Evaluation of Calphad Approach and Empirical Rules on the Phase Stability of Multi-principal Element Alloys

Abstract

The formation of single disordered solid solution phase in multi-principal element alloys (MPEAs) is crucial for the properties of the alloy, and thus several empirical rules have been proposed to predict the stability of disordered solid solution phase in MPEAs. Compared to these empirical rules, Calphad approach provides a more reliable and quantitative prediction. In the present work, we choose three model systems of Al x CoCrFeNi, CoCr x FeMnNi and Al x LiMgSnZn to evaluate these empirical rules by comparing with the Calphad calculated results. The Calphad calculated temperature-composition sections reveal the effect of composition on the phase formation under equilibrium condition. Corresponding diagrams along these sections illustrate parameter variations from empirical rules associated with alloy compositions and highlight predictions and limitations. The impact of the different sources of atomic size data is also discussed.

Atomic scale modeling of structural phase transformations in AlCrFeMnMo high-entropy alloys during thermal treatments

“…A remarkable number of research works on HEAs have been produced in the last years, most of them being experimental studies [7][8][9]. However, modeling and simulations of HEAs are currently paid increasing attention, as they provide powerful approaches complementing experiments and serving as predictive tools [10][11][12][13][14][15][16]. HEAs have high configurational entropy, which tends to stabilize the solid solution formation [17].…”

High Entropy and Sluggish Diffusion “Core” Effects in Senary FCC Al–Co–Cr–Fe–Ni–Mn Alloys

“…The enthalpy of mixing for an intermetallic phase can be determined using where Δ H ij IM represents the binary pair enthalpy of formation of the most stable intermetallic compound between i and j . The Δ H ij IM can be adopted from density-functional-theory (DFT) calculations . The Δ S IM is a function of Δ S mix and typically correlated by the structural ordering related parameter (κ 2 ) as Δ S IM = κ 2 Δ S mix The κ 2 parameter can be estimated by the site occupancy in the sublattice model of the intermetallic phase.…”

“…The ΔH ij IM can be adopted from density-functional-theory (DFT) calculations. 33 The ΔS IM is a function of ΔS mix and typically correlated by the structural ordering related parameter (κ 2 ) as ΔS IM = κ 2 ΔS mix 32 The κ 2 parameter can be estimated by the site occupancy in the sublattice model of the intermetallic phase. The value of κ 2 varies between 0 and 1; however, κ 2 is more than 0.4 for L1 2 or B2 crystal symmetry and increases with a decrease in level of ordering.…”

Stability of High Entropy Alloys to Spinodal Decomposition

“…These were the axes used in the pioneering work on HEA phase diagrams by Liang and Schmid-Fetzer. [20] The composition coordinate of a bisecting isopleth passes through two core compositions. For the ABCDE system above, one is when x ¼ 0, where is the core composition of the quaternary BCDE system.…”