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• The design method of hierarchical structure is proposed. • The proposed hierarchical structure has a dual function of stretching and bending. • The specific component ratio and size ratio can enhance energy absorption. With the development of additive manufacturing technology, lattice structures with complex topological shapes can be manufactured. In order to combine the advantages of stretch dominance and bend dominance, a hierarchical lattice structure composed of variable unit cell is proposed. The hierarchical lattice structures are manufactured by laser powder bed fusion (LPBF). Five different cell arrangement combinations are designed based on face centered cubic (FCC) with octet truss structure (OTS) at the macro scale. The mechanical performance and deformation behavior of the hierarchical lattice was investigated systematically through compressive experiments and numerical simulations. The deformation modes were captured with a digital camera. Then, the crashworthiness design on the Row layered structure parametric analysis was performed to discuss the effect of geometrical parameters including component ratio and size ratio. The results indicated that the hierarchical structure exhibits a mixed deformation mode among those the Row layered structure has the best energy absorption characteristics. And the specific ratios of these geometrical parameters significantly enhance the energy absorption of hierarchical structure. Overall, this work not only provides a novel solution for designing hierarchical structures, but also highlights the advantages of additive manufacturing techniques for manufacturing complex structures. [ABSTRACT FROM AUTHOR]

Triply periodic minimal surfaces (TPMSs) are extensively used as effective tools for the microarchitectural designing of cellular structures. CoCrNi medium-entropy alloy, known for its high strength and high ductility, is an ideal candidate for fabricating TPMS-based structures. However, few studies have focused on this topic. This study investigated the compressive mechanical and energy absorption properties of CoCrNi D-sheet TPMS cellular structures fabricated via selective laser melting (SLM). The surface morphology of the fabricated D-sheet TPMS structure was observed through scanning electron microscopy, and the deformation and failure mechanisms of the structure were analyzed by the quasi-static compression test. The results indicated that the SLM-ed CoCrNi D-sheet TPMS structure exhibited stable collapse mechanisms compared to other metal-based TPMS structures. Meanwhile, the energy absorption characteristics of the modified finite element (FE) model agreed well with the experimental results. Furthermore, the impact of the level constant on the energy absorption performance of the D-sheet TPMS structure was investigated using the FE model. Thus, an optimal D-sheet (OD-sheet) TPMS structure with lower density and higher energy absorption capacity was obtained. Additionally, the Gibson–Ashby prediction model was established to aid in selecting CoCrNi OD-sheet TPMS structures with controlled relative densities for energy absorption applications. [Display omitted] • CoCrNi D-sheet TPMS cellular structures were fabricated via selective laser melting. • SLM-ed CoCrNi D-sheet TPMS structure exhibited stable collapse mechanisms. • Optimal D-sheet TPMS structure with high energy absorption capacity was obtained. [ABSTRACT FROM AUTHOR]

This work aims to investigate the solubilizing ability of alkanolamines on steel slag (SS) and the chelating ability of alkanolamines with metal ions. In this paper, the chelation effect of four alkanolamines, including triethanolamine (TEA), triisopropanolamine (TIPA), diethanol-isopropanolamine (DEIPA), and methyl diethanolamine (MDEA), and metal ions on the dissolution of SS was investigated. The conductivity meter, pH meter, X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), total organic carbon (TOC) and isothermal calorimetry were used to investigate the solubilizing ability of SS impacted by alkanolamines. Additionally, the conductivity meter and chemical precipitation method (CPM) were used to investigate and explore the chelating ability of alkanolamines interacting with the metal ions. Finally, the nuclear magnetic resonance hydrogen (1HNMR) spectroscopy was adopted to investigate the chelating mechanism between alkanolamines and metal ions. The results showed that the alkanolamines increased the elemental concentrations of [Ca], [Al], [Fe] and [Si] in the liquid phase of SS through chelating and promoted the dissolution of the mineral phase of C 3 S, C 2 S and C 4 AF in SS. Among the different alkanolamines, DEIPA was present in the liquid phase for the longest time and possessed a more sustained ability to chelating metal ions. The result also shows that alkanolamines can chelate the Ca2+, Al3+ and Fe3+ in solution. The chelating ability of tertiary alkanolamines were stronger than the secondary alkanolamine. And the alkanolamine with asymmetric molecular structure have stronger chelating ability than those with symmetric molecular structure. Tertiary alkanolamines form ternary five-ring structure with metal ion through nitrogen and oxygen atoms. • Alkanolamines promoted the dissolution of the mineral phase in steel slag. • DEIPA possessed a more sustained ability to chelating metal ions. • Alkanolamine with asymmetric molecular structure have stronger chelating ability. • Ternary five-ring structure formed between the ternary alkanolamine and metal ion. [ABSTRACT FROM AUTHOR]

• The correlation between defects and thermal behavior is discussed, and the forming causes of defects are analyzed. • A physical model is proposed to simulate the thermal behavior of melt pool under different processing parameters. • Processing parameters have significant influence on macroscopic morphology but have little influence on dendrite spacing. Selective laser melting (SLM) is a kind of material forming technology which involves many processing parameters. The appropriate processing parameters are very important to the forming quality of manufactured samples. In this paper, the influence of laser power and scanning speed on the manufacturing defects, thermal behavior and compression properties of AlSi10Mg lattice structures during SLM were systematically investigated. By observing the macroscopic and microscopic morphology of manufactured samples, it was found that the processing parameters had a significant influence on the strut diameter and internal porosity but had little influence on the dendrite spacing and grain size. A physical model considering thermal loss and thermal conduction in temperature field was proposed to simulate the thermal behavior of melt pool under different processing parameters. The results showed that the thermal behavior was more sensitive to the laser power, and the manufacturing defects were related to the transient temperature and dimension of the melt pool. The digital image correlation (DIC) method was adopted to analyze the strain distribution of manufactured lattice during the compression process. Meanwhile, the relationship between processing parameters, thermal behavior and manufacturing defects was discussed in detail. Finally, based on the optimal processing parameters (250 W-1400 mm/s), the accuracy of manufactured lattice structure was verified by finite element method. The research results can provide a reference for the selection of processing parameters for manufacturing AlSi10Mg lattice structure. [ABSTRACT FROM AUTHOR]