Raffeis Iris, Adjei-Kyeremeh Frank, Vroomen Uwe, Richter Silvia, Bührig-Polaczek Andreas
Foundry Institute, RWTH Aachen University, Intzestraße 5, 52072 Aachen, Germany.
Central Facility for Electron Microscopy (GFE), RWTH Aachen University, Ahornstraße 55, 52074 Aachen, Germany.
Materials (Basel). 2020 Nov 17;13(22):5188. doi: 10.3390/ma13225188.
Al-Cu-Li alloys are famous for their high strength, ductility and weight-saving properties, and have for many years been the aerospace alloy of choice. Depending on the alloy composition, this multi-phase system may give rise to several phases, including the major strengthening T (AlCuLi) phase. Microstructure investigations have extensively been reported for conventionally processed alloys with little focus on their Additive Manufacturing (AM) characterised microstructures. In this work, the Laser Powder Bed Fusion (LPBF) built microstructures of an AA2099 Al-Cu-Li alloy are characterised in the as-built (no preheating) and preheat-treated (320 °C, 500 °C) conditions using various analytical techniques, including Synchrotron High-Energy X-ray Diffraction (S-HEXRD). The observed dislocations in the AM as-built condition with no detected T precipitates confirm the conventional view of the difficulty of T to nucleate on dislocations without appropriate heat treatments. Two main phases, T (AlCuLi) and T (AlCuLi), were detected using S-HEXRD at both preheat-treated temperatures. Higher volume fraction of T measured in the 500 °C (75.2 HV) sample resulted in a higher microhardness compared to the 320 °C (58.7 HV) sample. Higher T volume fraction measured in the 320 °C sample had a minimal strength effect.
铝铜锂合金以其高强度、延展性和减重特性而闻名，多年来一直是航空航天领域的首选合金。根据合金成分，这种多相体系可能会产生几种相，包括主要的强化相T（AlCuLi）相。对于传统加工的合金，已经有大量关于微观结构的研究报告，但很少关注其增材制造（AM）特征的微观结构。在这项工作中，使用包括同步加速器高能X射线衍射（S-HEXRD）在内的各种分析技术，对AA2099铝铜锂合金在激光粉末床熔融（LPBF）制造的未预热和预热处理（320°C、500°C）条件下的微观结构进行了表征。在未检测到T析出物的增材制造未预热状态下观察到的位错，证实了传统观点，即如果没有适当的热处理，T相很难在位错上形核。在两个预热处理温度下，使用S-HEXRD检测到了两个主要相，即T（AlCuLi）和T（AlCuLi）。与320°C（58.7 HV）的样品相比，在500°C（75.2 HV）的样品中测得的T相体积分数更高，导致显微硬度更高。在320°C的样品中测得的较高T相体积分数对强度的影响最小。
