Microscopic phase-field simulation of the atomic migration of L1₂ and DO₂₂ phase formation in Ni₆₄Al₂₁V₁₅ alloy

The phase transformation process of dynamic model of L1₂ and DO₂₂ phase in Ni₆₄Al₂₁V₁₅ alloy at 1150 K was studied by micro-phase field model. The migration of Al, V and Ni atoms in the two phases in the different lattice faces and at different sites was analyzed, and its evolution was researched. The results show that there are two types of crystallographic orientation relationship between L1₂ and DO₂₂: (001)_L12→(001)_DO22 and (001)_L12→(100)_DO22. In the structure transformation form L1₂ to DO₂₂, the atomic ordering is proceeded on each plane as the atoms migrate between different planes, Al and V occupy the β and β₁ sites prior to others, Ni occupy the α₁ and β₂ sites, and the nonordered domain gradually transforms to the L1₂ structure. Then, the atomic ordering is proceeded on each plane as the atoms migrate on planes only, Al occupy the β₁ and α₁ sites, V occupy the β and β₂ sites, Ni mainly occupy the α₁ site, and L1₂ structure transforms into DO₂₂ structure.