利用微柱压缩表征 Zircaloy-4 中基面、柱面和锥面滑移的应变速率敏感性
Characterisation of the strain rate sensitivity of basal, prismatic and pyramidal slip in Zircaloy-4 using micropillar compression
AI总结：
本文通过单晶微柱压缩在 10E-4–125 s^-1 范围内表征 Zircaloy-4 三类滑移系，拟合其应变速率敏感性并揭示变形机制差异。
摘要：
各个滑移系在不同应变速率下的滑移强度将控制力学响应，并强烈影响塑性变形的各向异性。在本研究中，通过采用单晶微柱压缩试验在可变应变速率（从 10E-4 s^-1 到 125 s^-1）下进行测试，探究了 <a> 基面、<a> 柱面和 <c+a> 锥面滑移系的滑移活性及应变速率敏感性。这些系统实验使得能够利用一个简单的解析模型直接拟合不同滑移的应变速率敏感性，并且该模型揭示，除应力状态（即 Schmid 定律）之外，多晶体中的变形还将根据变形的应变速率由不同的滑移系来协调。研究发现，工程屈服应力随应变速率增加而升高，且这种变化因滑移系而异。柱面滑移系的激活导致高密度、平行且明显离散的滑移面，而 <c+a> 锥面滑移的激活则导致微柱塑性坍塌，使变形后的微柱呈现“蘑菇”形形貌。这一表征和模型提供了有助于指导金属成形以及理解这些工程合金在极端服役条件下力学性能的洞见。
英文摘要：
The slip strength of individual slip systems at different strain rates will control the mechanical response and strongly influence the anisotropy of plastic deformation. In this work, the slip activity and strain rate sensitivity of the <a> basal, <a> prismatic, and <c+a> pyramidal slip systems are explored by testing at variable strain rates (from 10E-4 s^-1 to 125 s^-1) using single crystal micropillar compression tests. These systematic experiments enable the direct fitting of the strain rate sensitivities of the different slips using a simple analytical model and this model reveals that deformation in polycrystals will be accommodated using different slip systems depending on the strain rate of deformation in addition to the stress state (i.e. Schmid's law). It was found that the engineering yield stress increases with strain rate, and this varied by slip systems. Activation of the prismatic slip system results in a high density of parallel, clearly discrete slip planes, while the activation of the <c+a> pyramidal slip leads to the plastic collapse of the pillar, leading to a 'mushroom' morphology of the deformed pillar. This characterization and model provide insight that helps inform metal forming and understanding of the mechanical performance of these engineering alloys in the extremes of service conditions.
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