In this study, a hybrid wire arc additive manufacturing (HWAAM) process that combines low-frequency vibration with cold metal transfer (CMT) arc is proposed to address the problems of porosity, coarse grains, and low mechanical performance encountered in WAAM aluminum alloys. The effects of different vibration frequencies on the microstructure and mechanical properties were investigated. The results indicated that as the vibration frequency increases, the grain size refinement reaches a maximum of 19.1% compared with the non-vibrated specimen. Vibration can enhance the fluidity and the cooling rate of the weld pool. The fatigue fracture of dendrite arms is the main mechanism of microstructure grain refinement caused by vibration. The dynamic bending stress induced by vibration on the dendrite arms and the root remelting phenomenon are the dominant factors for the dendrite fragmentation. Increasing the vibration frequency did not result in an obvious improvement in the tensile strength of the specimens, but did significantly increase the elongation. With the increase in vibration frequency, the maximum transverse and longitudinal elongation reached 22.2% and 23.5% respectively, a raise of 15.6% and 38.2% compared with non-vibrated specimen. Vibration reduced the size and distribution density of pores on the fracture surface, and increased the dimpled microstructure, improving the mechanical performance of the aluminum alloy. 

Mechanical properties and microstructure revolution of vibration assisted wire arc additive manufacturing 2319 aluminum alloy

The flexibility of Additive Manufacturing (AM) technologies in the metal 3D printing process has gained significant attention in research and industry, which allows for fabricating complicated and intricate Near-Net-Shape (NNS) geometry designs. The achievement of desired characteristics in Wire-Arc Additive Manufactured (WAAM) components is primarily contingent upon the careful selection and precise control of significant processing variables, including bead deposition strategy, wire materials, type of heat source, wire feed speed, and the application of shielding gas. As a result, optimizing these most significant process parameters has improved, producing higher-quality WAAM-manufactured components. Consequently, this has contributed to the overall rise in the method's popularity and many applications. This article aims to provide an overview of the wire deposition strategy and the optimization of process parameters in WAAM. The optimization of numerous wire deposition techniques and process parameters in the WAAM method, which is required to manufacture high-quality additively manufactured metal parts, is summarised. The WAAM optimization algorithm, in addition to anticipate technological developments, has been proposed. Subsequently, a discussion ensues regarding the potential for WAAM optimization within the swiftly growing domain of WAAM. In the end, conclusions have been derived from the reviewed research work. 

Integrated approach to Wire Arc Additive Manufacturing (WAAM) optimization: Harnessing the synergy of process parameters and deposition strategies

Synchronous-hammer-forging-assisted wire arc additive manufacturing Al-Mg alloyss

Inceptive studies were done on using Rotational/Spin arc technique for Wire Arc Additive Manufacturing (WAAM). A wall of low alloy steel was build and the effect of rotating the arc on the mechanical properties and the microstructural properties were studied. Tensile testing conducted across multiple directions shows an average tensile strength of 550 MPa which is comparatively higher by approximately 90 MPa than other stationary arc techniques used to fabricate the same material, however with lesser percentage elongation. Microhardness testing revealed that the average hardness of the build to be 156 HV0.5. Microstructural studies revealed reduction in grain sizes and random grain orientation; with the misorientation and rotation angle plots exhibiting the presence of High Angle Grain Boundaries (HAGB's), which could be attributed as the primary factors for the improvement in the tensile properties. 

Effect of arc rotation on the enhancement of mechanical properties of ER70S6 in WAAM

Wire and arc additive manufacturing (WAAM) has been developed to be a highly efficient technique for making large Ti-alloy products. However, the deposition of metal by this method causes coarse texture, which limits its application. To address this, the study utilizes a wire and pulsed arc additive manufacturing (WPAAM) process for making TA15 alloy. Compared with the WAAM method, this WPAAM method inducts several current/voltage-impulse cycles under different pulse frequencies, which makes grains tiny and improves tensile strength. The study then uses a VOF model to discuss the effect of impulse cycles on the solidification process. The findings suggested that the impulse cycles deform the molten pool and influence the vibration in the solid/liquid interface. This makes the coarse columnar grains tiny and forms diminutive α laths. This paper further discusses the correlation between the microstructure and the mechanical properties. The results show that the CBGs and the α laths play a joint contribution to yield strength in the WAAMed TA15 alloy. This study provides a reference for optimizing the microstructure of WAAM titanium alloys by adjusting pulse frequencies and provides a theoretical basis for strengthening WAAMed Ti-alloy. 

Correlation between Pulse frequencies, Microstructure and Mechanical Properties of TA15 in Wire and arc additive manufacturing

In order to investigate the effect of arc characteristic on the mechanical properties of 5A56 Al alloy in wire arc additive manufacturing (WAAM), three different arc processes: CMT, CMT-VP and CMT-P arc were used for the additive manufacturing experiments in 5A56 respectively. The real-time waveforms of current and voltage and the high-speed dynamic droplet transfer arc images were captured by a high-speed camera and synchronous data acquisition system, and the microstructure and mechanical properties were investigated. The experiment results show that the arc characteristics have an effect on the arc behavior, droplet transfer and heat input on the layer, the CMT-VP process with a higher deposition rate without increased in heat input has better thermal management ability, and the as-deposited specimen were well formed with less surface waviness and the maximum layer height of 2.40 mm. The microstructure of CMT-VP specimen is composed of more fine and even equiaxed grains, and the mechanical properties are better than CMT and CMT-P process, where the micro-hardness reached in 86.01HV, and the maximum UTS was 344.68 MPa. The anisotropic percentage of UTS was the smallest, only 5.82%. The anisotropy of tensile property can be blamed for the existence of pores near the boundary between the inter-layer and the inner-layer region and the discontinuity of microstructure distribution. 

Investigate the effect of arc characteristic on the mechanical properties of 5A56 Al alloy in CMT arc additive manufacturing

Sugarcane (Saccharum officinarum L.) may be infected with Apiospora, which can produce the toxin 3-nitropropionic acid (3-NPA) during improper transportation and storage. The consumption of sugarcane that contains 3-NPA can lead to food poisoning. Therefore, this study sought to explore a novel biocontrol agent to prevent and control Apiospora mold. Bacteria were isolated from the soil of healthy sugarcane and identified as Bacillus velezensis T9 through colony morphological, physiological and biochemical characterization and molecular identification. The inhibitory effect of B. velezensis T9 on Apiospora mold on sugarcane was analyzed. Assays of the cell suspension of strain T9 and its cell-free supernatant showed that T9 had significant in vitro antifungal activities against Apiospora arundinis and thus, would be a likely antagonist. Scanning electron microscopy and transmission electron microscopy showed that treatment with T9 significantly distorted the A. arundinis mycelia, perforated the membrane, contracted the vesicles, and decomposed most organelles into irregular fragments. A re-isolation experiment demonstrates the ability of T9 to colonize the sugarcane stems and survive in them. This strain can produce volatile organic compounds (VOCs) that are remarkably strong inhibitors, and it can also form biofilms. Additionally, the cell-free supernatant significantly reduced the ability of A. arundinis to produce 3-NPA and completely inhibited its production at 10%. Therefore, strain T9 is effective at controlling A. arundinis and has the potential for further development as a fungal prevention agent for agricultural products.

Biocontrol ability of Bacillus velezensis T9 against Apiospora arundinis causing Apiospora mold on sugarcane

Green Synthesis of Iron Nanoparticles-Modified Biochar For Efficient Adsorption of Cd(II) From Aqueous Solution

AIMS
This study aimed to investigate the inhibitory effect of tannic acid (TA) on the growth of Apiospora arundinis and 3-Nitropropionic acid (3-NPA) production.


METHODS AND RESULTS
To investigate the antifungal mechanism, the effects of TA on the hypha growth, electrical conductivity, hypha morphology, defence-related enzymes and 3-NPA production of A. arundinis were studied. TA concentrations of 640 and 1280 μg⋅mL-1 exhibited strong antifungal activity against A. arundinis. The results of SEM and TEM showed that the hypha of the A. arundinis was severely deformed after TA treatment, and the cell membrane was blurred and thin, vacuoles were obviously shrunken and smaller, and most of the organelles were decomposed into irregular fragments. The increased of electrical conductivity and MDA content indicated that TA caused peroxidation of unsaturated fatty acids and damaged the structure of the cell membrane. The decrease of intracellular ATP and SDH content indicated that TA damaged the function of mitochondria, participated in the inhibition of respiratory metabolism. In addition, TA significantly reduced 3-NPA production, and completely inhibited 3-NPA production at 640 and 1280 μg⋅mL-1.


CONCLUSION
TA effectively inhibited both growth of A. arundinis in vitro and 3-NPA production.

Inhibitory effect of tannic acid on the growth of Apiospora arundinis and 3-Nitropropionic acid production.

In this study, a new biosorbent was prepared from sugarcane bagasse and polyethylenimine (MSCP). The effects of preparation parameters, including the polyethylenimine (PEI) concentration, the glutaraldehyde concentration, the reaction temperature, and ball milling time on the adsorption property of MSCP were studied. The optimum preparation conditions were as follows: the PEI concentration was 20%, the glutaraldehyde concentration was 2.0%, the reaction temperature was 318.15 K, and the ball milling time was 20 min. Under the optimum preparation conditions, the removal efficiency of Cu 2+ by MSCP was reached 93.3%. The physical and chemical properties of MSCP were determined by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and elemental analysis. The SEM micrographs revealed that surface morphol- ogy of MSCP was rough, with many irregular folds and small particles. The FTIR and elemental analysis results indicated PEI was successfully grafted to the surface of sugarcane bagasse cellulose (SC) with glutaraldehyde as a bridge and the adsorption mechanism of heavy metals by MSCP can be regarded as the complexation between heavy metals and –NH 2 groups of MSCP. Langmuir model showed the best fitting to the isotherm equilibrium data, the maximum adsorption capacities for Cu 2+ , Pb 2+ and Zn 2+ were 114.02, 165.56 and 95.79 mg/g, respectively. The adsorption experimental data were fitted well by pseudo-second-order. In multi-solute system, the competitive adsorption ability of heavy metals by MSCP followed the order of Pb 2+ > Cu 2+ > Zn 2+ .

/pdf/synthesis-of-polyethylenimine-modified-sugarcane-bagasse-1b588bax.pdf

Synthesis of polyethylenimine modified sugarcane bagasse cellulose and its competitive adsorption of Pb2+, Cu2+ and Zn2+ from aqueous solutions

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