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The August 2024 issue of the Journal of Materials Science features a cover paper titled "Stabilized CsPbBr3 quantum dots in flower-like LYH matrix for high-performance white light-emitting diodes" by Yanrui Yang and colleagues at Fuyang Normal University in China. The paper explores the production and properties of these materials, with a focus on their luminescence data. The paper is part of the "Chemical routes to materials" Topical Collection, but could also be relevant to the "Electronic materials" Topical Collection. The article is freely accessible online through the SharedIt link provided. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. [Extracted from the article]

The June 2024 cover image of the Journal of Materials Science features a paper by Liss et al. titled "Recrystallization of bulk nanostructured magnesium alloy AZ31 after severe plastic deformation: an in situ diffraction study." The image is an artistic representation of nanostructured magnesium alloy AZ31 undergoing heating, showcasing the process of recrystallization in reciprocal space. The paper is part of a Special Issue on "Processing Bulk Nanostructured Materials," which includes a total of 28 articles covering various aspects of severe plastic deformation (SPD) in the processing of bulk nanostructured materials. The Special Issue aims to highlight the enduring significance and resilience of research in this field. Both the paper and the preface of the Special Issue have SharedIt links for easy sharing with readers. [Extracted from the article]

The May 2024 issue of the Journal of Materials Science features a cover paper titled "Role of stacking fault energy in confined layer slip in nanolaminated Cu" by Ji et al. The paper explores the deformation of metallic nanolaminates and acknowledges the contribution of Professor Hussein Zbib. The issue is dedicated to honoring Professor Zbib's memory and was conceived by Guest Editors Tariq Khraishi, Georges Ayoub, Sinisa Mesarovic, and Mutasem Shehadeh. The paper includes references to previous work but does not mention any measurements of the intrinsic stacking fault energy. The corresponding author is Professor Shuozhi Xu from the University of Oklahoma, and the last author is Professor I.J. Beyerlein, who has a background in research and was born in Los Alamos. The paper is freely accessible through the SharedIt link provided. [Extracted from the article]

The February 2024 issue of the Journal of Materials Science features a cover paper titled "Enhancing the impact property of high-entropy alloys with graphene layers: a molecular dynamics study" by Qing-Xiang Pei et al. The paper explores the use of molecular dynamics simulations to study the impact of a projectile on a high-entropy alloy (HEA) containing layers of graphene. The authors highlight the broad interest in their research, as it appeals not only to the modeling community but also to other communities interested in the materials being modeled. The paper provides valuable insights into the behavior of composite materials and includes figures illustrating the preparation of the model material and the interaction between a projectile and the HEA. The article is freely accessible through the SharedIt link provided, and the corresponding authors can be contacted for access to the data. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. [Extracted from the article]

Microalloying has been an important method in aluminum alloy development for decades. Large number of papers have shown that the addition of trace element Erbium (Er) can effectively improve the comprehensive properties of aluminum alloys. Similar with the trace element Scandium (Sc), addition of trace element Er in aluminum alloys could form nano-sized L12-ordered Al3Er precipitates, which was coherent with the Al matrix. However, the dispersion precipitation strengthening effect of Al3Er was more significant than that of Al3Sc, at the same atomic content. In the case of the addition of both Er and Zr, core–shell-structured Al3(Er, Zr) precipitates formed instead of Al3Er precipitates. Those thermally-stable nanosized precipitates could significantly refine the grain size, retard the recrystallization, improve the mechanical properties and corrosion resistance. This paper reviewed several typical Er-containing microalloyed commercial aluminum alloys, like 2xxx (Al–Cu) alloys, 4xxx (Al–Si) alloys, 5xxx (Al–Mg) alloys, 7xxx (Al–Zn–Mg–Cu) alloys, as well as selective laser melting aluminum alloys. [ABSTRACT FROM AUTHOR]

In order to inhibit the corrosion of ADC12 aluminum alloy caused oxalic acid in engine coolant, corrosion inhibitor technology is usually used because of its simple operation, low cost, no impact on metal heat dissipation, and effectively suppressing metal corrosion at a lower concentration. In this paper, the corrosion inhibition, long-term and adsorption mechanisms of humic acid (HA) on ADC12 aluminum alloy were studied using electrochemical testing, surface analysis techniques, and theoretical calculations. The results showed that HA was a mixed corrosion inhibitor that followed the Langmuir adsorption model and belonged to physical chemical mixed adsorption. The corrosion inhibition efficiency of HA was the highest at a concentration of 1500 ppm and enhanced with the extension of soaking time. After soaking for 72 h, the corrosion inhibition efficiency of HA reached its maximum (92.7%), indicating that HA had a good long-term corrosion inhibition effect. HA had a high adsorption energy on the surface of ADC12 aluminum alloy, and HA molecules adsorbed on its surface through the carboxyl groups linked to N atom to form a protective corrosion inhibitor film, effectively inhibiting its corrosion. [ABSTRACT FROM AUTHOR]

Lightweight strategy is essential for the development of transportation vehicles and aerospace industries. As a type of lightweight material, high-strength aluminum alloys are limited to service temperatures below 200 °C due to the rapid coarsening of strengthening nano-precipitates, which cannot satisfy the increasing demands of practical applications. High-temperature applications beyond 250 °C become the bottle-neck problem of Al alloys. In this paper, we review existing literature on the improvement of high-temperature performance of aluminum alloys by stabilizing nano-precipitates. On the basis of atomic-scale microstructure regulation, several design strategies, such as interface segregation, co-precipitation, core/shell structure, and interstitial ordering, have been proposed, resulting in the development of a number of heat-resistant Al alloys for use at 300–400 °C. Moreover, the fundamental theories of solid-state phase transformation, especially precipitation aging and coarsening, are correspondingly advanced on the frontiers of science. [ABSTRACT FROM AUTHOR]

With development of present energy-saving society, lightweight and green development in the automotive and aerospace industries have put forward urgent demands for heat-resistant cast aluminum alloys. Present cast aluminum alloys are of lightweight and have excellent mechanical properties when serving in ambient environment. However, when serving at temperatures of 200–300 ℃ or even higher, the alloys inevitably soften and the high-temperature mechanical properties decline rapidly, hardly meeting the requirements for high-performance equipments. This paper summarizes the development process of classic heat-resistant aluminum alloys, especially the microstructural characteristics of heat-resistant cast aluminum alloys in the past decade, and reviews the current microstructure tuning strategies of heat-resistant aluminum alloys from the aspects of intrinsic heat resistance of the second phases, phase interface modification, diffusion-controlled phase transition, grain boundary stabilization and composite material design. Finally, we propose the prospects for the future development of heat-resistant aluminum alloys. [ABSTRACT FROM AUTHOR]

AA6101 Al alloy is widely used as a high-strength conductive aluminum alloy, and the contents and existence of Mg and Si can influence its electrical conductivity and mechanical properties obviously. In this paper, experiments were conducted to find the optimal Mg, Si additions and Mg/Si ratio and then combined with heat treatment to improve the EC and mechanical properties at the same time. Firstly, considering the proper Mg/Si ratio, two optimal Mg and Si additions were determined: Al–0.7Mg–0.5Si and Al–0.4Mg–0.7Si with EC of 51.5%IACS and 51.4%IACS, and through homogenization treatment, their EC improved to 57.0%IACS and 55.7%IACS, respectively. Then, appropriate Fe was added to further control Si to achieve the balance of EC and mechanical properties. Results showed that for AA6101 Al alloy the ideal Mg/Si mass ratio was 1.4 and high Mg and low Si can obtain good EC and mechanical properties. Besides, it can be found that at low Mg/Si ratio, the alloy conductivity takes longer to reach its peak hardness. So the best performance Al–0.7Mg–0.5Si–0.2Fe alloy was obtained within the range of AA6101 national standard. The EC of Al–0.7Mg–0.5Si–0.2Fe can reach 56.3%IACS, and hardness is 91.3 Hv. Based on the study, a schematic diagram was drawn to analyze the influence mechanisms of Mg, Si and Fe on EC and hardness of AA6101 Al alloy. [ABSTRACT FROM AUTHOR]

In this paper, the effect of deep cryogenic treatment (DCT) on the microstructure and properties of automotive 6063 aluminum alloy at different times was investigated with automotive 6063 aluminum alloy as the research object. The results show that under the conditions of deep cryogenic treatment, the lattice distortion occurs in the alloy matrix microstructure, and the resulting internal stress promotes the large proliferation of dislocations within the alloy and the increase of dislocation density; meanwhile, after the deep cryogenic treatment, the deformed grains are transformed into recrystallized and sub-crystals structural grains, the grains are refined, and the size of the grains is refined from the original 25.2 μm to 20.3 μm, with fine equiaxed crystals. Among them, the mechanical properties of the DCT36h specimen were the best, and its hardness, tensile strength, yield strength and elongation reached 142.44 HV, 328.32 MPa, 177.42 MPa, and 29.29%, which were 34.17%, 5.62%, 11.10%, and 32.77% higher than the original sample, respectively. We believe that the main mechanism for the increase in toughness is multiple reinforcement such as dislocation strengthening, grain refinement strengthening, precipitated phase strengthening and texture strengthening. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced thermoplastic composites (CFRTPs) are widely used in industrial manufacturing due to their excellent mechanical properties, and the joining of lightweight metal/CFRTP hybrid structure has gained more attention. Ultrasonic welding is a promising method for achieving metal/CFRTP dissimilar joining. In this study, 6061 aluminum alloy and carbon fiber-reinforced polyamide-66 (CF/PA66) were ultrasonically welded by preparing a PA6 coating on the surface of aluminum sheet as an interlayer. This paper investigates the effects of welding parameters on the joint mechanical property. Optimized process parameters (welding force 600 N, amplitude 60% and welding time 0.6 s) are determined by experiments. The effects of the thickness and crystallinity of the PA6 coating on the joint strength are investigated. The results show that there exists an optimal coating thickness that maximizes the joint strength. Low crystallinity of the coating contributes to high joint strength. Mixed failure mode (adhesive failure, substrate failure and cohesive failure) is observed based on the analysis on the fracture surface. [ABSTRACT FROM AUTHOR]

This paper presents experimental ductile fracture data for 2139-T8 aluminum alloy under various stress states for the ultimate purpose of probing the fracture envelope as a function of stress triaxiality and normalized Lode angle. A new ductile fracture model is also proposed and validated by experimental data, along with the evaluation of existing ductile fracture models. The data extracted from published literature on 2024-T351 aluminum alloy was also used as an additional experimental data set for validation. An extensive experimental program was implemented to produce data in a wide range of stress states, including tensile tests (with round smooth, round notched, and plate specimens), torsion, compression (with round smooth and round notched specimens), and shear-compression experiments (two different sizes). The combined effects of stress triaxiality and normalized Lode angle were used to define a 3D fracture envelope for fracture strain. A parallel finite element simulation (fine-tuned by the experimental results) has been performed for each experiment to evaluate the evolution of stress triaxiality and normalized Lode angle in the critical section of the specimens with complex geometries. Finally, these results were used to develop two fracture models whose predictions were compared with some of the existing models. [ABSTRACT FROM AUTHOR]

The control and removal of inclusions in the continuous casting process can significantly improve the performance of casting billet. In this paper, the aluminum alloy rod billets were prepared by the self-developed negative pressure continuous casting (NPCC) technique. The three-dimensional (3D) morphology and distribution of inclusions in the rod billet were analyzed by X-ray microtomography, the inclusions motion behavior was systematically studied by numerical simulation, and the inclusions removal mechanism was comprehensively revealed. The results show the volume fraction of inclusions in the aluminum alloy rod billet prepared by NPCC technique is 0.03%. Compared with the traditional vertical downward continuous casting (VDCC) technique, the inclusions are reduced by 81.3% and the maximum equivalent diameter is reduced from 24 to 13 μm. By changing the pressure difference inside and outside the melt (PDIOM), NPCC technique makes the melt and inclusions flow in the same direction, which accelerates the floating of inclusions to the melt surface to achieve dynamic solid–liquid separation. Simultaneously, the PDIOM increases the turbulent kinetic energy dissipation rate of melt by a maximum of 44.3 times, and the collision constant of inclusion particles increases by a maximum of 6.7 times. The inclusion particles are more likely to collision and aggregation, which is conducive to the floating and removal of inclusions, thereby further reducing the content and size of inclusions in the rod billet. Overall, this study provides a new continuous casting technique for the preparation of high-quality metal billet with low inclusions content and size. [ABSTRACT FROM AUTHOR]

In this paper, semi-solid compression of 2A14 aluminum alloy was conducted on the Gleeble1500D thermophysical simulation experimental compressor to investigate the rheological behavior of 2A14 alloy at high solid fraction in the semi-solid state. The main objective of the study was to establish the constitutive equation suitable for serving the simulation and practical thixoforging forming process of the 2A14 alloy. Another purpose is to investigate the effect of heat deformation parameters on the microstructure of 2A14 alloy. The apparent viscosity of semi-solid 2A14 alloy with high solid fraction as a function of equivalent shear rate was obtained. The constitutive equation for 2A14 aluminum alloy at true strain below 0.2 was established. Increasing the compression temperature or strain rate is beneficial to the deformation and grain refinement in the hard deformation zone, but at the same time, it will also intensify the aggregation of micro-voids in the transition zone into micro-cracks and the formation of macro-cracks. The macroscopic compression instability at true strains above 0.2 was discussed, mainly attributed to the dilatant shear bands generated in the strain localization region inherent in the compression deformation and the higher thermal crack sensitivity of the 2A14 alloy. [ABSTRACT FROM AUTHOR]

This paper presents a method for joining Si3N4 and 7A52 aluminum alloy using femtosecond laser surface modification of Si3N4 ceramics. This study investigated the impact of laser scanning speed on the morphology, chemical composition, and wettability of Si3N4 ceramic surfaces, as well as the mechanism behind the laser-assisted joining of Si3N4 and 7A52. After undergoing femtosecond laser processing, the ceramic material underwent modifications resulting in the creation of a periodic groove structure. This structure featured an ideal depth-to-width ratio that effectively increased the surface area for bonding with the solder. Furthermore, the surface of Si3N4 experienced thermal decomposition, which produced a recrystallized layer of 'Si.' This layer improved the solder's wetting effect on the ceramic surface, which led to a stronger diffusion of Al and Mg elements to the ceramic interface. The presence of the periodic groove structure also changed the fracture path of the joint, ultimately enhancing the strength of the brazed joint by approximately 52.4% when compared to the original joint. Notably, this significant improvement was achieved without the need for surface metallization. In summary, the femtosecond laser processing method significantly improved the strength of the ceramic–metal brazed joint through surface modifications, promoting a more reliable and robust bond. [ABSTRACT FROM AUTHOR]

The CMOS technology with MOSFETs below 70 nm node for Semiconductor Industry Association roadmap has outstanding resistance to short-channel effect and improves the scalability of the device. Cylindrical surrounding double-gate (CSDG) MOSFETs have been proposed as a suitable CMOS substitute to reduce the area and power tradeoff. This paper presents mathematical modeling of the electron density arrangement in the CSDG MOSFET for hybrid RF applications. In this device, the arbitrary alloy of Aluminum Gallium Arsenide (AlGaAs) has been used. This material lies between Aluminum Arsenide and Gallium Arsenide. High electron mobility and the lesser bandgap in AlGaAs make it suitable for the design of CSDG MOSFET for low-frequency applications. In the middle of CSDG MOSFET, the electron density (N2D) has been observed to be 1.92 × 1013 cm−2 for arbitrary alloy-based MOSFET and 1.02 × 1013 cm−2 for the conventional SiO2-based MOSFET towards the drain terminal. The electron density has been observed to be 7.90 × 1012 cm−2 for arbitrary alloy-based MOSFET and 5.86 × 1012 cm−2 for the conventional SiO2-based MOSFET along the channel. The results show that the average speed of the electron inside the device channel is submissive to the conventional MOSFET. [ABSTRACT FROM AUTHOR]

The aim of the present study was to determine the evolution of resistance to pitting corrosion and changes in the mechanical properties of ultrafine-grained aluminium during annealing. In contrast to the numerous papers devoted to the topic of the corrosion resistance of severely deformed aluminium alloys, a unique approach has been taken in this study. The size and distribution of the primary intermetallic particles, which are crucial in terms of corrosion resistance, remain constant during annealing. Therefore, the influence of other microstructural features could be investigated and compare with the results of mechanical properties. It was shown that the ultrafine-grained structure of commercially pure aluminium was stable up to 200 °C. Higher annealing temperatures caused significant grain growth and a reduction in dislocation density, which resulted in a drop in mechanical strength. Also, the corrosion resistance slightly decreased, since with an increase in annealing temperature a decrease in the corrosion potential, pit size, and the area damaged by corrosion attack were noted. The best combination of mechanical strength and resistance to pitting corrosion has been achieved for as-deformed state. [ABSTRACT FROM AUTHOR]

Enhancing the high temperature mechanical properties and the thermal stability of aluminum alloys are in urgent demand for the lightweight application scenarios (such as pistons, fan blades, crankshafts) working at elevated temperatures. The fabrication of aluminum matrix composites is a promising solution. In this work, TiB2 nanoparticles were in-situ introduced to a typical heat resistant Al–Cu–Mg–Fe–Ni (Al2618) alloy matrix and subjected to hot extrusion. Microscopically, the extruded TiB2/Al composite exhibited refined and bimodal sized grain structure, which was stable after long-time thermal exposure associated with TiB2 particle banding along the extrusion direction. The TiB2/Al composite showed an evident improvement in high temperature strength as well as the strength retention after long-time thermal exposure up to 300 °C, compared to the unreinforced alloy. The strengthening effect was remarkable especially at 200 °C with an increase of ~ 20% (60–70 MPa) in tensile strength and strength retention after thermal exposure but without the trade-off of ductility. The effects of TiB2 particles on the temperature-dependent strengthening mechanisms and microstructure evolutions were investigated. This work inspires the design, processing and evaluation of novel high strength and heat resistant particle-reinforced aluminum matrix composites for the potential applications under elevated temperature service conditions. [ABSTRACT FROM AUTHOR]

Aluminum anodes with fine grain have stronger electrochemical activity and higher corrosion resistance, but the microwave-smelted aluminum alloy anode can be prepared with fine grain. In this work, microwave smelting has been used to refine grain size and optimize the precipitated phase in an aluminum alloy anode. The results show that microwave can not only refine the grain and improve the corrosion resistance of aluminum anode, but also the distribution of precipitated phase is more uniform. The fine grain reduces the potential difference inside the aluminum anode, thus activating the electrochemical activity of the anode and improving the corrosion resistance. The corrosion form is also changed from the conventional pit corrosion to uniform corrosion, so as to improve the utilization rate of anode. The capacity density and energy density of 1000 W microwave-smelted aluminum anode were 1554.404 mAh/g and 1955.181 Wh/kg, respectively. Compared with conventional aluminum anode, the energy density and capacity density increased by 92.7% and 64.5%, respectively. Therefore, microwave technology can improve electrochemical performance and battery performance by optimizing microstructure uniformity and refining grain size. [ABSTRACT FROM AUTHOR]

The need for 2219 aluminum alloy and 2195 Al–Li alloy dissimilar friction stir welding (FSW) arises as the conventional 2219Al alloy was gradually replaced by the novel 2195Al alloy in fabrication of fuel tanks. However, the systematic investigation about the effect of welding parameters and material positioning on the microstructure evolution and mechanical properties of dissimilar FSW 2219Al/2195Al joints is lacking. In the present study, 2219Al-T8/2195Al-T8 plates were subjected to FSW under rotation rates of 800–1200 rpm and welding speeds of 200–800 mm min−1 with placing 2219Al-T8 alloys on the advancing side (AS) and retreating side (RS), respectively. The results showed that sound FSW joints were obtained under all the welding conditions. Welding parameters and material positioning affected the joint strength and fracture failure behavior. The FSW thermal cycle resulted in low hardness zones (LHZs) on both the 2219Al-T8 and 2195Al-T8 sides. The LHZ on the 2219Al-T8 side, characterized by partial coarsening of θ′ (Al2Cu) precipitates and dissolution of the residual precipitates, showed the minimum hardness in the entire FSW joints. When 2219Al-T8 alloy was placed on the AS, the LHZ on the 2219Al-T8 side experienced higher peak temperature, and therefore more dissolution of θ′ than that on the RS, thereby obtaining higher tensile strength. The tensile strength of the FSW joints at room temperature and − 196 °C largely increased as the welding speed increased from 200 to 400 mm min−1. The FSW joints presented much higher tensile strength at − 196 °C than that at room temperature under the identical welding parameters and material position. The FSW joints fractured along the LHZ on the 2219Al-T8 side during tension. For the bending testing, the up and down bending failure angles were about 91–117° and 88–109°, respectively, with the weak zone appearing in "S" line or HAZ on the 2195Al-T8 side. [ABSTRACT FROM AUTHOR]

In this work, micro-arc oxidation was applied to fabricate a high voltage resistance Al2O3-based ceramic coating on the surface of aluminum alloy. The microstructure and insulating properties of the coatings were characterized by XRD, SEM and breakdown voltage testers. The growth behavior and insulation property of the oxide layer in "soft" regime conditions of micro-arc oxidation were determined. The relative contents of α-Al2O3 increased with "soft" plasma discharge time. The soft plasma discharge brought about a tendency of the micro-arc oxide coating to grow outward, further repairing the coating defects and yielding a denser coating layer with improved corrosion protection. Due to the presence of negative currents, the thickness of the whole layer increased, while the inner layer became denser and thicker as a consequence of soft sparks, favoring an increase in the density of the bulk coating layer. The breakdown voltage reached values above 1000 V after 20 min of soft plasma discharge, improving the of micro-arc oxidation coating insulation properties. The oxide layer is thus proposed as a potential candidate for insulation shielding of etching equipment. [ABSTRACT FROM AUTHOR]

The microstructure and elemental composition evolution of Cf/SiC–Al composites prepared by combined precursor infiltration pyrolysis (PIP) and vacuum-pressure infiltration processes after high-temperature oxidation for different times was investigated. Meanwhile, the mechanical properties of the composites after oxidation treatment were characterized by nanoindentation and compressive performance tests. The results show that when the oxidation temperature was 400 °C and above, the weight loss rate of the composites gradually increased with the prolongation of the oxidation time, and the interface separation between the carbon fiber and SiC matrix became more obvious. Moreover, the nanoindentation elastic modulus of the Al alloy matrix and the SiC matrix decreased significantly with the increase in oxidation time, while the nanoindentation hardness of the aluminum alloy hardly changed. After oxidizing at 400 °C for 7 h, the in-plane compressive strength of the composites reached the maximum (584.7 MPa), and after oxidizing at 500 °C for 9 h, the compressive strength decreased to the minimum (347.8 MPa). [ABSTRACT FROM AUTHOR]

Cold rolling the CC AA 5754 aluminum alloy to different reductions was followed by an hour of annealing at 537 °C under varied pressures. The changes in microstructure and texture were studied. According to the findings, high-pressure heat treatment restricts recrystallization, and the restriction effect is stronger as pressure rises. The refining impact of high-pressure heat treatment can refine recrystallized grains, and it becomes stronger as the rolling reduction gets higher. The variation of recrystallization texture is significantly affected by high-pressure heat treatment. The sheet with a 19.6% reduction is found to have a weak cube texture at atmospheric pressure and 2 GPa, but the sheet that has been annealed at 4 GPa and 6 GPa has a strong cube texture and a weak β fiber rolling texture. High-pressure heat treatment improves the intensities of the cube and R textures in the fully recrystallized sheets with the same reduction. The strengthening impact of R texture from high-pressure heat treatment improves with increasing rolling reduction. [ABSTRACT FROM AUTHOR]

Friction stir spot welding on Al 6061-T6 aluminium alloy was performed to examine the influence of parameters, e.g. tool pin profile, shoulder plunge depth, diameter of shoulder and SiC particles on mechanical properties, macro-structural and micro-structural properties of welds. During the detailed experimentation the behaviour of hook formation, stir zone width, bonded region width and tensile-shear strength was scientifically measured, studied and discussed. Distribution of SiC particles was analysed as it affected the weld quality. Homogeneous distribution of SiC particles helped in entrapping the dislocations during tensile-shear loading of welds. A stronger weld was witnessed with the increase in diameter of the tool shoulder, while there was an increase and then a sudden decrease in weld strength with increase in shoulder plunge depth. Square tool pin was identified as optimum tool pin profile for obtaining stronger welds. The reduction in hook formation was observed with increased shoulder diameter and shoulder plunge depth. Square tool pin increased the material flow and reduced hook length by pushing it away from key hole due to increased stir zone width. SiC particles were observed to be homogeneously distributed with square tool pin profile, greater diameter of tool shoulder and optimum shoulder plunge depth. [ABSTRACT FROM AUTHOR]

The solution-aging behavior and properties of spray-formed 7055 aluminum alloy TIG weld metal (WM) reinforced by TiC–TiB2 (BC) ceramic particles are investigated, in detail. Weld joints were subjected to solution at 475 °C for 1, 2.5, and 5 h, followed by the aging process at 120 °C for 0–24 h. The results show that ceramic particles not only restrict the grain coarsening of WM during the heat treatment but also accelerate the solution and age-precipitation behavior. The optimum solution time of ceramic particle-reinforced WM is 2.5 h, which has superior aging kinetics due to the completely dissolved eutectic phases. More importantly, during the aging process, ceramic particles decrease the width of the precipitate free zone and modify the size and distribution of precipitates. With the 475 °C/2.5 h + 120 °C/15 h treatment, the tensile strength (530 ± 15 MPa) and elongation (3.9 ± 0.29%) of BC weld joints are higher than 7055 weld joints (358 ± 20 MPa, 2.38 ± 0.42%). Grain refinement, Zener pinning strengthening, coefficients of thermal expansion mismatch strengthening, and precipitation strengthening are the dominant strengthening mechanisms of ceramic particle-reinforced WM. [ABSTRACT FROM AUTHOR]

For improving the comprehensive mechanical properties of aluminum alloys (AAs) joint, the 6063-T6 AAs with thickness of 10 mm were bonded via the double-sided (DS) friction stir welding technique. Compared with the single-sided (SS) AAs joint, the grains in various regions of DS joints were refined in various degrees. In addition, the high-angle grain boundaries frequency of nugget zone reached to approximately 55%, which could hinder crack growth. Fatigue test result indicated that fracture positions of DS joints were either at thermo-mechanically affected zone or heat-affected zone near advancing side, resulting in the fatigue strength of 92 MPa. However, the fatigue strength of SS joints those mainly fractured on welding root was 76 MPa. The approximately 20% higher fatigue strength of DS joint than that of SS joint was mainly attributed to the elimination of the weak bonding at welding root as well as the grain refinement. [ABSTRACT FROM AUTHOR]

The solidification microstructure of aluminum foams is evidently different from that of bulk aluminum alloys. Generally, a single α-Al grain runs through the entire thickness of a cell-wall, and the grain morphology is irregular. However, the formation mechanism of the special microstructure in aluminum foams is unclear now, and few studies focused on optimizing the microstructure. In this study, grain refinement of aluminum foams by increasing cooling rate and inoculation were carried out, and thermal analysis was used to measure and judge solidification of aluminum foams. Experimental results show that grain refinement can be achieved by the above two methods, and the latter is more effective. The nucleation undercooling of aluminum foams decreases with the increase of Al–5Ti–1B addition. Grains can be well refined even in thin cell walls after inoculation, and the grain morphology changes from irregular to equiaxed. Under the same conditions, α-Al grains of Al foams are smaller than those of the bulk Al alloy, either with or without inoculation. An anisometric growth model of α-Al grains in foamed aluminum melt restricted by surrounding bubbles is proposed. The model shows that: (1) the size of the inhibited nucleation zone (INZ) around growing grains decreases due to the high constitutional undercooling caused by solute enrichment in cell walls, thus grains in cell walls are smaller than those of bulk Al alloy; (2) under normal solidification conditions, the shape of the INZ is irregular. Grains in aluminum foams will replicate contours of cell walls or Plateau borders, presenting irregular shapes. Increasing cooling rates and/or inoculation can reduce the size of INZ and change its shape. The grain morphology will change from irregular to equiaxed under proper conditions. [ABSTRACT FROM AUTHOR]

Additive manufacturing provides alternative solutions for complex geometry and design freedom for the customization of aluminum alloys, while the unique microstructure as well as the complex solidification behavior is of great concern due to the severe thermal stress in the layer-by-layer accumulated process. In this work, the effects of laser power, laser scanning speed, and hatch spacing on the microstructure and mechanical properties of a laser powder bed fusion (LPBF) fabricated thermal conductive aluminum alloy 6063 (AA6063) were studied. The relationship between processing parameters and metallurgical defects was investigated. The element distribution and misorientation between grains around the crack were characterized. The results revealed that the majority of cracks were parallel to the building direction. The crack density was suppressed by increasing the scanning speed. The orientated cracks lead to the anisotropy of mechanical properties. The strength and ductility of the vertical samples are both higher than those of the horizontal samples. After aging treatment, an ultimate tensile strength of 241 MPa, yield strength of 215 MPa, and elongation of 4.9% were obtained in the vertical specimen of the LPBF processed AA6063. It was demonstrated that cracks tend to stretch along the high-angle grain boundaries because of the concentration of local thermal stress at the final stage of solidification. This work provides guidance for defects suppression and mechanical properties optimization in additively manufactured AA6063 and other aluminum alloys. [ABSTRACT FROM AUTHOR]

Aluminum alloy is the optimum material for weight reduction and widely used in a lot of industries including automobile, rail transportation, aerospace, and so on. Ternary Ti3AlC2 powder was adopted in this study to improve the laser welding quality of 6061 Al alloy. Addition of the Ti3AlC2 powder could increase the width and stability of the molten pool, which was beneficial to inhibit the formation of defects such as pore, spatter, rugged surface, sagging, and undercut. Reaction products of Ti3AlC2 powders including Ti3AlxC2, TiAl3, and TiC impeded the growth of dendrites and could serve as nucleating agent, resulting in the formation of massive isometric crystals and dispersed precipitates. The refinement strengthening and dispersion strengthening could impede the extension of deformation and made up the influences of uneven melting loss of alloying elements, leading to the increase and uniformity of weld hardness from 53.1 HV0.2 to 74.9 HV0.2. Both of the welded joints with and without assistant powder fractured at the welds. Elimination of pores increased the loading area of weld while generation of precipitates impeded the extension and connection of dimples, leading to the improvement of tensile strengths from 191.0 to 232.5 MPa and displacements from 0.95 to 1.59 mm. [ABSTRACT FROM AUTHOR]

During homogenisation of the AA3104 cast ingot, a phase transformation of intermetallic particles from β-Al6(Fe,Mn) orthorhombic phase to harder α-Alx(Fe,Mn)3Si2 cubic phase occurs. The large constituent intermetallic particles, regardless of phase, assist in the recrystallisation nucleation process through particle stimulated nucleation (PSN). Ultimately, this helps to refine grain size. The sub-micron dispersoids act to impede grain boundary migration through a Zener drag mechanism. For this reason, the dispersoids that form during homogenisation are critical in the recrystallisation kinetics during subsequent rolling, with smaller dispersoids being better suited to reverse rolling mills. This work simulates an industrial two-step homogenisation practice with variations in the peak temperature of the first step between 560 °C and 580 °C. The effect of this temperature variation on the intermetallic particle-phase evolution is investigated. The aim is to identify the ideal intermetallic phase balance and the dispersoid structure that are best suited for hot rolling on a single stand reversing mill, in order to minimise recrystallisation during rolling through maximising Zener drag and maintaining galling resistance. The results indicate a trend where an increase in homogenisation temperature from 560 °C to 580 °C yields, firstly, an increase in the volume fraction of the α-phase particles to greater than 50% of the total volume fraction at both the edge and the center of the ingot and, secondly, it yields an increased dispersoid size. Thus, in the context of a reverse rolling operation, a lower temperature homogenisation practice produces a near-ideal combination of intermetallic particle-phase distribution, as well as dispersoid size, which is critical for Zener drag and the minimization of recrystallisation during the hot rolling processes. SEM BEI images and corresponding EDS maps, highlighting the variation in intermetallic particle phase balance, size and morphology after homogenisation at different temperatures. With a focus on the exaggerated differences seen between material the center of and at the edge of a DC cast ingot of AA3104 Aluminum alloy. [ABSTRACT FROM AUTHOR]

Improving the mechanical polishing of engineering surfaces in terms of the wetting and droplet evaporation theories is important for increasing the efficiency of modern equipment. Depending on the function of engineering surfaces, the mechanical polishing allows changing the wetting, as well as the liquid droplet evaporation rates and modes. However, the prediction of the processes occurring at the liquid/gas/solid contact line becomes more complicated after modification of metal surfaces, as well as under changing the environmental conditions. This work focuses on the study of wetting and evaporation of liquid droplets from polished aluminum alloy surfaces at constant and cyclically varying pressure. Wetting and droplet evaporation are key processes in equipment of the thermal power industry, in particular, operating at constant and cyclically varying high pressure: water-water steam generators, water vapor separators, droplet catchers, etc. Therefore, we investigated droplet wetting and evaporation modes after mechanical processes of surfaces, including polishing by tumbling, satin finishing, grinding and polishing by disks and pastes. We determined the condition when polishing of aluminum alloy surfaces by these methods does not affect the wettability by liquid droplets. Moreover, we established the effect of constant and cyclically varying high pressure on the droplet evaporation rate and evaporation modes. The pressure was found not to affect the characteristics of water droplet evaporation under conditions of periodically varied pressure in the chamber from the atmospheric (0.1 MPa) to high (0.5, 1.0, 1.5, and 2.0 MPa) values. [ABSTRACT FROM AUTHOR]

This study investigated the microstructures and properties of deposits protected by seven different proportions of N2 and Ar by performing wire-arc additive manufacturing of the 5356 aluminium alloy. The results show that when the proportion of N2 in the shielding gas was larger than and equal to 50%, flaky nitrides were generated in the deposits. With an increase in the proportion of N2 in the shielding gas, the number and size of nitrides in the deposits as well as the fluctuation frequency and amplitude of the microhardness of the deposits all increase. The existence of flaky nitrides incurs a low ultimate tensile strength of additively manufactured parts protected by a mixed gas containing N2. The presence of large-size flaky nitrides between layers in the deposits leads to a large difference in tensile properties in the horizontal and vertical directions of the deposit. Tensile fracture shows that the deposits were fractured in the mixed mode of ductile and brittle fracture. [ABSTRACT FROM AUTHOR]

Mold fouling during vulcanization is a widespread issue faced by tire industry that urgently needed to be addressed as it can degrade comprehensive performance of molded products and increase production time for cleaning mold, resulting in tremendous economic loss and resource consumption. Here, a novel and promising fouling mitigation strategy inspired by nature is presented, and its antifouling behavior in vulcanization conditions is investigated. The inspired slippery liquid-infused surfaces were successfully designed on aluminum alloy by anodic oxidation, followed by myristic acid modification and impregnation with perfluorinated oil. The prepared surfaces showed a water contact angle of 112.3° and sliding angle of 0.5°, accompanying with self-cleaning ability, stability for repelling hot water and under high-pressure condition as well as excellent corrosion resistance in 0.05 M H2SO4 corrosive medium. Moreover, remarkable antifouling performance was obtained for slippery liquid-infused surfaces as no trace of fouling was observed after vulcanization test and thus a potential strategy for practical industrial applications. [ABSTRACT FROM AUTHOR]

Al-Mg alloys are normally prone to lose part of their yield and tensile strength at high temperatures due to insufficient thermal stability of the microstructure. Here, we present a Ca-modified Al–Mg–Sc alloy demonstrating high strength at elevated temperatures. The microstructure contains Al4Ca phases distributed as a network along the grain boundary and Al3(Sc,Zr) nano-particles dispersed within the grains. The microstructure evolution and age-hardening analysis indicate that the combination of an Al4Ca network and Sc-rich nano-particles leads to excellent thermal stability even upon aging at 300 °C. The tensile strength of the alloy for temperatures up to 250 °C is significantly improved by an aging treatment and is comparable with the commercial heat-resistant aluminum alloys, i.e., A356 and A319. At a high temperature of 300 °C, the tensile strength is superior to the above-mentioned commercial alloys, even more so when expressed as the specific strength due to the low density of Ca-modified Al–Mg–Sc alloy. The excellent high-temperature strength results from a synergistic effect of solid solution strengthening, grain boundary strengthening and nanoparticle order strengthening. [ABSTRACT FROM AUTHOR]