Integrative material and process model for the correlation of phase morphology and flow behavior of spheroidization annealed low-alloyed carbon steels

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The mechanical properties of multiphase steel materials such as strength, toughness and ductility do not depend solely on their chemical composition and the volume fraction of phase constituents. Rather, the microstructure morphology used in the course of semi-finished product manufacture and heat treatment, e.g. of spheroidization annealing, has a pronounced influence. For example, the influence of cementite morphology on the mechanical properties of spheroidizing annealed steels has already been demonstrated by various investigations. However, the current state of research lacks a fundamental understanding of the integrative relationship between heat treatment conditions and the resulting flow properties and deformation behaviour of a steel material via the morphology change of its microstructure. The solution to this problem is devoted to this project, in which the complex interactions are determined experimentally and building on that, a numerical model will be created. Various experimental techniques from the field of purely thermal and external stress assisted heat treatment, SEM-in situ-, -2D- and -3D-metallography, the determination of individual phase properties as well as multiaxial bulk forming represent the experimental approach. The numerical model should comprise several simulative tools such as the phase field theory for temporal and spatial development of phases, representative volume elements for determining the final properties of the material and artificial neural networks for transferring the results obtained to other materials. To validate the model, experimental investigations of the practical characterization of formability are required. The results from modelling should contribute to an improved understanding of the relationships between strength properties and deformation behaviour, microstructure development and soft annealing parameters. A practice-relevant advantage opens up by the possibility of being able to control the required flow properties inversely via the established relationships in a targeted manner in accordance with the respective downstream forming process, to save unnecessary hours of annealing and to ensure the interchangeability of steel materials.