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Title: Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718
Authors: Radhakrishnan, R. Jayaraj
Kumar, Punit
Seet, Hang Li
Nai, Sharon Mui Ling
Wang, Pei
Ramamurty, Upadrasta
Keywords: Engineering::Materials
Issue Date: 2022
Source: Radhakrishnan, R. J., Kumar, P., Seet, H. L., Nai, S. M. L., Wang, P. & Ramamurty, U. (2022). Cascading of the as-built microstructure through heat treatment and its role on the tensile properties of laser powder bed fused Inconel 718. Materialia, 21, 101272-.
Project: A18B1b0061
Journal: Materialia
Abstract: The microstructures and mechanical properties of the Ni based superalloy, Inconel 718 (IN718), which was additively manufactured using the laser beam powder bed fusion (LB-PBF) technique in the as-built (AB) and heat treated (HT) conditions were investigated, with emphasis on the microstructural evolution from the AB to HT conditions and, in turn, on the tensile properties. Optimized LB-PBF parameters in two different processing instruments led to distinct textures in the AB alloys, which, in turn, impart diverging combinations of strength-ductility properties. These variations are rationalized by recourse to an analysis of the effective mean free path for dislocations within the solidification cell structures. Amongst the five different heat treatment schedules examined, one set led to the retention of as-built grain morphology and texture with the formation of the δ phase that is oriented at either ±45° to build direction in the alloy with 〈100〉 texture or at 0/ ± 90 ° in the alloy with 〈110〉 texture. The second set of heat treatments led to complete recrystallization, and hence loss of as-built microstructural signatures, with no δ phase. The critical role of δ phase in determining the grain growth kinetics and subsequently the anisotropy in mechanical properties of heat treated IN718 was elucidated. The absence of δ phase was found to enhance both strength and ductility, while its occurrence in the alloy with 〈110〉 texture along the build direction reduces ductility markedly. Implications of these results in terms of developing and designing the processing strategies of LB-PBF Inconel 718 with tailored microstructures and good mechanical properties are discussed.
ISSN: 2589-1529
DOI: 10.1016/j.mtla.2021.101272
Rights: © 2021 Acta Materialia Inc. Published by Elsevier B.V. All rights reserved.
Fulltext Permission: none
Fulltext Availability: No Fulltext
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