Thermal Stability and Two-Step Devitrification of Melt-Spun Cr₁₆Mn₁₆Fe₁₆Co₁₆Ni₁₆P₂₀ High-Entropy Metallic Glass

The thermal stability and devitrification pathway of melt-spun high-entropy Cr₁₆Mn₁₆Fe₁₆Co₁₆Ni₁₆P₂₀ metallic glass were investigated using transmission electron microscopy/selected-area electron diffraction (TEM/SAED), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and ⁵⁷Fe Mössbauer spectroscopy. TEM/SAED confirmed an amorphous ribbon structure, with diffuse rings and radial maxima at k₁ = 0.84799 nm^-1 and k₂ = 1.44459 nm^-1. Non-isothermal DSC revealed two exothermic events, Peak I at ~716-752 K and Peak II at ~881-930 K, both shifting to higher temperatures with increasing heating rate. Kissinger analysis yielded apparent activation energies of Ea₁ = 359.2 kJ/mol for Peak I and Ea₂ = 414.9 kJ/mol for Peak II. Specimens heated in the DSC under argon at 20 K/min to selected target temperatures were examined ex situ. The XRD patterns are consistent with the onset of crystallization during Peak I, with reflections tentatively attributed to an Fe₃P-type phase and an FCC solid solution. Peak II is associated with further phase evolution, including the development of reflections compatible with MnNi-type and Co₂P-type phases. Because of peak overlap in this multicomponent alloy, the proposed phase sequence should be regarded as a plausible interpretation based on combined DSC, XRD, and Mössbauer evidence rather than as a uniquely resolved quantitative phase analysis. Mössbauer spectra reveal three paramagnetic Fe environments. With increasing DSC target temperature, the high-QS Fe3 component, representing a highly distorted Fe environment, decreases systematically, whereas the low-QS Fe1 component, associated with a more symmetric, nearly cubic Fe environment, becomes dominant. The high apparent activation energies indicate a larger effective kinetic barrier than in many simpler transition-metal-phosphorus amorphous alloys.