Chen Longhui, Liu Chunhui, Yang Jianshi, Ma Peipei, He Jun
Light Alloy Research Institute of Central South University, State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Changsha 410083, China.
Light Alloy Research Institute of Central South University, State Key Laboratory of Precision Manufacturing for Extreme Service Performance, Changsha 410083, China; School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
Micron. 2025 Nov;198:103891. doi: 10.1016/j.micron.2025.103891. Epub 2025 Jul 20.
Aluminum-copper-lithium (Al-Cu-Li) alloy is a key structural material in the aerospace field. Its mechanical properties are closely related to the dynamic evolution of T phase during the aging process. To accurately capture this dynamic process, the in situ transmission electron microscope (TEM) combined with the microelectromechanical system (MEMS) heating chip was used to observe the T precipitation behavior in an Al-Cu-Li alloy in real time. All experimental samples were solution treated at 510 °C for 30 min and water quenched externally, and then heated to 180 °C on a MEMS heater chip at a heating rate of 1 °C/s. This study presents an improved sample preparation and transfer protocol to mitigate Ga infiltration. High-angle annular dark-field scanning TEM (HAADF-STEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the effects of preparation methods, transfer techniques, and sample thickness (80-300 nm) on gallium (Ga) and platinum (Pt) contamination and precipitation behavior. The results show that Ga segregation, in the form of ∼10 nm intragranular particles and grain boundary enrichment, significantly distorts the intrinsic precipitation of T phases. However, combining an external transfer method with low-energy ion milling at an accelerating voltage of 3 kV effectively suppresses Ga/Pt contamination. Furthermore, sample thickness critically influences precipitation kinetics in Al-Cu-Li alloys: sub-100 nm samples exhibit surface-driven abnormal coarsening of T precipitates, while samples exceeding 250 nm suffer from reduced imaging resolution due to limited electron transparency. A thickness range of 150-200 nm optimally balances resolution fidelity with representative precipitation dynamics.
铝铜锂（Al-Cu-Li）合金是航空航天领域的关键结构材料。其力学性能与时效过程中T相的动态演变密切相关。为了准确捕捉这一动态过程，采用原位透射电子显微镜（TEM）结合微机电系统（MEMS）加热芯片实时观察Al-Cu-Li合金中T相的析出行为。所有实验样品在510℃固溶处理30分钟后进行外部水淬，然后在MEMS加热芯片上以1℃/秒的加热速率加热至180℃。本研究提出了一种改进的样品制备和转移方案，以减轻镓的渗入。利用高角度环形暗场扫描透射电子显微镜（HAADF-STEM）和能量色散X射线光谱（EDS）评估制备方法、转移技术和样品厚度（80-300nm）对镓（Ga）和铂（Pt）污染及析出行为的影响。结果表明，以~10nm晶内颗粒和晶界富集形式存在的Ga偏析显著扭曲了T相的本征析出。然而，将外部转移方法与3kV加速电压下的低能离子铣削相结合可有效抑制Ga/Pt污染。此外，样品厚度对Al-Cu-Li合金的析出动力学有至关重要的影响：厚度小于100nm的样品表现出T析出物的表面驱动异常粗化，而超过250nm的样品由于电子透明度有限而成像分辨率降低。150-200nm的厚度范围能最佳地平衡分辨率保真度与代表性的析出动力学。
