Computer Simulation Of Microstructural Evolution Of Al-Cu-X Alloys During Initial Ageing Stage

Ageing strengthening is one of the important means that may intensify the aluminum alloys.The computer simulation of precipitation process in alloys during the initial ageing stage may indicate the precipitation mechanism and cover the shortage of experimental methods,thus the microstructure of the alloys can be exactly controlled.This is very significant to material science.The Monte Carlo Method,which bases on the Multi States Ising Model,was applied to establish a model using VC++6.0 to develop the effective application procedure to simulate the microstructural evolution of A1-4.0%Cu-X alloys.The analysis of the simulated result has profoundly investigated the evolution of Cu atomic clusters during the initial ageing stage.The influence of alloying element Mg,Ag and the vacancy density on the process of Cu atoms clustering in {100} plane has been indicated.The simulation results show that the Cu atoms in A1-4.0%Cu alloys are apt to clustering during the initial ageing stage.In several seconds of the initial ageing stage,the Cu atoms have apt to clustering intensely,there are big Cu-clusters in several continual {100} atoms planes.The simulation results about the Cu-clusters are in accordance with previous research which testifies the Cu atoms cluster in Al substrates onto the GP areas.The Cu-clusters aggregate gently in the Al-4.0%Cu-1.0%Mg alloys.1.0 percent of Mg already has far-reaching influence on restraining the Cu atoms clustering.The average size of Cu-cluster reduces rapidly.This inhibitory action has been soon shown out from the beginning of the initial ageing stage.Mg atoms capture the vacancy which the diffusion of Cu atoms depend on,thus restrain the Cu atoms clustering.Because of the strong interaction between Mg and Cu,a large number of Mg-Cu-vacancy clusters have appeared in matrix.In Al-4.0%Cu-1.0%Ag alloy,the addition of 1.0%Ag already has no significant influence on restraining the Cu atoms clustering.In Al-4.0%Cu-0.5%Mg-1.0%Ag alloy, the addition of Mg and Ag has obviously restrained the Cu atoms clustering in {100} atoms plane.The strong interaction between Mg and Ag promotes the formation of Mg-Ag atomic cluster,thus adjust the state of Cu-cluster.Because Mg-Ag atomic cluster increases the distortion of lattice,thus leading to the Cu atoms which are locked in clusters being replaced.Therefore Cu atoms clustered in {100} atoms plane have been restrained and the distribution of precipitated phase have been affected.