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Page 10 of 18 Lu et al. J Mater Inf 2022;2:11 I http://dx.doi.org/10.20517/jmi.2022.15

Figure 4. (A) Assessed enthalpy of formation at 298 K compared with DFT data. (B) Assessed heat capacities of Ni 4Mo and fcc at 80 at.%
Ni compared with experimental data (dotted line represents the calculated at 78 at.% Ni).

line). There was probably a deviation in the composition of the sample in the experiments by Brooks and
Meschter.

Mo­Re system
Knapton [37] conducted a careful study of this system by means of melting-point measurements, XRD and
metallographic methods, using both powder-metallurgical and arc-melting samples. Knapton did not clarify
which preparation method was used for each piece of data clearly. However, he showed that between 1673
and 1873 K, only the phase was stable at ∼68 at.% Re, while in the immediate vicinity of 70 at.% Re, the
phase decomposed. This means that the single phase region can reach as far as 68 at.% Re between 1673 and
1873 K. All other available experimental data [3,36,38–40] also manifest a wide single phase region over a wide
temperature range in the binary Mo-Re system. In addition, the previously assessed homogeneity range of the
phase at low temperatures was so narrow that the extrapolation to the ternary system cannot agree with the
[3]
experimental data , which will be discussed in the following ternary assessment. Any attempt to reproduce
a U-shape phase boundary led to a very poor fit of site occupancy. Considering the wide single phase
region over a wide temperature range and the fact of difficulty reaching equilibrium at lower temperatures, the
estimated eutectoid temperature may need further confirmation.

As mentioned in the literature review, when extrapolating the Mo-Re system with the parameters of Mathieu
et al. to the ternary system, the bcc phase of the three-phase equilibria (i.e., bcc + + bct and bcc + bct + ) has
a relatively high Mo content comparing to the experimental data [3,53] . It was found that the Gibbs energy of
the binary bcc phase assessed by Mathieu et al. was too positive by giving the sub-regular solution parameter
1
(i.e., ) in order to reduce the binary bcc+ two-phase region [53] . Thus, in the present work, a regular
,
solution model was adopted to solve the problem.

Figure 5 shows the present calculated phase diagram of the Mo-Re system and the assessment by Mathieu et
al. together with the experimental data [3,36–40,53] . A larger phase region is realized but fails at the Re-rich
side as the site occupancy discussed below exerts a constraint. Furthermore, the bcc single phase at 2673 K
and ∼40 at.% Re was not fitted by Mathieu et al. but is well considered in the present work [53] .

Figure 6 shows the calculated enthalpies of mixing at 298 K together with the SQS data from Mathieu et al. [53] .