Speaker
Description
High entropy alloys (HEA) [1] are alloys containing at least five elements in equiatomic or near-equiatomic concentration. They adopt simple crystallographic structures such as bcc, fcc and hcp structure solid solution phases. Identified rapidly for their outstanding mechanical properties, HEA have also been considered as potential coatings for thermal and diffusion barriers, and for oxidation resistance [2]. Synthesized as nanoparticles, HEA exhibit interesting catalytic properties towards ammonia oxidation for instance, adding to the long list of their attractive physical and chemical properties [3].
As explained above, several HEA potential applications make use of their surface properties. However, fundamental questions remain open on the structural and chemical stabilities of HEA surfaces under operating conditions.
Here, we will report our first investigation of two HEA model surfaces namely the FeCrMnNiCo(110) and (320), system also referred as Cantor alloy [4]. The structural and compositional evolutions of surfaces will be presented for various preparation conditions under ultra high vacuum using a multi-technique approach. While the (320) surface presents an ordered structure, the (110) surface reveals an important degree of structural disorder and local reconstructions. These works will also highlight important surface chemical segregation, demonstrate the influence of the sample annealing history on the surface composition and set an annealing upper limit above which elemental desorption occurs. Finally, the impact of the thermal history on this random solid-solution will be discussed based on transition electron microscopy experiments performed on HEA lamellae.
[1] J.W. Yeh, S.K. Chen et al., Adv. Eng. Mater. 6, (2004) 299.
[2] Y. Zhang, T.T. Zuo et al., Prog. Mater. Sci. 61, (2014) 1.
[3] Y. Yao, Z. Huang et al., Science 359, (2018) 1489.
[4] B. Cantor, I.T.H. Chang et al., Mater. Sci. Eng. A 375-377, (2004) 213.
| Speaker Country | France |
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