The asymptotic behavior of the minor element, Z, in a X-Y-Z ternary alloy associated with decomposition of the major element, Y, is classified into three groups according to the sign of the second derivative of the chemical free energy fI with respect to the concentration of Y, cY and the concentration of Z, cZ: In the case of ∂2f I/∂cY∂cZ > 0, the value of c Z along the trajectory of the peak top of the Y decreases with time. When ∂2fI/∂cZ∂cY < 0 at 0 ≤ t < ∞, peaks of cZ formed at peak tops of Y. The amplitudes of these peaks increase with time. If ∂2f I/∂cY∂cZ < 0 at 0 ≤ t < t0 and ∂2fI/∂cY∂ cZ > 0 at t0 < t < ∞, bifurcation of peaks occurs at the later stage.
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