Additively manufactured lightweight lattice structures typically consist of thin walls with thicknesses ranging from hundreds of micrometers to millimeters. Within this range, such thin walls exhibit a pronounced size effect. Despite extensive research on the topic, a clear mapping between key influencing factors and mechanical properties remains lacking. This gap makes it challenging to accurately predict mechanical performance across different wall thicknesses, especially for those below 500 μm. In this work, Ti-6Al-4V thin-walled tensile specimens with thicknesses ranging from 0.2 mm to 1.0 mm were fabricated via laser powder bed fusion (LPBF). The variations in mechanical properties, microstructure, surface defects, and internal defects were investigated. The results indicate that yield strength (YS) and ultimate tensile strength (UTS) decreased significantly as thickness decreased, dropping from 794.1 MPa to 471.7 MPa and from 910.7 MPa to 485.2 MPa, respectively. Printing defects were identified as the dominant factors governing the size effect: strength was jointly affected by surface and internal defects, whereas failure mode and ductility were primarily governed by internal defects. By introducing an effective thickness ratio parameter, a semi-empirical predictive model was developed to characterize the strength-thickness relationship and to quantify the individual contributions of surface defects and other coupled interior factors. Subsequently, ultra-thin specimens were subjected to surface grinding and polishing to alleviate surface defects, leading to improvements in YS and UTS of approximately 27–39% and 22–45%, respectively. The model-predicted strengths of the surface-treated specimens were in good agreement with the measured values, further validating the effectiveness of the proposed model.

Nickel-based superalloys are key materials for aerospace and gas turbine applications. Traditional manufacturing approaches struggle to produce controllable porous structures with complex topologies. This review focuses on additively manufactured porous Ni-based superalloys, and summarizes progress in porous structure design, including disordered, lattice, TPMS, bio-inspired, and AI-assisted structures. Common additive manufacturing technologies are introduced, along with their effects on microstructure evolution and defect formation. The review discusses non-equilibrium microstructures, elemental segregation, and typical defects such as lack-of-fusion, keyhole porosity, and residual stress, as well as their influences on strength, fatigue, and creep behavior. Post-processing strategies for defect mitigation and performance optimization are also summarized. This review highlights the unique mechanical and physical behavior of porous structures compared to bulk materials, with an emphasis on anisotropy, stress localization, and defect sensitivity. Finally, several critical and specific challenges are identified, including multi-scale modeling, microstructure control in complex topologies, fatigue prediction, and physics-constrained AI design. This review aims to provide a clear, focused, and structurally consistent overview of the current state of the field, and to support future research on additively manufactured porous Ni-based superalloys.

316L austenitic stainless steel is an ideal candidate for high-temperature applications. However, the relatively low strength and poor wear resistance at high temperatures significantly limit its application in high-temperature environments. In this study, we address this challenge by tracing TiB₂ microalloying austenitic steel via L-PBF (laser powder bed fusion), a micro-melting pool metallurgy method. The results show that adding 2.5 wt.% TiB₂ significantly refines the austenite grain size from ~19 μm to ~1 μm. The austenite grain size characterizes thermal stability at 300 °C and 600 °C. The fabricated TiB₂-reinforced steel shows extraordinarily high-temperature tensile strength, achieving 740 MPa and 636 MPa at 300 °C and 600 °C, respectively. The high tensile strength under high temperature is attributed to the TiB₂ phase strengthening and ultrafine austenite grain sizes. Regarding the high-temperature wear friction coefficient of 0.69 at 300 °C and 0.47 at 600 °C, the predominant wear mechanism is abrasive wear, accompanied by adhesive and oxidative wear mechanisms. The present study provides new insight for the development of L-PBF austenitic steels that combine high-temperature strength with superior wear resistance.