high-angle grain boundaries (HAGBs) caused by a discontinuous dynamic recrystallization (DDRX) enhanced by pinning of grain boundaries by GNPs. The sub-grains and grain structure modification within the HAZ and TMAZ regions are governed by dislocation annihilation and reorganization in the grain interiors/within grains which convert low-angle to high-angle grain boundaries via dynamic recovery (DRV). The FSP process and incorporation of GNPs produced a pre-dominantly {100} < 100 > cube texture component in the SZ induced by the stirring action of the rotating tool and hindering effect of nano-platelets. Although, a very strong {112} < 110 > simple shear texture was found in the HAZ and TMAZ regions governed by additional heating and deformation imposed by the tool shoulder. These grain structure and texture features lead to a hardness and tensile strength increases of about 55% and 220%, respectively. [ABSTRACT FROM AUTHOR]

Isothermal hot compression tests of Al-7.82Zn-1.96Mg-2.35Cu-0.11Zr alloy were carried out on a Gleeble-3500 thermo-simulator in the temperature range of 573–733 K and strain rate range of 0.001–1 s −1 . Stress-strain curves show that work hardening effect progressively exceeds softening effect with increasing strain rate. Microstructural evolution shows that two kinds of dynamic recrystallization exist in the hot compression process, which includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) and the dominant mechanism is continuous dynamic recrystallization, which occurs under the combined action of progressive subgrain rotation and misorientation increase. Five constitutive models were constructed to describe the hot deformation behavior. Weight optimization model has lower average absolute relative errors (AARE) value of 2.78%, root mean square error (RMSE) value of 2.73 and higher correlation coefficient (R) value of 0.997, and gives weight factors at different temperatures. The revised constitutive model with considering the comprehensive effects of lattice diffusion, grain boundary diffusion and the results of weight optimization gives relatively high prediction precision with AARE value of 4.64%, RMSE value of 4.92 and R value of 0.995, which is second to that of weight optimization model. The main diffusion mechanism is dominated by grain boundary diffusion at 573–693 K and lattice diffusion at 733 K. [ABSTRACT FROM AUTHOR]

Magnesium aluminate-based materials were prepared by applying different methods: ( i ) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and ( ii ) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure. [ABSTRACT FROM AUTHOR]

Layered materials, e.g., graphene and transition metal (di)chalcogenides, holding great promises in nanoscale device applications have been extensively studied in fundamental chemistry, solid state physics and materials research areas. In parallel, layered oxides (e.g., Aurivillius and Ruddlesden-Popper phases) present an attractive class of materials both because of their rich physics behind and potential device applications. In this work, we report a novel layered oxide material with self-assembled layered supercell structure consisting of two mismatch-layered sublattices of [Bi3O3+d] and [MO2]1.84 (M = Al/Mn, simply named BAMO), i.e., alternative layered stacking of two mutually incommensurate sublattices made of a three-layer-thick Bi-O slab and a one-layer-thick Al/Mn-O octahedra slab in the out-of-plane direction. Strong room-temperature ferromagnetic and piezoelectric responses as well as anisotropic optical property have been demonstrated with great potentials in various device applications. The realization of the novel BAMO layered supercell structure in this work has paved an avenue toward exploring and designing new materials with multifunctionalities. [ABSTRACT FROM AUTHOR]

In the present study, dissimilar welds of an Al–Mg–Mn alloy and a Zn-coated high-strength low-alloy steel were welded by refill friction stir spot welding. The maximum shear load recorded was approximately 7.8 kN, obtained from the weld produced with a 1600 rev min−1 tool rotational speed. Microstructural analyses showed the formation of a solid–liquid structure of an Al solid solution in Mg–Al-rich Zn liquid, which gives rise to the formation of Zn-rich Al region and microfissuring in some regions during welding. Exposure of steel surface to Mg–Al-rich Zn liquid led to the formation of Fe2Al5 and Fe4Al13 intermetallics. The presence of defective Zn-rich Al regions and Fe–Al intermetallics at the faying surface affects the weld strength. [ABSTRACT FROM AUTHOR]

Hard aluminum-magnesium boride (BAM) films were fabricated onto Corning® Gorilla® Glass by radio-frequency magnetron sputtering of a single stoichiometric AlMgB target. BAM films exhibit a Vickers hardness from 10 to 30 GPa and a Young's modulus from 80 to 160 GPa depending on applied loading forces. Deposited hard coating increases the critical load at which glass substrate cracks. The adhesion energy of BAM films on Gorilla® Glass is 6.4 J/m. [ABSTRACT FROM AUTHOR]

In the present research, multi-pass friction stir processing (FSP) was employed for the first time to disperse graphene in the form of graphene nano-platelets (GNPs) into an AA5052 aluminum‑magnesium alloy to fabricate a new Al-Mg/3 vol% GNPs nanocomposite. After five cumulative FSP passes, the GNPs were distributed within the metal-matrix. Field emission-scanning (FE-SEM) and transmission electron microscopy (TEM) analyses were used to examine the dispersion of GNPs, and suggested negligible deterioration of the graphene planar structure following FSP. Some clusters of graphene originating from the initial powder remained due to the high surface energy of these GNPs, while grain orientations were evaluated in the nanocomposite using electron back scattering diffraction (EBSD). A fine equiaxed recrystallized grain structure with an average size of 2.1 μm was formed in the stir zone (SZ) after FSP while dispersing GNPs. Indentation revealed the hardness of the nanocomposite increased by 53% compared to the processed Al-Mg alloy. Yield strength also was improved by more than three times while preserving ductility which achieved 20% strain before fracture. Fractographic studies of tensile test specimens revealed a mixed ductile-brittle fracture behavior. Based on the micromechanics theory, three models considering the microstructural parameters ( i.e. , aspect ratio, mean size, and volume fraction of GNPs, grain size, and clustering during process) were developed to predict the strengthening effects of GNPs in the terms of elastic modulus, yield strength, and indentation hardness. Correlation between these predicted values and experimental data are discussed in detail. [ABSTRACT FROM AUTHOR]

Various types of plastic instabilities that emerge in intermittent creep have been studied experimentally for AlMg6 aluminum-magnesium alloy. It has been shown that intermittent creep exhibits threshold dynamics. The deformation step on the creep curve of amplitude is ~1-6% and begins when the rate of the preceding continuous creep attains a certain critical value. In the course of evolution of the step, the strain rate varies in the interval that spans more than two orders of magnitude, and transitions occur between different dynamic regimes of type A and B characterized by different stress drop regularity levels in the force response. Nonlinear aspects of the deformation behavior of the alloy in the intermittent creep conditions are considered. [ABSTRACT FROM AUTHOR]

Investigations of an influence of various cavitation intensity on the cavitation erosion of AlMg2 alloy is presented. In order to learn an effect of low- and high-amplitude pulses on material degradation, long- and short-lasting tests were performed. Linear correlation between the cavitation load and mean depth of penetration rate of AlMg2 alloy in the long-lasting test occurs. Presence of particles of intermetallic precipitations in AlMg2 alloy accelerate the erosion. Changes of hardness during the short-lasting test are correlated with cavitation intensity. The exposition of AlMg2 alloy to cavitation of J = 26 kW/m 2 causes an increase of hardness that started with the beginning of the short-lasting test and was continued over the whole test. A decrease of cavitation intensity caused a delay in the beginning of the hardness increase, a decrease of rate of surface work-hardening and a decrease of hardness during the last minute of the short-lasting test. The dislocation investigations showed that the dense dislocation network, low-angle boundaries developed in the top layer of AlMg2 alloy, which was exposed to cavitation intensity J = 11 and 5 kW/m 2 , but in deeper layers the dislocation structure of dynamic recovery was observed. In the case of exposition of AlMg2 alloy to cavitation intensity J = 0.03 kW/m 2 , the structure of dynamic recovery is observed in the top layer. With an increase of cavitation intensity increases density of dislocations in the top layer and the depth, at which the dynamic recovery structure occurs. [ABSTRACT FROM AUTHOR]

Multi-element-doped α-Ni(OH) was prepared by an ultrasonic-assisted co-precipitation method. The crystal structures and morphologies of the prepared samples were characterized by x-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The results showed that the interlayer spacings of all samples were larger than that of pure α-Ni(OH) and that the structural stability became better with increases in the number of doped elements and the doped ratio. The electrochemical performances of the prepared samples, including cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge tests, were also analyzed. The results indicated that Al/Yb/Co/Mn-doped α-Ni(OH) had better electrochemical reversibility, lower charge-transfer resistance, a larger proton diffusion coefficient (8.47 × 10 cm/s) and a higher discharge capacity (288.2 mAh g at 0.5 °C) than Al/Co/Mn-doped α-Ni(OH) due to the synergistic effect of the doped elements. [ABSTRACT FROM AUTHOR]

The main objective of this study is to characterize the mechanical behaviour of an Al-Mg alloy in conditions close to those encountered during sheet forming processes, i.e. with strain path changes and at strain rates and temperatures in the range 1.2×10-1.2×10 s and 25-200°C, respectively. The onset of jerky flow and the interaction of dynamic strain ageing with the work-hardening are investigated during reversed-loading in specific simple shear tests, which consist of loading up to various shear strain values followed by reloading in the opposite direction, combined with direct observations of the sample surface using a digital image correlation technique. Both strain path changes and temperature are clearly shown to influence the occurrence and onset of the Portevin-Le Chatelier (PLC) effect. Moreover, the Bauschinger effect observed in the material response shows that the PLC effect has a major influence on the kinematic contribution to work-hardening as well as its stagnation during the reloading stage, which could open up interesting lines of research to improve theoretical plasticity models for this family of aluminium alloys. [ABSTRACT FROM AUTHOR]

The thermoluminescence of beta irradiated K-Mg-Al-Zn fluorophosphate glass is reported. A glow-curve corresponding to 10 Gy measured at 1 °C/s shows two peaks, a weaker-intensity one at 70 °C and a more prominent one at 235 °C, the subject of this report. The main peak was observed to fade with delay between irradiation and measurement and specifically, by 11% in 15 h. Its dose response is superlinear in the dose range 1–190 Gy although the change was linear for the initial 10 Gy. Regarding kinetic analysis, the activation energy of the higher temperature peak was evaluated as 1.31 eV and that of the lower temperature peak was found as 0.47 eV. It was also noted that the main peak is affected by thermal quenching with an activation energy for thermal quenching equal to 1.37 eV. It is proposed that the mechanism associated with the thermoluminescence in K-Mg-Al-Zn fluorophosphate glass is that electrons trapped by the metal cations are released during heating and then recombine with holes at oxygen sites. [ABSTRACT FROM AUTHOR]

Characterization of Mg-Si precipitates is crucial for optimizing the homogenization heat treatment of Al-Mg-Si alloys. Although sample preparation is key for high quality scanning electron microscopy imaging, most common methods lead to dealloying of Mg-Si precipitates. In this article we systematically evaluate different sample preparation methods: mechanical polishing, etching with various reagents, and electropolishing using different electrolytes. We demonstrate that the use of a nitric acid and methanol electrolyte for electropolishing a homogenized Al-Mg-Si alloy prevents the dissolution of Mg-Si precipitates, resulting in micrographs of higher quality. This preparation method is investigated in depth and the obtained scanning electron microscopy images are compared with transmission electron micrographs: the shape and size of Mg-Si precipitates appear very similar in either method. The scanning electron micrographs allow proper identification and measurement of the Mg-Si phases including needles with lengths of roughly 200 nm. These needles are β″ precipitates as confirmed by high resolution transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Significant grain refinement is attractive for improving mechanical properties at both ambient and elevated temperatures and improvements in the properties of light-weight metals has become indispensable for the practical and societal needs of materials selection. Experiments were conducted to examine the influence of grain refinement on the mechanical properties of an Al-3% Mg alloy processed though high-pressure torsion (HPT) at room temperature under a compressive pressure of 6.0 GPa for up to 10 turns. The hardness values from Vickers microhardness measurements demonstrated a strain hardening behavior with increasing torsional straining and a high level of homogeneous microstructure was achieved along the disk diameter after HPT for 10 turns. An X-ray diffraction analysis at the peripheral regions of the disks outside of the central areas showed an evolution towards a reasonably random texture together with increases in the dislocation density and lattice parameter of Al with increasing numbers of HPT revolutions. A maximum elongation of ∼430% was recorded in the alloy after HPT for 5 turns when testing at 673 K at 1.0 × 10 −4 s −1 but there was evidence for grain growth during testing and the flow behavior was controlled by viscous glide. Analysis shows that the improved hardness through HPT is well expressed by the Hall-Petch relationship with only limited contributions from solid solution strengthening and precipitation hardening. [ABSTRACT FROM AUTHOR]

This study first provides a concise review of natural aging in Al–Mg–Si alloys and its effect on artificial aging. The second part investigates prolonged natural aging at different temperatures for > 500 days of commercial and trace element added alloys. Together, the two parts improve the picture of underlying mechanisms and refine suggestions regarding the five stages of natural aging. Trace Sn- or Sn + In-added alloys show a trend towards higher activation energies of clustering, and a higher temperature dependency of natural aging than commercial alloys. This is attributed to an additional contribution of a thermally activated vacancy release from Sn- and In-vacancy pairs. Sn and In additions are suggested to decrease cluster number density while increasing cluster size. Prolonged natural aging increasingly retards artificial aging kinetics. This is interpreted according to increasingly slower cluster dissolution kinetics and slower preferential growth of β´´ needles. The reachable strength however seems to strongly depend on the ratio and size of coarse β´´ needles, preferentially grown, and the number of fine re-precipitated β´´ needles. Artificial aging after prolonged natural aging at 45 °C increases the artificial aging peak hardness due to a lower density of larger clusters than at lower temperatures. [ABSTRACT FROM AUTHOR]

The article deals with the pretreatment technique for preparing the surface of aluminum alloy EN AW 5754 before thermal spray. The surface after different pretreatments, including degreasing with acetone, chemical etching with acidic and alkali solutions, grit-blasting, cathodic cleaning, and some combinations of these techniques, has been studied. The investigation of pre-treated surfaces covered the topographical study (using scanning electron microscopy, atomic force microscopy, and 3D profilometry), the chemical analysis by x-ray photoelectron spectroscopy, the evaluation of surface wettability (sessile drop method), and the assessment of surface free energy. Compared with all the techniques used in present work, the cathodic cleaning and its combination with grit-blasting provide the most preferable chemistry of the surface. Due to the absence of hydroxides at the surface and, possible, due to the diffusion of magnesium to the surface of substrate, the surface wettability and the surface free energy have been significantly improved. No direct correlation between the surface topography and the surface wettability has been established. [ABSTRACT FROM AUTHOR]