Microscopic Phase-field Simulation Of Precipitation Process For Ni-Al-Ti Alloy

Nickel-based superalloy is widely used in aerospace field for its good high-temperatureproperty, antifatigue, oxidation resistance and corrosion resistance. Ni3X isthe main strengthening phase in nickel-based superalloy. But Ni3X precipitates in theprecipitation process, so it’s necessary to investigate the precipitation process of thenickel-based superalloy.The aging temperature, the composition of the alloy and the elasticstrain energy can influence the precipitation process and the occupation probability of theatom.The influence of the aging temperature, the composition of the alloy and the elasticstrain energy on the precipitation process and the atom occupation probability of the researchobject Ni-Al-Ti alloy are simulated using the microscopic phase-field dynamics model andMATLAB language program run in the MATLAB soft environment.By simulating the precipitation process of the Ni-Al-Ti alloy under different agingtemperature, different alloy composition and different elastic strain energy, the followingconclusions are founded. The Ni-Al-Ti alloy precipitates by the following sequence: soluteatom clustering, the precipitation of the L10phase, the ordering of L10phase and theprecipitation of the L12phase, the formation of the stoichiometric L12phase. The rules of thethree kinds of atoms on the lattices are as follows: the α1and α2sites are occupied by Niatoms, the β site is occupied by Al and Ti atoms and Ti atoms occupy β site preferentially. Butthe occupation of theAl atoms on the β site is always larger than Ti atoms’.The increase of the aging temperature promotes the occupation of the antisite atoms, butinhibits the occupation of the orthotopic atoms. The influence of the elastic strain energy on the atom occupation is opposite to the influence of the aging temperature.The increase of Al concentration promotes the occupation probability of Ni atoms on α1and α2sites, but inhibits the occupation probability of Ni atoms on β site. The increase of Alconcentration promote the occupation probability of Al atoms on three kinds of sites. But theincrease of Ti atoms suppress the occupation probability of Ti atoms on three kinds of sites.The order phase of the alloy trends to arrange along the elastic soft direction([100] and[001] direction). With the elastic strain energy increasing, the trend that the order phasearranges along the elastic soft direction increases. The order phase of the alloy changes fromirregular shape to strip and blocky shape. And with the elastic strain energy increasing, theorder phase becomes more regular.