The microstructural evolution and mechanical properties of the 2196 Al-Li alloy prepared by the vacuum gas atomization, hot-isostatic-pressing (HIP) and hot-extrusion were investigated. The results show that prior particle boundaries (PPBs) exist in the microstructure of the HIPed alloy, and hot-extrusion effectively breaks PPBs to restrict the element micro-segregations. The as-extruded alloy exhibits fine grains, and bears higher solution treatment temperature due to the absence of low-melting-point micro-segregations. In the ageing process, the alloy hardness continues to rise, and reaches the peak value at 48 h. The precipitation sequence of the alloy is determined to be: supersaturated solid solution (SSS) → GP zone + fine T + δ′ → T + θ′ + δ′, where T phase dominates the whole ageing process. The diameter of the T platelets increases gradually with the increase of ageing time, meanwhile the T number density slightly drops in the over-aged alloy. The 3% pre-stretching promotes the nucleation of T phase, and the peak-ageing time is shortened to 28 h. Besides, no over-ageing phenomenon is observed in the pre-stretched samples. The Mg-Cu and non-Cu clusters formed on the dislocations accelerate the precipitation of T phase and prevent the nucleation of θ′ phase. The yield strength (YS) and ultimate tensile strength (UTS) of the T8 sample are 490 MPa and 515 MPa, respectively, which is notably higher than the T6 sample. The tensile strength of the present alloy is relatively higher than that of the Al-Li alloys with a comparable Li content.

中文翻译：

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快凝热挤压2196铝锂合金的显微组织演变和力学性能

研究了真空气体雾化、热等静压（HIP）和热挤压制备的2196铝锂合金的显微组织演变和力学性能。结果表明，HIPed合金显微组织中存在原有晶界（PPBs），热挤压有效打破了PPBs，限制了元素的微观偏析。挤压态合金晶粒细小，由于不存在低熔点微观偏析，因此可承受较高的固溶处理温度。在时效过程中，合金硬度持续上升，并在48 h时达到峰值。确定合金的析出顺序为：过饱和固溶体（SSS）→GP区+细T+δ′→T+θ′+δ′，其中T相在整个时效过程中占主导地位。随着时效时间的增加，T片晶的直径逐渐增大，同时过时效合金中T数密度略有下降。 3%预拉伸促进T相形核，峰值时效时间缩短至28 h。此外，预拉伸样品没有观察到过度老化现象。位错上形成的Mg-Cu和非Cu团簇加速了T相的析出并阻止了θ'相的形核。 T8样品的屈服强度（YS）和极限拉伸强度（UTS）分别为490 MPa和515 MPa，明显高于T6样品。本合金的拉伸强度比具有可比Li含量的Al-Li合金的拉伸强度相对较高。