Exceptional nanostructure stability and its origins in the CoCrNi-based precipitation-strengthened medium-entropy alloy

Figures & data

Figure 1. (a) APT map displays the atomic-scale elemental distribution. (b) Frequency distribution analysis for Co, Cr, Ni, Al and Ti atoms, which shows a comparison of observed (solid line) and the ideal random distribution (bar) described by binomial distributions for average solute contents.

Figure 2. SEM images of the γ′ precipitates in the Al3Ti3 alloy after aging at 800°C for (a) 16 h, (b) 72 h, (c) 168 h and (d) 360 h; The corresponding statistical particle size distribution of the experimental data and the prediction of the LSW model were also shown as insets.

Figure 3. (a) and (b) APT-reconstructions of the Al3Ti3 MEA aged at 800°C for 4 h and 168 h, respectively; (c) Level rule for the calculation of the volume fraction of the γ’ phase.

Figure 4. (a) The LSW relationship illustrating the coarsening of the γ’ phase in the Al3Ti3 MEA and the reported (FeCoNiCr)₉₄Al₄Ti₂ MEA. (b) Comparison of coarsening rates for the Al3Ti3 MEA and a number of Ni-based superalloys at 800°C.

Table 1 Chemical compositions of γ’ phase in the Al3Ti3 MEA (at. %) aged at 800°C for 4 h and 168 h.

		Compositions
	Phases	Co	Cr	Ni	Al	Ti
4h	Matrix	34.46 ± 0.31	37.09 ± 0.31	25.80 ± 0.28	1.37 ± 0.08	1.27 ± 0.07
	Precipitate	10.53 ± 0.33	1.83 ± 0.14	62.92 ± 0.52	8.74 ± 0.31	15.99 ± 0.40
168h	Matrix	34.78 ± 0.28	37.30 ± 0.29	25.34 ± 0.26	1.30 ± 0.07	1.28 ± 0.07
	Precipitate	10.18 ± 0.31	1.73 ± 0.14	63.32 ± 0.50	9.00 ± 0.30	15.77 ± 0.38

Table 2. Mobility matrix for Al3Ti3 MEA calculated at 800°C for the γ-matrix composition determined via APT. Values are multiplied by 10⁻²³, and the units are m²·mol·J⁻¹·s⁻¹.

k\i	Al	Ti	Co	Cr
Al	3.5407	−0.0830	−1.0502	−1.4679
Ti	−0.0830	3.7245	−1.1187	−1.5361
Co	−1.0502	−1.1187	12.6088	−7.1367
Cr	−1.4679	−1.5361	−7.1367	20.3425