Warm formability and post-forming microstructure/property of high-strength AA 7075-T6 Al alloy
Warm formability and post-forming microstructure/property of high-strength AA 7075-T6 Al alloy
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DOI：
10.1016/j.msea.2016.08.054
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发表时间：
2016-10-15
期刊：
影响因子：
6.4
通讯作者：
Zhang, Jishan
中科院分区：
文献类型：
--
作者：
Huo, Wangtu;Hou, Longgang;Zhang, Jishan
本文研究了AA 7075-T6板材在室温~ 250 ℃范围内峰时效后的成形性能以及成形后的组织性能。结果表明，由于在200 ℃下具有更高的延展性和加工硬化能力，因此在200 ℃下获得了最佳的成形性。7075-T6、200 ℃温成形和250 ℃温成形样品中的主要相分别是细η '和GP区、发育良好的η'和较粗的η相。7075试样成形后和烤漆后的力学性能与相应的显微组织密切相关。具体而言，200 ℃温成形导致基体析出物（MPts）的有限粗化并产生一定数量的位错，由于析出强化降低和位错强化增加的综合作用，7075-T6固有的高强度在200 ℃成形后得到了完美的保留。然而，250摄氏度的成形由于MPt的急剧粗化而导致硬度严重降低。烤漆处理对MPts、晶界析出相和无析出相区的影响较小，因此烤漆对硬度的影响不明显。总的来说，200 ℃是峰值时效7000合金表现出增强的成形性并保持高的成形后强度的适当温度，在油漆烘烤之后，拉拔部件具有与回归和再时效（RRA）样品相似的微观结构/性能。(C)© 2016 Elsevier B. V.版权所有。
Formability of peak-aged AA 7075-T6 sheet across a temperature range from room temperature to 250 degrees C as well as post-forming microstructure/property were investigated in this paper. It showed that the optimized formability was obtained at 200 degrees C, due to the higher ductility and work hardening capacity at this temperature. The dominant phases in 7075-T6, 200 degrees C warm formed, and 250 degrees C warm formed samples were fines eta' and GP zones, well-developed eta', and coarser eta phases, respectively. Post-forming and post-paint-baking mechanical property of 7075 samples was closely associated with those corresponding microstructures. Specifically, 200 degrees C warm forming caused limited coarsening of matrix precipitates (MPts) and generated a certain number of dislocations, due to the combined effect of the decreased precipitation strengthening and increased dislocation strengthening, the inherent high strength of 7075-T6 was perfectly preserved after 200 degrees C forming. However, 250 degrees C forming led to severely decreased hardness due to the sharply coarsened MPts. Furthermore, the paint-baking treatment exerted little influence to MPts, grain boundary precipitates (GBPs) and precipitate free zone (PFZ), thus the hardness loss caused by paint-baking was unobvious. Overall, 200 degrees C was the appropriate temperature under which the peak-aged 7000 alloys exhibited enhanced formability and maintained high post-forming strength, after paint baking, the drawn component possessed microstructure/property similar to those of retrogression and re-aged (RRA) samples. (C) 2016 Elsevier B.V. All rights reserved.