Mn元素在7A99铝合金中微观组态分布的研究

通过半连续铸造方式向7A99铝合金中添加0.4%Mn(质量分数)元素,采用SEM、TEM、HRTEM与三维原子探针(3DAP)开展Mn元素在7A99铝合金铸锭、均匀化以及固溶时效过程中的微观组态分布的研究。结果表明,Mn元素在7A99铝合金铸锭中主要以晶界处鱼骨状的含AlZnMgCuMn的MgZn2型非平衡共晶化合物形式存在;均匀化处理后,Mn元素在7A99铝合金中主要以Al₆Mn析出相与断续、细小、颗粒状的含AlZnMgCuMn的S型(Al₂CuMg)第二相形式存在;固溶处理后,Mn元素主要以Al₆Mn析出相形式存在,其尺寸范围处于0.2~1μm;120℃时效过程中,Mn元素始终主要以与尺寸稳定、与铝基体非共格的Al₆Mn析出相形式存在;Mn元素在120℃时效过程中未析出新相,且未参与影响7A99铝合金中Zn、Mg元素的时效析出行为。

Study on Microscopic Configuration Distribution of Mn Element in 7A99 Aluminium Alloy

0.4%Mn element was added into 7 A99 alloy by semi-continuous casting.TEM,HRTEM and three-dimensional atom probe(3 DAP)were employed to study the microscopic configuration distribution of Mn element in the cast,homogenization treated and solution aged 7 A99 alloy.The result shows that Mn element in 7 A99 aluminum alloy ingot mainly exists in the form of fishbone shape Mg Zn2 non-equilibrium eutectic compound containing Al Zn Mg Cu Mn at grain boundary.After homogenization treatment,Mn element in 7 A99 alloy mainly exists in the form of Al6 Mn phase and intermittent,fine,granular S(Al₂ Cu Mg)second phase containing Al Zn Mg Cu Mn at grain boundary.After solution treatment,Mn mainly exists in the form of Al6 Mn precipitate with the size range of 0.2~1μm.Mn element always exists in the form of Al6 Mn precipitated phase which is stable in size and non-coherent with aluminum matrix in the aging process at 120℃.Mn element does not precipitate other new phase during the aging proceed and affect the aging precipitation process of Zn,Mg in 7 A99 alloy.