Surface Mechanical Properties Research Articles

Оценка качества и механических свойств получаемых слоев металла из низкоуглеродистой стали методом WAAM с использованием дополнительной механической и ультразвуковой обработки

Introduction. Additive manufacturing is a technology that enables three-dimensional (3D) components to be printed layer by layer according to digital models. Completely different from traditional manufacturing methods such as casting, forging, and machining, additive manufacturing is a near net shape manufacturing process that can greatly enhance design freedom and reduce manufacturing runtime. The material processing challenges in Wire and Arc Additive Manufacturing (WAAM) are related to achieving performance metrics related to geometric, physical, and material properties. Tight tolerances and stringent surface integrity requirements cannot be achieved by utilizing stand-alone AM technologies. Therefore, WAAM parts typically require some post-processing to meet requirements related to surface finish, dimensional tolerances and mechanical properties. It is therefore not surprising that the integration of AM with post-processing technologies into single and multi-setup machining solutions, commonly referred to as hybrid AM, has become a very attractive proposition for industry. The purpose of the work is to evaluate the quality and mechanical properties of the resulting metal layers of mild steel by WAAM method using additional mechanical and ultrasonic processing. Research Methods. To conduct the experiments, a set of welding equipment was used — a single-phase inverter device KEMPPI Kempomat 1701, designed for welding with wire in shielding gases. A mixture of argon and carbon dioxide (80 % argon and 20 % CO2) was used as a shielding gas. SV-08G2S (0.8 C-2 Mg-Si) wire was used as the surfacing material. A plate made of steel St3 with overall dimensions 150×100×5 mm was used as a base for surfacing. The surface of the plate before surfacing was thoroughly cleaned from the layer of oxides, oil, rust and other contaminants. For this purpose mechanical cleaning of the surface was used with BOSCH abrasive wheel with a diameter of 125 mm diameter and a grit size of 120. Before surfacing the surface of the product was degreased with white spirit. The gas flow rate was set at 8 dm3/min. To select the optimal wire feed rate and volt-ampere characteristic, surfacing was performed at each adjustment step of wire feed rate, and voltage. Mechanical statistical tensile tests, chemical composition analysis and metallographic studies were also performed. Results and Discussion. Gas porosity is a typical defect that occurs during the WAAM process and should be eliminated because it adversely affects the mechanical properties. Initially, gas porosity leads to a reduction in the mechanical strength of the part due to damage from microcrack formation. In addition, it often causes the surfaced layer to have worse fatigue properties due to the spatial distribution of different shape and size structures. In our experiments we found that a wire feed speed range of 5–6 m/min is optimal. Increasing the flow rate of shielding gas in the range of 8–14 l/min allows reducing porosity in the surfaced metal to almost zero. The mechanical properties of the surfaced beads show that the average value of yield strength after machining is higher than that of unprocessed specimens. The data obtained from these experiments are in good agreement with those reported in the literature. The presented results can be used in real WAAM technological processes.

Optimal Strategies for Filament Orientation in Non-Planar 3D Printing

The structural integrity and surface quality of parts produced using traditional fused deposition modeling depend on factors such as layer height, filament and build orientation, print speed, nozzle temperature, and, crucially for this study, both planar and non-planar slicing. Recent research on non-planar slicing techniques has shown significant improvements in surface smoothness and mechanical properties. Key approaches include non-planar slicing for 3-axis printers, adaptive slicing to optimize material placement in critical areas, and post-processing. However, current studies lack a comprehensive method for parameterizing filament direction across both planar and non-planar layers. This work presents an approach to generate optimal trajectories for planar and non-planar layers using contours derived from level set functions. The methodology demonstrates the advantages of non-planar printing, particularly with a filament orientation of 30° for inclined surfaces, ensuring better surface quality, uniformity, and structural integrity. This emphasizes the importance of trajectory planning and filament orientation in achieving high-quality prints on inclined geometries. This research highlights the necessity of a methodology that tailors filament paths based on the load-bearing requirements of each part, demonstrating its potential to enhance surface quality and structural performance, and further the advancement of the 3D printing industry.

Scalable Nickel Catalysts for Carbonylative Terpolymerization of Ethylene/α-Olefin with High Efficiency.

The carbonylative polymerization of olefin yields aliphatic polyketones, which are used as engineering plastics in the market due to their excellent mechanical strength, chemical resistance, and surface and barrier properties. However, the usage of precious palladium catalysts has restricted their extensive application as commodity materials. Herein, we present a series of phosphine-sulfonate Ni catalysts with a wide spectrum of electronic and steric substituents on the phosphorus moiety for the carbonylative polymerization of ethylene. Such efficient nickel-catalyzed copolymerization shows the on-demand transformation of ethylene/CO gas to polyketones with quantitative yield and product specificity. A remarkable productivity of up to 20 kg PK (g Ni)-1 was obtained during ethylene/propylene/CO terpolymerization, and the polymerization productivity is independent of the type and feeding amount of α-olefin. The resulting terpolymers show comparable crystallinity, thermal stability, and tensile properties with commercial POKETONE products from Hyosung. The nickel catalyst also features the advantages of using cheap raw material sources and simple synthetic procedures that can be scaled up easily, which enables it to be a promising candidate for industrial application.

Effect of vacuum heat treatment temperature on anti-corrosion and conductivity properties of C/TiC nanocomposite coated titanium foil for PEMFC bipolar plates

In this work, a C/TiC nanocomposite coating was prepared on titanium foil using a combination of magnetron sputtering and heat treatment technology to improve the corrosion resistance and conductivity of bipolar plates. The effect of heat treatment temperature on surface morphology, chemical composition, mechanical property, hydrophobicity, corrosion resistance and conductivity of coated samples was investigated. The results indicate that the roughness of the coating increase with heat-treated temperature and the corrosion current density (icorr) firstly decreases and then increases in 0.5 M H2SO4 solution containing 5 ppm HF at 80 ℃, reducing its smallest value at 700 ℃ (1.28 μA cm−2), which is declined by 3 orders of magnitude compared to the substrate (562.90 μA cm−2). After potentiostatic polarization experiment (PP) for 12 h, the polarization current density (ipp) of the coatings firstly reduces and then increases, with values of 1.48, 0.70, 0.36, 0.41, 1.32 and 1.35 μA cm−2 corresponding to the substrate and coated samples, respectively. Furthermore, the interface contact resistance (ICR) of coated samples firstly decreases and then increase with temperature rising, which are less than 10 mΩ cm2. After 12 h PP tests, the ICR increase, with values of 18.42, 26.28, 13.64, 10.26 and 11.56 mΩ cm2 corresponding to RT, 600 700 800 and 900 ℃, respectively. The water contact angle of the coated sample for 600 and 700 ℃ are higher than that of other samples and they reached 87.6°and 85.3°, exhibiting a good hydrophobicity.

Surface mechanical property and residual stress stability of nanostructured CNT/Al-Cu-Mg composites induced by shot peening

Shot peening (SP) is recognized for its capacity to enhance surface strength and induce compressive residual stresses (CRS). Nevertheless, quantifying the mechanical property improvements in thin shot peened layers remains challenging with traditional methods. In this study, CNT/Al-Cu-Mg composites were subjected to shot peening. The microstructure evolution of the peened layers along the layer depth direction was investigated by XRD and TEM. Meanwhile, the changes in the mechanical properties of the shot peened layers and the release rules of CRS during tensile cycling at different numbers loads were measured by an in-situ X-ray stress analyzer and a micro-tensile device in conjunction with the Von Mises stress criterion. The results showed that SP generated the nano-gradient deformation layer with nanograins size of 50–100 nm near the surface. The yield strength of the surface layer was increased from 352 MPa before SP to 435 MPa, an increase of 23.6 %. Moreover, the observation of fracture morphology indicated that SP reduced the material plasticit moderately and the agglomeration of the Al2Cu. In addition, in the case of a certain CRS on the initial surface, the relaxation of CRS was correlated with the magnitude of applied loads and the number of cycles and couldn't occur when the applied loads is below a specific value.

Enhancing the Surface Mechanical Properties of AL2618 Alloy Turbochargers Using a PLD Device with AI2O3

Abstract Pulsed laser deposition (PLD) has become a widespread technology for the fabrication of multicomponent thin films Material. In this research, the Microstructure phase, composition and effect of paint made from A nanomaterial (Alfa- Al2O3) were study, A Pulsed laser deposition used in order to improving mechanical performance of aluminum alloy (AL-2618) of turbocharger blades, The main advantages of using it in the manufacture of turbocharger blades to reduce corrosion and erosion, and to ensure high hardness and long-life fatigue, The Pulsed laser deposition used for turbocharger blade, to deposit a layer of aluminum dioxide (10 m) on the surface of the aluminum alloy. The mechanical properties of the blade improved where the hardness of the samples examined and conducted an (EDX) test before and after the deposition process. It was found that after depositing a Nano-layer of aluminum dioxide (Al2O3), the hardness increased and the corrosion and erosion were reduced.

Enhancing anti-icing efficacy in hybrid polyurethane coatings: Evaluating the significance of molecular weight, chemical structure, and content of PEG/PDMS

This study investigates the advantages of adding polydimethyl siloxane/polyethylene glycol (PEG/PDMS) copolymers to polyurethane coatings, with a particular focus on optimizing anti-icing efficacy. A range of characterization techniques are applied, including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) analysis, surface roughness measurements, wettability analysis, tensile testing, and ice adhesion measurements, to elucidate the intricate relationships between copolymer molecular weight, chemical structure, and content and their collective effect on the anti-icing properties of the developed coatings. Tailored PEG/PDMS copolymers significantly reduce ice nucleation temperatures and enhance the anti-icing properties of polyurethane coatings. Adding PEG/PDMS copolymers to polyurethane alters the surface roughness, wettability, and mechanical properties of the coatings to improve anti-icing performance. The presence of copolymers decreases ice adhesion strength (<50 kPa), attributed to the formation of a quasi-liquid layer that acts as a lubricant between the ice and the coatings, and delays ice formation. Furthermore, the enhanced durability of copolymer-containing coatings ensures a long-lasting anti-icing effect after multiple icing/de-icing cycles, although some degradation was observed over time. The tailored PEG/PDMS copolymers demonstrate potential for maximizing the anti-icing properties of polyurethane coatings and advancing anti-icing technologies.

Fabrication of micro holes with confined pitting corrosion by laser and electrochemical machining: pitting corrosion formation mechanisms and protection method

Laser and electrochemical hybrid machining (LECM) combines the advantages of high efficiency of laser processing and high surface quality of electrochemical machining and has been employed to process deep micro holes with high surface quality, high precision, and efficiency. However, surface pitting corrosion occurs around the entrance of the micro holes drilled by LECM, which deteriorates their surface quality and mechanical properties. This study revealed the mechanism of surface pitting corrosion formation mechanisms during LECM by characterizing surface micromorphology, chemical composition, microstructures, and surface stress. The difference between surface pitting corrosion area during LECM and the stray current corrosion during electrochemical machining was studied. Micro solid metal particles and inner microcavities were observed in micro pits. The depth of the micro pits was greater than that obtained using electrochemical machining. It has been concluded that in LECM, the surface pitting corrosion occurred owing to the enhanced stray current corrosion and the accumulation of solidified melt particles and cavitation microbubbles in the micro pits. Coaxial gas-assisted LECM was also proposed to restrict the surface pitting corrosion area. Experiments and simulations were conducted to verify the feasibility of minimizing the corrosion area using coaxial gas. The surface pitting corrosion area has been decreased by 85.1% at a coaxial gas pressure of 0.1MPa compared with that without coaxial gas assistance. Finally, the radial cooling holes with a diameter of 1.2mm and an aspect ratio of 125:1 in turbine blades with high surface quality were fabricated. This study provides a promising method to fabricate high-aspect-ratio micro-holes with high surface quality and high efficiency.

Advances in constructing Carbon Fiber‐MXene multilevel structures to reinforce interfacial properties of carbon fiber reinforced polymer composites

AbstractCarbon fiber reinforced polymers (CFRPs) have received widespread attention due to their excellent mechanical properties. However, the poor interfacial properties between CF and resin matrix urgently need feasible and efficient surface modification strategies of CF to regulate the interface. Due to its unique layered structure and abundant surface groups, MXene has been increasingly used in the field of CFRP interfacial modification in recent years. It possesses the advantages of good stability, large specific surface area, abundant adsorption sites and rich functional groups, which could effectively improve surface polarity, roughness and wettability of carbon fibers, thus enhancing effective interfacial bonding and enabling hierarchical regulation of interface in CFRPs. This paper reviews feasible strategies for constructing CF‐MXene multilevel structures, including electrophoretic deposition, chemical grafting, electrostatic self‐assembly, and sizing coating. Then, the strengthening mechanism involving surface morphology, mechanical properties, and interfacial strength of CFRPs are systematically evaluated centered on interfacial activity, interfacial adhesion, surface roughness and surface energy. Meanwhile, the problems in introducing MXene to CF surfaces and future research directions are systematically prospected. This paper could provide valuable guidance to construct CF‐MXene multilevel structures to reinforce interfacial properties of CFRPs composites, thus realizing hierarchical modulation of CFRPs interfaces.Highlights A feasible strategy for constructing CF‐MXene multilevel structures is built. The main methods for constructing CF‐MXene multilevel structures are provided. Treatment processes and reinforcing mechanisms of CFRPs are evaluated.

Effect of Bio‐Based Plasticizers From Modified Vegetable Oils in a New Formulation of PVC Materials

ABSTRACTThis study investigates the performance of polyvinyl chloride (PVC) plasticized with diisononyl phthalate (DINP), rapeseed oil epoxidized ester (ROE), and rapeseed oil carbonated ester (ROC). The formulations were evaluated for surface resistance, wettability, migration, mechanical properties, and resistance to aging and thermal degradation. PVC/ROC exhibited the highest surface resistance of 1.5 × 1016 Ω, indicating superior electrical insulation. Wettability tests showed PVC/ROE with the highest contact angle at 63°, while PVC/ROC and PVC/DINP demonstrated lower contact angles of 44° and 43°, respectively. Migration tests revealed that PVC/ROC had the lowest migration rates: 0.1% in distilled water and 1.5% in 95% ethanol. Mechanical testing under algae exposure demonstrated that PVC/ROC achieved the highest tensile strength of 43 MPa and a strain at break of 200%. After 1008 h of thermo‐oxidative aging, PVC/ROC retained superior tensile strength and hardness, while PVC/ROE showed a slight decrease. PVC/ROC also demonstrated improved thermal stability at 255°C compared with DINP (245°C). These results confirm that ROC is an effective bio‐based plasticizer, providing enhanced mechanical properties, reduced migration, and greater durability compared to conventional DINP, offering a sustainable alternative for diverse PVC applications in medical, automotive, and packaging industries.

Microstructure and Mechanical Properties of Laser Additive Repaired 20CrNi4Mo Piercing Plug with and without Preoxidized Layer

The 20CrNi4Mo alloy with excellent high‐temperature stability is often used to manufacture low‐alloy steel piercing plugs, which are subject to harsh service conditions and usually fail due to severe wear. Repairing and remanufacturing failed piercing plugs not only extends the product's lifecycle but also has significant resource and environmental benefits. In this work, the feasibility of laser additive repair of failed piercing plugs using 20CrNi4Mo powder by selective laser melting technology is explored and the effect of preoxidation on the surface microstructure and mechanical properties of the repaired layer is investigated. The results show that the repaired layer has good metallurgical bonding with the substrate, and the densification reaches 99.8%. Compared with the substrate, the ultimate tensile strength and microhardness of the repaired layer increase by 88.97% and 70.68% to 1287 MPa and 380 HV, respectively. The oxide film exhibits a clear two‐layer, with the repair layer exhibiting a thicker oxide film. The average friction coefficient of the oxidized repair layer (0.263) is reduced compared with that of the oxidized substrate (0.382). This work provides a feasible and effective way to realize the repairing and remanufacturing of failed piercing plugs with enhanced surface mechanical properties.

Enhanced Surface Mechanical and Tribological Properties of H13 Die Steel with TiAlSiN Coating Deposited by HiPIMS

TiAlSiN is a potential protection coating for die steel to improve the surface hardness, anti-wear performance and suitability. In the present study, TiAlSiN is deposited on H13 die steel by high power impulse magnetron sputtering and the effects of bias voltage, deposition temperature, and film thickness on the performance of coatings are studied. The microstructure, mechanical and tribological properties of coatings are analyzed by energy dispersive spectrometer, X-ray diffraction, nanoindentation, friction and wear tests. The results show that with the changes of sputtering parameters, the content of Ti, Al, Si, and N fluctuates slightly. With the increase of bias voltage, deposition temperature and film thickness, the diffraction peaks of Ti3Al2N2 phase become wider. Higher bias voltage, deposition temperature, and film thickness are beneficial for obtaining coatings with high hardness, and strong wear resistance. By observing the surface morphology of coatings after grinding with Si3N4 balls, it was found that the wear mechanism of coatings contains abrasive wear, fatigue wear, and oxidative wear.

Surface Nanocrystallization and Improvement of the Mechanical and Tribological Properties of AISI 304 Steel Using Multi-Pass Nanostructuring Burnishing.

Owing to their high producibility and resistance to corrosion, austenitic chromium-nickel steels are widely used in the chemical, petroleum, and food industries. However, their significant disadvantage lies in their poor structural performance, which cannot be improved by heat treatment. This significantly limits the usability of these steels in parts of machines that operate under friction loads. Hardening can be achieved by decreasing the size of grains and applying deformation-induced martensitic transformation. Nanostructuring burnishing (NSB) may be one of the technologies suited for producing parts of tribological assemblies with enhanced operating characteristics. Nanostructuring burnishing using a sliding indenter is being developed as a method of industrial surface nanocrystallization through severe plastic deformation used in the mechanical machining of various types of parts. This article investigates the possibility of enhancing the mechanical and tribological properties of nanocrystallized surfaces of austenitic steels, which are formed through nanostructuring burnishing using a tool with a natural diamond spherical indenter and a change in sliding speed from 40 to 280 m/min with one, three, and five passes. Increasing the tool sliding speed makes surface nanostructuring machining of big parts highly effective. This paper aims to establish the influence exerted by the sliding speed and number of indenter passes on the formation of a nanocrystalline structure, as well as on the modification of microhardness and residual stresses, texture, and tribological properties of the surface layer in the nanostructuring burnishing of AISI 304 steel. Transmission microscopy and microdurometry, 3D-profilometry, and tribological tests of surfaces nanocrystallized with the "ball-on-disk" scheme with dry and lubricated friction established the optimal values of speed and number of passes for a spherical indenter in nanostructuring burnishing.

Machining holes in CFRP with laser “drilling + boring” hybrid technique

ABSTRACT This paper presents a novel approach for machining carbon fiber reinforced polymer composite (CFRP), wherein a laser “drilling + boring” hybrid technique is employed. The method consists of initial high-energy pulsed laser drilling at high speeds, followed by subsequent low-energy short-pulsed laser trimming of the hole edges. A detailed examination was carried out on machining accuracy, taper angle, surface roughness, the heat affected zone (HAZ), microstructure, and mechanical properties of the CFRP samples machined with this technique. The findings revealed that the circular holes exhibit a machining accuracy of approximately 30 μm, accompanied by a taper angle measuring 0.37°. Moreover, the regions surrounding the holes display a smooth and pristine surface, devoid of burrs, fiber fractures and serrated textures. Notably, compared with laser rotary cutting method, the “drilling + boring” hybrid technique demonstrates enhancements in surface finish, HAZ control, and mechanical property of the machined holes.

Analysis of torque variation in bolt fastening on coated steel surfaces

As the number of parts ever increases, the push for automation in assembly processes is intensifying in advanced manufacturing industries. The drive to improve productivity through manufacturing automation is relentless, and minimizing torque variation in automated bolt fastening is crucial for achieving successful assembly. Therefore, a precise understanding of the mechanisms of interfacial friction between bolts and coated steel plates, along with a torque analysis based on the interactions of various involved parameters, is essential. This study examines the interactions between surface topography and mechanical properties of bolts and coated steel plates. We explain three primary friction modes (plowing, sliding, and penetrating) within the defined contact areas and propose a prediction model based on contact mechanics to estimate the frictional torque under the bolt head on coated surfaces. Additionally, we quantitatively evaluate how the proportions of these friction modes change under various axial loads and coating conditions, and how these variations affect torque values. We also assess how variations in key parameters influence changes in friction modes, providing insights into the critical factors that should be monitored for effective control of fastening torque. This study presents methods for analyzing and calculating friction torque, offering guidelines for monitoring bearing surfaces to address bolt topography deviations and solving key industrial challenges in automated assembly.

Surface integrity and mechanical properties of small elements fabricated through LPBF and post-processed with heat treatment and abrasive machining

The present research analyzes the impact of heat treatment atmosphere followed by finishing surface machining of small elements of Inconel 939 fabricated through laser powder bed fusion (LPBF). The analysis involved annealing in two gas mediums, solution treatment, and aging to achieve the desired microstructure and mechanical properties. The finishing surface was performed using various variants of abrasive machining. A more than fivefold reduction in the average roughness height Ra from 5.6 µm to 1.15 µm was achieved using metal balls as an abrasive, which was required for further processing. Residual stress tests have shown that due to heat and abrasive treatment, tensile stresses change into compressive ones. After printing, samples are characterized by tensile residual stresses on the surface (+ 428 MPa), while after heat treatment, compressive stresses occur (− 179 MPa). Abrasive machining with metal balls increases the value of compressive stresses to − 464 MPa. In addition, the impact of post-processing on the microstructure of Inconel 939 was discussed in terms of mechanical properties. The yield strength of 1184 MPa and elongation values of 19.3% were obtained for samples after HT in an argon atmosphere and abrasive machining with a ceramics roller. These studies provide valuable new information on the effective heat treatment and optimization of the finishing machining of Inconel 939, especially in achieving the desired surface roughness, microstructure, and mechanical properties for aerospace applications.

The microstructure and mechanical properties of electron beam welded Ti2AlNb-based alloy joint with the addition of TiB2

In this paper, 5 mm thick Ti-22Al-25Nb alloy plate was used for vacuum electron beam welding. The effect of TiB2 on the surface forming, macroscopic morphology, microstructure and mechanical properties of the joint was studied by optical microscope, scanning electron microscope and X-ray diffractometer. The results showed that TiB2 had an obvious effect on the microstructure and mechanical properties. The surface forming of the joint was good with the addition of TiB2, while the lower surface of the joint without the addition of TiB2 was discontinuous and presented a droplet state. The phase of WZ with TiB2 was composed of B2 phase, TiB and a small amount of O phase, while it mainly consisted of B2 phase for the joint without addition of TiB2. The hardness of the WZ with different addition of TiB2 was higher than that of the WZ without addition of TiB2. The breaking strength at high temperature of the joint without addition of TiB2 was 639 MPa, which was only 72.5 % of the BM and lower than that of the joint with different addition of TiB2.

Advancing optical transparency in 3D‐printed PLA parts using chemical post‐processing

AbstractFused filament fabrication (FFF) is an increasingly popular three‐dimensional (3D) printing technology known for its ability to produce complex 3D models at a low‐cost using polymer materials. Despite its advantages, the poor surface finish and high layer resolution in FFF‐printed parts have hindered its wider adoption, particularly for applications requiring high transparency. Thus, the current study investigates the transparency evaluation of chemically post‐processed 3D‐printed transparent polylactic acid (PLA) parts, focusing on enhancing optical transparency. Fused Filament Fabrication was employed to produce transparent parts made from PLA filament, which were subsequently treated at various time settings using various solvents, including tetrahydrofuran (THF), chloroform or trichloromethane (TCM), and ethyl acetate (EA). This study examines the impact of chemical post‐processing on the surface roughness, transparency, mechanical properties, and dimensional accuracy of solvent treated parts. It has been found that the THF solvent with 40 s of immersion time resulted in a maximum transmittance of 74.66% and minimum surface roughness of 1.777 μm. Based on this finding a case study was also conducted to apply the findings of the current investigation to a practical application. The findings highlight the potential of chemical‐based post‐processing techniques to improve the optical properties of 3D printed PLA, offering a promising approach for applications in optics, medical devices, and consumer goods requiring transparent components.Highlights Effect of chemical post‐processing on 3D‐printed PLA parts was investigated. Tetrahydrofuran, chloroform, and ethyl acetate were used as solvents. Surface roughness, transparency, hardness, and dimensional accuracy were analyzed. Reported a maximum transmittance of 74.66% and minimum surface roughness of 1.777 μm.

Effect of heat input on microstructure and mechanical properties of AA6061 alloys fabricated by additive friction stir deposition

Heat input (HI) is the major factor that affects the surface quality, microstructure and mechanical properties of the deposition during the additive friction stir deposition (AFSD) process. Effect of HI on the microstructure and mechanical performance of the AFSDed AA6061 has been in-depth explored via adjusting the values of traverse speed (v) and layer thickness (t). Results indicate that deposition with a higher HI promotes the material flow behavior as well as the plastic deformation, which effectively enhances the grain refinement and structural uniformity, and avoids the formation of defects. Meanwhile, TEM results confirm that the enhanced HI leads to the formation of a higher volume fraction of the finer precipitations (Mg2Si and AlFeSi phases), which assists in suppressing abnormal grain growth phenomenon and improves the bonding strength of the deposition. As HI decreases, the transfer efficiency of materials clearly reduces because of the incompletely softened materials, causing less plastic deformation and poor interlayer bonding strength of the deposition. The deposition with the lowest HI displays the worst tensile properties with the lowest micro-hardness (107 HV0.5), YS (273 MPa) and UTS (303 MPa).

Enhanced strength-ductility synergy in a Ni–W–Co–Ta medium-heavy alloy via cryogenic supersonic fine particle bombardment

This study explores the influence of cryogenic supersonic fine particle bombardment (CSFPB) on a Ni–W–Co–Ta medium heavy alloy (MHA), and focus on the effect of gas pressure and impact time on the surface integrity, microstructural evolution, and mechanical properties of the MHA. CSFPB treatment creates a gradient structure, including surface layer with nanograins down to 9.0 nm due to severe plastic deformation, subsurface layer with high density dislocation structures and deformation twins due to weakened impact energy, and undeformed matrix. A key advantage of CSFPB is seen to be the cryogenic environment, which promotes superior surface integrity by reduced roughness. As the impact duration and gas pressure increase, the depth of deformation layer, surface hardness and strength of the MHA progressively rise. The optimal combination of strength and ductility is achieved at a gas pressure of 1.0 MPa for a duration of 90 s. This setting results in a maximum ultimate tensile strength of 1351 MPa and yield strength 796 MPa, with uncompromising elongation. However, excessively long treatment durations or high gas pressures can lead to the formation of surface microcracks, ultimately reducing the MHA's strength. Therefore, CSFPB offers the benefit of improved surface integrity through the cryogenic environment while maintaining a desirable balance between enhanced strength and ductility.