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Friction stir processing (FSP) offers a unique opportunity to tailor the microstructure and improve the mechanical properties due to the combination of extensive strains, high temperatures, and high-strain rates inherent to the process. Reactive friction stir processing was carried out in order to produce in situ Al/(Al13Fe4 + Al2O3) hybrid nanocomposites on wrought/as-annealed (673 K) AA1050 substrate. The active mixture of pre-ball milled Fe2O3 + Al powder was introduced into the stir zone by pre-placing it on the substrate. Microstructural characterisation showed that the Al13Fe4 and Al2O3 formed as the reaction products in a matrix of the dynamically restored aluminium matrix. The aluminium matrix means grain size was found to decrease markedly to 3.4 and 2 μm from ~55 μm and 40–50 μm after FSP using wrought and as-annealed substrates employing electron backscattered diffraction detectors, respectively. In addition, tensile testing results were indicative that the fabricated surface nanocomposite on the as-annealed substrate offered a greater ultimate tensile strength (~160 MPa) and hardness (73 HV) than those (146 MPa, and 60 HV) of the nanocomposite formed on the wrought substrate.

An advanced and newly developed severe plastic deformation (SPD) method called accumulative fold-forging (AFF) was applied to produce layered nanostructured MgNi alloys exhibiting superior hydrogen storage capacity. Microstructural developments and storage properties were characterized in depth to correlate the structure and performance of this advanced material. The enhanced hydrogen storage performance of the magnesium-based layered composite material was investigated in comparison to the pristine state by conducting hydrogenation and dehydrogenation testing. It was also shown that the hydrogen uptake and release characteristics can be controlled by adjusting the layered structure or the Mg: Ni stoichiometry ratio. Refining the grain structure of the magnesium alloy down to the nano-scale range (∼400–900 nm) by applying high cycles AFF consolidation to promote creation of multi-million nanometric interfaces led to superior storage performance with a remarkable hydrogen absorption capacity of up to ∼1.425 wt%. X-ray diffraction (XRD) analysis of the hydrogenated products revealed the formation of MgH2 that indicates the dominance of the magnesium matrix for controlling the hydrogen storage behavior of the layered Mg/Ni composite material. Finally, the relationship between the directional hydrogen storage behavior and the induced structural features upon AFF treatment were also established using quantitative characterization and analytical tools.

An Nb-Ti low carbon HSLA steel with the application of Coiled Tubing steel in petroleum industry, was subjected to hot rolling followed by the subsequent cooling procedures including cooling and coiling. The effect of cooling rate and coiling temperature on final microstructure and texture was investigated via optical microscopy, SEM, and EBSD analyses. It was found that rolling at 800 °C results in the appearance of elongated ferrites due to the activation of the deformation-induced ferrite transformation mechanism. Cooling from the finish rolling with different rates of 2.4 to 15 °C/s leads to the formation of polygonal ferrite and retained austenite. Higher cooling rate increases the retained austenite, decreases the ferrite grain size and improves the grain size homogeneity. Coiling at 600 °C results in coarser ferrite with the texture of γ fiber which is due to the recrystallization of ferrite. On the other hand, coiling at 500 °C intensifies the {332} $$\left\langle {113} \right\rangle$$ and {113} $$\left\langle {110} \right\rangle$$ components indicating deformed austenite transformed to ferrite.

Powder metallurgy (PM) fabricated HITEMAL is a near- and sub-micrometer aluminum (Al) material that is stabilized by a small fraction of a nano alumina (Al2O3) secondary phase. This phase forms in situ from surface Al2O3 films present on as-atomized Al powders during compaction. HITEMAL showed unique mechanical properties and creep performance at high homologous temperatures owing to its ultra-fine Al grain structure effectively stabilized by Al2O3. However, conventional fusion welding is generally not applicable to PM Al. This study reports on friction stir welding (FSW) that was applied to join bars extruded from Al powders of different particle size. As PM Al performance crucially depends on the Al2O3 phase, we focused on changes to this phase that were, induced by FSW. Thermal stability, mechanical properties, and deformation behavior of the weld materials were studied versus changes in the morphology and distribution of the Al2O3 phase during FSW. The study confirmed that FSW can be successfully used to join PM Al, although some detrimental transformation of the Al2O3 phase occurred upon FSW. This transformed Al2O3 phase did not provide sufficient stabilization under severe plastic deformation induced by a rotating tool action. The transformation involved dynamic recrystallization and minor Al grain growth in weld zones. This led to a decrease in the mechanical strength of the weld compared with that of the respective base materials. While this negative effect was pronounced for HITEMAL with the finest Al grain size, it was negligible in the coarse-grained material produced from the coarsest Al powder.

A mixture of pre-milled Fe3O4 and Al powder was added to the surface of an aluminum alloy 1050 substrate to obtain hybrid surface nanocomposites using friction stir processing. In situ nano-sized products were formed by the exothermic reaction of Al and Fe3O4. The reaction is triggered by hot working characteristics of the process. The microstructure and crystallographic microtexture transition and grain boundaries evolution of the fabricated nanocomposite were investigated using optical microscopy, X-ray diffraction, field emission scanning electron microscopy, and electron backscattered diffraction analyses. It is illustrated that matrix means grain size decreased in the specimens, which is processed without and with the introduction of the powder mixture to ∼8 and 2 μm, respectively. In addition, high angle grain boundaries showed marked increasing that demonstrates the happening of dynamic restoration phenomenon in the aluminum matrix. Moreover, the fraction of low ΣCSL boundaries showed increasing (remarkably in the presence of hard particles); these boundaries play the main role in dynamic recrystallization. The incorporation of nano-sized products such as Al13Fe4 and Al2O3 in the dynamically recrystallized aluminum matrix produced a pre-dominantly CubeTwin texture component induced by the stirring function of the rotating tool. As a result, the effect of nano-sized products is constrained. Keywords: Friction stir processing, Grain refinement, Microtexture, Grain boundary, Nanocomposites, Aluminum matrix composite

The forensic scenario, on which the round robin study was based, simulated a suspected intentional manipulation of a real estate rental agreement consisting of a total of three pages. The aims of this study were to (i) establish the amount and reliability of information extractable from a single type of evidence and to (ii) provide suggestions on the most suitable combination of compatible techniques for a multi-modal imaging approach to forgery detection. To address these aims, seventeen laboratories from sixteen countries were invited to answer the following tasks questions: (i) which printing technique was used? (ii) were the three pages printed with the same printer? (iii) were the three pages made from the same paper? (iv) were the three pages originally stapled? (v) were the headings and signatures written with the same ink? and (vi) were headings and signatures of the same age on all pages? The methods used were classified into the following categories: Optical spectroscopy, including multispectral imaging, smartphone mapping, UV-luminescence and LIBS ; Infrared spectroscopy, including Raman and FTIR (micro-)spectroscopy ; X-ray spectroscopy, including SEM-EDX, PIXE and XPS ; Mass spectrometry, including ICPMS, SIMS, MALDI and LDIMS ; Electrostatic imaging, as well as non- imaging methods, such as non-multimodal visual inspection, (micro-)spectroscopy, physical testing and thin layer chromatography. The performance of the techniques was evaluated as the proportion of discriminated sample pairs to all possible sample pairs. For the undiscriminated sample pairs, a distinction was made between undecidability and false positive claims. It was found that none of the methods used were able to solve all tasks completely and/or correctly and that certain methods were a priori judged unsuitable by the laboratories for some tasks. Correct results were generally achieved for the discrimination of printer toners, whereas incorrect results in the discrimination of inks. For the discrimination of paper, solid state analytical methods proved to be superior to mass spectrometric methods. None of the participating laboratories deemed addressing ink age feasible. It was concluded that correct forensic statements can only be achieved by the complementary application of different methods and that the classical approach of round robin studies to send standardised subsamples to the participants is not feasible for a true multimodal approach if the techniques are not available at one location.

In this study, hydroxyapatite (HA) nanoparticles (~120 nm, 3 vol%) are incorporated within a subsurface layer based on commercial pure titanium using multi-step friction-stir processing (FSP) to fabricate an CP-Ti/HA surface nanocomposite. A combination of electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM) analyses are used to developed a correlation between microstructural features and crystallographic texture formed by material flow and dynamic restoration phenomena in the processed titanium versus CP-Ti/HA surface nanocomposite. An equiaxed ultra-fine grained structure with a mean size

Reactive friction stir processing was used to fabricate in situ hybrid nano-composite. Nano-sized Al2O3 and Al13Fe4 products were formed in the stir zone of rolled AA1050 through the addition of pre-milled Al + Fe3O4 powder mixture. The thermomechanical phenomena associated with the process and addition of active powder mixture provided the occurrence of the aluminothermy reaction. Microstructural investigations showed significant matrix grain refinement; the mean grain size of ~ 3 μm was achieved. The nano-sized reinforcement products prevented grain growth after dynamic recrystallization process by pinning the grain boundaries. The excellent matrix grain refining and formation of in situ hard reinforcements led to the increase of hardness and tensile strength to ~ 56% and 49% over those of the untreated substrate, respectively.

The tensile flow properties of austenitic (S316-L) and martensitic (S410-L) stainless steel wall structures deposited by powder-fed laser additive manufacturing (LAM) process are evaluated. The properties obtained by the LAM process are compared to commercial rolled sheets of these metals. Strain-rate sensitivity, work hardening, and fracture behavior are assessed by conducting uniaxial tensile testing at different strain rates (0.001, 0.01, 0.1, and 1.0 sec−1). Moreover, a correlation between the final microstructure and mechanical properties is established for the LAM products through detailed analyses of grain structures and hardness indentation measurements. The results indicate a strong dependency for the strain rate in martensitic alloys compared to austenitic alloys produced by the LAM process. Interestingly, the tensile strength of commercial rolled martensitic stainless steel sheet doubles (∼100% increase) by increasing the strain rate, while preserving its elongation to failure. Comparing the two manufacturing methods, a lower strain-rate sensitivity factor is recorded for the additive manufacturing material (m of ∼0.0336) compared to the commercial sheet (m of ∼0.0775). This lower sensitivity is attributed to coarser grain structure and greater microstructural heterogeneity of the LAM product, which stems from directional solidification and cooling phenomenon during the layer-upon-layer deposition process. In contrast, the work hardening exponent (n value) varies little (0.1834–0.2854) for the different materials and manufacturing methods. Fractographic studies reveal that the fracture mode varies from ductile rupture towards ductile-brittle with the formation of greater martensitic phases, which is in combination with the failure component changing from shear to tensile at high strain rates.

Solid-state butt-joining of powder metallurgy (PM) fabricated Al-Al2O3 nanocomposites was assessed using friction-stir welding (FSW), in which the PM materials were prepared from aluminum powder with different particle size distributions of

The high-temperature deformation of an Mn-Al alloy with a chemical composition of Mn51Al47C2 was assessed using hot compression testing at the temperature range of 600–800 °C and the strain rates ranging 0.001 s−1 to 1 s−1. Optical microscopy (OM), scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and X-ray diffraction (XRD) analyses were implemented to characterize the samples. It was found that during deformation, the τ phase dynamically transformed into γ2+ β + e phases and the transformation temperature reduced from the equilibrium value of about 790 °C down to

The deformation behaviour of bimodal sized Al

High-temperature corrosion tests of alloys, Nimonic 80A, Inconel 718 and Inconel C-276, were investigated at 680°C in molten alkali fluoride salt (LiF–NaF–KF: 46.5–11.5–42%) environment. In this wo...

The degradation of Al4C3 was investigated by exposing powder samples to atmospheric humidity at laboratory temperature for 150 days. Samples were monitored using powder x-ray diffraction analysis, scanning and transmission electron microscopy, thermal analysis, and energy-dispersive x-ray spectroscopy. Initially, the degradation resulted in an amorphous Al–O–OH network, which gradually recrystallized as low-crystalline boehmite (γ-AlOOH), and, later, partially, as Al(OH)3. Low-crystalline γ-AlOOH consisted of plate-like particles with diameter of 5 µm to 40 µm. The 020 diffraction position of γ-AlOOH was close to that of well-crystalline γ-AlOOH, which may be explained by accumulation of compressive stress along the b-axis of the γ-AlOOH structure.

In this study, SiC nanoparticles (∼50 nm, 3 vol%) are homogenously incorporated within an Al–Mg alloy metal matrix during multi-step friction-stir processing (FSP) to fabricate an Al-matrix surface...

Multipass friction-stir processing was employed to uniformly disperse multiwalled carbon nanotubes (MW-CNTs) within an Al-Mg alloy metal matrix. Decomposition of MW-CNTs occurs in situ as a result of solid-state chemical reactions, forming fullerene (C60) and aluminium carbide (Al4 C3 ) phases during reactive high temperature severe plastic processing. The effects of this decomposition on the microstructural features, dynamic restoration mechanisms and crystallographic microtextural developments are studied for the first time by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis. The formation of an equiaxed grain structure with an average size of ∼1.5 μm occurs within the stirred zone (SZ) under the influence of inclusions which hinder grain boundary migration via Zener-Smith pinning mechanisms during the discontinuous dynamic recrystallisation (DDRX). Formation of two strong Cubic and Brass microtextural components in the heat affected zone (HAZ) and thermomechanical affected zone (TMAZ) was noted as compared to the completely random and Cube components found in the base and SZ regions, respectively. The microstructural modification led to hardening and tensile strength improvement for the processed nanocomposite by ∼55% and 110%, respectively with respect to the annealed Al-Mg base alloy.

Dynamic recrystallization (DRX) grain size of a Nb-Ti microalloyed steel is investigated at various strain rates and temperatures. Electron microscopy reveals that Nb preferably precipitates on TiN particles at temperature range of T

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} 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} 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.

Combination of mechanical alloying and friction stir processing was used for the fabrication of Al/(Al13Fe4 + Al2O3) nano-composites. Pre-milled hematite + Al powder mixture was introduced into the stir zone generated on 1050 aluminum alloy sheet by friction stir processing. Uniform and active milled powder mixture reacted with plasticized aluminum to produced Al13Fe4 + Al2O3 particles. Al13Fe4 intermetallic showed elliptical shape with a typical size of ~ 100 nm, while nano-sized Al2O3 exhibited irregular floc-shaped particles that formed clusters with the remnant of iron oxide particles in the fine recrystallized aluminum matrix. As the milling time (1-3 h) of the introduced powder mixture increased, the volume fraction of Al13Fe4 + Al2O3 particles increased in the fabricated composite. The hardness and ultimate tensile strength of the fabricated nano-composites varied from 54.5 to 75 HV and 139 to 159 MPa, respectively; these are much higher than those of the friction stir processed base alloy (33 HV and 97 UTS). The highest hardness and strength were achieved for the nano-composite fabricated using the 3-h milled powder mixture; hard nano-sized reaction products and fine recrystallized grains of Al matrix had major and minor roles on enhancing these properties, respectively.

Closed-cell aluminium foams (nominal composition: AlSi12Mg0.6Fe0.3) were prepared by the powder metallurgical route (using 0.4 wt.% TiH2 untreated powder as the foaming agent). Pure foams and foams with the addition of 3 vol.% graphite or SiC powder were prepared. The microstructure and mechanical properties of the prepared aluminium foams containing reinforcing particles were investigated at constant density and compared to those of the pure foam. Vibration measurements were performed to determine the damping properties and modulus of elasticity of the foams. Uniaxial compression tests were performed to determine the following mechanical properties: collapse stress, efficiency of energy absorption, plateau length and densification strain of the foams. All the foams behaved in a brittle manner during compression. Finally, the effect of admixed graphite and SiC powders on the properties of the investigated foam was evaluated, discussed and modelled. The addition of powders changed all investigated properties of the foams. Only the efficiency of energy absorption at constant density was almost identical.

Summary The application of ball-milling for reactant powders (Fe2O3+Al) to form in situ nanosized reaction products in the stir zone of 1050 aluminium alloy was examined and the evolution of microstructure, grain boundaries and microtexture of the fabricated Al/(Al13Fe4+Al2O3) nanocomposite was investigated. The mean matrix grain size of the fabricated nanocomposites by the combination of ball milling and friction stir processing were found to be ∼3.2, 3.1 and 2.1 μm for 1, 2 and 3 h milled powder mixtures, respectively. The fraction of high-angle grain boundaries increased markedly in the stir zone indicating the occurrence of dynamic restoration of the aluminium matrix. This was also associated with increasing of the fraction of low ∑CSL boundaries. In addition, the fraction of high-angle grain boundaries increased as the reaction product increased. The developed textures were compared with the most important deformation and recrystallisation texture components of cubic close packed structure. Some of the main texture components formed due to the restoration of aluminium in the stir zone of the material with no powder addition were CubeND {001} , BR {236} and R (or retained S{123} ); these are usually found in the rolled materials. However, the presence of nanosized reaction products in the fabricated nanocomposite changed the texture components to the dominant Goss {011} , P {011} and R{124} textures.

The sound absorption ability of metallic foams is discussed with respect to the preparation method of foam, material composition, foam porosity, thickness, structure, and various treatments to make the foam structure permeable for sound. Both powder metallurgical route prepared foams and melt route prepared foams were studied. It was observed that the sound absorption properties of metallic foams depend predominantly on the foam porosity and opening of its structure and only after that on the properties of foam cell wall material itself.

In-situ Al/(Al13Fe4 + Al2O3) hybrid nano-composite was fabricated using reactive friction stir processing (FSP) by introduction of Fe2O3 powder into the stir zone of rolled AA1050 aluminum alloy. Composite reinforcements were produced in-situ by exothermic reaction of Al and Fe2O3 that initiated by hot working characteristics of FSP. However, the existence of intermediate phase (Fe3O4) suggests that the reaction was not completed due to short time of FSP. EBSD results showed that the matrix mean grain size decreased to 8 and 3 μm after FSP without and with introduction of powder, respectively; this was also associated with the marked increase in HAGB. The fabricated nano-composite exhibited superior hardness (45 HV) and ultimate tensile strength (~ 171 MPa) as compared to those of the base and FSPed alloy with no powder addition. Formation of in-situ reinforcements and grain refinement acted as major and minor contributors to enhancement of mechanical properties (hardness and ultimate tensile strength), respectively.

The development of efficient materials for heat storage has become recently a popular research topic as amount of energy gained from solar power depends significantly on day and night cycle. That's why the right choice of material for heat storage directly affects the utilization efficiency of solar thermal energy. Research on heat storage materials nowadays focuses on phase change materials (PCMs) enabling repeatedly utilize the latent heat of the phase transition between the solid and liquid phase. Most currently used PCMs have low thermal conductivity, which prevents them from overcoming problem of rapid load changes in the charging and discharging processes. To overcome this obstacle and to obtain excellent heat storage possibility, various techniques have been proposed for enhancing the thermal conductivity of PCMs, such as adding metallic or nonmetallic particles, in-corporating of porous or expanded materials, fibrous materials, macro-, micro-, or nanocapsules, etc.The authors of this study report particularly the huge potential of oxide nanoadditives, such as titania (TiO2), alumina (Al2O3), silica (SiO2) and zinc oxide (ZnO), that are even in small quantities (up to 3 wt.%) able significantly to enhance the heat storage characteristics of conventional PCMs. Moreover, the microstructure of the granules produced by recycling of aluminum scrap refers to the possibility of their utilizing for the purpose of low cost solutions enabling to increase the thermal conductivity of PCMs. The above mentioned technical solutions are therefore the important keys to successful commercialization of materials for latent heat storage in future building industry.

Rapid synthesis of delafossite CuAlO 2 using a mechanically activated mixture of microcrystalline Cu 2 O and nanocrystalline Al 2 O 3 powder was achieved after subsequent annealing under argon atmosphere. The results were analyzed by using X-ray diffractometry, thermal analysis, transmission and scanning electron microscopy, Raman and X-ray photoelectron spectroscopy and SQUID magnetometry. The presence of core–shell configuration of Cu 2 O nanoparticles with the thickness of the non-crystalline surface shell of about 1.0 nm associated with partial oxidation of Cu 2 O was evident. By calcining the precursor in the temperature range of 300–800 °C for 4 h under Ar flow, CuO and CuAl 2 O 4 were observed as main phases. At 900 °C, CuAlO 2 became a main phase. At 1100 °C, CuAlO 2 delafossite with a small admixture of α-Al 2 O 3 was observed. Paramagnetism was observed on our CuAlO 2 at room temperature with a weak ferromagnetism. In the 10 min activated mixture, a contamination with Fe was detected. A unique weak ferromagnetic feature of CuAlO 2 may be associated with the structural paramagnetic Cu 2+ and Fe 3+ ions. Antiferromagnetic short-range-order was developed below 60 K. This was ascribed to the mixed state of Cu + and Cu 2+ in the Cu O sub-lattice with a high amount of oxygen vacancies, similar to the states in the Cu 2- x O.

Accumulative fold-forging (AFF) as a newly developed severe plastic deformation (SPD) process based on the repetitive fold-forging steps is implemented for the production of the layered UFG (~200 nm) AA8006 alloy and AA8006-B4C nanocomposite (~35 nm, 10 vol%) materials from the initial AA8006 alloy foil. The remarkably refined grains and nanoparticles can control metallic materials' mechanical properties, including the strength, strain rate dependency, and thermal stability behavior. In this context, nano-grains' local mechanical response during nanoindentation can vary considerably depending on the testing temperature, and this has yet to be discussed. In this research, after materials characterization of produced nanostructured materials according to the AFF route, the relating depth-sensing thermal stability of them assessed by conducting the nanoindentation testing at different temperatures in the range of 300–523 K. Depth sensing softening behavior is elaborated to identify the low-temperature thermal stability of processed materials. The results enunciated the occurrence of thermal softening by refining the grain structure. However, introducing the reinforcing nanoparticles lead to a pinning action that stabilized the grain boundaries.

This article presents the experimental and modeling results of nanoindentation testing at ambient and elevated temperatures (i.e. 300 to 523 K), examining the small-scale plasticity of ultra-fine grained (UFG) alloy and nanostructured nanocomposite (NS) materials. The complex small-scale deformation mechanisms are highlighted to assess the material flow behavior under the indenter, which involves the interaction of dislocations and nanoparticles restricting the slip/glide of dislocations. Combined with UFG band propagation and transition stages, these lead to a stabilized mechanical strength at elevated temperatures. Accordingly, the activation energy for softening during localized deformation behavior of the nanocomposite is increased compared to the UFG alloy. It is attributed to a shift in the dislocations activation volume and energy aided by altered grain boundary diffusion and sliding mechanisms. It is shown that the straining role of nanoparticles leads to substantial grain size refinement to the nano-scale with enhanced generation of geometrically necessary dislocations. However, these nanoparticles' presence on the boundaries of nano-sized sub-grains can reduce the migration energy and restrict the sliding-based deformation mechanism.

Owing to the advantages of nanocomposites for structural applications, we present microstructural evolutions and texture development during dissimilar friction stir welding (DFSW) of an Al-matrix hybrid nanocomposite (Al-2 vol.-% Al2O3-2 vol.-% SiC) with AA1050. It is shown that DFSW can successfully be performed at a rotating speed of 1200 rev min−1 and a transverse speed of 50 mm min−1 while locating the nanocomposite at retreating side. Formation of macro-, micro-, and nano-mechanical interlocks between dissimilar base materials (BMs) as a result of FSW tool stirring action possessed an impact influence on the mechanical performance of dissimilar welds. Electron microscopy revealed formation of a three-modal grain structure from microscale (>1 µm) to nanoscale (

The aim of the work is to study interface formation between Al2O3 particles and Al(Ca) matrix in dependence of Ca content. Aluminium matrix composites (AMC) subjected to investigation were prepared by gas pressure assisted infiltration of alumina beds with aluminium-calcium alloys. It is shown that alumina particles in the AMC are covered with a monocalcium aluminates layer whose coherence increases with increasing amounts of Ca in the aluminium-calcium alloys. Moreover, Al4Ca intermetallic phases are formed with increasing Ca content and interconnect alumina particles. XRD confirms the presence of both CaAl2O4 and CaAl4O7 ternary phases. However, HRTEM analysis confirmed CaAl2O4 with a rather complex structure containing a high density of stacking faults. It appeared that annealing at 735 °C does improve consistency of interface for Al 2 wt.%Ca/Al2O3 AMC, but do not affect the thickness of the interface in dependence on annealing time. Keywords: Al2O3 particles, AlCa alloy, Gas pressure infiltration, Interface, Aluminium matrix composites

Ultrafine-grained (UFG) Al matrix composites reinforced with 15 and 30vol% in-situ Al3Ti filaments were fabricated by extrusion of Al-Ti powder mixtures followed by solid-state reactive diffusion. Fine Al powder particles (1.3μm) heavily deformed the coarser Ti particles (24.5μm) into filaments during extrusion. Upon a subsequent operation of hot isostatic pressing (HIP), the micrometric Al3Ti filaments elongated along the extrusion direction and formed in situ in the UFG Al matrix. Fabricated composites are free of pores and voids with perfect bonding created at the Al-Al3Ti interfaces. In parallel, a small portion (2.4vol%) of nanoscale γ-Al2O3 particles, which originate from native amorphous films on fine Al powders, formed in situ and were homogenously dispersed in the Al matrix. The microstructures of as-extruded and after HIP composites were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD). Owing to the presence of nanometric γ-Al2O3 particles with Al high angle grain boundaries (HAGBs), the UFG Al matrix remained stable even after HIP at 600°C for 9h. The mechanical properties and creep performance of composites at testing temperatures of up to 600°C were systematically studied. The Al-Al3Ti composites exhibited a combination of increased strength and Young's modulus in addition to excellent creep performance and structural stability, which indicates that the studied composites are potential structural materials capable of service at elevated temperatures. Fil: Krizik, Peter. Slovak Academy of Sciences; Eslovaquia Fil: Balog, Martin. Slovak Academy of Sciences; Eslovaquia Fil: Nosko, Martin. Slovak Academy of Sciences; Eslovaquia Fil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Dvorak, Jiri. Institute of Physics of Materials; República Checa Fil: Bajana, Oto. Slovak Academy of Sciences; Eslovaquia

The current study reflects the demand to mitigate the environmental issues caused by the waste from the agriculture and food industry. The crops that do not meet the supply chain requirements and waste from their processing are overfilling landfills. The mentioned wastes contain cellulose, which is the most abundant carbon precursor. Therefore, one of the possibilities of returning such waste into the life cycle could be preparing the activated carbon through an eco-friendly and simple route. Herein, the carrot pulp from the waste was used. Techniques such as thermogravimetric analysis (TGA), elemental analysis (EA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray diffraction (XRD) were used to investigate the thermal treatment effect during the carbon material preparation. The development of microstructure, phase formation, and chemical composition of prepared material was evaluated. The obtained carbon material was finally tested for water cleaning from a synthetic pollutant such as rhodamine B and phloxine B. An adsorption mechanism was proposed on the base of positron annihilation lifetime spectroscopy (PALS) results and attributed to the responsible interactions. It was shown that a significant carbon sorbent from the organic waste for water purification was obtained.

Poly(ethylene terephthalate) (PET) from domestic plastic waste was processed by electrospinning from solution hexafluoro-2-propanol/dichloromethane. The nanofibrous membrane with an average diameter of 95 ± 37 nm was prepared and filtration efficiency was tested. It was shown that the recycled PET (r-PET) nanofibrous membrane retained the particles with a size of around 120 nm with more than 98% efficiency. Moreover, users comfort characteristics such as vapour permeability and breathability were tested. Herein, it is shown that 94% of water vapour permeation is achieved. Breathability 39 mm.s−1 is in the lower limit of the comfortable range; despite this unfavorable result, the r-PET membrane could be used as a filtration media for personal protection because this disadvantage can be mitigated by the area and shape of the filter.

TiB2 samples were exposed to molten KF−AlF3−Al2O3: 54.8-42.1-3.1 mol% salt, at 680 °C for 50, 100 and 200 h. The corroded samples of TiB2 were investigated by SEM-EDX, EBSD, XRD, FT-IR and MAS NMR analysis. Corrosion was noted to occur predominantly as pitting attacks on the surface of the investigated materials. An inter-crystal and trans-crystal corrosion were identified on the cross-sections of the samples. A perturbation of Ti B bonds was detected (SEM-EDX and NMR analysis), at which a formation of orthorhombic TiO2 was also identified (EBSD analysis). The subsequent NMR, XRD and FT-IR analysis of the behaviour of TiB2 powder in molten KF−AlF3−Al2O3 supports the statement about the formation of orthorhombic TiO2 and mullite type of aluminium borates.

Plates of AA5052 (Al–Mg) alloy in both annealed (solution-treated) and wrought (rolled) temper conditions were subjected to friction stir processing (FSP) at various w/v pitch ratios from 4 to 28 rev.min/mm. The role of stored strain energy on the evolution of restoration mechanisms and crystallographic texture components were assessed in terms of microstructural features evaluated using electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) analysis. The results revealed that FSP significantly refined the grain structure and changed the crystallographic micro-texture components. The grain size of the annealed and wrought alloy was reduced from 49.4 and 9.7 μm initial values to 3.3 and 3.6 μm, respectively when w/v=4. Also, the formation of a { 112 } ⟨ 110 ⟩ crystallographic shear texture with a strong B / B ¯ component intensity were observed. The microstructural changes in the annealed alloy were related to the occurrence of discontinuous dynamic recrystallization (DDRX) mechanism, while operation of a static recrystallization (SRX) prior to a continuous (CDRX) mode in the wrought one, revealing the effect of stored strain energy. Evaluations of the mechanical properties also determined enhanced ultimate tensile strength, elongation, and indentation Vickers hardness while preserving the yield stress.

Expansion kinetics of aluminium foams is generally driven by foaming agent. Therefore, a proper type and pre-treatment of the foaming is important for improvement of its inner structure, mechanical properties and energy absorption ability. This paper is focused to reveal an effect of long-term oxidation of TiH 2 on foaming kinetics (expansion profile) and structure of heat-treatable 6061 alloy foam. Subsequently, a uniaxial compression test was performed to study the effect of structural changes due to pre-treatment of TiH 2 on the mechanical properties and absorption ability. Structural transformation of TiH 2 was also studied with respect to annealing conditions.

The work is focused to prepare Al based master-alloy pellet with 50 vol.% of Al2O3 for subsequent manufacturing of aluminum matrix composites with desired amount of reinforcement (5–20%). Since master-alloy is manufactured via pressure infiltration and proper interface between particles and melt is required for uniform particle distribution within the melt, fundamental correlation between parameters of pressure infiltration and quality of the Al/Al2O3 interface is revealed in this study. Standard observation techniques as 3-D computed tomography (CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) are used for structural characterization. Drop test was used to estimate effect of time, temperature, annealing of Al2O3 and its type on the wettability of Al2O3 with Al. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to study changes within the Al2O3 prior infiltration. Stir casting was used to prepare the final composite and dynamical mechanical analysis (DMA) was used to estimate the Young’s modulus of as-cast composite. The proper infiltration parameters was defined in this work and it were shown that the infiltration temperature and pressure have direct correlation on the interface between particle and aluminum.

Aluminum matrix nanocomposites were fabricated via friction stir processing of an Al–Mg alloy with pre-inserted TiO 2 nanoparticles at different volume fractions of 3%, 5% and 6%. The nanocomposites were annealed at 300–500 °C for 1–5 h in air to study the effect of annealing on the microstructural changes and mechanical properties. Microstructural studies by scanning and transmission electron microscopy showed that new phases were formed during friction stir processing due to chemical reactions at the interface of TiO 2 with the aluminum matrix alloy. Reactive annealing completed the solid-state reactions, which led to a significant improvement in the ductility of the nanocomposites (more than three times) without deteriorating their tensile strength and hardness. Evaluation of the grain structure revealed that the presence of TiO 2 nanoparticles refined the grains during friction stir processing while the in situ formed nanoparticles hindered the grain growth upon the post-annealing treatment. Abnormal grain growth was observed after a prolonged annealing at 500 °C. The highest strength and ductility were obtained for the nanocomposites annealed at 400 °C for 3 h.

The oxidation behavior of gas-atomized Al and Al alloy powder green compacts during heating prior to hot extrusion compaction was studied at laboratory and industrial scales by TGA, DSC, DTA, EDX, TEM and XRD methods. The effect of the heating of green compacts on the mechanical properties of the powder-extruded samples was assessed. Significant oxidation of Al and Al alloy powder green compacts takes place in the solid state during heating in air. The onset and intensity of oxidation were affected by the Mg content, the surface area of the powder and the volume of the powder green compacts. An exothermic heat associated with the oxidation of Al and Al alloy powders resulted in intense overheating of bulky powder green compacts during heating in air. The samples extruded from the powder green compacts heated in air exhibited reduced strength. The loss in strength was especially pronounced in the case of Mg-containing Al alloy powders. Mg diffuses from a powder metallic core toward the native Al 2 O 3 surface layer present on as-atomized Al alloy powders; it reacts with oxygen present in air and in the Al 2 O 3 surface layer where the MgO phase forms, eventually resulting in the depletion of Mg from the powder core. Materials extruded from Al powders depleted of Mg do not exhibit effective Al-Mg solid solution strengthening or strengthening by Mg-containing precipitates. Economically viable approaches to avoiding the detrimental effects of powder oxidation during the heating of green compacts prior to hot working consolidation are discussed.

Annealed and wrought AA5052 aluminum alloy was subjected to friction stir processing (FSP) without and with 3 vol pct TiO2 nanoparticles. Microstructural studies by electron backscattered diffraction and transmission electron microscopy showed the formation of an ultra-fine-grained structure with fine distribution of TiO2 nanoparticles in the metal matrix. Nanometric Al3Ti and MgO particles were also observed, revealing in-situ solid-state reactions between Al and Mg with TiO2. Tensile testing at different strain rates determined that FSP decreased the strain rate sensitivity and work hardening of annealed Al-Mg alloy without and with TiO2 nanoparticles, while opposite results were obtained for the wrought alloy. Fractographic studies exhibited that the presence of hard reinforcement particles changed the fracture mode from ductile rupture to ductile-brittle fracture. Notably, the failure mechanism was also altered from shear to tensile rupture as the strain rate increased. Consequently, the fracture surface contained hemispherical equiaxed dimples instead of parabolic ones.

Aluminum matrix nanocomposites were fabricated by friction stir processing of Al–Mg alloy sheets with pre-placed TiO 2 nanoparticles at a concentration of 2 to 6 vol%. Microstructural studies showed that solid state reactions between the metal matrix and TiO 2 particles caused in situ formation of MgO and Al 3 Ti nanophases with an average size ~50 nm. These nanophases were homogenously distributed in an ultra-fine grain structure (0.2–2 µm) of the base metal. The results of pole figures evaluation obtained by electron back scattered diffraction studies revealed that the random orientation of initial annealed sheet was changed to components near to shear and silver texture in the friction stir processed alloy without and with pre-placed powder, respectively. The concentration of TiO 2 particles affected the preferred texture orientation as the ceramic inclusion restricted the severe plastic deformation and dynamic recrystalization of the metal matrix. Hardness and tensile yield strength of the Al–Mg alloy sheet were also significantly improved by employing friction stir processing in the presence of TiO 2 nanoparticles (up to ~3.1 vol%). Fractographic studies showed a mixture of ductile–brittle fracture modes with an increase in the content of catastrophic manner at higher TiO 2 fractions.