Influence of laser-based powder bed fusion processing parameters on the microstructure of a metastable HEA

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dc.contributor.authorAnilkumar, Vishnu
dc.contributor.departmentChalmers tekniska högskola / Institutionen för industri- och materialvetenskapsv
dc.contributor.departmentChalmers University of Technology / Department of Industrial and Materials Scienceen
dc.contributor.examinerGuo , Sheng
dc.contributor.supervisorBala , Malladi
dc.date.accessioned2022-12-08T09:15:04Z
dc.date.available2022-12-08T09:15:04Z
dc.date.issued2022
dc.date.submitted2022
dc.description.abstractHigh entropy alloys (HEAs) constitute a novel class of alloys containing multiple principal elements in nearly equiatomic proportions. This compositional complexity increases the configurational entropy and hence stabilizes the formation of solid solutions. The unprecedented compositional complexity has reportedly enabled HEAs to perform better than conventional alloys in various situations. Manufacturing HEAs using additive manufacturing techniques such as laser based powder bed fusion (LB-PBF) helps in preventing the formation of detrimental phases, owing to high solidification rates compared to conventional casting. Rapid melting and solidification during the layer-by-layer printing could also result in martensitic transformations in some metastable HEAs. This work focuses on the development of non-equiatomic metastable HEAs based on the CoCrFeNi grade, aiming to engineer martensitic transformation via tuning the printing parameters. After evaluating the relative densities of the specimens from the parametric development using the design of experiments methodology, two specimens printed with a significant difference in laser power were selected for further analysis. Scanning electron microscopy analyses of as-printed specimens revealed the presence of banded features spanning across the microstructure. Subsequent analyses using transmission Kikuchi diffraction revealed that these bands correspond to the HCP phase, indicating the occurrence of the martensitic transformation during printing. Tensile testing of as-printed specimens with two different processing parameters exhibited a similar yield strength of 560 ± 10 MPa and an engineering strain of 34 %. This could be due to the similar transformation induced plasticity (TRIP) behavior of the two materials during loading.
dc.identifier.coursecodeIMSX30
dc.identifier.urihttps://odr.chalmers.se/handle/20.500.12380/305900
dc.language.isoeng
dc.setspec.uppsokTechnology
dc.subjectHigh entropy alloys
dc.subjectlaser-based powder bed fusion
dc.subjectmetastability
dc.subjectmartensite
dc.subjectmicrostructural characterization
dc.titleInfluence of laser-based powder bed fusion processing parameters on the microstructure of a metastable HEA
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster's Thesisen
dc.type.uppsokH
local.programmeMaterials engineering (MPAEM), MSc
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