Journal of Materials Engineering and Performance最新文献

Previous studies have reported on polyvinylidene fluoride (PVDF)-based filaments for fabricating bio-sensors with material extrusion (MEX)-based 3D printing. However, little has been reported on developing PVDF-Cu-doped ZnO-BaTiO₃-based composite filament for MEX of pacemakers. This study highlights the development of PVDF-Cu-doped ZnO-BaTiO₃-based composite filament by varying the extrusion process parameters (such as types of heat treatment, extrusion speed, and processing temperature). The parametric combination of pre-heat treatment (PreHT), 7 rpm screw speed, and 220 °C processing temperature has resulted in maximum peak strength (30.7820 MPa). However, from a flexibility viewpoint, a maximum break strain (0.0821) was observed with a parametric combination of PreHT, 8 rpm extrusion speed, and 200 °C processing temperature. The thermogravimetric analysis (TGA) confirmed that the sharp degradation of reinforced composites started earlier than the virgin PVDF. However, no significant adverse effect on the thermal stability of the proposed composites was observed due to reinforcement and processing (confirmed by differential scanning calorimetry (DSC) test). The piezoelectric coefficient (D₃₃) was significantly improved from 118pC/N in virgin PVDF to 162pC/N in PVDF-Cu-doped-ZnO-BaTiO₃-based composites. The simulated forward transmission coefficient (S₂₁) for PVDF and PVDF-based composites has shown acceptable sensing abilities in S-band and may be used for the MEX of pacemakers.

In this work, medium-Mn steels with ultra-high strength and good ductility have been developed through a conventional hot rolling process. The microstructural characteristics and superior mechanical properties of the steels were investigated, focusing on 3Mn and 5Mn compositions. Both steels have martensite microstructures with a high dislocation density, and a small amount of retained austenite. Their ultra-high strengths are primarily attributed to martensitic strengthening and high work-hardening capability. The 5Mn steel demonstrates higher tensile strength and ductility, attributed to finer lath size, greater work-hardening capability, and superior grain boundary strengthening. This study emphasizes the synergy between dislocation dynamics, lath martensite strengthening, and work hardening, offering valuable insights for designing advanced structural steels with balanced mechanical properties.

One of the propitious concepts in additive manufacturing is wire arc additive manufacturing (WAAM) as it can be used to fabricate customized parts with high deposition rates. This process consists of the deposition of wire on the substrate through a heat source via an electric arc. Path planning strategies and thermal management are important aspects as they can affect the accuracy of the part. The objective of the present work is to observe the temperature profile and heat flux distribution of the model throughout the welding cycle. The temperature profiles at different sections of the model are also presented. Moreover, transient structural analysis has also been performed by coupling with the thermal load to predict the mechanical behavior of the body to determine the deformation and thermal strain caused. In this study, a finite element model was developed and analyzed by transient thermal module in ANSYS 2021 R2 software through a Gaussian moving heat source. The materials used for the substrate and filler wire were AA 6061-T6 and Al 5183 respectively. It was found that the temperature of the deposited layer reached about 1380 °C at the end of the deposition path. The temperature increased abruptly when the moving heat source passed at the turning edges along the deposition path. The total deformation was approximately 0.427 mm. The minimum and maximum thermal strains were approximately 0.012 and 0.035, respectively. The strain energy was higher on the substrate than on the weld bead because of greater thermal strain.

In this study, the TiSiN-Ag composite coating and TiSiN-Ag/TiN multilayer nanostructured coatings with varying modulation periods were deposited using magnetron sputtering technology. The microstructure and tribological behavior of the TiSiN-Ag/TiN multilayer coatings depending on modulation periods were investigated. The results revealed that the TiSiN-Ag coating and TiSiN-Ag/TiN multilayer coatings consisted of TiN phases, Ag phases, and amorphous SiNx phases. The TiSiN-Ag(15 nm)/TiN(15 nm) multilayer coating exhibited the highest hardness (9.86 ± 1.15 GPa), the resistance to elastic strain failure (0.0556) and plastic strain to failure (0.0304 GPa), as well as the lowest elastic modulus (177.43 ± 5.46 GPa). Additionally, it also demonstrated the lower friction coefficient (0.55 ± 0.056) and wear rate (3.164 × 10^-5 mm³/(N·m)). The multilayer design of the TiSiN-Ag coatings significantly improved its wear resistance. The wear track morphology indicate that the wear mechanisms of the TiSiN-Ag and TiSiN-Ag/TiN multilayer coatings mainly include adhesive and oxidative wear.

In this study, the effect of the rare earth cerium (Ce) element on the microstructure and high-temperature mechanical properties of aged Al-Cu-Mn alloy is investigated via optical microscopy, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy. The results demonstrate that the addition of Ce significantly refines the grain size and enhances the tensile strength. At room temperature, the tensile strength of the alloy initially increases and then decreases with increasing Ce content. At the 0.1 wt.% Ce content, the maximum tensile strength reaches 453.9 MPa. At 300 and 350 °C, the high-temperature tensile strength of the alloy increases initially and then decreases with increasing Ce content. The maximum tensile strength is observed at the 0.3 wt.% Ce content, reaching 161.4 MPa at 300 °C and 116.3 MPa at 350 °C. Moreover, Ce primarily exists in the form of the Al₈CeCu₄ phase, which promotes the ductile-to-brittle fracture mode transition at high temperatures.

The objective of this study was to enhance the comprehensive performance of tungsten alloys through the rotary swaging strengthening process. A series of mechanical property evaluations, including tensile, compressive tests, and heat treatments, were carried out on 90W-7Ni-3Fe alloys obtained at different rotary swaging parameters (rotary swaging temperatures: 850, 900, 950, 1000 °C; rotary swaging deformation: 19, 31, 41, 56%). The experimental results demonstrate that the strength and Rockwell hardness of 90W-7Ni-3Fe alloy after rotary swaging deformation are significantly increased. The ultimate tensile strength reaches approximately 1227 MPa, and the elongation achieves 7%. Both under room temperature quasi-static compression and dynamic compression conditions, the rotary swaged 90W-7Ni-3Fe alloys show significant strain rate sensitivity. Notably, during dynamic compression at a strain rate of 2300 s⁻¹, an adiabatic shear band structure of 20-30 μm is observed. Even under a larger amount of rotary swaging deformation, the rotary swaged 90W-7Ni-3Fe maintains commendable impact toughness. After heat treatment, the ultimate tensile strength of the rotary swaged 90W-7Ni-3Fe alloys reaches up to about 1212 MPa, and the elongation improves to 13.7%, achieving an optimal balance between strength and plasticity.

In this study, the wear and corrosion behavior of gas-nitrided high manganese steel (HMS) was investigated. Vacuum gas nitriding was carried out for surface treatment of HMS at 520 and 570 °C for 12, 18 and 24 h. The base metal contained α and ε martensite, while austenite was also observed in heat-treated base metal. Although all gas-nitrided samples contain Fe₃N, Fe₄N, γ, α and ε martensite, FeSi phase was only determined in N1-N6 samples. Expanded martensite and white layer (complex S phase) were observed in N1-N6 and N7-12, respectively. The gas-nitriding process significantly increased the surface hardness of HMS due to the iron nitride. Daimler-Benz Rockwell-C adhesion test shows that gas-nitriding HMS has sufficient adhesion behavior. The gas-nitriding process increases the wear and corrosion resistance of the HMS significantly.

Additive manufacturing processes are advanced technologies that enable the production of complex geometries. One of the most significant of these processes is fused deposition modeling (FDM). A key application of FDM in the medical industry is the fabrication of bone scaffolds. This study investigates the effect of FDM process parameters and annealing heat treatment on the specific energy absorption (SEA) of porous structures with interconnected porosity, intended for use as bone scaffolds in tissue engineering. The samples are 3D printed using polylactic acid (PLA). The studied parameters include extrusion width, layer height, infill percentage, and infill pattern. The samples are fabricated with three different patterns—grid, zigzag, and honeycomb—and with infill percentages of 40, 70%, and maximum density. As a novel approach, implementing an 18° interlayer rotation significantly enhances pore interconnectivity in 3D-printed structures. In addition to examining the effect of printing parameters, the influence of annealing on SEA is also evaluated. The results indicate that extrusion width and heat treatment have the most significant impact on SEA, with annealing increasing the SEA by up to 35%. The maximum SEA value of 36.2 kJ/g is achieved for an annealed sample with the following printing parameters: an extrusion width of 0.8 mm, a layer height of 0.2 mm, maximum infill percentage, and a grid infill pattern.

Refractory high-entropy alloys (RHEAs) are promising candidates as potential high-temperature materials. However, the high density and poor room-temperature ductility limit their industrial applications. In this study, a series of lightweight RHEAs with the compositions of (NbTiV)_100-xB_x and (NbTiV)_100-xC_x (x = 0.5, 1, 5, 10 and 15) were designed and prepared by microalloying with boron (B) and carbon (C). The microstructure evolution and mechanical properties of these alloys were systematically investigated. The results revealed that with increasing alloying content, the matrix phase in (NbTiV)_100−xB_x alloys transitioned from dual body-centered cubic (bcc₁ and bcc₂) solid solutions to a singular bcc₂ phase, whereas the (NbTiV)_100−xC_x alloys exhibited a structural evolution from a bcc configuration to a face-centered cubic (fcc) arrangement. The (NbTiV)₉₀B₁₀ and (NbTiV)₉₀C₁₀ alloys exhibited excellent room-temperature mechanical properties, with compressive strengths of 1494 MPa and 1466 MPa and fracture strains of 25% and 29%, respectively. At elevated temperatures (800-1000 °C), the strengths of (NbTiV)₉₀B₁₀ and (NbTiV)₉₀C₁₀ alloys decreased from 943 MPa and 1042 MPa to 326 MPa and 358 MPa, respectively. Notably, although both alloys achieve a balance between low density and outstanding mechanical properties, the (NbTiV)₉₀C₁₀ alloy demonstrates superior strength to the (NbTiV)₉₀B₁₀ alloy at all temperatures. This study provides a new approach for developing lightweight RHEAs with enhanced performance for medium-temperature applications.