Advanced Engineering Materials最新文献

Milling-induced surface topography of porous titanium, critical for its functional performance, is governed by cellular pore deformation. This study establishes how milling parameters control this deformation to tailor the generated surface topography in terms of porosity, roughness, and fractal dimension. The key finding is that the axial depth of cut dictates the deformation mode: low depths (≤1.5 mm) promote plastic smearing, reducing surface porosity by up to 49% for densified surfaces, while high depths (≥2.0 mm) trigger brittle peeling, increasing porosity by up to 74% for enhanced permeability or osseointegration. Areal roughness (S_a: 40.69–114.95 μm) is primarily governed by pore-induced topography, with axial depth being the most influential parameter (65.85% contribution). Fractal dimension (1.39–1.95) peaks at a 2.0 mm depth, indicating maximum complexity from pore fragmentation. These insights provide a direct parameter selection framework for engineering porous titanium surfaces to meet application-specific demands.

Reliable cryogenic performance of welded joints is critical for the safety of liquefied natural gas storage and transport systems, yet conventional 316L flux-cored wires often exhibit limited toughness due to ferrite embrittlement and oxide inclusions. In this study, the composition and processing parameters of flux-cored 316L welding wire are synergistically optimized to enhance microstructural stability and cryogenic toughness. The primary ferrite solidification mode, stacking fault energy, and Md₃₀ parameters are calculated to guide alloy design, and welds produced under different heat inputs (12–20 kJ cm⁻¹) are systematically evaluated at ambient and −196 °C. The optimized addition of deoxidizing and austenite-stabilizing elements effectively reduce ferrite content and refine oxide inclusions, resulting in a homogeneous microstructure. Increasing heat input improves molten pool fluidity and inclusion flotation, yielding a 45.3 J average impact energy at −196 °C—≈45% higher than that of commercial wires. Microanalysis reveals complex MnSiCrO oxides, while cryogenic tensile testing confirms transformation-induced plasticity behavior involving γ → ε → α′ martensitic transformation, which substantially enhances low-temperature strength and ductility.

This study presents a novel two-step manufacturing approach for fabricating multifunctional metal–polymer lattice composites by combining laser powder bed fusion (LPBF) of FeSi2.9 electrical steel with pressure infiltration of Bakelite polymer. Gyroid lattice structures with varying cell sizes and solidity levels are successfully printed, achieving high relative densities under optimized parameters. Bakelite infiltration fully occupies the internal voids, forming robust composites with enhanced mechanical stability. Compression testing reveals that infiltrated lattices exhibits yield strengths (273.7 ± 1.03 MPa), surpassing those of dense samples (253.64 ± 4.52 MPa), while maintaining structural integrity up to 60% engineering strain without fracture. Magnetic characterization reveals that Bakelite infiltration does not significantly alter the intrinsic soft magnetic properties of FeSi2.9, despite the pronounced magnetic anisotropy observed, which is driven by the crystallographic texture developed during LPBF processing. These results demonstrate a promising strategy for creating lightweight multifunctional composites with combined structural and functional properties.

The advent of powder bed fusion (PBF) technology marked a significant development in metal additive manufacturing (AM), offering unrivaled design flexibility, precision, and deposition rates. This review examines the intricacies of the PBF process, with a particular emphasis on titanium (Ti) and its alloys (Ti-alloys). Although the microstructural evolution under various PBF conditions has been extensively studied, the unique advantages of PBF in alloy design and processing remain underexplored. It systematically compares the performance characteristics of Ti-alloys fabricated via laser and electron beam technologies, with a particular focus on their forming properties, microstructure, and mechanical properties. Key challenges hindering the progress of PBFs, along with potential solutions, are identified. In addition, it explores the unique processing characteristics of PBF and advocate innovative alloy design to achieve superior microstructures and properties not possible with conventional methods. This study's findings provide important insights and future directions for optimizing Ti-alloys development through PBF, paving the way for further development of PBF and Ti-alloys.

Crystallographic Textures

This cover emphasizes the unique features of structural materials on various magnifications for a PBF LB/M austenitic steel. In their Research Article (10.1002/adem.202500412), Nico Möller and co-workers present a 1 kW top-hat and a 400 W Gaussian laser that create distinct grain sizes and crystallographic texture. Mechanical properties are linked to microstructural evolution driven by processing conditions. Residual stress analysis via incremental hole drilling reveals a pronounced in-depth gradient.

In light of the success of the special issue dedicated to advances in the field of structural materials published in 2023 we decided to organize a follow-up issue in 2025. Contributions in this special issue are based on presentations given at the Materials Science and Engineering Congress (MSE2024).

The MSE, organized by the Deutsche Gesellschaft für Materialkunde (DGM) every two years, is the leading international congress dedicated to materials science in Germany since many years. In September 2024, with Sweden being the guest country, researchers from all over the world met in Darmstadt to present recent advances in the field. Again, one of the major topics was “Structural Materials”. This topic focuses on the relationships between the structure of materials and their properties and performance and provides a scientific basis for developing engineering materials for advanced structural applications.

The present special issue of Advanced Engineering Materials contains papers from different sessions organized under the topic.

We hope that all readers will take their time to read the excellent papers and receive inspiration from the results presented. As is the common basis in engineering science and application, insights presented will foster intense discussions and help to guide their own research toward reliable use of novel structural materials in any environment.

With best regards,

316 stainless steel (316 SS) is processed by ultrasonic nanocrystal surface modification (UNSM) with different processing parameters, including static load, strike amplitude (dynamic load), scanning speed, tip diameter, and interval (distance between neighbor scans). The effects of these parameters on surface finish, microstructure evolution, and microhardness are systematically investigated. It is found that within the scope of this study, the influence of static load, scanning speed, and strike amplitude to the surface roughness is insignificant, while the surface roughness is significantly affected by the tip diameter and increases monotonically with increasing interval from 0.01 to 0.5 mm. Hierarchical structures, nanoscale wrinkles embedded in microscale grooves, are fabricated on the 316 SS surface. In addition, plastic deformation zone also becomes thicker when the interval decreased from 0.5 to 0.01 mm. It has been demonstrated that surface finish, gradient microstructures, and martensite transformation in the top surface layer of 316 SS could be artificially modified by individually controlling the UNSM interval. This work provides valuable guidance for tailoring specific surface microstructures and mechanical properties of metallic materials via UNSM.

Laser melting deposition fabricated Ti-6Al-4V (TC4-LMD) demonstrates exceptional mechanical properties and has been widely adopted in aerospace applications. However, the dimensional constraints of additive manufacturing equipment necessitate welding of TC4-LMD components with other parts fabricated via conventional processes (e.g., forging). Significant microstructural and mechanical property gradients across distinct zones of a dissimilar welded joint frequently lead to poor overall mechanical performance. This study investigates the microstructural characteristics and mechanical behavior of electron beam welded joints between TC4-LMD and forged damage tolerance TC4 (TC4-DT). Digital image correlation (DIC) analysis is employed to elucidate localized strain distribution patterns during tensile deformation of the joint. Postwelding solution-aging heat treatments with varying solution temperatures and cooling rates are used to tailor the properties of the joint. Results indicate that pronounced heterogeneous microstructures are formed in the initial joint, which substantially deteriorates the tensile properties, particularly ductility. Through solution heat treatment at 950 °C followed by air cooling and aging, the heterogeneous microstructure has been largely eliminated. Furthermore, fine β-transformed structures are precipitated during the postwelding heat treatment, which also contribute to enhancing the strength-ductility synergy.

In this study, Cr_0.9Si_0.1 coatings are deposited onto Mg₂Si_0.89(Sn_0.1Sb_0.01) thermoelectric (TE) materials using a closed-field unbalanced magnetron sputtering system. The cyclic oxidation behavior of uncoated and Cr_0.9Si_0.1-coated TE materials is thoroughly investigated at 500 °C for 10 and 50 cycles, with each cycle lasting 1 h. Surface morphology, phase constitution, cross-sectional layer structure, and elemental distribution are analyzed using scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. Oxidation kinetics are assessed by measuring the mass gain of samples after cyclic oxidation testing. The uncoated TE material exhibits significant surface degradation after cyclic oxidation, initially forming MgO particles, followed by the development of SiO₂ and Mg₂SiO₄ phases in later stages. Encouragingly, the Cr_0.9Si_0.1 coating demonstrates excellent thermal stability on the n-type Mg₂Si_0.89(Sn_0.1Sb_0.01) substrate. Although some oxygen diffusion occurs along grain boundaries within the coating, it is effectively trapped, thereby preventing further penetration into the underlying substrate. The high oxygen affinity of Cr and/or Si atoms plays a critical role in blocking oxidation, offering robust protection. These findings strongly support the use of Cr_0.9Si_0.1 coatings as an effective antioxidant barrier for TE materials under harsh operational conditions, ensuring the long-term operation of TE modules at elevated temperatures.