Anisotropy of additively manufactured AlSi10Mg: threads and surface integrity

Abstract

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In this experimental study, the objective was to evaluate anisotropy in part properties (i.e., flatness, surface roughness, surface porosity, surface hardness, pre-hole shrinkage, drilling thrust force, and thread-stripping force) when the part orientation (i.e., print inclination and recoater angle) was independently changed. This study developed and investigated an innovative procedure for determining anisotropy in part properties. The part properties were evaluated by designing specific features on a tailor-made flat plate. The replicas of the aluminum plate were additively manufactured at varying orientations using two commercial EOS parameter sets for the laserbased powder bed fusion technique. Conventional measurement equipment was used to analyze all the part properties, except the thread-stripping force, which was measured using a custom-made setup. All the part properties indicated a considerable degree of anisotropy, excluding the drilling thrust force. The printing parameters dictate the significance of the anisotropy. The anisotropy in flatness and pre-hole shrinkage decreases with an increased substrate temperature and a decrease in energy input and thermal gradient. The presence of surface overlapping contours in the scan strategy and an increased energy input can reduce anisotropy in surface roughness and hardness. No significant anisotropy was detected when the recoater angle was changed. This study helps designers establish and substantiate design for additive manufacturing that is within the limits of appropriate anisotropy for a robust design.

Cumulative Inaccuracies in Implementation of Additive Manufacturing Through Medical Imaging, 3D Thresholding, and 3D Modeling: A Case Study for an End-Use Implant

“…This is most likely caused by the conglomeration of semi-fused particles (size:~32-60 um) to the outer surface of the implant that was in contact with the surrounding powder owing to a high platform temperature of 200 • C during the build. Further, the stair-case effect [75] induced by the freeform geometry containing angled, curved, or lofted shapes (complex shapes) of the implant can also contribute to the NLD uncertainty. Considering that the machine was calibrated, and standard printing parameters were used for the standard material profile (i.e., particle size distribution and shape), this error can describe the capability of the used machine to manufacture shapes as designed when followed by a standard heat treatment process and manual support removal process.…”

“…Shrinkage can vary as a function of print inclination [75]. Freeform surfaces of the implant can have a fluctuating print inclination resulting in non-linear shrinkage because the microstructural morphology shifts dependency between the melt pool overlaps and the layer overlaps for resisting contractions.…”

The Electropolishing of Additively Manufactured Parts in Titanium: State of the Art

“…The layer thickness and the inclination angle adopted during the building process could affect the surface finish. [ 4 ] For these reasons, the stair‐step effect is especially evident for inclined or curved parts.…”

Analysis of the machinability when milling AlSi10Mg additively manufactured via laser-based powder bed fusion

“…Ullah et al [30] studied the thrust forces when drilling a L-PBF and wrought AlSi10Mg. The magnitude of the thrust forces depended on the manufacturing parameters used for L-PBF, which affect the properties of the material.…”

“…It was assumed that this is due to greater plastic deformation of the material during chip formation and the continuous chips that were formed. The thrust forces during the drilling of the wrought reference material were smaller compared to the aluminum alloy manufactured via L-PBF [30]. Struzikiewicz et al [31] investigated the machinability of AlSi10Mg workpieces.…”