Project objectives and specific aims
Motivation for doing research
With the progress of fusion technology there is a growing demand for the alloys applicable in reactor vessels that are respecting the so-called fail-safe scenarios. Currently, the best performing materials are the W-Cr alloys. However, since they are produced as saturated/unstable solid solution, the fail-safe-performance is dependent on preservation of the unstable state. Studies show that the solid solution decomposition rate at 1000 °C is already significant. Our knowledge of the W-Cr system is limited, since its lack (until recently) of industrial importance that did not motivate the research interest in the system. Hence, for the fusion safety, it is of the utmost importance to understand the thermodynamical behavior W-Cr system and devise theory of the stabilization of the solid solution.
Our main hypothesis:
The ab-initio methods, coupled with model calculations of electronic structure, with concomitant experimental verification, will provide us with better understanding on what effect causes the melting temperature diverge from the miscibility gap in W-Cr alloys and what slows down the kinetics of diffusion of W and Cr.
Our approach
We approach our goal by doping the W-Cr alloy with different transition metals from 6th period and analyzing how change of elastic properties influence the phononic spectra. Such stiffening/softening of the acoustic branches will in turn changes both miscibility gap and melting temperature. In this approach we can also identify the role of entropy in such a process, and using the output as an input to model calculations based on extended Hubbard model. This, on the other hand, should give us the answer how itinerancy and electronic correlations affect the phase diagram.
This work was supported by the Czech Science Foundation (GAČR), project No. 20-18392S.