Formation of duplex microstructure in Zr–2.3Nb alloy and its plastic behaviour at various strain rates
Formation of duplex microstructure in Zr–2.3Nb alloy and its plastic behaviour at various strain rates
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DOI：
10.1016/j.ijplas.2013.08.013
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发表时间：
2014-03
影响因子：
9.8
通讯作者：
Z. N. Yang;Fucheng Zhang;L. Qu;Zhigang Yan;Y. Xiao;Riping Liu;X. Zhang
中科院分区：
文献类型：
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作者：
Z. N. Yang;Fucheng Zhang;L. Qu;Zhigang Yan;Y. Xiao;Riping Liu;X. Zhang
本文研究了Zr-2.3Nb合金在850 ~ 925℃温度范围内双相组织的形成、在不同应变速率下的塑性行为以及在拉伸变形过程中各相在双相组织中的迁就。结果表明，随着温度的升高，β的维数呈指数增长，而α的维数基本保持不变，主要是由于晶粒长大和α向β相变的竞争。由于ω相的强化和均匀的晶粒尺寸，850℃下获得的双相组织比在更高温度下获得的其他双相组织具有更高的强度和相当的塑性。随着应变速率的增加，双相组织的强度增加，而塑性参数伸长率（EL）和面积收缩率（RA）则呈现相反的趋势，EL减小，RA增大。分析表明，EL的降低是由于在高应变速率下较高的位错湮灭率降低了加工硬化速率，导致颈缩提早发生。RA的增加与断裂面观察结果一致：凹窝的平均大小和平均深度增加，表明颈后EL增加，随后EL下降趋势减慢。α相和保留β相的界面上容易形成微孔洞。SEM和TEM分析表明，这些相的变形顺序依次为：β、αs、αp。然后，提出了一个简单的变形模型来描述各相的变形行为。
The formation of duplex microstructure in Zr–2.3Nb alloys at a temperature range of 850–925 °C, its plastic behaviour at various strain rates and the accommodation of each phase in duplex microstructure during the tensile deformation process were investigated thoroughly in this paper. It is shown that with increasing temperature, the dimension ofβpexponentially increased, while the dimension ofαpremained nearly unchanged due to the competition of grain growth and phase transformation fromαtoβ. The duplex microstructure obtained at 850 °C displayed a higher strength and a comparable plasticity compared with other duplex microstructures obtained at higher temperatures, due to the reinforcement of theωphase and the uniform grain size. With increasing strain rate, the strength of the duplex microstructure increased, while the plasticity parameters – elongation (EL) and reduction of area (RA), showed opposite tendencies, a decreased tendency for EL and increased tendency for RA. Analysis indicated that the decreased EL was due to the fact that the higher dislocation annihilation rate at higher strain rate reduced the work hardening rate, resulting in an early onset of necking. The increased RA was consistent with the fracture surface observation: the increased mean size and mean depth of dimples, which revealed an increased post-necking EL and then slowed down the falling tendency of EL. Microvoids were prone to form along the interfaces of theαpand retainedβphases. Finally, SEM and TEM observations revealed the deformation sequence of these phases as follows:β,αs,αp. And then a simple deformation model illustrating the deformation behaviour of each phase was proposed.