The present study investigates the tensile properties, activation of slip, and grain boundary cracks in Al–Cu–Li ternary alloys with varying precipitations resulting from different aging treatments. The size and distribution of precipitations were ascertained using transmission electron microscopy. The slip activtiy with tensile strain was observed by the electron back-scatter diffraction and scanning electron microscopy. Furthermore, the influence of precipitated strengthening was quantitatively evaluated. The presence of precipitations hinders dislocation movement, increasing strength but reducing the appearance of deformation mechanisms like slip activity, slip transfer, intragranularly misoriented grain boundaries, and lattice rotation, ultimately resulting in reduced ductility. In the sample of T6 aging for 72 h, the coarsed θ′ phase promotes the formation of dislocation rings, resulting in a decrease in the percentage of grains activated with slip to 9.7%. The percentage of grain boundaries with crack initiation reaches 6.9%. On the contrary, in the sample dominated by the T1 phase, the percentage of grains that activate slip is 14.6%, and the percentage of grain boundaries that initiate cracks is only 1.4%. This is because the continuous shear of the T1 phases helps disperse coplanar slip, thereby avoiding cracking caused by excessive stress concentration. Hence, to enhance alloy strength while preserving a certain level of ductility, it is vital to promote the precipitation of the T1 phase and avoid the coarsening of the θ′ phase. This study provides a new insight into the influence of precipitations on the strength and plasticity of Al–Cu–Li alloys.

Graphical Abstract

中文翻译：

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析出相对Al-Cu-Li合金强塑性影响及变形机制的准原位EBSD研究

本研究研究了不同时效处理产生不同析出物的 Al-Cu-Li 三元合金的拉伸性能、滑移活化和晶界裂纹。使用透射电子显微镜确定沉淀物的尺寸和分布。通过电子背散射衍射和扫描电子显微镜观察了拉伸应变下的滑移行为。此外，定量评价了析出强化的影响。析出物的存在阻碍位错运动，增加强度，但减少变形机制的出现，如滑移活动、滑移转移、晶内定向错误的晶界和晶格旋转，最终导致延展性降低。在T6时效72 h的样品中，粗化的θ'相促进了位错环的形成，导致滑移激活晶粒的百分比下降至9.7%。裂纹萌生晶界比例达到6.9%。相反，在以T1相为主的样品中，引发滑移的晶粒百分比为14.6%，引发裂纹的晶界百分比仅为1.4%。这是因为T1相的连续剪切有助于分散共面滑移，从而避免因应力过度集中而导致开裂。因此，为了提高合金强度，同时保持一定的延展性，促进T1相的析出并避免θ'相的粗化至关重要。这项研究为沉淀对 Al-Cu-Li 合金强度和塑性的影响提供了新的见解。

图形概要