Mechanical alloying mechanism in fcc, bcc, hcp metallic powder blends – an experimental and phase-field modelling approach

• Applicants: Professor Dr.-Ing. Karsten Durst; Professorin Dr.-Ing. Bai-Xiang Xu
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576175114

Mechanical alloying using severe plastic deformation is a promising method to achieve new nanocomposites and nanostructured materials with compositions well beyond the possibilities of conventional metallurgical approaches. Applying High Pressure Torsion (HPT) deformation on elemental powders allows a continuous intermixing and refinement of the microstructure even for immiscible elements. The exact mechanism during mechanical alloying in the context of HPT processing of powders are not fully understood and will be addressed in this joint experimental and theoretical project. As an important and interesting model system, we will work within the compositional parameter space of multi-element alloys, such as the Co-Cr-(Ni,Cu) system. The ternary equimolar Co-Cr-Ni system exhibits after conventional metallurgical processing a single phase fcc crystal structure. Furthermore, this medium entropy alloy system has recently received a lot of attention due to its tuneable deformation modes and resulting interesting mechanical properties. In this project, we want to apply a new powder-based HPT route starting from elemental powders to study how the consolidation, intermixing and structure formation take place in dependence of the binary solubilities of the individual elements. Whereas in the Co-Cr-Ni system the formation of a single phase fcc solid solution is expected, the Co-Cr-Cu system shows lower solubilities and a different structure formation is expected. The intermixing behaviour will be studied using phase-field modelling considering coupling between mechanical fields and solubilities. To reveal the intricated interplay among mechanical deformation, chemical diffusion and structural transition after a quasi-equilibrium grain size is reached, a multi-physics phase-field model will be developed with regards to thermodynamics and kinetics. Finite element simulations, after essential experimental parameterization and validation, will be performed to unveil the degree of supersaturation, and their dependency on the key aspects, e.g. volume fraction of elements, deformation level, heat of mixing, dislocation shuffling effect. The project aims to thus improve our understanding of structure formation and mechanically enforced supersaturation in the Co-Cr-(Ni,Cu) system, providing guidelines for the development of new nanostructured alloys based on free selection of individual elemental powders and compositions.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Christian Kübel