Nickel-based superalloys are critical materials for high-temperature components in core equipment, such as aerospace engines and gas turbines. In recent years, with the rapid advancement of metal additive manufacturing (AM) technologies, the fabrication of complex geometries using nickel-based superalloys has been successfully applied in modern engines and gas turbines. These components demonstrate significant advantages in integration, weight reduction, multifunctionality, and performance enhancement. However, due to the complex alloy composition and multiphase microstructure of nickel-based superalloys, the AM process is accompanied by intricate phase transformations and high thermal stresses. This often leads to defects, such as hot cracking—particularly in the vicinity of the molten pool. In addition, the rapid non-equilibrium solidification and repeated thermal cycles from layer-by-layer deposition result in complex microstructural evolution and phase transformations during both solidification and subsequent solid-state reactions. These factors significantly influence the strengthening and toughening behavior of the superalloys. Consequently, the comprehensive mechanical properties of additively manufactured nickel-based superalloys still lag behind those of their traditionally forged counterparts. This article reviews recent domestic and international research progress on the mechanisms of crack formation and control strategies in AM of nickel-based superalloys, as well as the evolution of microstructure and the associated strengthening and toughening mechanisms. Furthermore, it discusses the design of nickel-based superalloys tailored specifically for AM, and offers insights and future perspectives on the development of advanced strengthening strategies and alloy design methodologies for AM applications.

Aquatic activities, particularly swimming, have been demonstrated to enhance physical conditioning and psychological well-being. However, the risk of water-induced otitis externa—caused by microbial colonization in the external auditory canal—often deters sustained participation in aquatic sports. Traditional swimming earplugs are typically limited in terms of comfort, water resistance, and antimicrobial protection, which can lead to potential ear canal infections and reduced effectiveness in preventing water ingress. In this study, we proposed using 3D scanning and printing technology to produce personally customized swimming earplugs to address these challenges. Embedded-suspension 3D printing technology was applied to fabricate structures using non-self-supporting Polydimethylsiloxane (PDMS) ink, printing hydrophobic ink in a hydrophilic system. The 3D-printed PDMS/Ag-3% composites exhibited an excellent inhibition rate (99.89%), good sound insulation performance (>30 dB, 1000–6300 Hz, 8 mm thickness), elasticity (elongation at break of 62.93%), and low modulus (0.85 MPa). We then recruited 60 beginner swimmers for a wear trial to demonstrate the effectiveness of personalized earplugs in preventing otitis externa and reducing ear canal irritation. This approach not only highlights the potential of 3D printing technology in sports equipment but also offers new insights for developing customized wearables.

Laser powder bed fusion (LPBF) enables the production of Ti-6Al-4V alloys with tailored porous structures, which are beneficial for biomedical applications due to their reduced elastic modulus and enhanced bone integration potential. This study examines the effect of hot isostatic pressing (HIP) on the microstructure and mechanical properties of diamond and gyroid porous structures fabricated by LPBF. Solid tensile specimens served as reference materials. HIP significantly reduced porosity, decreased ultimate tensile strength and hardness, but markedly increased ductility (from 6% to 17%). Compressive strengths reached approximately 100 MPa (diamond) and 240 MPa (gyroid), with HIP causing only a slight increase in strain. However, HIP notably improved bending performance, raising the flexural strength of gyroid structures from 280 MPa (as-printed) to 340 MPa (post-HIP). The strength of LPBF-fabricated Ti-6Al-4V porous structures is reduced by HIP, but their ductility and bending performance are enhanced, making them more suitable for biomedical applications.

As the manufacturing readiness level of laser powder bed fusion (L-PBF) advances, post-processing has become increasingly important for achieving net-shape components and to enhance surface texture and integrity. Apart from surface roughness, one concern is the unique morphology of printed surfaces with vertical, upskin, and downskin inclinations. In this study, we characterized the surface texture and integrity of L-PBF Ti6Al4V with respect to build orientation. In the as-built condition, the downskin surfaces possessed the highest roughness, the largest effective surface stress concentration(),Ktand the greatest presence of partially melted powder particles fused to the surface. Cavitation abrasive surface finishing (CASF) was adopted to improve surface quality, with consideration of the build orientation. The results indicated that CASF reduced roughness, lowered Kt posed by the surface texture, and introduced compressive residual stress regardless of the build orientation. Downskin surfaces were the most challenging to treat; they exhibited substantially greater Ktthan the other orientations after treatment (>2×) and lower compressive residual stress (50%). More extensive powder coverage of the downskin surfaces appears to shield the underlying substrate from abrasive attack and direct implosion of cavitation bubbles, which are central to the CASF treatment mechanism. The importance of orientation to the effectiveness of CASF treatment is discussed, as well as strategies to overcome this challenge. Overall, downskin surfaces require greater surface treatment intensity or duration to obtain the same degree of improvement.

The escalating incidence of bone defects has prompted a substantial demand for orthopedic implants, and additively manufactured biodegradable porous magnesium and magnesium alloy orthopedic implants have demonstrated significant potential for clinical applications. However, the mismatch between degradation-induced changes in mechanical properties and tissue regeneration remains a major challenge hindering their applications. As porous structure is a critical factor influencing the degradation behavior of magnesium/magnesium alloy orthopedic implants, this study aims to comprehensively review the current state of research in this area. The degradation behavior of magnesium/magnesium alloy orthopedic implants has been investigated using both experimental and numerical simulation methods. Degradation experiments have enabled direct observations of the influences of structures on degradation behavior and underlying mechanisms. Numerical simulations have been employed to analyze the stress and strain distributions within the structure during degradation and surrounding tissue regeneration, facilitating the investigation of the “structure-stress-tissue regeneration” regulation on degradation. Porous structures play critical roles in regulating mechanical properties, bearing physiological loads, and establishing a localized mechanical microenvironment of magnesium/magnesium alloy orthopedic implants. Design variables, including porosity, specific surface area, pore size, shape, and interconnectivity, influence the macroscopic mechanical properties, structural deformation, stress distribution, and contact with surrounding tissues, thereby regulating degradation behavior and tissue regeneration of implants. However, models that quantitatively describe the “porous structural variables-degradation-tissue regeneration” interaction remain to be developed. This study systematically summarizes the influences of porous structures on the degradation behavior of additively manufactured magnesium/ magnesium alloy orthopedic implants and the “structure-mechanics-degradation-biology” interaction mechanisms. This review provides a systematic understanding of the state-of-the-art research and future directions to guide the development and applications of orthopedic implants.

Additive manufacturing, particularly fused deposition modelling (FDM), has gained increasing attention in aerospace applications due to its capability to produce complex geometries with reduced material usage, making it a promising approach for manufacturing lightweight yet strong unmanned aerial vehicle (UAV) parts. In this study, an integrated framework was developed to optimize FDM parameters for producing UAV parts that are both lightweight and high in strength. A response surface methodology was used to analyze the effects of infill percentage, layer height, number of walls, and build plate temperature on the mass and tensile strength of the printed parts. Two regression models with high predictive accuracy were constructed (R2 = 98.2% for mass, R2 = 88.5% for tensile strength). A multi-objective optimization approach was applied, using the non-dominated sorting genetic algorithm II Pareto front analysis in combination with Minitab’s Response Optimizer tool, to identify the optimal combination of parameters. The results showed that layer height, number of walls, and infill percentage, along with their interaction effects and quadratic effects, had the most significant effects on both mass and tensile strength, whereas build plate temperature had negligible effects. The results from the Pareto front analysis revealed the trade-off between minimizing mass and maximizing tensile strength for the parts. The optimal parameter settings (e.g., 58.26% infill percentage, 0.1635-mm layer height, 4 walls, and 65°C build plate temperature) achieved a tensile strength of 47.08 MPa and a mass of 1.60 g, offering a well-balanced strength-to-weight ratio suitable for UAV applications.

Among nickel-based superalloys, Inconel® 725 (IN725) stands out for its excellent strength and corrosion resistance. Despite this, its application in additive manufacturing remains largely unexplored. This study investigates laser powder bed fusion of metals (PBF-LB/M) applied to IN725 powder derived from recycled industrial waste, addressing sustainability and process optimization goals. Using the design of experiments approach, the laser power–scan speed process parameter space was explored. Gaussian process regression models were developed to predict surface roughness, relative density, and microhardness. Both direct process parameters and volumetric energy density were evaluated as model inputs to assess predictive performance. The findings established a broad optimal process window for manufacturing high-quality IN725 parts using PBF-LB/M. Specifically, an optimal combination of 99.99% relative density, 7.3 μm roughness, and 311 HV microhardness was achieved by processing the powder at 250 W and 1,500 mm/s. By demonstrating the feasibility of using recycled IN725 powder, this study contributes to the development of sustainable manufacturing practices and supports wider adoption of PBF-LB/M in oil and gas, marine, and chemical processing industries, where IN725 is widely employed.

Three-dimensional concrete printing (3DCP) has emerged as a promising innovation in the construction industry, significantly reducing its reliance on intensive labor while minimizing material waste. Despite its benefits, a major limitation of current 3DCP practices is the high reliance on cement as the primary binder, which often exceeds 60% of the total solid content. This high cement usage contributes significantly to CO2 emissions, raising sustainability concerns. In this study, a 3D-printable concrete mix incorporating large aggregates (up to 10 mm) was developed, replacing over 7% of fine aggregate and reducing cement content to approximately 29% by weight. The effects of CO2 gas and a steam–CO2 mixture on the mechanical performance and CO2 uptake of the printed concrete were assessed. Thermogravimetric analysis was used to quantify CO2 sequestration over time. Compared to control samples without gas treatment, those exposed to the steam–CO2 mixture showed enhanced buildability, improved compressive and flexural strength, and greater CO2 uptake. The results suggest that surface spraying of the steam–CO2 mixture during the 3D printing process offers a viable and scalable approach to improving both the structural performance and environmental footprint of printed concrete elements.

Additive manufacturing of silicon carbide (SiC) is challenging due to uncontrollable quality, surface roughness of fabricated parts, expensive post-processing, and long production times for customized components. Developing cost-effective, rapid manufacturing techniques that maintain high quality and design freedom is therefore highly desirable. In this study, laser powder bed fusion (LPBF) followed by ultra-fast post heat treatment was applied to produce SiC-based composites using silicon and carbon powders as raw materials. The influence of processing parameters on silicon-carbon reaction and sintering was investigated. Boron carbide was used as an additive to enhance sintering. Substantial SiC formation occurred despite the limited heating time. Boron carbide influenced both SiC formation and grain growth. The maximum Vickers hardness (1218 HV0.2) was achieved in boron carbide-containing heat-treated samples printed at a laser power of 48 W. This novel approach enables the efficient fabrication of SiC-based composites with enhanced hardness, underscoring the potential of LPBF for cost-effective and customizable ceramic component manufacturing.

Biodegradable magnesium-based scaffolds for bone tissue engineering are considered a promising treatment approach for repairing large bone defects. In this study, porous magnesium-neodymium-zinc-zirconium alloy (JDBM) scaffolds were fabricated using laser powder bed fusion (L-PBF) followed by dynamic electrochemical polishing. The effects of laser energy input and contour scan strategy on the formation quality of L-PBF scaffolds were systematically investigated. A novel scanning strategy, C64F84, combining low laser power for contour scans with high laser power for filling scans, was developed to achieve good fusion quality while controlling surface powder adhesion and dross defects. The printed specimens achieved a maximum relative density of 99.54%. The effects of electrochemical polishing on L-PBF scaffolds with different contour scan strategies were further evaluated. Electrochemical polishing effectively removed excess adhered powder and brought the scaffold porosity in line with the intended design value. The polished C64F84 scaffold exhibited higher dimensional accuracy, with smaller mean deviations, due to improved geometric consistency in the L-PBF process. Finite element analysis results were consistent with compression test data, confirming the high quality of the prepared C64F84 scaffolds. The yield strength (23.88 MPa) and elastic modulus (0.855 GPa) were comparable to those of cancellous bone, highlighting the medical potential of L-PBF-fabricated JDBM scaffolds.