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The phase diagram of nickel silicides is very complex and consists of various phases (some are shown in Figure 2475a). For instance, there are three polymorphic Ni₃Si structures (β₁, β₂ and β₃), Ni₃₁Si₁₂ (γ), NiSi₃(D0₃, D0₂₂), Ni₅Si₂ (D8_h),  two polymorphic Ni₂Si structures (δ = C23, and θ = B82), Ni₂Si (C37, D0₃, D0₂₂), Ni₃Si₂ (ε), NiSi (MnP), NiSi₂ (α= CaF₂, β),  Ni₃Si₂-ε', NiSi₂ (CaCl₂ = C35), and NiSi (L1₀). Even at room temperature, there are still 6 stable phases: Ni₃Si, Ni₃₁Si₁₂ or Ni₅Si₂, Ni₂Si, Ni₃Si₂, NiSi and NiSi₂. [4]

Figure 2475a. Si-Ni phase diagram.

Figure 2475b. Ti-Ni phase diagram. [1-3]

[1] K. Otsuka, X. Ren, Physical metallurgy of Ti–Ni-based shape memory alloys, Progress inMaterials Science 50 (2005) 511–678.
[2] Massalski TB, Okamoto H, Subramanian PR, Kacprzak L, editors. Binary alloy phase diagrams, 2nd edition, vol. 3. Materials Park, OH: ASM International; 1990. p. 2874.
[3] Otsuka K, Kakeshita T. MRS Bulletin2002;27:91.
[4] Handbook of Binary Alloy Phase Diagrams (CD Version 1.0), ASM International, ISBN PC-0-87170-562-1, (1996).