Carneiro V H, Rawson S D, Puga H, Withers P J
CMEMS-UMinho, University of Minho, Campus of Azurém, 4800-058, Guimarães, Portugal.
Department of Materials, The Henry Royce Institute, The University of Manchester, Manchester, M13 9PL, UK.
Sci Rep. 2021 Mar 2;11(1):4974. doi: 10.1038/s41598-021-84524-y.
Cellular materials are recognized for their high specific mechanical properties, making them desirable in ultra-lightweight applications. Periodic lattices have tunable properties and may be manufactured by metallic additive manufacturing (AM) techniques. However, AM can lead to issues with un-melted powder, macro/micro porosity, dimensional control and heterogeneous microstructures. This study overcomes these problems through a novel technique, combining additive manufacturing and investment casting to produce detailed investment cast lattice structures. Fused filament fabrication is used to fabricate a pattern used as the mold for the investment casting of aluminium A356 alloy into high-conformity thin-ribbed (~ 0.6 mm thickness) scaffolds. X-ray micro-computed tomography (CT) is used to characterize macro- and meso-scale defects. Optical and scanning electron (SEM) microscopies are used to characterize the microstructure of the cast structures. Slight dimensional (macroscale) variations originate from the 3D printing of the pattern. At the mesoscale, the casting process introduces very fine (~ 3 µm) porosity, along with small numbers of (~ 25 µm) gas entrapment defects in the horizontal struts. At a microstructural level, both the (~ 70 μm) globular/dendritic grains and secondary phases show no significant variations across the lattices. This method is a promising alternative means for producing highly detailed non-stochastic metallic cellular lattices and offers scope for further improvement through refinement of filament fabrication.
多孔材料因其高比力学性能而闻名，使其在超轻量级应用中备受青睐。周期性晶格具有可调节的性能，并且可以通过金属增材制造（AM）技术制造。然而，增材制造可能会导致未熔化粉末、宏观/微观孔隙率、尺寸控制和微观结构不均匀等问题。本研究通过一种新技术克服了这些问题，该技术将增材制造与熔模铸造相结合，以生产详细的熔模铸造晶格结构。使用熔融丝材制造来制造一种图案，该图案用作将铝A356合金熔模铸造到高一致性细肋（厚度约0.6毫米）支架中的模具。X射线微计算机断层扫描（CT）用于表征宏观和中观尺度的缺陷。光学显微镜和扫描电子显微镜（SEM）用于表征铸造结构的微观结构。轻微的尺寸（宏观尺度）变化源于图案的3D打印。在中观尺度上，铸造过程引入了非常细（约3微米）的孔隙率，以及水平支柱中少量（约25微米）的气体截留缺陷。在微观结构层面，（约70微米）的球状/树枝状晶粒和第二相在整个晶格中均未显示出明显变化。这种方法是生产高度详细的非随机金属多孔晶格的一种有前途的替代方法，并为通过改进丝材制造进一步改进提供了空间。
