形变时效对Al-2.4Cu-0.9Li-0.7Mg合金的显微组织和力学性能的影响

形变时效对Al-2.4Cu-0.9Li-0.7Mg合金的显微组织和力学性能的影响

邹富强，李石勇，伍翠兰^*，巩向鹏，罗世芳，周  琳

（湖南大学材料科学与工程学院高分辨电镜中心，湖南 长沙 410082）

摘  要  本文采用透射电镜观察、硬度测试和拉伸性能测试等手段，研究了形变时效对Al-2.4Cu-0.9Li-0.7Mg (wt.%)合金的显微组织和力学性能的影响。结果表明：固溶后直接150~180℃时效的T6试样主要析出相为高密度弥散分布的GPB区和少量的S相、T₁相。时效前引入预变形的T8工艺可显著提高合金的强度但塑性大幅降低，T8试样中主要析出相为S相和T₁相；相对T6工艺，T8工艺析出的S相和T₁相尺寸减小，但由于其易于在位错胞或亚晶界上形核长大，因此析出相分布不均匀。在预变形前引入预时效的TMT工艺不仅提高合金的强度且塑性得到改善，其主要原因是，TMT工艺使得合金基体内S相与T₁相数量密度增加、尺寸更细小、分布更均匀。

关键词  形变时效；析出相；强度；塑性；TEM表征

中图分类号：TG156.9；TG113；TG155.1；TG115.21⁺5.3  文献标识码：A    doi:10.3969/j.issn.1000-6281.2019.06.007

Effect of thermo-mechanical treatment on the microstructure and mechanical properties of Al-2.4Cu-0.9Li-0.7Mg alloy

ZOU Fu-qiang，LI Shi-yong，WU Cui-lan^*，GONG Xiang-peng，LUO Shi-fang，ZHOU Lin

(College of Material Science and Engineering of Hunan University，Changsha Hunan 410082, China)

Abstract  Effect of thermo-mechanical treatment on the microstructure and mechanical properties of Al-2.4Cu-0.9Li-0.7Mg (wt.%) alloy were investigated by means of transmission electron microscopy, hardness test and tensile test. The results show that after solution treatment followed by ageing at 150~180℃, the main precipitates of T6 samples are high density dispersed GPB zone, a few S and T₁ phases. The T8 process, which involves large pre-deformation and aging, can significantly improve the strength of the alloy, but decrease the plasticity. The main precipitates of T8 samples are S phase and T₁ phase. Compared with T6 samples, the size of S phase and T₁phase precipitating during T8 process is smaller. However, the distribution of S precipitates and T₁ precipitates is heterogeneous because these precipitates tend to nuclear and grow along the dislocation cell or sub-grain boundary. Compared with the T8 process, TMT process introducing pre-aging before pre-deformation not only improves the strength of alloy, but also improves the plasticity. The main reason is that the TMT process increases the number density of S phase and T₁ phase, reduces the size of precipitates and makes the precipitates to distribute more uniformly in the alloy matrix.

Keywords   thermo-mechanical treatment；precipitate；strength；plasticity；TEMcharacterize

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