Relating processing-microstructure-mechanical properties of inconel 718 fabricated by selective laser melting

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dc.contributor Acoff, Viola L.
dc.contributor Weaver, Mark Lovell
dc.contributor Mewes, Claudia K. A.
dc.contributor Genau, Amber
dc.contributor.advisor Li, Lin Holland, Sharniece 2018-12-14T18:11:41Z 2018-12-14T18:11:41Z 2018
dc.identifier.other u0015_0000001_0003061
dc.identifier.other Holland_alatus_0004D_13591
dc.description Electronic Thesis or Dissertation
dc.description.abstract Selective laser melting (SLM), uses a computer controlled scanning beam to selectively melt pre-spread powders in a layer by layer fashion. SLM has become a powerful tool to fabricate Inconel 718 due to the ability to obtain a desired microstructure and mechanical properties such as hardness and tensile strength. The combination of rapid melting and solidification in the SLM process, produces a very unique microstructures, which results in different material properties in comparison to conventional routes. Although Inconel 718 has been thoroughly studied, an in-depth analysis of grain boundary (GB) network structures and multiscale correlation of microstructure and mechanical behaviors is lacking. This work aims to relate the processing-microstructure-property relationship of Inconel 718 fabricated by SLM using experimental characterization, computational simulation, and theoretical analysis. These investigations reveal: 1. The as-SLM Inconel 718 exhibits spatial heterogeneity with a typical fast solidification structure with melting pool, columnar and equiaxial grains. In the melt pools, finer dendritic structure and a cellular structure, reflecting micro-segregation due to the laser induced localized thermal history. Upon heat treatment, the unique SLM structures are completely removed. The HT sample displays a fully recrystallized grain structure with appearance of twin boundaries and precipitates along the GBs and within the grain interiors. 2. Effective properties are influenced by the character and connectivity. The GBs diffusivity for both random and crystallographically consistent networks exhibits two types of behaviors, based on the contrast of local diffusivity of individual GBs. The as- SLM samples are occupied by one large connected general cluster reflecting the dominance of J0 triple junctions. While the HT sample multiple special clusters reflecting the interweaving of general and special boundaries. 3. The Vickers hardness of the as-SLM sample is ~ 3.14 GPa and the measured wear rate is ~ 2.16 10-6 mm2 while the HT sample had a significant increase in the Vickers hardness to ~ 4.49 GPa, and a reduction of wear rate to 1.7510-6 mm2. Such enhancement of the mechanical performance can be contributed to the improvement of part quality via lowering the porosity, the removal of residual thermal stress, and the precipitation of nanoscale strengthening phases.
dc.format.extent 145 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Materials Science
dc.title Relating processing-microstructure-mechanical properties of inconel 718 fabricated by selective laser melting
dc.type thesis
dc.type text University of Alabama. Department of Metallurgical and Materials Engineering Materials Science The University of Alabama doctoral Ph.D.

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