Investigation of sluggish diffusion in FCC Al_0.25CoCrFeNi high-entropy alloy

Figures & data

Figure 1. Concentration profiles superimposed on backscatter electron micrographs of Al₆Co₁₉Cr₂₈Fe₂₈Ni₁₉ vs. Al₆Co₂₈Cr₁₉Fe₁₉Ni₂₈ diffusion couples isothermally annealed at (a) 900°C for 240 h, (b) 1000°C for 120 h, (c) 1100°C for 48 h, and (d) 1200°C for 24 h. (e) Temperature dependence of average effective interdiffusion coefficients (${\overline{\tilde{D}}}_i^{\text{eff}}$) for Co, Cr, Fe, and Ni.

Figure 2. (a) A schematic representation of sandwich diffusion couple assembly utilized to determine the tracer diffusion coefficient of Ni in Al_0.25CoCrFeNi. Concentration profile of Ni from thin film interface (Spike profile) superimposed on the Concentration profile of Ni from interdiffusion interface (Interdiffusion profile) and corresponding Gaussian fitted concentration profile obtained after mathematical subtraction of interdiffusion concentration profile from spike profile after annealing the sandwich diffusion couple at (b) 900°C for 12 h, (c) 950°C for 6 h, and (d) 1000°C for 2 h. (e) Temperature dependence of the Trace diffusion coefficients of Ni in Al_0.25CoCrFeNi.

Table 1. Ni tracer diffusion coefficients in various compositions of Al-Co-Cr-Fe-Ni high-entropy alloys.

	This study	Numerical extrapolation approach [14,19]
T (K)	Al0.25 CoCrFeNi	AlpCoqCrr FesNit [14]	Al6.64Co23.82 Cr23.66 Fe23.01Ni22.87 (∼ Al0.29 CoCrFeNi) [19]	Al4.88Co29.53 Cr18.58 Fe19.62Ni27.39 [19]
1173	3.7 × 10^−17	1.3 × 10^−17	7.9 × 10^−17	6.2 × 10^−17
1223	7.4 × 10^−17	3.4 × 10^−17	2.2 × 10^−17	1.8 × 10^−16
1273	1.9 × 10^−16	1.0 × 10^−16	5.9× 10^−16	5.0 × 10^−16

Figure 3. Average effective interdiffusion coefficients of (a) Co, (b) Cr, (c) Fe, (d) Ni, (e) Al, and (f) Mn in various FCC alloys as a function of temperature.

Figure 4. Tracer diffusion coefficient of Ni ($D_{\text{Ni}}^{\ast }$) in various FCC alloys as a function of temperature.

Figure 5. (a) Normalized potential energy fluctuation (p) as a function of temperature and (b) Ni tracer diffusion coefficient as a function normalized potential energy fluctuation (p) at 1000°C for Ni, FeNi, FeCrNi, CoCrFeNi, CoCrFeNiMn_0.5, CoCrFeNiMn, Al_0.25CoCrFeNi, Al_0.29CoCrFeNi, and Al_4.88Co_29.53Cr_18.58Fe_19.62Ni_27.39 alloys.

Dąbrowa J, Kucza W, Cieślak G, et al. Interdiffusion in the FCC-structured Al-Co-Cr-Fe-Ni high entropy alloys: experimental studies and numerical simulations. J Alloys Compd. 2016;674:455–462.

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Li Q, Chen W, Zhong J, et al. On sluggish diffusion in FCC Al–Co–Cr–Fe–Ni high-entropy alloys: an experimental and numerical study. Met (Basel). 2018;8(1):16.

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