In this work, we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy, which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 K. The deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation study. The results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K, whereas at 77 K, vague grain surfaces dominate, indicating the simultaneous operation of multiple slip systems. Transmission electron microscopy (TEM) analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature, confirming the activation of multiple slip systems. The accumulation of dislocations facilitated by these multiple slip systems, combined with the high dislocation density, contributes to strain hardening and remarkable uniform elongation at 77 K. A modified dislocation density-based crystal plasticity model, incorporating the effect of grain boundary hardening (GBH) and temperature, was developed to gain a better understanding of the underlying mechanisms governing alloy's strength and plasticity. The GBH effect significantly enhances statistically stored dislocation (SSD) density and screw dislocation proportion, which promote homogeneous deformation and enhance strain hardening capacity at cryogenic temperature. These findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.

中文翻译：

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深入了解 Al1Mg0.4Si 合金在低温下的变形机理：实验与晶体塑性建模的整合


在这项工作中，我们研究了 Al1Mg0.4Si 合金的机械性能和相应的变形机制，与 298 K 的同类合金相比，该合金在 77 K 时表现出显着更高的强度和出色的应变硬化能力。通过实验和模拟相结合的研究，阐明了在低温下导致出色的强度-延展性协同作用和非凡应变硬化能力的变形机制。结果显示，在 298 K 的变形过程中，整个晶粒表面存在许多滑移痕迹和微带，而在 77 K 时，模糊的晶粒表面占主导地位，表明多个滑移系统同时运行。使用双光束衍射技术的透射电子显微镜 （TEM） 分析表明，在低温下，颗粒内部存在几种不同 Burgers 矢量的位错，证实了多个滑移系统的激活。这些多滑动系统促进的位错积累，加上高位错密度，有助于在 77 K 下实现应变硬化和显着的均匀伸长率。开发了一种改进的基于位错密度的晶体塑性模型，该模型结合了晶界硬化 （GBH） 和温度的影响，以更好地了解控制合金强度和塑性的潜在机制。GBH 效应显著提高了统计存储位错 （SSD） 密度和螺钉位错比例，促进了低温下的均匀变形并增强了应变硬化能力。 这些发现加深了对低温下塑性变形的理解，并为开发用于低温应用的超高性能金属材料铺平了道路。