Columnar-to-equiaxed grain transition in powder bed fusion via mimicking casting solidification and promoting in situ recrystallizationShow others and affiliations
2021 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 46, article id 102086Article in journal (Refereed) Published
Abstract [en]
Columnar grain structure typically formed along the build direction in the electron beam-powder bed fusion (EBPBF) technique leads to anisotropic physical and mechanical properties. In this study, casting solidification condition was mimicked, and in situ recrystallization was promoted in EB-PBF to facilitate columnar-to-equiaxed grain structure transition in Alloy 718. This is achieved via a unique linear melting strategy coupled with a specific selection of process parameters in EB-PBF. It was found that site-specific melting using line order number (LON) function affected the cooling rate and temperature gradient, which controlled grain morphology and texture. A high LON resulted in a large equiaxed grain zone with a random texture, whereas a fixed LON with a high areal energy density led to a strong texture. The main driving force in the formation of cracks and shrinkage defects during the transition was investigated. A high LON at a fixed areal energy density reduced the average total shrinkage defects and crack length. The hardness was decreased through the transition, which was linked to the reduction in the size of the gamma ‘’ precipitates.
Place, publisher, year, edition, pages
ELSEVIER , 2021. Vol. 46, article id 102086
Keywords [en]
Additive manufacturing; Electron beam-powder bed fusion; Alloy 718; In situ recrystallization; Grain structure
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-17560DOI: 10.1016/j.addma.2021.102086ISI: 000697020200002Scopus ID: 2-s2.0-85110462749OAI: oai:DiVA.org:hv-17560DiVA, id: diva2:1609515
Note
Funding from the European Regional Development Fund, the Simulation and Control of Material affecting Processes (SiCoMap) and the Sustainable Manufacturing Through Next-Generation Additive Process (SUMAN-Next) projects with funding from the KK Foundation, are highly acknowledged.
2021-11-082021-11-082022-03-31