Analysis of precipitate density of an aluminium alloy by TEM and AFM

Abstract The quantification of nanometric precipitates in Al-Zn-Mg-Cu alloys has been performed by a series of experimental techniques. Especially in the AA7050 alloy, after ageing heat treatment, the particles responsible for the hardening become very thin. Typically, these precipitates of nanometric sizes are mainly characterized by transmission electron microscopy (TEM), which in this particular case, requires a very meticulous preparation. This study investigated a possible alternative quantification of the precipitates by atomic force microscopy (AFM) to complement the technique by TEM. For this, three conditions for heat treatment of an aged aluminium alloy AA7050 were therefore chosen to produce different density and sizes of precipitates. The experimental results showed that the AFM technique proved to be a valid qualitative tool and may complement the results obtained by TEM an exploratory analysis for the microstructures.

摘要 针对Al-Zn-Mg-Cu合金中的纳米析出相，本研究已采用一系列实验技术开展定量表征工作。尤其是AA7050合金，经时效热处理后，其强化相颗粒会变得极为轻薄。通常，这类纳米级析出相主要通过透射电子显微镜（Transmission Electron Microscopy, TEM）进行表征，但针对该研究对象，该技术需要极为精细的样品制备流程。本研究探索了采用原子力显微镜（Atomic Force Microscopy, AFM）对析出相进行定量表征的可行性，以作为TEM技术的补充手段。为此，我们选取了AA7050铝合金的三种时效热处理工艺条件，以制备出具有不同密度与尺寸的析出相。实验结果表明，AFM技术是一种有效的定性表征工具，可作为TEM所得结果的补充，用于开展微观结构的探索性分析。