【作者】 孙媛；

【导师】 王桂青；

【作者基本信息】 山东建筑大学 ， 材料加工工程， 2010， 硕士

【摘要】 本文采用Monte Carlo方法建立计算机模拟模型,利用MATLAB语言编制了模拟铝合金时效初期溶质原子分布的源程序。利用该模拟程序,只需输入合金成分和时效温度,即可得到时效初期溶质原子分布演变模拟图,并且可以统计出溶质原子团簇个数及其平均尺寸随Monte Carlo步数的变化。利用编制的模拟程序,模拟研究了Al-Mg-Si合金和Al-Zn-Mg合金时效初期溶质原子分布的演变及合金元素和时效温度对其时效初期溶质原子分布演变的影响。根据模拟分析结果,探讨了铝合金某些人工时效析出硬化行为的微观机制。对Al-Mg-Si合金时效初期溶质原子分布演变进行模拟研究的结果显示：25℃和65℃低温时效初期,溶质原子容易发生偏聚形成尺寸较大的Mg-Si团簇和Si-Si团簇、尺寸较小的Mg-Mg团簇,Mg-Si团簇和Si-Si团簇容易在空位处偏聚形成,团簇尺寸及分布不均匀；140℃和170℃时效初期,形成的大尺寸溶质原子团簇较少,团簇尺寸偏差小；200℃时效初期,溶质原子不容易发生偏聚,由2-3个原子组成的原子团簇均匀地分布于铝基体内；Al-Mg-Si合金时效初期形成的溶质原子团簇尺寸及组成与Mg:Si比具有相关性,随着Mg:Si质量比减小,时效初期形成的Mg-Si团簇尺寸减小,Mg-Si团簇中Si原子的比例增大,且形成的Si-Si团簇数量增多,尺寸增大。根据模拟分析结果,探讨了Al-Mg-Si合金淬火后的自然时效、合金组成和二次时效工艺对其人工时效硬化效果的影响。合金元素对Al-Mg-Si合金人工时效硬化的影响与时效初期溶质原子分布演变密切相关。在Al-1.5Mg-1.2Si(at%)合金中添加0.4at%Cu,时效初期形成的原子团簇有：尺寸较大的Mg-Si团簇和Si-Si团簇,尺寸较小的Mg-Mg团簇、Cu-Mg-Si团簇、Cu-Mg团簇和Cu-Si团簇,与不含Cu的Al-1.5Mg-1.2Si(at%)合金相比,原子团簇数量增多,团簇尺寸及分布趋于均匀；在Al-1.5Mg-1.2Si(at%)合金中添加1at%Cu,时效初期还出现了尺寸较大Cu-Mg团簇；在Al-1.5Mg-1.2Si(at%)合金中添加0.4at%Sn,时效初期形成了Mg-Si团簇、Si-Si团簇、Mg-Sn团簇、Sn-Sn团簇和少量小尺寸的Mg-Mg团簇,团簇平均尺寸减小,分布趋于均匀；少量Ag添加到Al-1.5Mg-1.2Si (at%)合金中,对时效初期溶质原子分布演变的影响不明显。利用模拟结果,分析了元素Cu和Sn的添加对Al-Mg-Si合金人工时效析出硬化行为影响的微观机制。对Al-2.1Zn-1.4Mg(at%)合金时效初期溶质原子分布演变进行模拟研究的结果显示：Al-2.1Zn-1.4Mg(at%)合金时效初期形成了大量的Zn-Mg团簇；微量元素Sc添加到Al-2.1Zn-1.4Mg(at%)合金抑制了时效初期Zn-Mg团簇的强烈偏聚,使Zn-Mg团簇分布均匀细小,形成大量的Sc-空位团簇；微量元素Zr对Al-Zn-Mg合金时效初期溶质原子分布演变影响较小；元素Sc和Zr复合添加到Al-Zn-Mg合金中,时效初期溶质原子分布演变与单独添加元素Sc类似。在Al-Zn-Mg合金中添加0.7%at Cu和3%atLi,对时效初期溶质原子团簇的形成及分布影响不明显。利用模拟结果,分析了元素Sc的添加对Al-Mg-Si合金人工时效析出硬化行为影响的微观机制。更多还原

【Abstract】 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.更多还原