Advanced Engineering Materials最新文献

Microvibration Suppression

Inspired by the distribution of pores and the morphology of mineralized fibers of goat tibia, in their Research Article (10.1002/adem.202402969), Qing Luo, Chang Liu, and Dongxu Li propose a multi-scale biomimetic structure design method. By irregularly embedding micro-scale biomimetic cells into a macroscopically regular biomimetic layout framework, the micro-vibration suppression performance typical flywheel-cabin plate system in the spacecraft is optimized.

Welded joints suffer from reduced fatigue life due to geometric stress concentrations and metallurgical changes in the heat-affected zone that promote crack initiation under cyclic loading. This study investigates a novel postweld treatment, utilizing a Cu/Ni nanometallic multilayer thin film deposited onto the welded butt joint. Deposition current densities and individual Cu/Ni layer thicknesses are systematically varied to optimize fatigue performance. A multiscale residual stress (RS) analysis characterizes stress states within individual multilayers and in the steel substrate, indicating all substrate RS are compressive in nature after thin film deposition. Results demonstrate a direct correlation between compressive RS magnitude and fatigue strength improvement. Tested at Δσ_R = 0.75 × f_y, a more than a 300% increase in cycles to failure is seen compared to the as-welded condition. This postweld treatment offers a promising approach for extending the operational life of welded structures across industrial applications.

Ni-rich NiTi is a distinctive functional smart alloy well-suited for biomedical and aerospace applications, owing to its exceptional thermomechanical properties, biocompatibility, and corrosion resistance. The wear resistance and long-term service life of NiTi alloys are strongly dependent on their phase transformation behavior, which is intrinsically linked to microstructural evolution. In this context, the present study investigates the critical role of Ti₃Ni₄ precipitates in governing phase transformation kinetics, microstructure, and tribological performance through controlled aging treatments at 450 °C and 650 °C. Results reveal that Ti₃Ni₄ precipitation significantly hardens the alloy, inhibiting martensitic phase transformation while substantially improving wear resistance compared to precipitate-free conditions, despite exhibiting higher surface roughness and friction coefficient. In contrast, the absence of Ti₃Ni₄ precipitates (achieved by aging at 650 °C) accelerates the thermally induced transformation rate by 78% but severely degrades wear resistance, increasing both wear rate and wear depth by 67%. The findings establish a microstructure–property framework for tailoring Ni-rich NiTi shape memory alloys: Ti₃Ni₄-rich microstructure optimizes wear-critical applications, while unprecipitated microstructure favors rapid phase transformation. This work advances the design of NiTi alloys by decoupling the antagonistic effects of precipitates on transformation kinetics and wear performance, offering actionable guidelines for application-specific heat treatments.

Defect dipoles in piezoceramics have recently been recognized as key regulators of electromechanical behavior, giving rise to a previously unidentified phenomenon: the electrobending effect. Unlike inverse piezoelectric and inverse flexoelectric effect, electrobending effect originates from the asymmetric response of defect dipoles in surface layers under external electric fields, producing pronounced bending deformation in thin ceramic samples. This article reviews the formation and dynamic response of defect dipoles, their symmetry-conforming behavior, and the contrasting roles of [001]- and [110]-oriented defect dipoles. Further, surface-layer defect dipole configurations, bidirectional and unidirectional electrobending models, and newly proposed metrics for quantifying bending performance are discussed. Finally, challenges and prospects for defect dipole engineering and electrobending research are outlined, emphasizing their potential to enable next-generation lead-free piezoelectric materials and multifunctional devices.

Experiments were conducted to investigate the microstructure and properties of Ti-6Al-4V rotational arc welded joints using tungsten electrodes with varying eccentricities. The arc's rotation during welding expanded the heated area around the groove, increasing the heat-affected zone (HAZ) width. The weld zone primarily consists of lath martensite. Increasing electrode eccentricity reduces low-angle grain boundaries and causes a nonlinear change in grain size. At 0.75 mm eccentricity, the average grain size reaches a minimum of 0.72 μm. The dislocation angle range for the α phase in the weld zone is 1.05°–4.35°, 55.6°–65.3°, and 88.3°–90.45°. Static tensile strength values for the HAZ and weld zones exceed the base metal by over 97% (940 MPa), with elongation after fracture reaching 80% (11.14%) of the base metal's value. Impact toughness also surpasses over 80% (490.25 KJ m⁻²). Furthermore, at 0.75 mm eccentricity, impact toughness increases by more than 10% compared to other eccentricities, emphasizing the strengthening effect of fine grains on material impact toughness.

The M2052 alloy (Mn-20Cu-5Ni-2Fe at%) exhibits excellent damping capacity and favorable mechanical strength, making it a promising candidate for vibration damping and energy absorption. However, its potential in lattice structures has not been reported to date. In this article, M2052 alloy lattice structures are fabricated via selective laser melting to evaluate their mechanical properties and energy absorption capabilities. Three lattice architectures with comparable relative densities are designed and manufactured: body-centered cubic (BCC), BCC with vertical struts (BCCZ), and reinforced hollow BCCZ (RHBCCZ) featuring hollow struts and strengthening ribs. Quasi-static compression tests and finite element simulations are conducted to analyze their mechanical responses and deformation mechanisms. Furthermore, the effects of heat treatment on the compressive properties and microstructural evolution of BCC lattices are investigated. Results demonstrate that the RHBCCZ structure delivers optimal performance, with a Young's modulus of 1506.3 MPa, yield strength of 18.41 MPa, and maximum energy absorption of 22.69 J cm⁻³. Heat treatment enhanced the yield strength and altered the deformation mode of the lattice. This article highlights the potential of M2052 alloy in load-bearing, energy-absorbing, and lightweight structural applications.

Structures with triply periodic minimal surfaces (TPMS) are characterized by continuous and smooth geometries, providing design versatility well-suited for mechanical enhancement and energy dissipation functions. Although metal additive manufacturing (AM) is a powerful method for fabricating TPMS structures, its application at large scales is often limited by high production costs, build size constraints, and challenges in achieving fully dense structures in complex enclosed geometries. To address these practical limitations, this study proposes a modular investment casting strategy using 3D-printed polylactic acid patterns to fabricate Schwarz Primitive TPMS structures. By decomposing the structure into castable modules, the proposed method enables flexible scaling while reducing common casting defects such as cold shuts and incomplete filling. Six configurations with different wall thicknesses and unit cell counts are successfully produced. Experimental results demonstrate that increasing the wall thickness significantly enhances the yield strength, elastic modulus, and energy absorption, with the best-performing specimen exhibiting a specific energy absorption of 19.9 J g⁻¹. Compared with conventional lattice topologies and stainless-steel cellular metal foams, the modular TPMS structures demonstrate superior tunable energy absorption in the high-density regime (1.8–3.5 g cm⁻³). This work establishes a cost-effective and scalable alternative to AM for manufacturing high-performance TPMS structures for engineering applications.

Additive manufacturing offers potential benefits in tooling, such as reduced lead times and improved service life. However, carbon martensitic tool steels are prone to cold cracking during additive manufacturing. This can be mitigated by adjusting alloying compositions to stabilize ductile austenite during manufacturing, which can later be transformed to martensite through heat treatment. In situ alloying is a rapid process for this, in which powder mixtures are processed, thereby avoiding the elaborate gas atomization of prealloyed melts. However, this promotes chemical inhomogeneities, particularly with high-melting refractory metal powders. In this study, two powder mixtures are prepared to produce chemically homogeneous tool steel samples containing refractory elements Mo and W. In the first mixture, these are provided by adding commercial high-speed steel powder. In the second mixture, high-speed steel grinding chips, a waste material typically disposed by landfill or combustion, are used. Both mixtures are processed using single- and double-laser exposure. The chemical homogeneity and tempering behavior of the samples are compared to prealloyed references. Double-laser exposure achieves sufficient densification and chemical homogenization, resulting in similar hardness compared to the references. However, excessively long chips are demixed during powder application, altering the global composition of samples made with recycled chips.

With the advancement of high-power devices and wide bandgap semiconductors, electronic packaging materials face increasing demands for high temperature and power density performance. Copper nanopaste is promising due to its low cost and high interconnect strength. However, its susceptibility to oxidation in air significantly weakens bonding performance. In this study, copper nanoparticles with high oxidation resistance were prepared via co-treatment with 2-pyridine methanol and oxalic acid. XRD and XPS confirmed the absence of oxides. Rheological and surface profiling determined the optimal mixing ratio, yielding pastes with excellent printability and uniform particle dispersion. Uniform nanoparticle distribution promoted strong Cu-Cu joint formation. Bonding experiments under varying vacuum conditions revealed that insufficient temperature, pressure, or time led to void-rich joints. Optimal bonding at 300 °C, 5 MPa for 40 minutes achieved a shear strength of 120 MPa. EBSD analysis showed nanocrystalline sintered bulks with 96% large-angle grain boundaries and 22.9% twin boundaries, enhancing dislocation resistance and shear performance. Fracture analysis indicated that high-strength joints fractured along the substrate, while low-strength ones cracked within the bulk. This self-reducing Cu nanopaste holds great potential for high-power device packaging.