Phase-field study on the pre-precipitated phase of ordered intermetallic compounds in binary and ternary Ni–Al base alloys

• The pre-precipitated phase of ordered intermetallic compound is studied at atomic scale.
• There exists L10 or L10 (M = 1) pre-precipitated phase before ordered phase formed.
• The pre-precipitated phase is L10 phase in Ni–Al alloy.
• For Ni–Al–V alloy, if DO22 ordered phase appears first, the pre-precipitated phase is L10 (M = 1) phase.
• For Ni–Al–V alloy, if L12 ordered phase appears first, the pre-precipitated phase is L10 phase.

The pre-precipitation processes of ordered intermetallic compound L12 (Ni3Al) in binary Ni–14.0 at.%Al alloy, L12 (Ni3Al) and DO22 (Ni3V) in ternary Ni–Al–V alloy were studied using the microscopic phase-filed dynamic model. It is found that prior to the formation of L12 or DO22 ordered phase, a pre-precipitated phase appears first. For the binary alloy, Ni atoms aggregate on (0 0 2) plane and deplete on (0 0 1) plane, Al atoms aggregate on (0 0 1) plane and deplete in (0 0 2) plane, the pre-precipitated phase is L10 phase. For the ternary alloy, if the DO22 ordered phase appears first, Ni atoms aggregate on (0 0 2) plane and deplete on (0 0 1) plane, the aggregation and ordering of V atoms on (0 0 1) plane are faster than those of Al atoms, the pre-precipitated phase is L10 (M = 1) phase; if the L12 ordered phase appears first, Ni atoms aggregate on (0 0 2) plane and deplete on (0 0 1) plane, the aggregation and ordering of Al atoms on (0 0 1) plane are faster than those of V atoms, the pre-precipitated phase is L10 phase.

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