Search

Open‐cell aluminum foams are gaining importance for the design of lightweight structures and as electrodes in lithium‐ion batteries. AlSi7Mg0.3 foams are produced by a modified investment casting process. By tuning the mold temperature, a change from the usual nearly monocrystalline dendritic to a polycrystalline globular grain structure is achieved. Tension and compression tests on single struts and foam specimens, respectively, are combined with digital image correlation, scanning electron microscopy, and phase contrast‐enhanced microcomputed tomography in a synchrotron facility to correlate the mechanical properties and the failure mechanisms with the microstructure. The "globular" foams exhibit a lower strength and a less pronounced subsequent stress drop than the "dendritic" foams and the deformation mechanism changes from shear band‐dominated failure to a layer‐by‐layer collapse, because of the lower strength and higher ductility of the "globular" struts. The "dendritic" struts have a more homogeneous microstructure, while the "globular" struts often contain silicon agglomerates in their central region. Accordingly, the latter struts exhibit a higher degree of scatter for the fracture strain. Thus, the arrangement of the silicon particles and the eutectic determines the mechanical properties on the strut level and thereby the failure behavior on the foam level. [ABSTRACT FROM AUTHOR]

Ice‐templating, a versatile manufacturing process, is widely utilized to create porous materials by freezing aqueous solutions. Notably, this technique is material independent, allowing for the fabrication of microstructured bulk or sheet materials of ceramic, glass, metal, polymer, and composite materials. Herein, the influence of freeze‐cast zinc electrodes on zinc–air batteries is investigated. The analysis includes the charge and discharge cycling behavior of pure powder, gel matrix, and sintered freeze‐cast zinc electrodes, complemented by the study of the distribution of relaxation times. Remarkably, the best cycling performance is achieved with the combination of a gel electrolyte and a freeze‐cast zinc electrode, highlighting the potential significance of this microstructure–electrolyte pairing for enhancing the performance of zinc–air batteries. [ABSTRACT FROM AUTHOR]

Open‐cell gray cast iron foams are a class of porous materials of increasing interest, with great potential to be used in energy damping applications and for sound isolation. We created finite element (FE) models from 3D reconstructed data of foams and of isolated struts imaged with resolutions spanning from 0.65 to 10.5 μm. Representative volume elements (RVE) are loaded in tension to simulate and analyze foam mechanical behavior. A ductile damage model is used for tensile testing of single struts and compression testing of foams. RVEs loaded along three axes demonstrate important effects of orientation of graphite particles in the microstructure. Only simulation results that take failure into consideration are consistent with experimental findings. Strut fracture initiation strongly depends on the cross‐sectional area and its circularity and foam simulation results are heavily influenced by damage modeling. The complexity of the open‐cell foam behavior is revealed at several hierarchical levels. Simulations in which material properties are assigned excluding damage overestimate the experimental results of the foam; conversely, a very good agreement is observed if damage is considered. The models exhibiting anisotropic mechanical properties fully reproducing large fluctuations in the mechanical properties of the struts are observed in in situ experiments. [ABSTRACT FROM AUTHOR]

Component production via laser‐based powder bed fusion of metals (PBF‐LB/M) is becoming reality for multiple applications. Especially for sophisticated parts, as in case of gas turbines, assurance of repeatable properties involves control of process and machine parameters. PBF‐LB/M is used to build configurable open‐porous structures—designed materials (DMs)—out of the high temperature superalloy Haynes 282 with relative densities from 35% to 65%. The objective is investigating positioning influence and process stability based on their relative densities in discrete scan fields and build jobs. As DMs made from Haynes 282 are not yet scientifically investigated, first the process boundaries are identified. The used PBF‐LB/M machine—EOS M 400‐4—works with four lasers in four quadrants—a quadrant benchmarking is carried out. The experiment is repeated in a second build job. Scatter is identified in quadrant and build job benchmarking. A further aspect under investigation is positioning within laser quadrants. However, keeping laser and parameter combinations constant, sample locations are assessed. A relative density dependency on the laser deflection angle—as a positional measure—is observed. The results of positioning influence and scatter are used to formulate a tolerance equation for relative densities of DMs. [ABSTRACT FROM AUTHOR]