Mechanism of Stress Relaxation and Phase Transformation in Additively Manufactured Ti-6Al-4V via in situ High Temperature XRD and TEM Analyses

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Title: Mechanism of Stress Relaxation and Phase Transformation in Additively Manufactured Ti-6Al-4V via in situ High Temperature XRD and TEM Analyses
Authors: Rossi Kaschel, FredericoVijayaraghavan, R. K.Shmeliov, A.Dowling, Denis P.Celikin, Mertet al.
Permanent link: http://hdl.handle.net/10197/11945
Date: 15-Apr-2020
Online since: 2021-02-15T16:45:19Z
Abstract: Additive manufacturing is being increasingly used in the fabrication of Ti-6Al-4V parts to combine excellentmechanical properties and biocompatibility with high precision. Unfortunately, due to the build-up of ther-mal residual stresses and the formation of martensitic structure across a wide range of typical processingconditions, it is generally necessary to use a post-thermal treatment to achieve superior mechanical perfor-mance. This investigation aims to obtain a deeper understanding of the micro/nanostructural evolution(a0martensite phase decomposition), accounting for the kinetics of phase transformation during the heattreatment of 3D-printed Ti-6Al-4V alloy. As the mechanism of phase transformation and stress relaxation isstill ambiguous, in this study the changes in crystal lattice, phase, composition and lattice strain were investi-gated up to 1000°C using bothin situhigh temperature X-ray diffraction (XRD) and transmission electronmicroscopy (TEM). Based on the result a mechanism of phase transformation is proposed, via the accommo-dation/substitution of Al, V and Ti atoms in the crystal lattice. The proposed mechanism is supported basedon elemental concentration changes during heat treatment, in combination with changes in crystal structureobserved using the high temperature XRD and TEM measurements. This study provides a deeper under-standing on the mechanism of phase transformation through martensitic decomposition, as well as a deeperunderstanding of the influence of post-thermal treatment conditions on the alloy’s crystal structure.
Funding Details: European Research Council
Science Foundation Ireland
Type of material: Journal Article
Publisher: Elsevier
Journal: Acta Materialia
Volume: 188
Start page: 720
End page: 732
Copyright (published version): 2020 Acta Materialia
Keywords: Additive manufacturingTi-AI-4VIn situHigh temperature transmission electron microscopyHigh temperature X-ray diffractionPhase transformationStress relaxation
DOI: https://doi.org/10.1016/j.actamat.2020.02.056
Language: en
Status of Item: Peer reviewed
This item is made available under a Creative Commons License: https://creativecommons.org/licenses/by-nc-nd/3.0/ie/
Appears in Collections:Mechanical & Materials Engineering Research Collection
I-Form Research Collection

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