Phase field modeling of rapid solidification for thin films and additive manufacturing

Tatu Pinomaa

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Several advanced industrial manufacturing processes operate in rapid solidification conditions, including laser welding, thermal spray coating deposition, and additive manufacturing. These processes lead to materials with drastically altered properties, when compared to low solidification rate manufacturing methods such as casting. This is due to the unique microstructural features emerging in rapid solidification. Rapid solidification conditions alter growth dynamics, for example through kinetically selected metastable phases, notable interface attachment kinetics, and solute trapping. Therefore there is a strong motivation to adjust these manufacturing processes to target specific microstructures, in order to reach desirable material properties. These process-structure-property links can be established by computational modeling. In the past decades, the phase field method has become the state-of-the-art model to simulate solidification on microstructural scales. Its success in the materials science community can be attributed to its connection to statistical physics and thermodynamics, simplicity, and relative ease with which new physical phenomena can be implemented. In this thesis, a computationally efficient and quantitative phase field modeling framework is presented for the rapid solidification regime. The phase field model is made computationally efficient through adaptive mesh refinement and shared memory parallelization. A quantitative near-equilibrium alloy phase field model is extended to operate in the rapid solidification regime through matched interface asymptotics analysis, allowing for controllable solute trapping kinetics that follow the continuous growth model in the thin interface limit. The rapid solidification simulations are compared to thin film solidification experiments with time-resolved in-situ imaging. This phase field model is applied to the study of additive manufacturing, first for stainless steel to understand the process-microstructure relationships, and then as a method to investigate the effects of inoculation to alter the polycrystalline structures. The presented rapid solidification phase field modeling framework will assist systematic process-structure-properties based design of novel engineering materials.
Translated title of the contributionNopean jähmettymisen faasikenttämallinnusta ohutkalvoille ja materiaalia lisäävälle valmistukselle
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Ala-Nissilä, Tapio, Supervising Professor
  • Laukkanen, Anssi, Thesis Advisor, External person
  • Provatas, Nikolas, Thesis Advisor
Publisher
Print ISBNs978-952-64-0008-2
Electronic ISBNs978-952-64-0009-9
Publication statusPublished - 2020
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • rapid solidification
  • phase field modeling
  • additive manufacturing

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