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Thermal simulation and phase modeling of bulk metallic glass in the powder bed fusion process
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0003-4061-4632
Ångström Laboratory, Uppsala University, Uppsala.
Ångström Laboratory, Uppsala University, Uppsala.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0002-0053-5537
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2019 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 27, p. 345-352Article in journal (Refereed) Published
Abstract [en]

One of the major challenges with the powder bed fusion process (PBF) and formation of bulk metallic glass (BMG) is the development of process parameters for a stable process and a defect-free component. The focus of this study is to predict formation of a crystalline phase in the glass forming alloy AMZ4 during PBF. The approach combines a thermal finite element model for prediction of the temperature field and a phase model for prediction of crystallization and devitrification. The challenge to simulate the complexity of the heat source has been addressed by utilizing temporal reduction in a layer-by-layer fashion by a simplified heat source model. The heat source model considers the laser power, penetration depth and hatch spacing and is represented by a volumetric heat density equation in one dimension. The phase model is developed and calibrated to DSC measurements at varying heating rates. It can predict the formation of crystalline phase during the non-isothermal process. Results indicate that a critical location for devitrification is located a few layers beneath the top surface. The peak is four layers down where the crystalline volume fraction reaches 4.8% when 50 layers are built.

Place, publisher, year, edition, pages
Elsevier, 2019. Vol. 27, p. 345-352
Keywords [en]
Additive manufacturing simulation, BMG, Heat input modeling, PBF, Phase evolution
National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-73489DOI: 10.1016/j.addma.2019.03.011ISI: 000466995800034Scopus ID: 2-s2.0-85063396910OAI: oai:DiVA.org:ltu-73489DiVA, id: diva2:1302925
Note

Validerad;2019;Nivå 2;2019-04-08 (svasva)

Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2021-06-11Bibliographically approved
In thesis
1. Modelling of laser-based powder bed fusion for bulk metallic glass formation
Open this publication in new window or tab >>Modelling of laser-based powder bed fusion for bulk metallic glass formation
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Modellering av laserbaserad pulverbäddfusion för additiv tillverkning av glasmetall
Abstract [en]

The work presented in this thesis aims to develop a modelling approach to predict crystalline phase evolution in bulk metallic glass during additive manufacturing with laser-based powder bed fusion (PBF-LB). Metallic glasses are non-crystalline metallic materials that generally possess exceptional properties because of its amorphous struc-ture. Manufacturing of metallic glass is possible by rapid cooling of a liquid metal alloy. The required cooling rates to avoid crystallisation generally limits traditional manufac-turing techniques to small/thin samples. The desirable properties of metallic glasses motivate manufacturing of larger samples. PBF-LB is one promising method by which bulk metallic glass potentially can be produced without size limitation. Cooling rates in this process are generally several orders of magnitude higher than critical cooling rates to bypass crystallisation in glass forming alloys. Crystalline structures may still evolve within the solid material because of thermal cycling during the manufacturing process. Numerical simulation can assist development of process for bulk metallic glass formation by predicting the phase evolution. Simulations can also help to increase the understand-ing of where and when crystalline structures develop with respect to process parameters and scanning strategy. Simulation of bulk metallic glass formation during PBF-LB is a challenge. The thermodynamic and kinetic properties of the material and the large variations in time and length scales in the process makes accurate simulations difficult. This thesis address these challenges by developing a modelling approach for simulation of the temperature history and crystalline phase evolution. The objective is to assist the development of process parameters for bulk metallic glass formation. The approach includes finite element modelling to compute the temperature history in the heat affected zone. The modelling includes approximations of the energy input and approaches to sim-ulate the large variations in time and length scales associated with PBF-LB. Computed temperature histories acts as input in calculations of the crystalline phase evolution in the metallic glass. The phase transformation modelling approach includes a modified isothermal model and classical nucleation and growth theory. The result is a coupled thermal and phase transformation model that can predict the trend in crystalline phase evolution in a bulk metallic glass with respect to the process parameters. The predictions show very good agreement to experimental estimates of the crystalline volume fraction. Comparison of simulations makes it possible to evaluate the process parameters in terms of crystalline size distribution. The model is a powerful tool that help the development and fine tuning of process parameters to produce bulk metallic glass.

Place, publisher, year, edition, pages
Luleå University of Technology, 2021
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Applied Mechanics
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-83431 (URN)978-91-7790-793-0 (ISBN)978-91-7790-794-7 (ISBN)
Public defence
2021-05-26, E632, Luleå, 15:00
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , GMT14-0048
Available from: 2021-03-29 Created: 2021-03-29 Last updated: 2022-01-12Bibliographically approved

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Lindwall, JohanLundbäck, AndreasLindgren, Lars-Erik

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