Microstructure specific process chain design for the manufacturing of Al-Li-strips by means of twin-roll casting

Al-Li合金由于其性能上级常规铝合金而在航空航天领域具有广泛的应用前景。它们的特殊性能归因于在Al基体中形成了细分散的非平衡富Li相。Al-Li合金的主要问题是各向异性行为伴随着有限的可成形性。其主要原因是在直接激冷或模铸以及随后的热机械加工（TMP）过程中形成的强化相、晶粒显微结构和晶体学织构的特定特征。由于常规制备的合金的潜力是有限的，合金化学适应的方法，新的铸造和TMP技术必须应用于改善Al-Li合金的成形性，同时保持其高的比强度。富含Mg和Cu的沉淀物进一步强化了Al-Li合金，而含Sc和Zr颗粒的沉淀物将稳定细晶显微组织。双辊铸造（TRC）和TMP的组合-包括热不对称轧制-将用于提供合金元素在过饱和铝基体中的宏观均匀分布，以产生有益的晶体织构，设计晶粒微观结构以及沉淀物的尺寸和形态，并提高材料的可成形性。该项目的主要目标是建立高强度Al-Li-Mg-Cu-Sc-Zr合金薄带TRC和随后TMP过程中的工艺条件与其显微组织特征以及机械性能之间的相关性。

Al-Li alloys are attractive for aircraft and aerospace applications because their properties are superior to those of conventional Al alloys. Their exceptional properties are attributed to the formation of a finely dispersed non-equilibrium Li-rich phase in the Al-matrix. The main issue of Al-Li alloys is an anisotropic behaviour accompanied by a limited formability. The main reasons for this are the specific features of the strengthening phases, the grain microstructure and the crystallographic texture, which are formed during direct chill or mould casting and subsequent thermomechanical processing (TMP). Since the potential of conventionally prepared alloys is limited, methods of alloy chemistry adaptation, novel casting and TMP techniques have to be applied to improve the formability of Al-Li alloys while maintaining their high specific strength. Precipitates rich in Mg and Cu further strengthen the Al-Li alloy, while the fine-grained microstructure will be stabilised by precipitates of Sc and Zr containing particles. The combination of twin-roll casting (TRC) and TMP - including hot asymmetric rolling - will be used to provide a macroscopic homogeneous distribution of alloying elements in a supersaturated Al-matrix, to create a beneficial crystallographic texture, to engineer the grain microstructure and the size and morphology of the precipitates, and to enhance the formability of the material. The main objective of the project is to establish correlations between the processing conditions during TRC and the subsequent TMP of thin strips of high-strength Al-Li-Mg-Cu-Sc-Zr alloys and their microstructural characteristics as well as the mechanical properties.