Mn元素在7A99铝合金中微观组态分布的研究

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

摘要:

通过半连续铸造方式向7A99铝合金中添加0.4%Mn元素,采用SEM、TEM、HRTEM与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。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；固溶处理过程中,小部分Al6Mn析出相发生回溶,使得残留Al6Mn析出相尺寸范围处于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。

Abstract:

0.4%Mn element was added into 7A99 alloy by semi-continuous casting in the study. TEM, HRTEM and 3DAP were employed to study the microscopic configuration distribution of Mn element in the cast, homogenization and solution aging of 7A99 alloy. The result shows that Mn element in 7A99 aluminum alloy ingot mainly exists in the form of fishbone shape MgZn₂non-equilibrium eutectic compound containing AlZnMgCuMn at grain boundary. After homogenization treatment, Mn element in 7A99 alloy mainly exists in the form of Al₆Mn phase and intermittent, fine, granular S(Al₂CuMg) second phase containing AlZnMgCuMn at grain boundary. A small part of Al₆Mn precipitated phase is dissolved back to the matrix, so that the size range of residual Al₆Mn precipitated phase is 0.2~1μm in the process of solid solution treatment. Mn element always exists in the form of Al₆Mn precipitated phase which is stable in size and non-coherent with aluminum matrix in the aging process of 120℃. Mn element does not precipitate other new phase during the aging proceed and affect the aging precipitation process of Zn, Mg in 7A99 alloy.