Figure 4. Calculated results and theoretical consideration for forming L1₀ from the amorphous and crystalline phases.

(a) FeNi phase diagram calculated with SSOL5 database. (b) Gibbs free energy curves at T = 673 K for liquid, bcc, and fcc phases calculated with the SSOL5 database as functions of the Ni fraction together with G = –35 kJmol^–1 for the L1₀ phase estimated from previous studies. (c) Characteristics of the phases of interest, including the driving force to precipitate L1₀ at T = 673 K. (d) Changes in Gibbs free energy (G) of fcc phase as a function of Si content in a hypothetical Fe₅₀Ni₅₀-Fe_50−x/2Ni_50−x/2Si_x system where G = –35 kJmol⁻¹ was considered for L1₀ Fe₅₀Ni₅₀ phase. Based on lever rule (marked by red arrow), the volume fraction of the L1₀ phase is evaluated to be ~13% in Fe₄₂Ni_41.3Si₈B₄P₄Cu_0.7 alloy under an assumption that L1₀ FeNi phase precipitates from the fcc Fe₄₅Ni₄₅Si₁₀, which is an equilibrium phase at T = 673 K in the alloy.