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Microstructure Evolution and Mechanical Properties of AA2099 Al–Li Alloy with Tailored Li‐Containing Precipitates in Uniaxial Compression at Medium Temperature
Metals and Materials International ( IF 3.5 ) Pub Date : 2021-06-09 , DOI: 10.1007/s12540-021-00977-w
Li Hu , Mengdi Li , Weijiu Huang , Xusheng Yang , Fei Guo , Haipeng Dong

Abstract

Microstructure characteristics and mechanical behavior of AA2099 Al–Li alloy with no pre-existing Li-containing precipitates (AA2099-1 sample), pre-existing δ′ precipitates (AA2099-2 sample), pre-existing T1 phase (AA2099-3 sample) and pre-existing T2 phase (AA2099-4 sample) are systematically investigated via isothermal uniaxial compression at 250 °C in the present study. Experimental results demonstrate that at the onset of plastic deformation, dynamic precipitation of small-sized T1 phase occurs rapidly within AA2099-1 sample, while it will be hindered within AA2099-2 sample. The increasing plastic strain benefits to dynamic precipitation of small-sized T1 phase in AA2099-2 sample. Consequently, AA2099-1 and AA2099-2 samples possess similar and intermediate mechanical behaviors. In terms of AA2099-3 sample, the existence of large-sized T1 phase results in the maximum yielding stress. However, some regions within these large-sized T1 precipitates are suspected to be sheared by cross-slip, leading to the destruction of crystallographic structure and the formation of Al matrix intervals. This aspect is responsible for the gradual degradation in true stress-strain curve after peak stress. As for AA2099-4 sample, dynamic precipitation rarely happens during plastic deformation and the interaction between dislocation and the pre-existing T2 phase belongs to Orowan looping, resulting in the minimal mechanical response. Besides, AA2099-1 sample possesses the average minimum deviation angle (MDA) of ~ 16.5° between the loading direction and the <110> crystal direction, whereas AA2099-4 sample owns the average MDA of ~ 7.5°. The difference in MDA is mainly attributed to δ′ phase and T1 phase, which will separately accelerate and postpone the rotation of orientation towards the <110> crystal direction.

Graphic Abstract



中文翻译:

AA2099含锂析出物的铝锂合金在中温单轴压缩中的显微组织演变和力学性能

摘要

无含锂析出物(AA2099-1 样品)、δ' 析出物(AA2099-2 样品)、T 1相(AA2099-3样品)的 AA2099 铝锂合金的显微组织特征和力学行为样品)和预先存在的 T 2相(AA2099-4 样品)在本研究中通过等温单轴压缩在 250 °C 进行系统研究。实验结果表明,在塑性变形开始时,AA2099-1 试样内部会迅速发生小尺寸T 1相的动态析出,而AA2099-2 试样内部则受阻。增大的塑性应变有利于小尺寸 T 1 的动态析出AA2099-2 样品中的相。因此,AA2099-1 和 AA2099-2 样品具有相似的中等机械性能。就AA2099-3样品而言,大尺寸T 1相的存在导致最大屈服应力。然而,这些大尺寸T 1析出物中的一些区域被怀疑被交叉滑移剪切,导致晶体结构的破坏和铝基体间隔的形成。这方面是造成峰值应力后真实应力-应变曲线逐渐退化的原因。对于 AA2099-4 样品,在塑性变形和位错与预先存在的 T 2相互作用过程中很少发生动态析出。相位属于 Orowan 循环,导致最小的机械响应。此外,AA2099-1 样品在加载方向和 <110> 晶向之间具有~16.5° 的平均最小偏差角 (MDA),而 AA2099-4 样品具有~7.5° 的平均 MDA。MDA的差异主要归因于δ'相和T 1相,它们将分别加速和推迟取向向<110>晶向的旋转。

图形摘要

更新日期:2021-06-09
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