Power of mesoscale modelling in materials processing, Professor Maria Cecilia Poletti
Channel: bhadeshia123
Date: 27/07/2021

A talk by Professor  Maria Cecilia Poletti of the Technical University Graz, Austria, as a part of the "Modern Steel Development and Modelling" meeting, 2021. Video recording courtesy of Dipl.-Ing. Dr. Ludovic SAMEK, Professor of Metals Science, of the University of Applied Sciences in Upper Austria. The link to the meeting web site is:
https://www.fh-ooe.at/campus-wels/msdm2021/


Thermomechanical treatments are widely used to modify the microstructure and give shape to metallic products. Wrought alloys are the usual choice when a combination of fatigue resistance and high strength is required. Thermomechanical treatments consist of several amounts of hot and/or cold deformation steps, followed or alternated with heat treatments. The material undergoes plastic deformation, recovery, recrystallization, allotropic phase transformation and phase modification. Within the workpiece, many of these phenomena can occur simultaneously and heterogeneously. During thermomechanical processing of workpieces, also damage can take place. Although experiments are irreplaceable at the laboratory scale to identify and explain metallurgical phenomena, they cannot describe and predict the microstructural changes within the workpiece. The materials modelling and finite element simulation are applied especially for materials design, materials variations and modifications in the processing route, 
In this talk, we present a mesoscale physical model coupled with finite element modelling (FEM) to describe the local microstructure evolution during complex thermomechanical processing. The simulations allow predicting the dependency of the final microstructure on initial microstructures and processing parameters. 
The model is based on the evolution of internal variables such as dislocation densities, subgrain and grain size, the grade of recrystallization, morphological aspect of phases and phase fraction. The model combines the concepts of continuous dynamic recrystallization and recovery, dislocation reactions, the evolution of secondary phases, load partition and static restoration phenomena.
The mesoscale physical models are implemented a FEM-based software (DEFORMTM 2D) to obtain gradients of strain, temperature and microstructural features. A phenomenological model is additionally developed to predict flow localization during hot deformation of complex geometries. Finally, the evolutions of the microstructural features are correlated with the occurrence of flow localization. The models have been validated for high stacking fault energy metals and can be used for a wide range of alloys.