Diffusion in high entropy alloys

Basic data for this project

Type of project: Individual project
Duration: 01/08/2016 - 31/07/2019 | 1st Funding period

Description

"High Entropy Alloys" (HEAs) are solution phases with almost equal concentration of 5 or more solute elements. They show high entropy of mixing and a low Gibbs energy with respect to the unary end-members. The proposed work aims to investigate systematically the tracer diffusion in multicomponent FeNiCrCoMn high-entropy alloys. For the first time tracer diffusion of all constituting elements will be examined using corresponding tracers (59Fe, 63Ni, 51Cr, 57Co and 54Mn). We plan to start with equiatomic FeNi adding sequentially Mn, Co and Cr and tracing the change in the tracer diffusivity as a function of number of components in the alloy. Furthermore, the tracer diffusion experiments will be accompanied by interdiffusion studies. Special experiments will be performed combining inter-diffusion and tracer diffusion measurements which will directly provide the atomic diffusivities as a function of composition in the ternary and higher component alloys. These atomic mobilities will serve as direct input for thermodynamic-kinetic modelling of the HEAs. In parallel a novel multicomponent diffusion model will be established using a symmetric expansion of the multicomponent diffusion potential. This expansion avoids the necessity to specify a reference (balance) element as necessary in standard approaches, which is problematic for HEAs. The measured tracer diffusion will be values converted to atomic mobilities , serving as direct input to construct a novel chemical mobility database. The database will be verified by transient simulation of the diffusion profiles in the diffusion couple experiments.

Keywords: Materialphysik; Hochentropie-Legierungen; Materialforschung