Topological fidelity of additively manufactured AlSi10Mg gyroid structures

Abstract

Additively manufactured Triply Periodic Minimal Surfaces (TPMS), walled gyroid structures (WGS) in particular, have garnered research and industry attention recently, especially in realizing compact and efficient heat exchangers. Methodologies for topological and geometric fidelity assessment of as-printed samples against their as-designed models are pertinent to predict and evaluate their performance, as deviations can impact heat transfer rates and energy dissipation. In this study, 7 WGS samples with cell sizes and relative densities ranging from 3 mm to 7 mm and 8.5 % to 26.2 % respectively were manufactured via laser powder bed fusion (LPBF) in AlSi10Mg. Geometric (3D) and layer-wise (2D) topological fidelity analyses were done by comparing micro x-ray computed tomography (μ−CT) scans of the WGS samples with corresponding computer-aided designed (CAD) models. Metrics such as the degree of overlap, underprint, overprint, and percentage deviation were defined and quantitatively assessed. Results show bonded partially melted powder particles on downfacing surfaces resulting in higher average surface roughness of up to 41μm in these regions. Topological conformities in terms of the degree of layer-wise overlap, and the degree of overprint and underprint improve as the ratio of the relative density to cell length increases from 2 to 5 (% per mm) for a cell size of 5 mm.