Simulating Solutes Distribution And Evolution During The Initial Aging Stage Of Aluminum Alloys

The solutes distribution and evolution during the initial stage of aluminum alloys have been modeled based on Monte Carlo method and has been programed using MATLAB language. Diagrams simulating solutes distribution and evolution during the initial stage of aluminum alloys can be obtained by typing alloy compositions and aging temperature using this simulation program, as well as the number and the mean size of solutes clusters. The solutes distribution and evolution during the initial stage of Al-Mg-Si and Al-Zn-Mg alloys and the effects of some elements and aging temperature have been studied using this simulation program. The micromechanisms of age precipitation and hardening behaviours of aluminum alloys have been discussed according to the simulation results.The simulation results on the solutes distribution evolution during the initial aging stage of Al-Mg-Si alloys show that there are large Mg-Si clusters and Si-Si clusters, small Mg-Mg clusters forming during the initial aging stage at 25℃and 65℃,Mg-Si clusters and Si-Si clusters easily forming near vacancies, and the size and distribution of clusters are non-uniform. During the initial aging stage at 140℃and 170℃,the number of large clusters is less and the size deviation among varies clusters is smaller than at 25℃and 65℃,During the initial aging stage at 200℃, there are weak solutes clustering and only some solutes clusters with 2-3 atoms form and distribute within Al base uniformly. The size and composition of clusters forming during the initial aging stage of Al-Mg-Si alloy are related to the Mg:Si ratio. With the decreasing of Mg:Si ratio, the mean size of Mg-Si clusters decreases, the proportion of Si atoms in Mg-Si clusters and the number and size of Si-Si cluster increase. The effects of natural aging between quenching and artificial aging, alloy composition and secondary aging process on artificial aging hardening of Al-Mg-Si alloys have been discussed according to the simulation results.The effect of some elements on artificial age hardening behaviors of Al-Mg-Si alloys should be related to the solutes distribution and evolution during the initial aging stage. There are large Mg-Si clusters and Si-Si clusters, small Mg-Mg clusters, Cu-Mg-Si clusters, Cu-Mg clusters and Cu-Si clusters forming during the initial aging stage of Cu addition of Al-1.5Mg-1.2Si-0.4Cu (at%) alloy. Comparison with Cu-free Al-1.5Mg-1.2Si (at%) alloy, the cluster number increases, the size and distribution of clusters are more uniform.Large Cu-Mg clusters formed during the initial aging stage of Cu containg Al-1.5Mg-1.2Si-1Cu (at%) alloy. Adding 0.4at%Sn to Al-1.5Mg-1.2Si (at%) alloy, Mg-Sn clusters and Sn-Sn clusters appear except Mg-Si clusters and Si-Si clusters during the initial aging stage, and the size and the distribution of clusters are more uniform. Small additions of Ag to Al-1.5Mg-1.2Si (at%) alloy cause little effect on the solutes distribution and evolution during the initial aging stage. The micromechanism of Cu and Sn addition on age precipition and hardening behaviors of Al-Mg-Si alloys has been analyzed according to the simulation results.The simulation results on solutes distribution and evolution during the initial aging stage of Al-2.1Zn-1.4Mg (at%) alloy show that large Zn-Mg clusters form. Addition of Sc to this alloy should restrain Zn-Mg clustering, which causes a number of small Zn-Mg clusters and Sc-vacancy clusters forming during the initial aging stage. There is no clear influence on solutes distribution and evolution during the initial aging stage by adding Zr to this alloy. Effect of adding Sc and Zr together to Al-2.1Zn-1.4Mg (at%) alloy on solutes distribution and evolution during the initial aging stage is simlier to that of adding Sc only. Additions of 0.7at% Cu and 3.9at% Li together to Al-2.1Zn-1.4Mg (at%) alloy causes little effect on solutes distribution and evolution during the initial aging stage. The micromechanism of Sc addition on age precipition and hardening behaviors of Al-Zn-Mg alloys has been analyzed according to the simulation results.