Superplastic deformation behaviour of friction stir processed 7075Al alloy
Superplastic deformation behaviour of friction stir processed 7075Al alloy
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DOI：
10.1016/s1359-6454(02)00278-1
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发表时间：
2002-10-09
期刊：
影响因子：
9.4
通讯作者：
Mahoney, MW
中科院分区：
文献类型：
--
作者：
Ma, ZY;Mishra, RS;Mahoney, MW
对工业7075Al轧制板材进行了不同工艺参数的搅拌摩擦处理，得到了两种细晶7075Al合金，其晶粒度分别为3.8和7.5um。在490℃热处理1h，细晶组织在高温下稳定。在420~530℃温度范围和1×10~(-3)~1×10~(-1)应变速率范围内的超塑性研究表明，随着晶粒度的减小，超塑性显著增强，并向较高的最佳应变速率和较低的最佳变形温度转变。3.8um7075Al合金在3x10(-3)-3x10(-2)S(-1)的应变速率范围内，在480℃时的超塑性延伸率为1250%，而7.5um7075Al合金在500℃和3x10(-3)S(-1)的应变速率下的最大延伸率为1042%。对两种合金超塑性数据的分析表明，应力指数为2，晶粒度与应力指数成反比，激活能接近晶界自扩散激活能。这表明晶界滑移是FSP 7075Al的主要变形机制。通过对变形试件表面的扫描电子显微镜检查，证实了这一点。(C)爱思唯尔科学有限公司出版的2002 Acta Materialia Inc.保留所有权利。
Commercial 7075Al rolled plates were subjected to friction stir processing (FSP) with different processing parameters, resulting in two fine-grained 7075Al alloys with a grain size of 3.8 and 7.5 mum. Heat treatment at 490 degreesC for 1 h showed that the fine grain microstructures were stable at high temperatures. Superplastic investigations in the temperature range of 420-530 degreesC and strain rate range of 1x10(-3)-1x10(-1) s(-1) demonstrated that a decrease in grain size resulted in significantly enhanced superplasticity and a shift to higher optimum strain rate and lower optimum deformation temperature. For the 3.8 mum 7075Al alloy, superplastic elongations of >1250% were obtained at 480 degreesC in the strain rate range of 3x10(-3)-3x10(-2) s(-1), whereas the 7.5 mum 7075Al alloy exhibited a maximum ductility of 1042% at 500 degreesC and 3x10(-3) s(-1). The analyses of the superplastic data for the two alloys revealed a stress exponent of 2, an inverse grain size dependence of 2, and an activation energy close to that for grain boundary self-diffusion. This indicates that grain boundary sliding is the main deformation mechanism for the FSP 7075Al. This was verified by SEM examinations on the surfaces of deformed specimens. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.