Abstract:With microscopic phase-field kinetic model, atomic-scale computer simulation program for the precipitation sequence and microstructure evolution of the ordered intermetallic compound γ′ and θ in ternary Ni₇₅Al_xV_25-x alloy were studied. The simulation results show that Al concentration has important effects on the precipitation sequence. When Al concentration in Ni₇₅Al_xV_25-x alloy is low, θ(Ni₃V) ordered phase will be firstly precipitated, followed by γ′(Ni₃Al) ordered phase. With Al concentration increasing, θ and γ′ ordered phases are simultaneously precipitated. With Al concentration further increasing, γ′ ordered phase is firstly precipitated, followed by θ ordered phase. There is a competition relationship between θ and γ′ ordered phases during growth and coarsening process. No matter which first precipitates, θ ordered phase always occupies advantage in the competition process of coarsening, thus, the microstructure with preferred orientation is formed.

Key words: Ni-Al-V alloy; microstructure evolution; precipitation process; phase-field method