Metamaterials are excellent candidates for application in smart morphing aircraft owing to their high designability, excellent mechanical and functional properties. However, existing designs often utilize passive structures and polymer-based materials, limiting the lightweight and strength of the morphing wings. Hence, we proposed a novel active flexible metal metamaterial inspired by the embedded characteristics and wavy interfaces of epidermal cells in the Portulaca oleracea seedcoat, with network honeycomb configuration. The formability, mechanical properties, deformation mechanisms, and the shape memory effect (SME) of network honeycombs manufactured by laser powder bed fusion (LPBF) were systematically investigated. By regulating the number of cell walls per junction, network honeycombs achieved tunable mechanical properties with the Poisson’s ratio ranging from −0.21 to +0.47. The hexagonal network honeycombs (HNHs) demonstrated a fracture strain up to 38% and achieved an excellent shape recovery ratio of 96.10% under thermal activation with 10% pre-programmed strain. The reconfigurable deformation capability of the biomimetic metamaterial was demonstrated in morphing wings within a wide application temperature range, enabling smooth and continuous deformation within a range of −25° to 25°. This study highlights the integration of shape memory alloy to endow metamaterials with active and reconfigurable properties, advancing the engineering applications of smart morphing aircrafts.

Transpiration cooling is crucial for the performance of aerospace engine components, relying heavily on the processing quality and accuracy of microchannels. Laser powder bed fusion (LPBF) offers the potential for integrated manufacturing of complex parts and precise microchannel fabrication, essential for engine cooling applications. However, optimizing LPBF’s extensive process parameters to control processing quality and microchannel accuracy effectively remains a significant challenge, especially given the time-consuming and labor-intensive nature of handling numerous variables and the need for thorough data analysis and correlation discovery. This study introduced a combined methodology of high-throughput experiments and Gaussian process algorithms to optimize the processing quality and accuracy of nickel-based high-temperature alloy with microchannel structures. 250 parameter combinations, including laser power, scanning speed, channel diameter, and spot compensation, were designed across ten high-throughput specimens. This setup allowed for rapid and efficient evaluation of processing quality and microchannel accuracy. Employing Bayesian optimization, the Gaussian process model accurately predicted processing outcomes over a broad parameter range. The correlation between various processing parameters, processing quality and accuracy was revealed, and various optimized process combinations were summarized. Verification through computed Tomography testing of the specimens confirmed the effectiveness and precision of this approach. The approach introduced in this research provides a way for quickly and efficiently optimizing the process parameters and establishing process-property relationships for LPBF, which has broad application value.

The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites. In this work, AZ91D magnesium alloys and 2 wt.% TiC/AZ91D composites have been manufactured by laser powder bed fusion (LPBF) with variations of laser processing parameters. The effect of TiC reinforcement addition on the laser absorption behaviors, forming quality, microstructure evolution and mechanical properties of the magnesium alloys is investigated. The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder, and decreases powder spatter of powder bed. The results show that high relative density of ~99.4% and good surface roughness of ~12 µm are obtained for the LPBF-fabricated composites. The TiC addition promotes the precipitation of β-Mg₁₇Al₁₂ in the alloys and the transformation of coarse columnar to fine equiaxed grains, where the grains are refined to ~3.1 µm. The TiC/AZ91D composites exhibit high microhardness of 114.6 ± 2.5 HV_0.2, high tensile strength of ~345.0 MPa and a uniform elongation ~4.1%. The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening from β-Mg₁₇Al₁₂ precipitates and Al₈Mn₅ nanoparticles. In the composites, the unmelted TiC particles can act as an anchor for the network structure of β-Mg₁₇Al₁₂ precipitates, effectively impeding crack propagation and enhancing their performance. This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.

High cracking susceptibility of Al-Li alloys with Ti/CeB₆ addition is thoroughly suppressed in laser powder bed fusion (LPBF) processing of Ti/Ce co-modified 2195 alloys at relatively high scan speeds, while the cracking suppression mechanism and phase formation in these composites are not clarified. In this work, microstructure evolution and mechanical performance of the LPBF-fabricated Ti/Ce co-modified 2195 are investigated to reveal their cracking suppression and strengthening mechanisms. The results show that apparent grain refinement of the composites is ascribed to high supercooling from rapid formation of constitutional supercooling zone in front of solid–liquid interfaces by high-Q-value Ti solute, and heterogeneous nucleation of in situ formed Al₃Ti and Al₁₁Ce₃ precipitates. Their synergistic interactions promote formation of fine equiaxed grains and thus inhibit crack initiation. The composites exhibit high microhardness of 100 ± 5 HV_0.2, nano-hardness of 1.6 ± 0.1 GPa and elastic modulus of 97 ± 3 GPa, where the elastic modulus increases by ~27% and ~31% compared to those of LPBF-processed and conventionally manufactured 2195 alloys, respectively. A tensile strength of ~336 MPa and an elongation of ~3% are obtained from in-situ synchrotron X-ray diffraction measurement. The improved properties are derived from grain refinement and Orowan strengthening. Based on the optimal processing parameter and composition, a bracket component filled with lattice structures is designed and manufactured with good manufacturing quality and processing accuracy.

Lightweight porous materials with high load-bearing, damage tolerance and energy absorption (EA) as well as intelligence of shape recovery after material deformation are beneficial and critical for many applications, e.g. aerospace, automobiles, electronics, etc. Cuttlebone produced in the cuttlefish has evolved vertical walls with the optimal corrugation gradient, enabling stress homogenization, significant load bearing, and damage tolerance to protect the organism from high external pressures in the deep sea. This work illustrated that the complex hybrid wave shape in cuttlebone walls, becoming more tortuous from bottom to top, creates a lightweight, load-bearing structure with progressive failure. By mimicking the cuttlebone, a novel bionic hybrid structure (BHS) was proposed, and as a comparison, a regular corrugated structure and a straight wall structure were designed. Three types of designed structures have been successfully manufactured by laser powder bed fusion (LPBF) with NiTi powder. The LPBF-processed BHS exhibited a total porosity of 0.042% and a good dimensional accuracy with a peak deviation of 17.4 μm. Microstructural analysis indicated that the LPBF-processed BHS had a strong (001) crystallographic orientation and an average size of 9.85 μm. Mechanical analysis revealed the LPBF-processed BHS could withstand over 25 000 times its weight without significant deformation and had the highest specific EA value (5.32 J·g⁻¹) due to the absence of stress concentration and progressive wall failure during compression. Cyclic compression testing showed that LPBF-processed BHS possessed superior viscoelastic and elasticity energy dissipation capacity. Importantly, the uniform reversible phase transition from martensite to austenite in the walls enables the structure to largely recover its pre-deformation shape when heated (over 99% recovery rate). These design strategies can serve as valuable references for the development of intelligent components that possess high mechanical efficiency and shape memory capabilities.

Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g⁻¹ at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.

Three types of scanning strategies, including the chessboard scanning strategy, the zigzag scanning strategy and the remelting scanning strategy, were conducted to study the effects of scanning strategies on surface morphology, microstructure, mechanical properties and the grain orientation of selective laser melted pure tungsten. The results showed that the pores and cracks were main defects in SLM-processed tungsten parts. The pores could be eliminated using the remelting scanning strategy. However, the cracks seemed to be inevitable regardless of the applied scanning strategies. The microstructures of SLM-processed tungsten were columnar grains and showed strong epitaxial growth along the building direction. A compressive strength of 923 MPa with an elongation of 7.7% was obtained when the zigzag scanning strategy was applied, which was the highest among the three scanning strategies. By changing the scanning strategies, the texture of SLM-processed tungsten in the direction of processing could be changed.