Variation of the deformation mechanisms in a nanocrystalline Pd-10 at.% Au alloy at room and cryogenic temperatures
Variation of the deformation mechanisms in a nanocrystalline Pd-10 at.% Au alloy at room and cryogenic temperatures
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DOI：
10.1016/j.ijplas.2014.04.011
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发表时间：
2014-09
影响因子：
9.8
通讯作者：
Y. Ivanisenko;E. Tabachnikova;I. Psaruk;S. Smirnov;A. Kilmametov;A. Kobler;C. Kübel;L. Kurmanaeva;K. Csach;Y. Mishkuf;T. Scherer;Y. Semerenko;H. Hahn
中科院分区：
文献类型：
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作者：
Y. Ivanisenko;E. Tabachnikova;I. Psaruk;S. Smirnov;A. Kilmametov;A. Kobler;C. Kübel;L. Kurmanaeva;K. Csach;Y. Mishkuf;T. Scherer;Y. Semerenko;H. Hahn
首次详细研究了纳米晶Pd-10at.%对平均晶粒尺寸为14 nm的Au合金在4.2 ~ 300 K温度范围内进行压缩试验，分析了相应的微观结构变化。结果表明，当温度从300 K降低到77 K时，晶粒尺寸从10 μm减小到14 nm，所施加的应力增加了4.7-6.4倍。然而，温度的进一步降低不会导致这些纳米晶样品中所施加的应力的额外增加。纳米晶样品显示了一个扩展的微塑性阶段，抛物线应变硬化高达4.2%的应变在室温下。随着温度的降低，发生微塑性的应变范围缩小，在40 K时降至2%。当样品在宏观塑性区变形时，它们在室温和210 K下表现出弱的应变硬化，但在低至40 K的低温下观察到应变软化。随后的显微组织研究表明，应变硬化行为伴随着显着的晶粒生长，表明反向Hall-Petch关系。在10 K下的变形曲线显示锯齿状的塑性流动。为了解释所观察到的细节nc合金的变形行为，提出了一个具体的变形机制的nc状态，其中塑性由晶界滑动（GBS）和容纳的滑移位错发射的晶界。这是基于这样的事实，即GBS允许位错发射所需的应力集中，并且位错提供了一种方式来适应沿着GBS路径出现的几何不相容性。
For the first time, the details of plastic deformation in a nanocrystalline Pd–10 at.% Au alloy with an average grain size of 14 nm were investigated in compression tests over the temperature range between 4.2 and 300 K and the corresponding microstructural changes were analyzed. It was established that decreasing the grain size from 10 μm to 14 nm resulted in a 4.7–6.4 increase in the applied stress as the temperature was decreased from 300 to 77 K. However, a further decrease in the temperature did not lead to an additional increase in the applied stress in these nanocrystalline samples. The nanocrystalline samples revealed an extended microplasticity stage with parabolic strain hardening up to 4.2% strain at room temperature. With decreasing temperature, the strain range over which microplasticity occurred shrank and was down to 2% at 40 K. As the samples were deformed in the macroplastic regime, they demonstrated weak strain hardening at room temperature and at 210 K, but strain softening was instead observed at cryogenic temperatures down to 40 K. Subsequent microstructural investigations revealed that the strain hardening behavior was accompanied by significant grain growth indicating a reverse Hall–Petch relationship. Deformation curves at 10 K displayed serrated plastic flow. To explain the observed details of the deformation behavior of nc alloys, a specific deformation mechanism for the nc state is proposed where plasticity was governed by grain boundary sliding (GBS) and was accommodated by the slip of dislocations emitted from grain boundaries. This is based upon the fact that GBS allows for the stress concentration necessary for dislocation emission and that dislocations provide a way to accommodate geometric incompatibilities arising along the GBS path.