The continuous miniaturization of modern electromechanical systems calls for a comprehensive understanding of the mechanical properties of metallic materials specific to micrometer and sub-micrometer scales. At these scales, the nature of dislocation-mediated plasticity changes radically: sub-micrometer metallic samples exhibit high yield strengths, however accompanied by detrimental intermittent strain fluctuations compromising forming processes and endangering structural stability. In this paper, we studied the effects of plate-like $\theta^\prime$-Al$_2$Cu precipitates on the strength, plastic fluctuations and deformation mechanisms of Al-Cu alloys from micro-pillar compression testing. The plate-like precipitates have diameters commensurate with the external size of the Al-Cu micro-pillars. Our results show that these plate-like precipitates can strengthen the materials and suppress plastic fluctuations efficiently at large sample sizes ($\geq 3 \mu m$). However, the breakdown of the mean-field pinning landscape at smaller scales weakens its taming effect on intermittency. Over an intermediate range of sample sizes allowing the precipitates to cross the entire pillar, an enhanced apparent strain hardening and a sharp decrease of jerkiness are observed, in association with the presence of {100}-slip traces along the coherent $\theta^\prime$-Al$_2$Cu precipitate/$\alpha$-Al matrix interface and precipitate shearing. These complex effects of plate-like precipitates on plasticity are analyzed, experimentally and theoretically, in view of the interferences between external and internal sizes, and the related modifications of the underlying plastic mechanisms.

中文翻译：

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微米至亚微米尺度下板状沉淀对Al-Cu合金塑性的影响

现代机电系统的不断小型化要求全面了解特定于微米和亚微米尺度的金属材料的机械性能。在这些尺度上，位错介导的塑性性质发生了根本性的变化：亚微米金属样品表现出高屈服强度，但伴随着有害的间歇性应变波动，损害了成形过程并危及结构稳定性。在本文中，我们通过微柱压缩试验研究了板状$\theta^\prime$-Al$_2$Cu 析出物对Al-Cu 合金强度、塑性波动和变形机制的影响。板状沉淀物的直径与 Al-Cu 微柱的外部尺寸相称。我们的结果表明，这些板状沉淀物可以在大样本尺寸（$\geq 3 \mu m$）下有效地增强材料并抑制塑性波动。然而，平均场钉扎景观在较小尺度上的分解削弱了其对间歇性的驯服效果。在允许沉淀物穿过整个柱子的中间样本尺寸范围内，观察到明显的应变硬化增强和急动度急剧下降，这与沿相干 $\theta^\ 的 {100} 滑移迹线的存在有关。素$-Al$_2$Cu沉淀/$\alpha$-Al基体界面和沉淀剪切。鉴于外部和内部尺寸之间的干扰，板状沉淀物对塑性的这些复杂影响在实验和理论上进行了分析，