Computer Simulation of the Early Stage of Precipitation of L1₂-Ni₃(Al,V) Using Microscopic Phase Field Method

E-ISSN： 1662-9752|2015|817|809-815

ISSN： 0255-5476

Source： Materials Science Forum, Vol.2015, Iss.817, 2015-05, pp. : 809-815

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Abstract

Based on the phase field theory, the long-range order (LRO) parameter related interatomic potentials equations were utilized to calculate the interatomic potentials of L1₀-Ni₃(Al,V), L1₂-Ni₃Al and L1₂-Ni₃(Al,V) phases varying with temperature and concentrations. Using these potentials, the simulated microstructure evolution and the order parameter with the time of Ni₇₅Al₂₀V₅ ternary alloy are simulated at temperature 1000K during the early stage of the precipitation process in this research. Results testify that the precipitation sequence during the early stage of Ni₇₅Al₂₀V₅ alloy is the disordered phase →L1₀ pre-precipitation phase →L1₂ equilibrium phase. Firstly, the nonstoichiometric L1₀ pre-precipitation phase formed by congruent ordering precipitation mechanism; secondly, the nonstoichiometric L1₂ phase formed by transforming from L1₀ phase; thirdly, the stoichiometric equilibrium L1₂ phase formed by spinodal decomposition precipitation mechanism. It is discovered that the precipitation mechanism (congruent ordering+ spinodal decomposition) process was closely related to free energy and interatomic potentials: L1₀ pre-precipitation phase’s free energies are higher and interatomic potentials are smaller than those of L1₂ equilibrium phase.