Abstract
The thorough description of the peculiarities of additively manufactured (AM) structures represents a current challenge for aspiring freeform fabrication methods, such as selective laser melting (SLM). These methods have an immense advantage in the fast fabrication (no special tooling or moulds required) of components, geometrical flexibility in their design, and efficiency when only small quantities are required. However, designs demand precise knowledge of the material properties, which in the case of additively manufactured structures are anisotropic and, under certain circumstances, inhomogeneous in nature. Furthermore, these characteristics are highly dependent on the fabrication settings. In this study, the anisotropic tensile properties of selective laser-melted stainless steel (1.4404, 316L) are investigated: the Young’s modulus ranged from 148 to 227 GPa, the ultimate tensile strength from 512 to 699 MPa, and the breaking elongation ranged, respectively, from 12% to 43%. The results were compared to related studies in order to classify the influence of the fabrication settings. Furthermore, the influence of the chosen raw material was addressed by comparing deviations on the directional dependencies reasoned from differing microstructural developments during manufacture. Stainless steel was found to possess its maximum strength at a 45° layer versus loading offset, which is precisely where AlSi10Mg was previously reported to be at its weakest.
Highlights
Additive manufacturing (AM) methods, such as the selective laser melting (SLM), represent powerful freeform fabrication techniques which can fabricate direct deployable components without the necessity of special tooling, and are highly efficient when only small quantities are required [1,2,3].Since full melting of the raw metal powder enables the generation of fully dense parts within a single production step, with mechanical properties exceeding the specifications of the conventional material, the fabrication of highly specialized components using AM is increasing [4,5,6,7]
The findings show that in SLM the properties of the generated part are greatly affected by the applied scanning pattern, and a thorough prediction of the properties of additively manufactured components prior to fabrication is, a challenge
The peculiarities of additively manufactured material were addressed using the example of stainless steel
Summary
Additive manufacturing (AM) methods, such as the selective laser melting (SLM), represent powerful freeform fabrication techniques which can fabricate direct deployable components without the necessity of special tooling, and are highly efficient when only small quantities are required [1,2,3].Since full melting of the raw metal powder enables the generation of fully dense parts within a single production step, with mechanical properties exceeding the specifications of the conventional material, the fabrication of highly specialized components (like tools, moulds, ultra-lightweight components or medical implants) using AM is increasing [4,5,6,7]. Additive manufacturing (AM) methods, such as the selective laser melting (SLM), represent powerful freeform fabrication techniques which can fabricate direct deployable components without the necessity of special tooling, and are highly efficient when only small quantities are required [1,2,3]. Materials 2017, 10, 1136; doi:10.3390/ma10101136 m s www.mdpi.com/journal/materials It appears that this convenient approach through characterization with a single number is not able to sufficiently express the entire complexity of powder-bed based AM processes, like SLM [10,11,12]. At this stage, a proper description of the manufacturing process still requires the listing of the individual irradiation parameters. In addition to the pure irradiation, information about the raw metal powder, mainly its size and distribution, is of great importance and should not be neglected
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