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This paper focusses on the investigation of the mechanical properties of lattice structures manufactured by selective laser melting using contour-hatch scan strategy. The motivation for this research is the systematic investigation of the elastic and plastic deformation of TiAl6V4 at different strain rates. To investigate the influence of the strain rate on the mechanical response (e.g., energy absorption) of TiAl6V4 structures, compression tests on TiAl6V4-lattice structures with different strain rates are carried out to determine the mechanical response from the resulting stress-strain curves. Results are compared to the mechanical response of stainless steel lattice structures (316L). It is shown that heat-treated TiAl6V4 specimens have a larger breaking strain and a lower drop of stress after failure initiation. Main finding is that TiAl6V4 lattice structures show brittle behavior and low energy absorption capabilities compared to the ductile behaving 316L lattice structures. For larger strain rates, ultimate tensile strength of TiAl6V4 structures is more than 20% higher compared to lower strain rates due to cold work hardening

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Abstract:Metal additive manufacturing has strongly gained scientific and industrial importance during the last decades due to the geometrical flexibility and increased reliability of parts, as well as reduced equipment costs. Within the field of metal additive manufacturing methods, selective laser melting (SLM) is an eligible technique for the production of fully dense bulk material with complex geometry. In the current study, we addressed the application of SLM for processing a high-manganese TRansformation-/TWinning-Induced Plasticity (TRIP/TWIP) steel. The solidification behavior was analyzed by careful characterization of the as-built microstructure and element distribution using optical and scanning electron microscopy (SEM). In addition, the deformation behavior was studied using uniaxial tensile testing and SEM. Comparison with conventionally produced TRIP/TWIP steel revealed that elemental segregation, which is normally very pronounced in high-manganese steels and requires energy-intensive post processing, is reduced due to the high cooling rates during SLM. Also, the very fast cooling promoted ε-and α'-martensite formation prior to deformation. The superior strength and pronounced anisotropy of the SLM-produced material was correlated with the microstructure based on the process-specific characteristics.

World market competition currently boosts trends like mass customization and open innovation which result in a demand for highly individualized products at costs matching or beating those of mass production. This work focus on the resolution of the production related dilemma between scale and scope, e.g. either the low-cost production of high quantities or the high-end and thus costintensive low-volume production of individualized goods. One of the areas of greatest potential for the resolution of this dilemma are rapid manufacturing (RM) technologies due to their almost infinite geometrical variability and freedom of design without the need for part-specific tooling. Selective Laser Melting (SLM) is one of the RM technologies that additionally provides series identical mechanical properties without the need for downstream sintering processes, etc. However, the state-of-the-art process and cost efficiency is not yet suited for series production. In order to improve this efficiency and enable SLM to enter series production it is indispensable to increase the build rate significantly by means of increased laser power and larger beam diameters. To exploit this potential, a new generation production machine including a kW laser and an optical multi-beam system is developed and experimental results and real life components are shown.