Nanocomposites and nanomaterials

Diffusion of 63Ni in as-cast high-entropy alloys AlхFeNiCoCuCr
Makarenko S.Yu., Mazanko V.F., Mordyuk B.М. 
G.V.Kurdyumov Institute for Metal Physics, NAS of Ukraine,36 Academician Vernadsky Blvd., Kyiv 03142, Ukraine.
E-mail: serg_makar@ukr.net 

Fig. 1. The distribution of the radioactive isotope 63Ni in depth(d) in high-entropy alloys AlxFeNiCoCuCr with the Al concentrations x = 1; 1,5 after diffusion ageing at 1200оС during τ = 3,6.104 s.	
The diffusion of nickel in as-cast high-entropy alloys AlхFeNiCoCuCr (x = 1; 1,5) was studied in this work by means of the tracer diffusion method using 63Ni [1]. The diffusion ageing of samples were carried out at 1200оС during 10 hrs in vacuum. The diffusion coefficient of Ni in the alloys was determined upon concentration isotope distribution curves (Fig. 1) and turned out D = (1,6-5,3)10-11 cm2/s that is abnormally less more than by one order as compared to self-diffusion of Ni. It was shown that diffusion in these HEA proceeds mainly in a volume by a vacancy mechanism. The value of D is increased approximately in three times with the increasing Al concentration from x = 1 to x = 1,5. As result the sluggish diffusion of Ni in Al containing high-entropy alloys AlхFeNiCoCuCr occurs preferably in a volume by a vacancy mechanism and explained by difference of the atomic radius of Al and other metals of this alloy (Al have the highest atomic radius) and relatively high value of enthalpy of mixing of the Al and Ni system 

1.	Larikov L. N., Isaichev V. I. Diffusion in metals and alloys, Naukova Dumka, Kiev, 1987.