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Erlangen, Germany

Ammer R.,Cauerstr. | Markl M.,Martensstr. | Ljungblad U.,Arcam | Korner C.,Martensstr. | Rude U.,Cauerstr.
Computers and Mathematics with Applications | Year: 2014

This paper introduces a three dimensional (3D) thermal lattice Boltzmann method for the simulation of electron beam melting processes. The multi-distribution approach incorporates a state-of-the-art volume of fluid free surface method to handle the complex interaction between gas, liquid, and solid phases. The paper provides a detailed explanation of the modeling of the electron beam gun properties, such as the absorption rate and the energy dissipation. Additionally, an algorithm for the construction of a realistic powder bed is discussed. Special emphasis is placed to a parallel, optimized implementation due to the high computational costs of 3D simulations. Finally, a thorough validation of the heat equation and the solid-liquid phase transition demonstrates the capability of the approach to considerably improve the electron beam melting process. © 2013 Elsevier Ltd. All rights reserved. Source

Scharowsky T.,Martensstr. | Juechter V.,Martensstr. | Singer R.F.,Martensstr. | Korner C.,Martensstr.
Advanced Engineering Materials | Year: 2015

Selective electron beam melting (SEBM) is perhaps the fastest production process for additive manufacturing techniques from powder beds. In the present investigation, scan speeds of 10 m s-1 have been used successfully for the melting. Nevertheless, the beam power has to be adjusted to guarantee a density of more than 99.5% for the build samples. The aim of this paper is to investigate the effect of the scan speed and beam power on the microstructure and the mechanical properties of Ti-6Al-4V. Therefore, a process map with a window for samples with a density higher than 99.5% and a good geometrical accuracy was developed. But, there are strong differences in microstructure and the resulting mechanical properties. These differences result from changes in the total energy input. In the presented work, strength is found to increase somewhat with decreasing volume energy (60-30 J mm-3) at a scan speed of 4 m s-1 as the cooling rate increases. This causes a change in microstructure, as the α platelet size varies in the range between 400 nm and 1.3 μm. Thus, an increase in ultimate tensile strength of 5% could be realized by adjusted energy input. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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