Modeling and Simulation of Microstructure Evolution for Additive Manufacturing of Metals: A Critical Review
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Modeling and Simulation of Microstructure Evolution for Additive Manufacturing of Metals: A Critical Review CAROLIN KO¨RNER, MATTHIAS MARKL, and JOHANNES A. KOEPF Beam-based additive manufacturing (AM) of metallic components is characterized by extreme process conditions. The component forms in a line-by-line and layer-by-layer process over many hours. Locally, the microstructure evolves by rapid and directional solidification. Modeling and simulation is important to generate a better understanding of the resultant microstructure. Based on this knowledge, the AM process strategy can be adapted to adjust specific microstructures and in this way different mechanical properties. In this review, we explain the basic concepts behind different modeling approaches applied to simulate AM microstructure evolution of metals. After a critical discussion on the range of applicability and the predictive power of each model, we finally identify future tasks. https://doi.org/10.1007/s11661-020-05946-3 Ó The Minerals, Metals & Materials Society and ASM International 2020
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INTRODUCTION
ADDITIVE manufacturing (AM) of metal components allows the generation of very complex parts even from high performance alloys such as titanium or nickel base superalloys.[1–5] Generally, powder bed fusion (PBF) based on the laser (L-PBF)[6] or the electron beam (E-PBF)[7] or direct energy deposition (DED)[8] also known as laser engineered net shaping (LENS) are used for high materials quality. The DED process is characterized by injecting metal powder into a melt pool generated by a coaxial laser. In contrast, the beam locally melts powder in a powder bed during PBF. Generally, AM is involved with rapid and directional solidification. Typically, the solidification velocity decreases from L-PBF to E-PBF to DED. The component evolves during several hours in a line-by-line and layer-by-layer process defined by a variety of process parameters such as beam velocity, beam power, distance between lines, layer thickness, line length, etc. The resulting microstructure is governed by all these parameters since they determine the local solidification conditions, i.e., the solidification velocity v and the thermal CAROLIN KO¨RNER, MATTHIAS MARKL, and JOHANNES A. KOEPF are with the Institute of Materials Science and Engineering for Metals, Friedrich-Alexander-Universita¨t Erlangen-Nu¨rnberg, Martensstr. 5, 91058 Erlangen, Germany Contact e-mail: [email protected]. Manuscript submitted March 25, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
gradient G at the solidification front.[9] Thus, the microstructure reflects the scanning strategy with the inherent periodicity and symmetry. We observe elongated grains following the solidification front as well as equiaxed microstructures.[10–12] The directional solidification conditions very often lead to strong texture formation, typically the orientation is preferred.[13] Specific scanning strategies may even result in single crystals.[14] As a consequence, the mechanical properties of additively build parts are dependent
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