Smart Materials in Manufacturing最新文献

The deformation of Mg is made up of elastic, anelastic and plastic components. Unlike the elasticity and plasticity which have been widely studied, the anelasticity has been routinely ignored in many published works when characterising the behaviour of Mg and its alloys, due mainly to the difficulty in measuring the small region of anelasticity during deformation. This paper reviews the anelastic deformation of Mg and Mg alloys, covering its potential causes, affecting factors, and its implications on several material properties. The evidence from the literature suggests two possible mechanisms which may be responsible for the anelastic deformation: reversible {10 $\bar{1}$ 2} twinning and reversible incipient kink bands in the form of basal dislocation loops. Several factors, such as grain size, loading direction, solute concentration, precipitation, strain rate and temperature, are also observed to influence the magnitude of anelasticity. A direct consequence of anelastic deformation is the variation of elastic modulus values. This can lead to ambiguities and errors in determining stiffness, yield strength and fatigue behaviour if a constant nominal elastic modulus is used in engineering analyses. This review paper has shown that the anelastic deformation of Mg remains under-reported and suggested some possible directions for future research.

In this study, laser-cladding technology was used to create Cu-based amorphous–crystalline composite coatings on the surface of Nickel-aluminum bronze (NAB), and the microstructure, mechanical properties, corrosion and wear resistance of the coatings were systematically investigated. The coatings consisted of a combination of amorphous and intermetallic compounds, with a positive correlation observed between the amorphous content and the laser scanning speed. Microstructural observations confirmed excellent metallurgical bonding between the coatings and substrate without any noticeable defects. Furthermore, electron back-scatter diffraction testing demonstrated a gradient structure from the substrate to the coating, confirming its composition as an amorphous–crystalline composite. At a laser scanning speed of 20 mm/s, the volume fraction of the amorphous phase of the coating reached 68.8%, with a microhardness approximately 4.5 times higher than that of the substrate and an average friction coefficient half that of the substrate. Moreover, the coatings showed a shift in corrosion potential by 149 mV with nearly an order-of-magnitude decrease in corrosion current density.

Elastomer/carbon nanotube (CNT) nanocomposites play a pivotal role in the evolution of flexible electronics, aerospace and automotive components, biomedical devices and smart materials. This article explores recent advancements and challenges in elastomer/CNT nanocomposites, with a focus on the role of mechanochemical treatment in dispersing multiwalled CNTs (MWCNTs) and single-walled CNTs (SWCNTs). The review starts with a brief overview of the structure, synthesis and purification methods of CNTs, providing essential background for new researchers to the field. The paper explores various nanocomposite preparation methods, including solution mixing, melt compounding, in situ-polymerisation and latex compounding, highlighting their impact on the dispersion of CNTs in elastomers as well as the limitations. Special attention is given to mechanochemistry, particularly ball milling, as a key technique for enhancing the dispersion of CNTs within the elastomer matrix. The relevant reinforcement mechanisms are also discussed, focusing on the role of the Halpin-Tsai and Einstein-Smallwood-Guth models, as well as the Payne and Mullins effects. Key application areas are discussed, demonstrating the versatility and significance of elastomer nanocomposites. This review identifies critical challenges in the field, including the need for uniform dispersion of CNTs within the elastomer matrix, improvement of interfacial bonding between the CNTs and the elastomer, and the necessity to balance these technological advancements with cost-effectiveness and sustainability considerations. It highlights the need for continued research and development to fully harness the potential of these materials. Conclusively, elastomer/CNT nanocomposites are poised to shape future technological advancements while facing critical challenges that necessitate innovative solutions.

This study aims to comprehensively analyze the phase and microstructure evolution and related hardness variations of the Ti–6Al–2Sn–4Zr–6Mo wt.% (Ti6246) alloy produced by laser powder bed fusion (LPBF) under various laser conditions and to gain insight into the mechanisms of these changes using numerical thermal analysis. Higher laser volumetric densities (VEDs) resulted in a finer α/α' microstructure and increased hardness, exhibiting a positive correlation with the VED, except under extremely high conditions. This contrary trend, reported for the first time, is attributed to the solid-phase transformation from the β phase to metastable α' martensite during LPBF induced by rapid cooling. Despite the finer microstructure, the samples under very high VED conditions showed lower hardness, deviating from the overall trend. The X-ray diffraction peaks in the high-VED samples suggested a partial decomposition of α' to α + β owing to laser-induced reheating of the underlying layers, which is considered a contributing factor to the hardness reduction. The numerical analysis showed that the underlying layer was exposed to high temperatures for a relatively long time under high-VED conditions. It was revealed that the hardness of LPBF-fabricated Ti6246 was influenced by unique thermal processes: rapid cooling and reheating of the pre-solidified part, leading to the formation of a metastable α' phase and partial decomposition into α + β. These findings provide insights for tailoring Ti6246 with desired physical properties via LPBF.

Rare earth elements such as Dy, Gd and Y have been utilized in the fabrication of binary Mg alloys due to their beneficial effects on the formation of oxidation layers on the surface and intermetallics in the Mg matrix. These effects have been shown to enhance the corrosion resistance and mechanical properties of the alloys. Therefore, the study of Mg–Dy intermetallic phases is regarded as significantly important. These phases are considered to hold great potential effects on the properties of Mg–Dy alloys for various applications, thereby making their investigation essential in the academic and scientific domains. In this study, the energy, density of states, optical properties and elastic properties of the Mg₁Dy₁, Mg₂Dy, Mg₃Dy, and Mg₂₄Dy₅ intermetallic phases were calculated using first principles calculations. Based on the calculated formation enthalpy (derived from the energy) and density of states, it is suggested that the Mg₁Dy₁ phase exhibits greater stability compared to the other three Mg–Dy intermetallic phases. The calculated formation enthalpy results indicate that all four Mg–Dy phases are stable, while the band structure and density of states plots show metallic characteristics for these phases. The optical properties of the intermetallic phases were investigated, and the static dielectric constants for Mg₁Dy₁, Mg₂Dy, Mg₃Dy, and Mg₂₄Dy₅ were calculated to be 266.47 eV, 285.80 eV, 257.75 eV, and 373.98 eV, respectively. In addition, concerning the study of absorption spectra, the maximum values of the absorption coefficients for all four intermetallic phases occur within the energy range of 40–65 eV for incident light. Born-Huang's mechanical stability theory was employed to calculate the elastic constants of each Mg–Dy phase, and the bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (υ), and theoretical hardness (H_V) were derived. The results of the elastic modulus calculations indicate that the B, G, E, υ, H_V of the Mg₁Dy₁ phase are higher than those of the other Mg–Dy intermetallic phases. The Poisson's ratio (υ) and the ratio of bulk modulus to shear modulus (B/G) indicate that the Mg₂₄Dy₅ phase is ductile, while the other three phases are brittle. Finally, the universal anisotropy (A^U) is ranked as Mg₃Dy > Mg₁Dy₁ > Mg₂₄Dy₅ > Mg₂Dy, with the Mg₃Dy phase exhibiting the most pronounced elastic anisotropy.

The development of smart actuators based on renewable or biocompatible materials, which are able for delivery of specific cargo is of great importance in robotics, medical and material science engineering, food industry, etc. Here, we report the original design of a bilayer polymer actuator consisting of two polymer materials with an interface adhesive layer between them, able for macroscopic locomotion step by step on a special ratchet substrate through repetitive bending and straightening. This was triggered by heat alternation due to incandescent lamp radiation on/off switching, with a rapid reaction time of the actuator to heat exposure of the order of few seconds. Specifically, a relatively fast locomotion of the actuator was achieved due to the large amplitude of its reversible bending deformation of up to ∼40% measured in terms of the actuator's elevation-to-length ratio. As a result, a typical actuator demonstrated the locomotion velocity of about 3 cm/min, where each cycle of contraction/expansion yielded a walking step of ∼1 cm for about 20 s. It was demonstrated that the actuator, while moving, is able to carry a cargo almost twice heavier than the mass of the carrier itself. Based on optical microscopy and atomic force - infrared spectroscopy data it was concluded that the adhesive interface layer plays an important role in the stable operation of the actuator as it retards linear expansion of the rear polymer layer and thus assists conversion of different linear expansion of the adjacent layers into their effective bending.

The microstructure and mechanical property regime of laser powder bed fusion fabricated Al₂O₃–ZrO₂ hypereutectic ceramic samples were thoroughly investigated by tailoring the printing parameters. The findings indicate that both the hypereutectic and eutectic microstructure are obtained depending on the varying printing parameters. The ZrO₂ dendrites in the hypereutectic structure gradually refine as the laser energy density increases, while the surrounding eutectic structure evolves continuously. The uniform eutectic microstructure is developed until the dendrites disappear. Simultaneously, it is observed that coarse Al₂O₃ particles were formed in the overlap part of the eutectic structure where the laser energy is higher. In terms of mechanical properties, the samples with alumina particles in the eutectic microstructure have a maximum hardness of 1616.13 HV, while the sample with uniform eutectic microstructure has the highest fracture toughness of 5.87 MPa⋅m^1/2. These findings can contribute to the introduction of a unique microstructure in Al₂O₃–ZrO₂ ceramic.

One common problem in using titanium (Ti) dental implants is peri-implantitis. To prevent peri-implantitis on Ti implants in an oral environment, we introduced novel topographic microstructures onto the surfaces of pure Ti implants via sandblasting, acid etching, and hydrothermal treatment before adding ZnO nanocomposite coatings and TiO₂ nanocomposite coatings via magnetron sputtering. We comprehensively investigated the influence of surface topographic morphologies and elemental composition of coatings on the physicochemical properties and antibacterial efficacy of the specimens. Our results indicate that the novel topographic surfaces and magnetron sputtered coatings both exhibit good cytocompatibility. Our results also suggest that coating composition, rather than surface topographic morphology, is the primary factor influencing the antibacterial performance of Ti implants. Therefore, the magnetron sputtering of ZnO and TiO₂ coatings onto surfaces can be an effective technique for improving the antibacterial properties of Ti implants for oral applications.

Multiprocess additive manufacturing (MPAM) unlocks new materials and design spaces where multimaterial components consisting of polymers, metals, and ceramics can be produced as one consolidated part. MPAM enables state-of-the-art 3D-printed electronics and devices with embedded functionality by combining fused deposition modeling with chemical deposition and electroplating processes. However, the metalized plastic devices produced by these processes have a short lifespan because of their poor structural integrity due to the low adhesion at the metal–polymer interface. In this study, we elaborated on the adhesion mechanism at the 3D-printed metal–polymer interface and identified the MPAM factors that elevated significantly the integrity of metalized plastic components. The effects of the 3D-printed surface texture and surface treatment on the adhesion strength of copper plated on acrylonitrile–butadiene–styrene parts were analyzed. We found that a certain 3D-printed topography modified by quick acid etching created a hierarchically structured interface with superimposed macroscale, microscale, and nanoscale roughness that symbiotically improved the metal–polymer adhesion. These results have practical implications for automated equipment manufacturers and the electronic industry adapting MPAM for the 3D printing of multimaterial components and devices with embedded functionality.