Optimization design of support structure based on 3D printing technology.

Parts are often warped and deformed when they are molded using selective laser melting (SLM) technology. Thus, it is necessary to study the addition support modes of parts molded using SLM. Consequently, we designed dendritic, E-stage and conical supports, having different structural parameters and different partitions using Magics, and then, we analyzed their performances using the finite element software Abaqus. The structural parameters of the supports were optimized and finally tested using SLM molding technology. The maximum stress concentration was found for dendritic supports, followed by E-stage supports, and then conical supports. The stress concentration and deformation level of Scheme 2 were less than those of Scheme 1. The stress intensity and deformation levels for two partitions were less than those for three partitions. For parts molded by SLM, the deformation was maximum for conical supports, followed by dendritic supports, and then E-stage supports. When gradient supports of similar volumes were added, additional partitions did not effectively improve the molding quality. When supports of similar volumes were added, adding gradient supports did not effectively improve the molding quality. The results provide a basis for the application of SLM in molding high-precision parts.

Corrosion and Interfacial Contact Resistance of NiTi Alloy as a Promising Bipolar Plate for PEMFC.

Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale commercial application in proton exchange membrane fuel cells (PEMFCs). In this paper, we proposed a NiTi alloy prepared by suction casting as a promising bipolar plate for PEMFCs. This NiTi alloy exhibits significantly decreased ICR values (16.8 mΩ cm2 at 1.4 MPa) compared with pure Ti (88.6 mΩ cm2 at 1.4 MPa), along with enhanced corrosion resistance compared with pure nickel (Ni). The superior corrosion resistance of NiTi alloy is accredited to the nobler open circuit potential and corrosion potential, coupled with low corrosion current densities and passive current densities. The improved ICR can be interpreted by the existence of high-proportioned metallic Ni in the passive film, which contributes to the reduced capacitance characteristic of the passive film (compared with Ti) and enhances charge conduction. This work provides a feasible option to ameliorate BPP material that may have desirable corrosion resistance and ICR.

A study on microstructural, mechanical properties, and optimization of wear behaviour of friction stir processed AZ31/TiC composites using response surface methodology.

The primary objective of this study is to investigate the microstructural, mechanical, and wear behaviour of AZ31/TiC surface composites fabricated through friction stir processing (FSP). TiC particles are reinforced onto the surface of AZ31 magnesium alloy to enhance its mechanical properties for demanding industrial applications. The FSP technique is employed to achieve a uniform dispersion of TiC particles and grain refinement in the surface composite. Microstructural characterization, mechanical testing (hardness and tensile strength), and wear behaviour evaluation under different operating conditions are performed. Response surface methodology (RSM) is utilized to optimize the wear rate by considering the effects of process parameters. The results reveal a significant improvement in hardness (41.3%) and tensile strength (39.1%) of the FSP-TiC composite compared to the base alloy, attributed to the refined grain structure (6-10 µm) and uniform distribution of TiC particles. The proposed regression model accurately predicts the wear rate, with a confirmation test validating an error percentage within ± 4%. Worn surface analysis elucidates the wear mechanisms, such as shallow grooves, delamination, and oxide layer formation, influenced by the applied load, sliding distance, and sliding velocity. The enhanced mechanical properties and wear resistance are attributed to the synergistic effects of grain refinement, particle-accelerated nucleation, the barrier effect of TiC particles, and improved interfacial bonding achieved through FSP. The optimized FSP-TiC composites exhibit potential for applications in industries demanding high strength, hardness, and wear resistance.

Microstructural characterization of gadolinium-rich phases in titanium alloys.

This study explores the microstructural characteristics of gadolinium (Gd)-rich phases in titanium (Ti) alloys through comprehensive electron microscopy analysis. The Ti alloys were produced using plasma arc melting and subsequently hot-forged. Elaborate material characterization, including scanning electron microscopy, electron backscatter diffraction, and energy dispersive spectroscopy, revealed the formation of round or angular Gd oxides and elongated Gd-rich grains within the alloy. High-magnification transmission electron microscopy and X-ray diffraction confirmed the presence of the FCC-type γ-Gd phase, influenced by the oxygen intake during casting, coexisting with Gd2O3 due to their similar crystal structures. The study also observed internal twins in the Gd grains, potentially delaying the transformation to the stable α-Gd phase. The significant mechanical property differences between the Gd-rich phases and the Ti matrix caused defects at phase interfaces during hot processing, weakening the Gd phase. This work enhances the understanding of Gd phase formation and its implications on the mechanical properties of Ti-Gd alloys.

The influence of various welding wires on microstructure, and mechanical characteristics of AA7075 Al-alloy welded by TIG process.

Owing to their exceptional mechanical properties, the various welding wires used to combine aluminum can meet the needs of many engineering applications that call for components with both good mechanical and lightweight capabilities. This study aims to produce high-quality welds made of AA7075 aluminum alloy using the GTAW technique and various welding wires, such as ER5356, ER4043, and ER4047. The microstructure, macrohardness, and other mechanical characteristics, such as tensile strength and impact toughness, were analyzed experimentally. To check the fracture surface of the AA7075 welded joints, the specimens were examined using optical and scanning electron microscopy (SEM). A close examination of the samples that were welded with ER5356 welding wire revealed a fine grain in the weld zone (WZ). In addition, the WZ of the ER4043 and ER4047 welded samples had a coarse grain structure. Because the hardness values of the welded samples were lower in the WZ than in the base metal (BM) and heat-affected zone (HAZ), the joints filled with ER5356 welding wire provided the highest hardness values compared to other filler metals. Additionally, the ER4047 filler metal yielded the lowest hardness in the weld zone. The welding wire of ER5356 produced the greatest results for ultimate tensile stress, yield stress, welding efficiency, and strain-hardening capacity (Hc), whereas the filler metal of ER4043 produced the highest percentage of elongation. In addition, the ER4047 fracture surface morphology revealed coarser and deeper dimples than the ER5356 fine dimples in the welded joints. Finally, the highest impact toughness was obtained at joints filled with the ER4047 filler metal, whereas the lowest impact toughness was obtained at the BM.

A Novel Scaffold of Icariin/Porous Magnesium Alloy-Repaired Knee Cartilage Defect in Rat by Wnt/ß-Catenin Signaling Pathway.

Cartilage defects caused by joint diseases are difficult to treat clinically. Tissue engineering materials provide a new means to promote the repair of cartilage defects. The purpose of this study is to design a novel scaffold of porous magnesium alloy loaded with icariin and sustained release in order to explore the effect and possible mechanism of this scaffold in repairing SD rat knee articular cartilage defect. We constructed a novel type of icariin/porous magnesium alloy scaffold, observed the structure of the scaffold by electron microscope, detected the drug release of icariin in the scaffold and the biological safety, and established an animal model of cartilage defect in the femoral intercondylar fossa of the knee joint in rats; the scaffold was placed in the defect. After 12 weeks of repair, the rat knee articular cartilage repair was evaluated by gross specimens and micro-CT, HE, safranin O-fast green, and toluidine blue staining combined with the modified Mankin's score. The protein expressions of the Wnt/ß-catenin signaling pathway-related factors (ß-catenin, Wnt5a, Wnt1, sFRP1) and chondrogenic differentiation-related factors (Sox9, Aggrecan, Col2α1) were detected by immunohistochemical staining. We found that the novel scaffold of icariin/porous magnesium alloy can release icariin slowly and has biosafety in rats. Compared with other groups, icariin/porous magnesium alloy can significantly promote the repair of cartilage defects and the expressions of ß-catenin, Wnt5a, Wnt1, Sox9, Aggrecan, and Col2α1 (P < 0.05). This novel scaffold can promote the repair of rat knee cartilage defects, and this process may be achieved by activating the Wnt/ß-catenin signaling pathway.

Hydrogen inhibition of wet AlLi alloy dust collector systems using a composite green biopolymer inhibitor based on chitosan/sodium alginate: Experimental and theoretical studies.

Aluminum­lithium (AlLi) alloy polishing and grinding processes in wet dust collector systems could cause hydrogen fire and explosion. From the fundamental perspective of preventing hydrogen explosions, a safe, nontoxic, and sustainable modified green hydrogen inhibitor based on chitosan (CS) and sodium alginate (SA) was developed in this study and was used as a hydrogen evolution inhibitor for the processing of waste dust from AlLi alloys. The structure and elemental distribution of the synthesized material were characterized through characterization experiments. Hydrogen evolution experiments and a hydrolysis kinetic model were used to explore the inhibitory effect of modified CS/SA on AlLi alloy dust, and the results revealed that the inhibitory concentration of the hydrogen explosion lower limit was 0.40 wt%, with an inhibition efficiency of 91.96 %, indicating an 11.88-61.44 % improvement over that of CS and SA. As the inhibitor concentration increased and the temperature decreased, the hydrogen inhibition effect increased. Characterization experiments and density functional theory showed that CS/SA primarily formed a dense physical protective barrier on the dust surface through chemical adsorption and complexation reactions, interrupting the hydrogen evolution reaction between the metal and water. This study introduces a novel green modified hydrogen inhibitor that fundamentally addresses hydrogen generation and explosion.

Biocompatibility and osteogenic capacity of additively manufactured biodegradable porous WE43 scaffolds: An in vivo study in a canine model.

Magnesium is the most promising absorbable metallic implant material for bone regeneration and alloy WE43 is already FDA approved for cardiovascular applications. This study investigates the cyto- and biocompatibility of novel additively manufactured (AM) porous WE43 scaffolds as well as their osteogenic potential and degradation characteristics in an orthotopic canine bone defect model. The cytocompatibility was demonstrated using modified ISO 10993-conform extract-based indirect and direct assays, respectively. Additionally, degradation rates of WE43 scaffolds were quantified in vitro prior to absorption tests in vivo. Complete blood cell counts, blood biomarker analyses, blood trace element analyses as well as multi-organ histopathology demonstrated excellent biocompatibility of porous y WE43 scaffolds for bone defect repair. Micro-CT analyses further showed a relatively higher absorption rate during the initial four weeks upon implantation (i.e., 36 % ± 19 %) than between four and 12 weeks (41 % ± 14 %), respectively. Of note, the porous WE43 implants were surrounded by newly formed bony tissue as early as four weeks after implantation when unmineralized trabecular ingrowth was detected. After 12 weeks, a substantial amount of mineralized bone was detected inside and around the gradually disappearing implants. This first study on AM porous WE43 implants in canine bone defects demonstrates the potential of this alloy for in vivo applications in humans. Our data further underscore the need to control initial bulk absorption kinetics through surface modifications.

Pressure induced mechanical, elastic, and optoelectronic characteristics of Cd0.75Zn0.25Se alloy.

The change in composition and pressure, both of which lead to new desired properties by altering the structure, is particularly important for improving device performance. Given this, we focused here on the mechanical, elastic, and optoelectronic characteristics of the Cd0.75Zn0.25Se alloy using density functional theory at various pressures from 0 GPa to 20 GPa. It is found that the bulk modulus of the material rises with increasing pressure and exhibits mechanical stability as well as cubic symmetry. In addition, the increased pressure leads to a rise in the direct bandgap energy of the material from 2.03 eV to 2.48 eV. The absorption coefficient of the alloy also increases as the pressure increases, where the effective range of absorption covers the broad spectrum of light in the visible range from orange to cyan. This is due to the electronic transitions caused by the altered pressure. The optical parameters, including optical conductivity, extinction coefficient, reflection, and refractive index, are also analyzed under the influence of pressure. Based on this research, effective applications of the Cd substituted Zn-chalcogenides (CdZnSe) alloys in the fields of optoelectronics and photovoltaics are outlined, especially concerning fabricating solar cells, photonic devices, and pressure sensors for space technology.

Increasing ductility beyond post-uniform deformation through Zn lamellae deformation in Al at room temperature.

The Zn element precipitates during aging in the Al-Zn binary alloy. Increased Zn content and prolonged aging leads to discontinuous Zn precipitation. The addition of 2 wt% Cu to the Al-43 wt%Zn alloy accelerates this discontinuous precipitation, resulting in decreased thickness of Zn layers and inter-distance between them. This acceleration is attributed to the influence of Cu solutes on the Zn phase, thereby reducing the interface energy between Zn precipitates and the Al matrix. The Al-Zn-Cu alloy demonstrates exceptional behavior during tensile tests, displaying a simultaneous increase in tensile strength and ductility alongside an 75 % reduction in area at room temperature drawing. Notably, despite the drawn beyond uniform deformation limit, there is an observed increase in total elongation. Our demonstration highlights this phenomenon, attributing it to the sustained coherent interface between the Zn layer and the Al matrix, as well as the uninterrupted continuity of Zn layers during drawing.

Conferring NiTi alloy with controllable antibacterial activity and enhanced corrosion resistance by exploiting Ag@PDA films as a platform through a one-pot construction route.

The lack of antibacterial activity and the leaching of Ni ions seriously limit the potential applications of the near equiatomic nickel-titanium (NiTi) alloy in the biomedical field. In this study, a silver nanoparticles (Ag NPs) wrapped in a polydopamine (Ag@PDA) film modified NiTi alloy with controllable antibacterial activity and enhanced corrosion resistance was achieved using a one-pot approach in a mixed solution of AgNO3 and dopamine. The controllable antibacterial activity could be achieved by adjusting the initial concentration of dopamine (Cdop), which obtained Ag@PDA films with varying thickness of polydopamine layers coated on Ag NPs, thereby conferring different levels of antibacterial activity to the modified NiTi alloy. In vitro antibacterial ratios (24 h) of Ag@PDA film-modified NiTi alloy against E.coli and S.aureus ranged from 46 % to 100 % and from 42 % to 100 %, respectively. The release curves of Ag ions indicated the persistent antibacterial effect of Ag@PDA film-modified NiTi alloy for at least 21 days. Moreover, in vitro cytotoxicity and in vivo implantation tests demonstrated the satisfactory biosafety of the Ag@PDA film-modified NiTi alloy when used as bioimplants. This research offers valuable insight into meeting various antibacterial demands for NiTi alloy implantations and highlights the potential of Ag-containing film-modified biomaterials in addressing different types of infections induced by implantations.

Semi-quantitative analysis on sea buckthorn phenolic-rich extract coating bone-like open porous NiTi-based alloy.

This study investigates the feasibility of coating Ni-Ti alloy with sea buckthorn extract via a hydrothermal method for targeted delivery of beneficial phenolic compounds to bone tissue. The qualitative analysis confirmed the presence of flavonoids and tannins in sea buckthorn extract, supporting its osteogenic potential. The microhardness of the NiTi alloy substrate was suitable for biomedical applications, and successful coating was achieved without compromising its properties. NiTi alloy samples were coated with 18.1, 20.1, and 12.4 mg of extract, respectively. Comprehensive evaluations confirmed the successful integration of the extract onto the alloy's surface. The coated system exhibited sustained release properties over five days, with the highest release occurring on the first day (on average 32.1 % for the first peak and 72.1 % for the second peak), as determined by HPLC analysis. The findings demonstrate the potential of this novel approach in developing dual-functionality implants for bone health promotion. Overall, this study underscores the promising potential of Ni-Ti alloy coated with sea buckthorn extract as a targeted drug delivery system for bone tissue.

Platinum-Ruthenium Bimetallic Nanoparticle Catalysts Synthesized Via Direct Joule Heating for Methanol Fuel Cells.

Platinum-Ruthenium (PtRu) bimetallic nanoparticles are promising catalysts for methanol oxidation reaction (MOR) required by direct methanol fuel cells. However, existing catalyst synthesis methods have difficulty controlling their composition and structures. Here, a direct Joule heating method to yield highly active and stable PtRu catalysts for MOR is shown. The optimized Joule heating condition at 1000 °C over 50 microseconds produces uniform PtRu nanoparticles (6.32 wt.% Pt and 2.97 wt% Ru) with an average size of 2.0 ± 0.5 nanometers supported on carbon black substrates. They have a large electrochemically active surface area (ECSA) of 239 m2 g-1 and a high ECSA normalized specific activity of 0.295 mA cm-2. They demonstrate a peak mass activity of 705.9 mA mgPt -1 for MOR, 2.8 times that of commercial 20 wt.% platinum/carbon catalysts, and much superior to PtRu catalysts obtained by standard hydrothermal synthesis. Theoretical calculation results indicate that the superior catalytic activity can be attributed to modified Pt sites in PtRu nanoparticles, enabling strong methanol adsorption and weak carbon monoxide binding. Further, the PtRu catalyst demonstrates excellent stability in two-electrode methanol fuel cell tests with 85.3% current density retention and minimum Pt surface oxidation after 24 h.

A Concept of Local Coordination Number for the Characterization of Solute Clusters within Atom Probe Tomography Data.

Identifying clusters of solute atoms in a matrix of solvent atoms helps to understand precipitation phenomena in alloys, for example, during the age hardening of certain aluminum alloys. Atom probe tomography datasets can deliver such information, provided that appropriate cluster identification routines are available. We investigate algorithms based on the local composition of the neighborhood of solute atoms and compare them with traditional approaches based on the local solute number density, such as the maximum separation distance method. For an ideal solid solution, the pair correlation functions of the kth nearest solute atom in the coordination number representation are derived, and the percolation threshold and the size distribution of clusters are studied. A criterion for selecting optimal control parameters based on maximizing the phase separation by the degree of clustering is proposed for a two-phase system. A map of phase compositions accessible for cluster analysis is constructed. The coordination number approach reduces the influence of density variations commonly observed in atom probe tomography data. Finally, a practical cluster analysis technique applied to the early stages of aluminum alloy aging is described.

Encapsulating Nickel-Iron Alloy Nanoparticles in a Polysilazane-Derived Microporous Si-C-O-N-Based Support to Stimulate Superior OER Activity.

The in situ confinement of nickel (Ni)-iron (Fe) nanoparticles (NPs) in a polymer-derived microporous silicon carboxynitride (Si-C-O-N)-based support is investigated to stimulate superior oxygen evolution reaction (OER) activity in an alkaline media. Firstly, we consider a commercial polysilazane (PSZ) and Ni and Fe chlorides to be mixed in N,N-dimethylformamide (DMF) and deliver after overnight solvent reflux a series of Ni-Fe : organosilicon coordination polymers. The latter are then heat-treated at 500 °C in flowing argon to form the title compounds. By considering a Ni : Fe ratio of 1.5, face centred cubic (fcc) NixFey alloy NPs with a size of 15-30 nm are in situ generated in a porous Si-C-O-N-based matrix displaying a specific surface area (SSA) as high as 237 m2 ⋅ g-1. Hence, encapsulated NPs are rendered accessible to promote electrocatalytic water oxidation. An OER overpotential as low as 315 mV at 10 mA ⋅ cm-2 is measured. This high catalytic performance (considering that the metal mass loading is as low as 0.24 mg cm-2) is rather stable as observed after an activation step; thus, validating our synthesis approach. This is clearly attributed to both the strong NP-matrix interaction and the confinement effect of the matrix as highlighted through post mortem microscopy observations.

In-situ tensile testing of fracture and strain in a selective laser melted AlSi10Mg alloy.

The melt pools, the most basic units of the components fabricated by the selective laser melting (SLM) technology, play an important role in the mechanical properties of the structures. A self-developed in-situ tensile observation platform was used to carry out the in-situ tensile test of SLMed AlSi10Mg alloy specimens under the observation of optical microscope. With a series of obtained experimental data on mechanical properties and metallurgical images, combined with the digital image correlation(DIC) technology, the melt pool of the specimen and the strain of defects were analyzed, and the deformation and fracture mechanism of the SLMed AlSi10Mg alloy specimens was obtained. The results show that the proposed method successfully obtains the deformation field evolution data of the melt pool and defects, which provides experimental and theoretical support for the further study of crack extension characteristics and fatigue life prediction of SLMed metallic material components.

Thickness Effect of 2195 Al-Li Alloy Friction Stir Weld Fracture Toughness.

For damage tolerance design in engineering components, the fracture toughness value, KIC, of the material is essential. However, obtaining specimens of sufficient thickness from stir friction welded plates is challenging, and often, the experimental test values do not meet the necessary criteria, preventing the experimental fracture toughness, Kq, from being recognized as plane strain fracture toughness KIC. The fracture toughness Kq of 2195 Al-Li alloy welding seams with different thicknesses was measured on the forward and backward sides. Microstructure characterization was conducted by scanning electron microscope (SEM). The results indicated minimal significant differences in grain size between the advancing and retreating sides of the weld nugget zone. In specimens of the same thickness, fracture toughness measurements along the normal direction of the joint cross-section showed a high similarity between the advancing and retreating sides of the weld nugget zone. Utilizing the quantitative relationships between fracture toughness and sample thickness derived from both the fracture K and G criteria, it is possible to predict the fracture toughness of thick plates using thin plates. This study employs these relationships to calculate the fracture toughness KIC of 2195 aluminum-lithium alloy friction stir welds. The KIC values obtained are 41.65 MPa·m1/2 from the fracture K criterion and 43.54 MPa·m1/2 from the fracture G criterion.

Uncovering Nanoindention Behavior of Amorphous/Crystalline High-Entropy-Alloy Composites.

Amorphous/crystalline high-entropy-alloy (HEA) composites show great promise as structural materials due to their exceptional mechanical properties. However, there is still a lack of understanding of the dynamic nanoindentation response of HEA composites at the atomic scale. Here, the mechanical behavior of amorphous/crystalline HEA composites under nanoindentation is investigated through a large-scale molecular dynamics simulation and a dislocation-based strength model, in terms of the indentation force, microstructural evolution, stress distribution, shear strain distribution, and surface topography. The results show that the uneven distribution of elements within the crystal leads to a strong heterogeneity of the surface tension during elastic deformation. The severe mismatch of the amorphous/crystalline interface combined with the rapid accumulation of elastic deformation energy causes a significant number of dislocation-based plastic deformation behaviors. The presence of surrounding dislocations inhibits the free slip of dislocations below the indenter, while the amorphous layer prevents the movement or disappearance of dislocations towards the substrate. A thin amorphous layer leads to great indentation force, and causes inconsistent stacking and movement patterns of surface atoms, resulting in local bulges and depressions at the macroscopic level. The increasing thickness of the amorphous layer hinders the extension of shear bands towards the lower part of the substrate. These findings shed light on the mechanical properties of amorphous/crystalline HEA composites and offer insights for the design of high-performance materials.

Study on the Migration Patterns of Oxygen Elements during the Refining Process of Ti-48Al Scrap under Electromagnetic Levitation.

This study investigated the migration patterns of oxygen in the deoxidation process of Ti-48Al alloy scrap using electromagnetic levitation (EML) technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to analyze the oxygen distribution patterns and migration path during EML. The refining process resulted in three types of oxygen migration: (1) escape from the lattice and evaporation in the form of AlO, Al2O; (2) formation of metal oxides and remaining in the alloy melt; (3) attachment to the quartz tube wall in the form of metal oxides such as Al2O3 and Cr2O3. The oxygen content of the scrap was dropped with a deoxidation ratio of 62%. It indicated that EML can greatly promote the migration and removal of oxygen elements in Ti-Al alloy scrap.

The Effect of Heat Aging on the Microstructure and Properties of Spray-Deposited AlZnMgCu Alloy Extruded Plates.

The heat-aging process, a practical aging technology that not only improves the comprehensive performance of Al alloys but also reflects the requirements of short processes, has an extremely practical significance. The effects of the heating rate and termination temperature on the "heat-aging" behavior of a spray-deposited AlZnMgCu alloy hot-extruded plate were investigated using hardness, electrical conductivity, room-temperature tensile strength, exfoliation corrosion experiments, and transmission electron microscopy microstructure (TEM) observation. The results show that as the termination temperature increases, the hardness of the spray-deposited AlZnMgCu alloy first increases to a peak and then rapidly decreases, while the electrical conductivity continues to increase. The increase in the heating rate improves the peak hardness corresponding to the termination temperature. The heat treatment process of heating at a speed of 20 °C/h to 200 °C after the spray deposition has similar mechanical and corrosion resistance properties to the RRA process and can effectively reduce the heating time from 40 h to 8 h, thus establishing a heat treatment process for spray-deposited AlZnMgCu alloy extruded plate with high aging efficiency.