Lecture
Diffusion in Ni-CoCrFeMn alloys: Experimental and theoretical study on the transition from dilute solid solution to high-entropy alloy
We investigate the concentration dependent tracer diffusion properties of the Cantor alloy system. The Ni concentration is systematically increased to understand the transition of the diffusional properties from a dilute Ni alloy towards the equimolar HEA.
Radioactive Cr, Co, Fe, Mn, and Ni isotopes are used to experimentally study the temperature dependent bulk tracer diffusion coefficients in Ni_x(CoCrFeMn)_(1-x) with x in the range from 0.2 to 0.92 [1,2]. The measurements are combined with high-throughput calculations of the concentration dependent vacancy formation and vacancy migration energies. The atomistic calculations rely on the recently developed interatomic potential for the Cantor alloy [3].
We develop a kinetic Monte-Carlo algorithm using the vacancy migration barriers and their distribution determined from the high-throughput calculations as input to calculate concentration dependent diffusion constants and tracer correlation factors. This approach is different from the established random alloy model as species are not assigned constant mean jump rates but full distributions instead. The comparison of model and experiment gives insights in the different roles of the migration barrier distributions, tracer correlation factors, and vacancy formation energies.
[1] Kottke, J., Laurent-Brocq, M., Fareed, A., Gaertner, D., Perrière, L., Rogal, Ł., Divinski, S.V., Wilde, G., 2019. Scripta Mater. 159, 94–98.
[2] Vaidya, M., Pradeep, K.G., Murty, B.S., Wilde, G., Divinski, S.V., 2018. Acta Mater. 146, 211–224.
[3] Choi, W.-M., Jo, Y.H., Sohn, S.S., Lee, S., Lee, B.-J., 2018. npj Comput Mater 4, 1.
