This work investigates a ferrite matrix with multiple non-metallic inclusions to evaluate their influence on the global and local deformation and damage behavior of modified 16MnCrS5 steel. For this purpose, appropriate specimens are prepared and polished. The EBSD technique is used to record local phase and orientation data, then analyze and identify the size and type of inclusions present in the material. The EBSD data are then used to run full phase crystal plasticity simulations using DAMASK-calibrated material model parameters. The qualitative and quantitative analysis of these full phase simulations provides a detailed insight into how the distribution of non-metallic inclusions within the ferrite matrix affects the local stress, strain, and damage behavior. In situ tensile tests are carried out on specially prepared miniature dog-bone-shaped notched specimens in ZEISS Gemini 450 scanning electron microscope with a Kammrath and Weiss tensile test stage. By adopting an optimized scheme, tensile tests are carried out, and local images around one large and several small MnS inclusions are taken at incremental strain values. These images are then processed using VEDDAC, a digital image correlation-based microstrain measurement tool. The damage initiation around several inclusions is recorded during the in situ tensile tests, and damage initiation, propagation, and strain localization are analyzed. The experimental results validate the simulation outcomes, providing deeper insight into the experimentally observed trends.

Process maps according to Parasad et al. are already widely used to make statements about the formability of materials and their forming energy. However, these process maps only apply to conventional incompressible materials. At the TU Bergakademie Freiberg, these process maps have already been extended for particle-reinforced incompressible solid materials with a homogeneous particle distribution. The next step is to adapt the model for compressible particle-reinforced matertials so that they can also be used in powder metallurgy. The problem here is that the volume decreases as a result of compaction during powder forming. In powder metallurgy, however, compaction plays an important role. On the one hand, the compaction of the components leads to an increase in the material properties. On the other hand, pores pose a high risk of fractures and cracking. For this reason, it is the aim of this paper to make the existing process maps for incompressible materials usable for compressible materials by corresponding adaptations of the models prevailing in powder metallurgy. Furthermore, the effects of a homogeneous particle distribution and a graded particle distribution within the TRIP matrix composites on the process maps will be investigated. For this reason, process maps are produced in the temperature ranges between 700 – 1050 °C, with forming speeds of 0.001 – 100 s^-1 and residual porosity of 10 – 30 %. For this purpose, specimens with corresponding residual porosity and homogeneously distributed ZrO₂ 5 vol.%, 10 vol.%, 15 vol.% and 20 vol.% as well as a graded layer structure of corresponding ZrO₂ proportions are prepared. With the aid of these specimens, flow curves are determined and adjusted at appropriate temperatures and forming speeds during compression tests. The energy dissipation and an instability map are then modelled from these flow curves and a process map is derived. It was found that with increasing ZrO₂ content in the homogeneous and the graded structure, the areas that allow damage-free forming become smaller. The same applies with decreasing residual porosity. Nevertheless, the areas, which allow failure-free forming, are larger than the possible forming areas of solid components. However, the power dissipation efficiency of incompressible specimens is significantly lower than that of compressible specimen [1]. In addition, it was observed that with increasing ZrO₂ content and decreasing residual porosity, the efficiency of the power dissipation in the formable areas decreases. It was also found that the distribution of the reinforcing particles has a significant influence on the flow curves and the associated process maps, then the graded specimen do not represent a superposition of the individual process maps of the homogeneous specimens.

The ability to fabricate complex graded structures would be a significant step towards the manufacturing of material systems with properties tailored to individual applications. While powder metallurgy has had some success in this regard, it requires that the semi-finished products be exactly similar to the final component. However, it is significantly cheaper to produce simple, semi-finished products and then join them to form complex components with the desired graded structure through powder forging and simultaneous compaction. It is also essential that the graded structure of the semi-finished products is retained during the forming process. In this study, pre-sintered cylindrical semi-finished products consisting of identical homogeneous layers as well as graded components consisting of non-identical homogeneous layers were joined using powder forging at 1100 °C. The microstructures and densities as well as the mechanical properties of the final components were investigated. It was observed that, upon compaction, the components formed solid structures, in which the reinforcing ZrO₂ particles were completely integrated within the transformation-induced plasticity steel matrix. Finally, it was confirmed that the graded structure of the semi-finished products was retained in the final components.

This chapter addresses bulk forming processes-especially powder forging-used to produce complex shaped components from presintered TRIP-matrix composites. Based on experimentally determined material and process parameters (e.g., shrinkage, Poisson’s ratio, elastic modulus, oxidation behavior), extended process maps for compressible materials were presented. Subsequently, a characterization of the material flow as a function of the material conditions was reproduced via the visioplastic method and metallographic analysis, and then connections were drawn between the results and the extended process maps. The knowledge gained was used to develop a powder forging tool for a Gleeble HDS-V40, which was used to conduct model tests aiming to improve the component properties. The tool was equipped with compensating gaps to provide better compaction to the components. To find the optimal compaction for the solid material, different variants of compensating gaps were investigated. The components obtained through this approach were examined on the basis of their mechanical properties and microstructures. Furthermore, the deformation of graded components was analyzed in this study. In addition to the formation of a damage-tolerant interface and the shear strength of the different layers, special attention was paid to process-relevant parameters, such as the maximum deformation degree, the tool and specimen temperature and the pressure holding time.

Powder metallurgy is one way of producing complex, graded structures that could allow material systems to be produced with properties tailored to individual applications. However, powder metallurgy requires that the semi-finished products are very similar to the final component. It is much more economical to produce simple semi-finished products and then combine them by powder forging and simultaneous compaction than forming complex components with the desired graded structure. However, it is absolutely necessary that the graded structure of the semi-finished products is maintained during the forming process. In this study, pre-sintered cylindrical semi-finished products, consisting of axially graded as well as radially graded components, were produced by powder forging at 1100 °C. The microstructures, densities and mechanical properties of the final components were investigated to verify the effectiveness of the process route. It was observed that the components formed solid structures after compaction, in which the reinforcing ZrO₂ particles were fully integrated into the transformation-induced plasticity steel matrix.