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In traditional wire arc additive manufacturing process, it is difficult to control the chemical composition of deposition layer. A double filler wire with alternating current was proposed to fabricate the NiTi alloy. In this process, Ni filling wire and Ti filling wire were connected to alternating current. The macrographic, phase evolution, and mechanical properties of the as-printed sample at various wire feed speed ratios were studied. The results show that the deposition layers were consistently uniform in the deposition process. The coarse dendritic grain structure gradually changed with decreasing Ni wire feed speed. Columnar and equiaxed microstructures were observed in the deposition sample at different wire feed speed ratios. Different wire feeding speed ratios lead to variations in Ni concentration in the molten pool. The content of Ni might affect the formation of martensite and austenite during solidification. The average microhardness increases with increasing Ni wire feed speed. When the wire feeding ratio of Ni/Ti was 1.2, the compressive strength reached 1664 MPa. This study introduces an innovative method in arc additive manufacturing of NiTi alloy by utilizing an AC power source into the double filler wires.

Surface modification of magnesium alloys was performed using a coating process to optimize their performance. Friction stir processing for preparing magnesium-based high-entropy alloy coatings effectively addressed issues such as oxidation, pores, cracks, and poor coating quality found in existing processes. In addition, it substantially enhanced the hardness and wear resistance of magnesium alloys. The micro-structure and elemental distribution for the cross-section and surface for the magnesium-based high-entropy alloy coating had been studied. The impact of magnesium-based high-entropy alloy upon hardness and wear resistance of the magnesium alloy had been analyzed, focusing on its favorable forming and binding characteristics. Finally, the heat conduction process during friction stir processing were discussed in detail. The theoretical basis for the preparation of magnesium-based high entropy coatings was improved.

Cu/Ti dissimilar metal welding components have significant potential applications in aerospace, nuclear industries, and other fields. To achieve a robust connection between titanium (TA2) and copper (T2), this study conducted laser-welding experiments using nickel as an intermediate layer. The influence of a nickel intermediate layer on the joint formation, microstructure, mechanical properties, melting, and element diffusion behavior were investigated. The results revealed that without the addition of a nickel intermediate layer, when the laser beam was biased toward the titanium side during welding, a 17 μm thick layer of intermetallic compounds formed in the copper-side weld region. In this area, a notable concentration of fragile Ti–Cu intermetallic compounds forms, rendering it the weakest point in the joint. As a consequence, the ultimate tensile strength of the joint measures at 131 MPa, which is roughly 55 % of the tensile strength of the copper base material. The introduction of a nickel intermediate layer led to a change in the microstructure of the fusion zone, with Cu–Ti intermetallic compounds dispersed within, preventing the formation of brittle Ti–Cu phases at the copper interface. The addition of the nickel interlayer increased the tensile strength of the TA2-T2 joint to 224 MPa, which is approximately 94 % that of the copper parent material, and the joint exhibited ductile fracture behavior in the copper parent material's heat-affected zone.

Based on the experiment and first-principles calculation methods, the evolution of microstructure, mechanical properties and electrical conductivity of low-carbon steel were investigated at various annealing conditions. The results show that with the increase of annealing temperature, the morphology of ferrite matrix grain undergoes a transformation from narrow and long fibrous to, accompanied by the continuous growth in size. The strength of α-fibre texture is reduced continuously while the strength of γ-fibre texture increases evidently. The tensile and conductivity testing results indicate that with the increase of annealing temperature, both the yield strength and tensile strength of the steel decrease, while the elongation exhibits an opposite tendency due to the continuous growth of ferrite grains and dissolution of tertiary cementites. Additionally, the electrical conductivity increases because the reduction in the number of grain boundaries weakens their scattering ability to electronic waves. The first-principles calculation results indicate that with increasing distance to the interface, the segregation energy of Nb atom in ferrite matrix is reduced, as well as the interfacial energy of the structure is also decreased. The interface segregation preference of Nb atoms induces the transfer of charge, which is beneficial to enhance the conductivity of the ferrite matrix.

In the field of petroleum extraction, the welding technology of the core wire (the hybrid structure of copper and the Ni-Cr alloy) in high-power oilfield heaters is a key process that determines the efficiency of the heater. Using the tungsten inert gas (TIG) welding method of filling pure copper wire, this work effectively joins the dissimilar metals of red copper and the Cr20Ni80 nickel–chromium alloy. The microstructure, mechanical properties, and conductivity of the joint were analyzed. The results showed that the surface of the welded dissimilar metal joint was smooth and uniform; radiographic nondestructive testing did not reveal any macroscopic forming defects such as pores or cracks. The microstructure of the joint fusion zone exhibits an equiaxed grain morphology. The interface between the copper and the fusion zone displays a columnar grain structure, growing perpendicular to the fusion line. An interdiffusion layer of elements was formed at the interface between the Ni-Cr alloy and the fusion zone. The microhardness of the joint shows a stepwise decreasing trend, with the highest hardness on the nickel–chromium alloy side, followed by the fusion zone, and the lowest on the copper side. The joint fractures at the copper base material, with a tensile strength greater than 220 MPa, indicating a ductile fracture mode. During the electrical heating process, the joint temperature does not significantly increase compared to the copper side, demonstrating good thermal stability.

Abstract A three-dimensional numerical model based on the volume-of-fluid (VOF) method is typically preferred for studying high-current gas metal arc welding (GMAW) metal transfer mechanism and then controlling it. It is informed that the rotating spray transfer is extremely complicated, and some researchers have focused on simplified models without considering the energy conservation to make analysis manageable for the unstable metal transfer process. Using our created numerical model, the metal transfer of high-current GMAW with shielding gas of different conductivities has been studied by analyzing acting forces and fluid flows in the metal liquid column, especially for the contributions of the self-induced electromagnetic force, equivalent volume force of the capillary pressure of the surface tension (Named surface tension force in this work), static arc pressure. It is found that the unbalanced electromagnetic force greatly promotes the metal rotating motion in 500 A metal inert gas (MIG) welding with pure argon shielding gas and it pushes the metal liquid column to rotate. Considering the arc constricting effect in active shielding gas by simply changing the arc conductivity, it is found that the metal liquid column no longer rotates, it turns to swing since the unbalanced electromagnetic force is large enough to break the rotating motion. The calculated results of the metal liquid column deflected angle and rotating/swing frequency agree well with the experiment of high-speed camera observations.

A novel controller, employing a variable-structure single-neuron adaptive PSD (proportional integral derivative) approach, was proposed for regulating the deposition width variation in the Directed Energy Deposition-Arc (DED-Arc) layer. During experimental trials, the deposition speed was chosen as the manipulated variable, while the width of the deposition layer served as the measured parameter. To facilitate controller design, a vision sensor was custom-designed to accurately detect the width of the deposition layer. The captured image of the deposition layer’s dimensions enabled the precise determination of the deposited thickness, forming the basis for subsequent controller development. In performance assessments, deliberate interference was intentionally introduced into the deposition current, deposition layer height, and the targeted deposition layer width. The assessment involved the controlled deposition of ten-layer components, focusing on width regulation for each deposition layer. The results demonstrate that the proposed controller significantly enhances the deposition process stability, particularly within a range of desired deposition widths from 7.5 mm to 8.3 mm.

In this paper, the partially crystallized Zr70Cu13.5Ni8.5Al8 bulk metallic glasses (BMGs) were prepared, and their superplastic deformation ability in the supercooled liquid region was studied via compression over a wide range of strain rates from 5 × 10−4 s−1 to 1 × 10−2 s−1. It has been found that the superplastic deformation behavior of the BMGs is strongly dependent on the strain rate and temperature. The flow behavior of the BMGs transformed from Newtonian fluid to non-Newtonian fluid with the increase in the strain rate and the decrease in temperature. Based on the high-temperature compression results, a thermalplastic forming map was constructed, and the optimal superplastic forming parameters were obtained. Then, gears were successfully extruded using part of the optimal thermal processing parameters. Further studies showed that high-temperature extrusion induced the crystallization of the BMGs, which increased the microhardness of the gears.

The interdiffusion and atomic structure of the interface between metallic glass Cu50Zr50 and crystalline Cu were investigated using molecular dynamics simulations. We show that the interdiffusion of atoms at the amorphous/crystalline interface is mainly manifested as the diffusion of crystalline Cu atoms into amorphous atoms, and only a very small amount of amorphous atoms diffuse into crystalline Cu. And the temperature and diffusion time are proportional to the thickness of the diffusion layer. The H-A bond index and Voronoi polyhedron distribution method were used to analyze the structure type and cluster distribution of the interface atoms. the results show that the diffusion will cause the amorphization of the atoms on the crystal side of the interface, and the higher the temperature and the longer the diffusion time, the higher the degree of amorphization of the interface atoms. And the size of the amorphized region is related to the temperature, and the dividing plane between the amorphized atoms and the crystal atoms gradually moves to the crystal side with the increase of temperature. In addition, the diffusion behavior of atoms at the amorphous/crystal interface with different crystal orientations exhibits anisotropy, and some atoms at the interface between the 〈110〉 oriented crystal and amorphous are transformed from FCC structure to HCP structure during the diffusion process.

Amorphous alloys show interesting mechanical properties as well as unique physical and chemical properties due to their atomic stacking structure. However, when partial crystallization occurs in amorphous alloys, it can impact the properties of the original amorphous alloy. To study the crystallization phenomenon in the Zr-based amorphous alloy, a three-dimensional Zr-based amorphous alloy atomic-stacking model was established by molecular dynamics simulations, and the atomic structure evolution of the Zr-Cu amorphous system after partial crystallization was analyzed by the radial distribution function g(r), HA bond index and Voronoi polyhedron. The results showed that adding more copper (Cu) atoms to the Zr-Cu amorphous system greatly improves its stability at high temperatures. The atomic diffusion was analyzed by root-mean-square displacement of atoms (MSD); as the temperature rose, the MSD of atoms also increased, suggesting that the crystallization of the amorphous material occurs due to the short-range diffusion of atoms. The analysis of the mechanism of the high-temperature action time on the Zr80Cu20 amorphous alloy showed that the crystallization phase precipitation rate of the amorphous alloy gradually increases with time, but it does not change linearly.

Abstract Researchers have recently attempted to monitor pool oscillations using the three-dimensional laser vision method. However, the deficiency of simulation software will result in significant capital expenditure. Both simulations and experiments are performed in this study, and the Bessel equation is used to analyze the oscillation mode of a weld pool. The laser dot matrix images of (0, 1), (1, 1), (2, 1), and (0, 2) oscillation modes at different times are obtained via structured laser optical measurement simulation. The oscillation mode of a stationary gas tungsten arc weld pool is analyzed based on laser dot matrix images obtained from a structure laser experiment. Results show that the simulated laser dot matrix images are consistent with the experiment results. The oscillation mode of the weld pool can be recognized based on the laser dot matrix image. This study not only provides conditions for assessing the penetrating state of a weld pool, but also enable a further understanding of the oscillation mode of a weld pool and the development of more effective observation methods and measurement tools to effectively control and improve welding quality.

Background and Objective: The guidelines on the factors to determine whether a patient with concomitant stroke and hip fracture is a good candidate for surgical hip repair are still debatable. This study was carried out to investigate the relationship between the management of acute hip fracture and the recovery of neurological function and prognosis in patients with concomitant acute cerebral infarction. Methods: Thirty patients with acute cerebral infarction combined with acute hip fracture, who were hospitalized and did not accept surgical treatment, and matched 60 cases as control group having acute cerebral infarction without hip fracture admitted in the same period were selected. The neurological function recovery, hospitalization period, 6 months recovery rate, frequency of complications, and 1 year mortality rate between the groups were compared. Results: Compared with common acute cerebral infarction patients, the NIH Stroke Scale/Score of acute cerebral infarction group with hip fracture was higher (7.2 ± 5.4 vs. 5.6 ± 4.3, p = 0.034). The hospitalization period was prolonged (16.1 ± 8.9 vs. 12.2 ± 5.3, p = 0.041), and 6 months recovery rate was lower (26.7% vs. 53.3%, p = 0.016), the frequency of pulmonary infection and lower extremity deep vein thrombosis was higher (30% vs. 11.7%, p = 0.03; 6.7% vs. 0, p = 0.043). The 1-year mortality rate in patients with combined hip fracture was higher than in patients with cerebral infarction only. Conclusion: Acute cerebral infarction combined with hip fracture lead to worse neurological recovery, prolonged hospitalization period, increased complications, decreased patient prognosis, and increased 1 year mortality. Surgical treatment of hip fracture with concomitant acute cerebral infarction may improve the prognosis of patients. According to the statistics of neurological function and mortality after 1 year of follow-up, the prognosis of patients with Modified Rankin Scale below 3 was considered good.

Abstract Wire arc additive manufacturing (WAAM) has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost. However, in the process of automatically manufacturing the high-quality metal parts by WAAM, several problems about the heat build-up, the deposit-path optimization, and the stability of the process parameters need to be well addressed. To overcome these issues, a new WAAM method based on the double electrode micro plasma arc welding (DE-MPAW) was designed. The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically. The effects between the parameters, wire feed rate and torch stand-off distance, in the process of WAAM were investigated experimentally. In addition, a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance. Finally, a series of tests were performed to evaluate the control system’s performance. The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system. Further, the deposition paths about the metal part’s layer heights in WAAM are simplified. Finally, the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.

Using wire arc additive manufacturing (WAAM), an alternating current (AC)-assisted WAAM method was proposed to fabricate a Titanium alloy functionally gradient material. The AC was added at the Ti6Al4V filling wire to regulate the microstructure variation from bottom to top during the deposition process. In this study, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to analyze the microstructure change. Transmission electron microscopy (TEM) was used to study the micro-mechanism. The mechanical performance was tested by Vickers hardness and tensile experiments. Results were obtained for the microstructures of different deposition layers with gradient changes. The results showed that β-lath accumulated around the dislocations, which were hindered by the β phase. Grain size and grain character distributions were remarkably different as the AC increased. The maximum hardness was 480 HV when the value of AC was 20 A, and the highest elongation of the deposited layer was 10.22% with a strength of 650.2 MPa when the AC value was 30 A. The effect of the magnetic field generated by the AC on the flow behavior of the molten pool, the gradual change in microstructure, and the solidification behavior of the molten pool are also discussed.

The formation of intermetallic compounds (IMC) at the Al/Fe interface determined the mechanical property of steel-aluminum welded joint. To understand the interfacial microstructure evolution and relate diffusion mechanism of atoms cross the Al/Fe interface, the effect of welding parameters on the interfacial IMC was studied, and the molecular dynamics method (MD) was used to simulate the diffusion process of Al and Fe atoms. Four temperatures (950 K, 1000 K, 1050 K, and 1100 K) were selected in the simulation model. The interfacial IMC are distributed in a laminar pattern, and their physical phases are mainly composed of Fe2Al5, controlling the Al/Fe atomic ratio of 5:2 in the IMC configuration, the Embedded Atom Method (EAM) potential is used to describe the interactions between Al and Fe atoms. In the Al-Fe system IMC conformation, the mean square displacement and diffusion (MSD) coefficient of Al atoms at different temperatures were small, and the main diffusion path is the Al atoms across the IMC conformation into the Fe crystal structure. The diffusion in the IMC conformation was mainly along the direction perpendicular to the interface. The diffusion mechanisms were mainly vacancy diffusion and interstitial diffusion mechanisms.

Twin-wire and arc additive manufacturing (T-WAAM) has potential advantages in improving deposition efficiency and manufacturing functionally graded materials (FGMs), thus attracting much attention. However, there are few studies on the droplet transfer mode of T-WAAM. This paper analyzes the droplet transfer mode and arc swing in the “TIG + AC” twin-wire cross-arc additive manufacturing by in-situ observation with high-speed photography, revealing what factors influence the T-WAAM on deposition shaping the quality and what are the key mechanisms for process stability. Experiments show that with the main arc current provided by TIG 100 A and the twin-wire AC arc current 10 A, three different droplet transfer modes, namely the “free transfer + free transfer, bridge transfer + free transfer, bridge transfer + bridge transfer,” can be observed with the twin wires under different feeding speeds. The corresponding deposition and arc swing are quite different in quality. Through comparative analysis, it is found that the frequent extinguishment and ignition of the arc between electrode wires is the main factor for the instability in the additive manufacturing process. The “bridge transfer + free transfer” mode can obtain a large arc swing angle and a stable deposition, in which the cross arc has a significant stirring effect on the molten pool, and the deposition shape is well-made.

As a high-efficiency and high-quality welding technology, laser-tungsten inert gas (laser–TIG) hybrid welding has been widely used in the aerospace and marine equipment industries. Through laser–TIG hybrid welding of TC4 titanium alloy, the effect of the current on the weld formation, the microstructure and mechanical properties of the arc zone, and the laser zone was studied. The results show that the molten pool in the arc zone will flow periodically, and the flow becomes more intense with an increase in the current, which will result in a finer grain size in the arc zone than in the laser zone, having the effect of eliminating pores. The spacing of the α′ martensite beams in the laser zone is narrower, with an average spacing of 0.41 μm. The β phase increases gradually with the increase in the current, which will lead to a downward trend in the average hardness of both zones. The average hardness value of the laser zone, containing more α′ martensite and less β phase, is slightly higher than that of the arc zone. The hardness uniformity of the laser zone is also significantly better than that of the arc zone. The tensile strength of the joint shows a trend of increasing first and then decreasing, and the joint with I = 50 A presented the highest tensile strength of 957.3 MPa, approaching 100% of the base metal, and fractured in the fusion zone.

Background/Aims: This study focused on evaluating the effect of MALAT1 and MDM2 on ischemic stroke through regulation of the p53 signaling pathway. Materials: Bioinformatics analysis was performed to identify abnormally expressed lncRNAs, mRNAs and their associated pathways. Oxygen-glucose deprivation/reoxygenation (OGD/R) in cells and middle cerebral artery occlusion/reperfusion (MCAO/R) in mice were performed to simulate an ischemic stroke environment. Western blot and qRT-PCR were used to examine lncRNA expression and mRNA levels. Fluorescence in situ hybridization (FISH) LncRNA was used to locate mRNA. MTT and flow cytometry were performed to examine cell proliferation and apoptosis. Finally, immunohistochemistry was used to observe the expression of genes in vivo. Results: MALAT1 and MDM2, which exhibit strong expression in stroke tissues, were subjected to bioinformatics analysis, and the p53 pathway was chosen for further study. MALAT1, MDM2 and p53 signaling pathway-related proteins were all up regulated in OGD/R cells. Furthermore, Malat1, Mdm2 and p53 pathway related-proteins were also up regulated in MCAO/R mice. Both MALAT1 and MDM2 were localized in the nuclei. Down regulation of MALAT1 and MDM2 enhanced cell proliferation ability and reduced apoptosis, resulting in decreased infarct size in MCAO/R brains. Conclusion: These results indicate that MALAT1/MDM2/p53 signaling pathway axis may provide more effective clinical therapeutic strategy for patients with ischemic stroke.

Abstract We used pulsed laser beam welding method to join Pd43Cu27Ni10P20 (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high ductility in bending which is accomplished through the operation of multiple shear bands. Our results reveal that pulsed laser beam welding under appropriate processing parameters provides a practical viable method to join bulk metallic glasses.

Using laser beam as main heat source, and trailing arc as an assisted role, aluminum alloy was joined to galvanized steel in a butt configuration. Under suitable welding parameters, a sound welding seam was obtained. The interface intermetallic compounds layer and wetting behavior of weld joint were studied. The assisted arc can improve the wetting and spreading ability of weld pool duo to large temperature field. There are two different types of IMCs: near to the steel side one is Fe2Al5 with tooth-like shape and near to the weld seam side is the other one Fe4Al13 with flocculent-like shape. The highest tensile strength can reach 163 MPa when the fracture occurred at the weld seam.

The objective of the present study was to investigate the effects of 3-n-butylphthalide (NBP) on a 1-methyl-4-phenylpyridinium (MPP+)-induced cellular model of Parkinson’s disease (PD) and to illustrate the potential mechanism of autophagy in this process. For this purpose, rat PC12 pheochromocytoma cells were treated with MPP+ (1 mM) for 24 h following pretreatment with NBP (0.1 mM). Cell metabolic viability was determined by the MTT assay and cell ultrastructure was examined by transmission electron microscopy. The intracellular distribution and expression of α-synuclein and microtubule-associated protein light chain 3 (LC3) were detected by immunocytochemistry and Western blotting. Our results demonstrated that: 1) NBP prevented MPP+-induced cytotoxicity in PC12 cells by promoting metabolic viability. 2) NBP induced the accumulation of autophagosomes in MPP+-treated PC12 cells. 3) Further study of the molecular mechanism demonstrated that NBP enhanced the colocalization of α-synuclein and LC3 and up-regulated the protein level of LC3-II. These results demonstrate that NBP protects PC12 cells against MPP+-induced neurotoxicity by activating autophagy-mediated α-synuclein degradation, implying that it may be a potential effective therapeutic agent for the treatment of PD.

The present study was designed to evaluate the effects of Prunella Vulgaris (P. vulgaris) on the immune function in mice. The mice were randomly divided into one control group and three treatment groups of 10 mice each. The control group received pure water and the treatment groups received P. vulgaris extract at concentrations of 0.15, 0.30 and 0.90 g/kg BW orally for 30 days, respectively. Changes in cell immune function, non-specific immunity and humoral immunity function were evaluated. Active lymphocytes and T lymphocyte subsets were determined by fluorescence-activated cell sorting (FACS). Certain Serum concentrations of cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The results showed that, for cell immune function, compared with the control group, foot pad thickness in high dose group increased significantly (p0.05). For non-specific immunity, NK cell activity increased significantly in a dose-dependent manner in P. vulgaris treated mice (p0.05). The percentage of active T and Th lymphocytes of mice peripheral blood in high dose group were significantly higher than that of the control group (p0.05). The data indicated that 0.90 g/kg BW P. vulgaris extract (equivalent to 7.5 g/kg BW crude drug) had some effect on cellular immune function and non-specific immune function in mice.