Article (Scientific journals)
A New Concept for Modeling Phase Transformations in Ti6Al4V Alloy Manufactured by Directed Energy Deposition
Tchuindjang, Jérôme Tchoufack; Paydas, Hakan; Tran, Hoang Son et al.
2021In Materials, 14 (11), p. 2985
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Keywords :
directed energy deposition; microscopy and microanalysis techniques; Ti6Al4V alloy; phase transformation mechanisms; thermal modeling; experimental validation
Abstract :
[en] The microstructure directly influences the subsequent mechanical properties of materials. In the manufactured parts, the elaboration processes set the microstructure features such as phase types or the characteristics of defects and grains. In this light, this article aims to understand the evolution of the microstructure during the directed energy deposition (DED) manufacturing process of Ti6Al4V alloy. It sets out a new concept of time-phase transformation-block (TTB). This innovative segmentation of the temperature history in different blocks allows us to correlate the thermal histories computed by a 3D finite element (FE) thermal model and the final microstructure of a multilayered Ti6Al4V alloy obtained from the DED process. As a first step, a review of the state of the art on mechanisms that trigger solid-phase transformations of Ti6Al4V alloy is carried out. This shows the inadequacy of the current kinetic models to predict microstructure evolution during DED as multiple values are reported for transformation start temperatures. Secondly, a 3D finite element (FE) thermal simulation is developed and its results are validated against a Ti6Al4V part representative of repair technique using a DED process. The building strategy promotes the heat accumulation and the part exhibits heterogeneity of hardness and of the nature and the number of phases. Within the generated thermal field history, three points of interest (POI) representative of different microstructures are selected. An in-depth analysis of the thermal curves enables distinguishing solid-phase transformations according to their diffusive or displacive mechanisms. Coupled with the state of the art, this analysis highlights both the variable character of the critical points of transformations, and the different phase transformation mechanisms activated depending on the temperature value and on the heating or cooling rate. The validation of this approach is achieved by means of a thorough qualitative description of the evolution of the microstructure at each of the POI during DED process. The new TTB concept is thus shown to provide a flowchart basis to predict the final microstructure based on FE temperature fields.
Research center :
CAREM - Cellule d'Appui à la Recherche et à l'Enseignement en Microscopie - ULiège
Disciplines :
Materials science & engineering
Author, co-author :
Tchuindjang, Jérôme Tchoufack  ;  Université de Liège - ULiège > Département d'aérospatiale et mécanique > Metallic materials for additive manufacturing
Paydas, Hakan ;  Université de Liège - ULiège > Département d'aérospatiale et mécanique > Metallic materials for additive manufacturing
Tran, Hoang Son ;  Université de Liège - ULiège > Département ArGEnCo > Département Argenco : Secteur MS2F
Carrus, Raoul;  Sirris Research Centre
Duchene, Laurent  ;  Université de Liège - ULiège > Département ArGEnCo > Analyse multi-échelles des matériaux et struct. du gén. civ.
Mertens, Anne  ;  Université de Liège - ULiège > Département d'aérospatiale et mécanique > Metallic materials for additive manufacturing
Habraken, Anne  ;  Université de Liège - ULiège > Département ArGEnCo > Département ArGEnCo
Language :
English
Title :
A New Concept for Modeling Phase Transformations in Ti6Al4V Alloy Manufactured by Directed Energy Deposition
Publication date :
31 May 2021
Journal title :
Materials
eISSN :
1996-1944
Publisher :
MDPI, Basel, Switzerland
Volume :
14
Issue :
11
Pages :
2985
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
IAWATHA; PDR T.0039.14 Lasercladding
Funders :
FEDER - Fonds Européen de Développement Régional [BE]
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
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