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Evaluation of microstructure and tensile properties of grain-refined, Ti-alloyed ferritic stainless steel fabricated by laser powder bed fusion

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Ikehata,  Hideaki
Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society;

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Jägle,  Eric Aimé
Alloys for Additive Manufacturing, Project Groups, Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society;
Institute of Materials Science, Universität der Bundeswehr München, Neubiberg, Germany;

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Citation

Ikehata, H., & Jägle, E. A. (2021). Evaluation of microstructure and tensile properties of grain-refined, Ti-alloyed ferritic stainless steel fabricated by laser powder bed fusion. Materials Science and Engineering A: Structural Materials Properties Microstructure and Processing, 818: 141365. doi:10.1016/j.msea.2021.141365.


Cite as: http://hdl.handle.net/21.11116/0000-0009-414A-B
Abstract
Many alloys produced by Laser Powder Bed Fusion (LPBF) suffer from coarse grains and anisotropic mechanical properties. Here, we investigate how the addition of Ti can cause significant strengthening via grain refinement in a model ferritic stainless steel. We perform LPBF experiments using elemental Fe, Cr, and Ti powders (with significant O impurity in the Fe powder) and perform microstructural analysis by SEM, EDS and EBSD as well as tensile tests on the alloys Fe-19at.Cr and Fe-19at.Cr-5at.Ti. The Fe-Cr alloy displays very large grains after LPBF and a strong cube texture, rendering its mechanical properties similar to a single crystal. In the Fe-Cr-Ti alloy, TiO particle formation in the melt causes strong grain refinement, leading to a texture-free microstructure consisting of equiaxed grains ~1.6 μm in diameter. The 0.2 proof strength of the ternary alloy is more than double that of the binary alloy (281 MPa → 591 MPa), and the work hardening rate is also increased. While the elongation at fracture is reduced for the Fe-Cr-Ti alloy, at ~15 , it remains sufficient, and samples show ductile fracture surfaces. We estimate that the grain refinement accounts for the majority of the strengthening, however, solid solution strengthening and the effect of the texture are also significant. © 2021 Elsevier B.V.