TY - BOOK

T1 - Predictive modeling of microstructure and toughness in aerospace components made from maraging steel 15-5 PH

AU - Hönigmann, Thomas

N1 - embargoed until 20-06-2029

PY - 2024

Y1 - 2024

N2 - This work presents a semi-empirical model framework able to predict the microstructurual development of the steel 15-5 PH during a multi-step forging and heat treatment process as well as the resulting yield strength, fracture toughness and ductile-brittle transition temperature. The model framework will aid computational process development of large structural aircraft parts, by only relying on the output of a finite element simulation of the forging process and the heat treatment parameters. It will be able to predict the performance at different positions of the final component in order to identify critical positions. Furthermore, by identifying the influence of the different process steps and parameters, the production process can be improved regarding e.g. process stability or efficiency. The microstructural constituents included in the model framework are niobium carbonitrides (NbC), the austenite grain size and the resulting substructure size of the martensitic matrix, and reverted austenite. Another constituent important for the mechanical properties, which is only considered intrinsically in this work are copper precipitates. In order to model the microstructural development during forging, laboratory-scale experiments using a Gleeble physical simulation set-up as well as industrial-scale die-forgings have been conducted. Grain growth during pre-heating in-tandem with NbC solution as well as grain refinement via recrystallization and NbC precipitation due to deformation and the effect of NbC clustering will be studied and modeled. The microstructural developement during annealing and aging will be investigated using dilatometry, X-ray diffraction, optical light microscopy, electron backscatter diffraction and atom probe tomography. Furthermore, tensile testing with in-situ high energy X-ray diffraction will be used identify the mechanical stability of reverted austenite. Finally, a set of microstructural conditions will be tuned and tensile testing, Charpy-V testing J-Integral testing will be used to determine the influence of the microstructure on the yield strength, ductile-brittle transition temperature and fracture toughness. Calibration and R^2 analysis of the model frameworks sub-models indicate a high accuracy.

AB - This work presents a semi-empirical model framework able to predict the microstructurual development of the steel 15-5 PH during a multi-step forging and heat treatment process as well as the resulting yield strength, fracture toughness and ductile-brittle transition temperature. The model framework will aid computational process development of large structural aircraft parts, by only relying on the output of a finite element simulation of the forging process and the heat treatment parameters. It will be able to predict the performance at different positions of the final component in order to identify critical positions. Furthermore, by identifying the influence of the different process steps and parameters, the production process can be improved regarding e.g. process stability or efficiency. The microstructural constituents included in the model framework are niobium carbonitrides (NbC), the austenite grain size and the resulting substructure size of the martensitic matrix, and reverted austenite. Another constituent important for the mechanical properties, which is only considered intrinsically in this work are copper precipitates. In order to model the microstructural development during forging, laboratory-scale experiments using a Gleeble physical simulation set-up as well as industrial-scale die-forgings have been conducted. Grain growth during pre-heating in-tandem with NbC solution as well as grain refinement via recrystallization and NbC precipitation due to deformation and the effect of NbC clustering will be studied and modeled. The microstructural developement during annealing and aging will be investigated using dilatometry, X-ray diffraction, optical light microscopy, electron backscatter diffraction and atom probe tomography. Furthermore, tensile testing with in-situ high energy X-ray diffraction will be used identify the mechanical stability of reverted austenite. Finally, a set of microstructural conditions will be tuned and tensile testing, Charpy-V testing J-Integral testing will be used to determine the influence of the microstructure on the yield strength, ductile-brittle transition temperature and fracture toughness. Calibration and R^2 analysis of the model frameworks sub-models indicate a high accuracy.

KW - Toughness

KW - ductile-brittle transition temperature

KW - DBTT

KW - Martensite

KW - Austenite

KW - yield strength

KW - NbC

KW - Niobium Carbonitride

KW - recrystallization

KW - grain size

KW - reverted austenite

KW - Cu precipitates

KW - Fracture

KW - Synchrotron

KW - Tensile

KW - Charpy-V

KW - J-Integral

KW - precipitation

KW - deformation

KW - forging

KW - mechanical properties

KW - model

KW - modeling

KW - austenite memory

KW - maraging

KW - 15-5 PH

KW - grain growth

KW - solution

KW - block size

KW - brittle

KW - ductile

KW - Zähigkeit

KW - Spröd-duktil Übergangstemperatur

KW - DBTT

KW - Martensit

KW - Austenit

KW - Streckgrenze

KW - NbC

KW - Niobkarbonitride

KW - Rekristallisation

KW - Korngröße

KW - Rückgebildeter Austenit

KW - Cu Ausscheidungen

KW - Bruch

KW - Synchrotron

KW - Zug

KW - Charpy-V

KW - J-Integral

KW - Ausscheidugn

KW - Umformung

KW - Schmieden

KW - mechanische Eigenschaften

KW - Modell

KW - Modellierung

KW - Austenit Gedächtnis

KW - Maraging

KW - 15-5 PH

KW - Kornwachstum

KW - Auflösung

KW - Blockgröße

KW - Spröd

KW - Duktil

M3 - Doctoral Thesis

ER -