The development of advanced steels and forming processes with reduced environmental impact is a critical objective in modern materials science. This dissertation investigates strategies for damage-controlled forming, a strategy which aims to improve material properties with only minimal changes, by systematically analysing how microstructure, mechanical contrast, and stress state influence damage nucleation and growth in steels, particularly dual-phase (DP) and multi-phase alloys such as 16MnCrS5.To this end, two complementary automated tools for quantifying damage prevalence using scanning electron microscopy were developed: one uses inclusion-based localization to enable high-throughput analysis in steels where inclusions drive damage formation. The other employs segmentation of etched microstructures to provide detailed correlations between local constituent arrangement and damage occurrence. These approaches were validated on 16MnCrS5 steel, revealing both their strengths and limitations: one offers greater generality and robustness to imaging conditions, while the other provides higher information density but is applicable only to more specific microstructures. Experimental investigations demonstrated that strategic manipulation of strain paths and loading directions can significantly reduce damage prevalence. For example, sequencing compressive before tensile deformation was found to promote strain hardening in ferrite and minimise damage prevalence by reducing mechanical contrast. The role of mechanical contrast was also elucidated in 16MnCrS5 through temperature-dependent testing: non-linear relationships between constituent hardening rates at different temperatures, rather than yield strength alone, were shown to govern incompatibility during plastic deformation, thereby affecting overall material integrity. A particular focus was placed on understanding how local phase environments affect damage behaviour in multi-phase microstructures. It was shown that while nucleation of new damage sites is not strongly dependent on local environment, subsequent growth is highly sensitive to the surrounding phases: MnS inclusions engulfed by ferrite experience greater void growth, whereas encapsulation within pearlite provides effective shielding. These findings challenge the direct transferability of dual-phase design principles to more complex alloys.
Maximilian Aeneas Wollenweber (Thu,) studied this question.