Papers by Author: Mischa Crumbach

Abstract: Modeling and simulation of recrystallization, grain growth, and related phenomena are important tools for the fundamental understanding of microstructural evolution and prediction of engineering properties. In particular for ultra fine grained and nanocrystalline materials proper account of microstructural evolution is essential for the optimal processing of these materials. It is shown that for modeling of softening phenomena it is important to discriminate between discontinuous primary recrystallization and discontinuous grain growth owing to their quite different underlying physics. Recent developments in recrystallization modeling and simulation of grain growth are addressed, in particular nucleation of recrystallization and junction effects in grain growth. Major progress is also expected from atomistic modeling and quantum-mechanical computations for making available specific material properties.

Abstract: The predictions from a grain cluster deformation texture model, GIA, are utilized to study the nucleation texture of recrystallisation of aluminium alloys. In combination with a dislocation based work hardening model, the propensity of specific grains in their granular environment for select nucleation mechanisms is investigated. Quantitative criteria for the nucleation events can be formulated. The results can be fed into a growth model of recrystallisation to predict recrystallisation textures and lend themselves to through-process modelling.

Abstract: This paper contains a review of microstructural through-process modelling (TPM) and the particular role of ingot metallurgy from an industrial perspective, focusing on recent advances in solidification theory, solidification and homogenisation software, and software environments that allow models to interface. To illustrate how as-cast microstructure can impact on downstream processing steps, a sensitivity analysis has been performed on an AA1xxx alloy using an in-house homogenisation model. Thus, knowledge gaps in theory and model application are highlighted.

Abstract: Through-Process modelling (TPM) of microstructure evolution during thermomechanical processing of sheet produced from direct chill (DC) cast non-heat treatable aluminium alloys is discussed. In a companion paper [1] the upstream processes of casting and homogenisation were dealt with, whereas the present paper focuses on the downstream deformation and annealing steps. Some recent advances in relevant model development are reviewed, and the important microstructural descriptors and their interactions are outlined. Together with two application examples – coiling of hot strip, and cold rolling of foil – current knowledge gaps in theory and modelling capability are highlighted.

Abstract: We introduce a simulation procedure for through-process texture and anisotropy prediction, in particular for AA5182 sheet production from hot rolling through cold rolling and annealing. The FEM package ‘T-Pack’ based on the software LARSTRAN served as a process model. It was combined with physics based microstructure models for deformation texture (GIA), work hardening (3IVM), nucleation texture (ReNuc), and recrystallization texture (StaRT). The terminal sheet texture was used for a FEM simulation of cup drawing. A new concept of interactively updated texture based yield locus predictions was employed. The simulation predictions were compared to experimental data. The procedure can be applied to a wide variety of Aluminum alloys.

Abstract: Schemes to model deformation inhomogeneities and nuclei distributions based on the grain cluster model for deformation texture simulation GIA are presented. The orientation distributions of nuclei in stable orientations, nuclei in grains with orientation gradients and nuclei due to subgrain growth at grain boundaries are predicted. Additionally, nuclei with a random orientation distribution are considered, reflecting nucleation at shear bands or large constituent particles. Furthermore, models for a quantitative assessment of the participating nucleation mechanisms are proposed. The resulting nucleation texture was input to the static recrystallization texture model StaRT. The through-process texture development during a sequence of several hot rolling, cold rolling and annealing steps in industrial production of the aluminum alloy AA5182 is presented.