The Influence Of Elastic Strain Energy On Ni₇₅Al₅V₂₀ Alloy Precipitation By Microscopic Phase-field Simulation

Nickel base alloy is widely used in the environment of high temperature,and it also plays a very important role in the gas turbine engine and advanced aerospace engine.Ni-Al-V alloy has been paid much attention because of its superior high temperature performance and the process of microstructure evolution regularity has been widely studied,but it is difficult through the experimental method to analysis the whole process of precipitation.But computer simulation has its unique advantages,it can deal with the alloy precipitation process,such as highly nonlinear and nonequilibrium state through the use of microscopic phase field dynamics model,so we can obtain intuitive clear instantaneous morphology of ordered phase from atomic level.Due to elastic strain energy will directly affect the precipitated phase,such as nucleation growth,microstructure evolution,atomic diffusion and occupation probability evolution,and so on.Therefore,in the process of nickel baseprecipitation,the simulation has more practical significance by temperature coupled with the elastic strain energy.This paper based on microscopic phase field dynamics model to research,with Ni₇₅Al₅V₂₀ alloy as the research object,we have researched the influence of different elastic strain energy on microstructure evolution,occupation probabilitye volution,average order parameter,volume fraction when the temperature is 1250 K.The process of atomic diffusion in Ni₇₅Al₅V₂₀ alloy phase internal and boundary under the elastic distortion energy.By analysing the precipitation process of Ni₇₅Al₅V₂₀ alloy at temperature 1250 K under different elastic strain energy,the results show that: under different elastic strain energy,the microstructure evolution process can be roughly divided into four stages,and the color of the precipitated phase L12 change for: light blue to yellow to light yellow into cyan.With the increase of the elastic strain energy,the incubation period of alloy was shorten,L12 and DO₂₂ phase from precipitation to coarsening had more directional,two phase had more refinement and its shape had also more rules.Finally,their shape turned into strip and block.And in the whole precipitation process,it is conducive to L12 phase precipitation,but has little influence on the amount of DO₂₂ phase precipitationNi atoms are positive atoms in ?1??2 position,V atoms are positive atoms in ? position.Along with the increase of the elastic strain energy,it has little influence on occupation probability of all kinds of atoms in ?1 position,and promotes the occupation probability of positive atoms in ?2 position;In ? position,it has little influence on eventual occupation probability of Ni atoms,eventual occupation probability of Al atoms is reduced,eventual occupation probability of V atoms is increased.And with the increase of elastic strain energy,the equilibrium value of average composition order parameter is reduced;the equilibrium value of average long range order parameter is increased.The result showed that the elastic strain energy exist,the occupation probability of V atoms far more than the Al atomsin the early precipitation of L12 phase.With the evolution of the time,the occupation probability of Al atoms gradually rise,the occupation probability of V atoms gradually reduced,but V atoms in L12 phase have some place holders when they reach their equilibrium state.The Al atoms gradually diffuse from boundary to internal of L12 phase but V atoms gradually diffuse from internal to boundary of L12 phase when the stoichiometric ratio L12 ordered phase are precipitated in Ni₇₅Al₅V₂₀ alloy.All kinds of atoms nearer the boundary of L12 phase,the diffusion velocity more faster,on the contrary,their diffusion velocity more slower.And the color of the early precipitation of L12 phase shows in yellow,with the evolution of the time,the color gradually becomes cyan from boundary to internal of L12 phase.There is only one type interfacebetween L12 phase and DO₂₂ phase in the precipitation process when the elastic strain energy is 600 of Ni₇₅Al₅V₂₀ alloy,namely,?200?L/?100?D,but there are three kinds of interface structure between the DO₂₂ phases,namely,?001?//?002?,?001?//?001?and the twin boundary{101}.