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Hamburg, Germany

Siddique S.,TU Dortmund | Imran M.,TU Dortmund | Rauer M.,University of Applied Sciences Aschaffenburg | Kaloudis M.,University of Applied Sciences Aschaffenburg | And 4 more authors.
Materials and Design | Year: 2015

Components manufactured by maturing additive manufacturing techniques like selective laser melting (SLM) find potential competence in several applications especially in automotive and aerospace industries as well as in medical applications like customized implants. The manufactured parts possess better, or at least comparable, yield strength and tensile strength values accompanied with a reduced fracture strain. Though their fatigue performance in the as-built condition is impaired due to surface roughness, it can be sufficiently improved by post-process surface treatments. Even then, there exists a high fatigue scatter due to remnant porosity. Characterization of remnant porosity is necessary for a reliable component design to be employed for cyclic applications. Computed tomography has been used in this study to evaluate the influence of porosity-incited stress concentration on the corresponding fatigue scatter. Microscopic analysis, tensile tests, fatigue tests with continuous load increase and constant amplitudes as well as finite element analysis have been used for this purpose. Critical pore characteristics and a modification in the process scanning strategy have been recommended so that the components can be reliably used in fatigue-loaded applications. © 2015 Elsevier Ltd.

Siddique S.,TU Dortmund | Imran M.,TU Dortmund | Wycisk E.,Laser Zentrum Nord LZN | Emmelmann C.,Laser Zentrum Nord LZN | And 2 more authors.
Journal of Materials Processing Technology | Year: 2015

Selective laser melting (SLM) offers high potential for manufacturing complex geometries and custom-made parts due to its unique layer-wise production process. A series of samples of AlSi12 have been manufactured by SLM process to study the effect of process parameters and post-build heat treatment on the microstructure and the corresponding mechanical properties. Optical microscope, scanning electron microscope, quasistatic tests, continuous load increase fatigue tests and constant amplitude fatigue tests have been employed for characterization. A remarkable eutectic microstructure, with dendritic width changing with SLM process parameters, has been observed. Relationship between SLM process parameters, resulting microstructure and the consequent changes in mechanical properties has been discussed. Base plate heating has been found critical in controlling the in-process microstructure. Mechanical properties of SLM parts outperform those of conventionally manufactured alloy, and can be varied as per requirement, by altering the build rate, keeping the process costs in control. Fatigue scatter can also be controlled by heating the base plate during the process. © 2015 Elsevier B.V. All rights reserved.

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