Flash-annealed metastable alloys with novel microstructures and surface topographies

• Applicant: Dr.-Ing. Konrad Kosiba
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 401689894

The current proposal focuses on the investigation of fundamental scientific as well as technological aspects of bulk metallic glasses (BMGs) subjected to rapid heating in order to create novel metastable materials. In the course of this flash-annealing treatment, thermoplastic forming (TPF) is additionally applied to adjust the surface topography of the BMGs enabling the functionalization of their surface. Thereby, the BMG is present as a viscous metastable liquid with high deformability allowing the precise replication of micro-, nanoscale and hierarchical structures. Thus, one can adjust surface topographies with superhydrophobic and/ or –philic wetting characteristics. Particularly, the correlation between wetting characteristics, roughness, and aspect ratio of the surface structures is investigated. Such surfaces are of high interest for materials with a self-cleaning effect or as implants.During flash-annealing BMGs are crystallized in order to create metastable materials with novel microstructures. The phase formation depends on the heating rate and can be controlled. Furthermore, crystallization occurs at large undercoolings which are accompanied by high nucleation and lower crystal growth rates. Thus, flash-annealing of BMGs enables the formation of high-strength and at best ductile materials with fine-grained to nanocrystalline and at suitable process control even bimodal microstructures. Their mechanical properties shall be characterized in depth.So far, materials created from flash-annealing of BMGs as well as the thereby arising phenomena have been hardly studied and, thus, represent a new research field. The phase formation and crystallization kinetics as a function of the heating rate shall be investigated for two selected glass-forming alloys with different crystallization mechanisms: Cu44Zr44Al8Hf2Co2 and Ti40Zr10Cu34Pd14Sn2. The CuZr-based alloy has a high-temperature phase showing the shape memory effect and the resulting microstructures which could be obtained by flash-annealing are of high interest. The Ti-based alloy is biocompatible and could be used as implant material. The biocompatibility also depends on the wetting characteristics of the surface and could be enhanced by an appropriate surface structuring using TPF.Therefore, within the framework of the current proposal, a unit enabling thermoplastic embossing is going to be developed and integrated into the infrastructure of the already existing flash-annealing device.The superior objective of the current proposal is the creation of materials with enhanced mechanical and surface properties, which cannot be attained by conventional metallic materials, in order to enlarge the range of application for metastabile alloys.

• DFG Programme: Research Grants