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La基非晶合金的动力学弛豫调控机制研究

PROBING INTO THE REGULATION MECHANISM OF DYNAMIC RELAXATION IN LA-BASED AMORPHOUS ALLOYS

  • 摘要: 作为典型长程无序亚稳态材料, 非晶合金的动力学弛豫行为受时间、温度及加载历史等因素显著影响. 然而, 由于其具备独特非平衡时空演化特征并在外场激励下呈现多级弛豫行为, 其宏观变形响应与微观结构演化之间的物理图像不甚清晰, 相关动力学调控机制仍有待深入探究. 本研究选取具有显著 \beta 弛豫特征的La60Ni15Al25非晶合金作为模型体系, 在广泛温度区间内开展了不同初始能量状态样品的应力松弛实验. 结合特征弛豫时间、扩展指数、名义激活能与名义激活体积等动力学弛豫参数演化信息, 揭示了温度与物理老化在非晶合金动力学弛豫行为调控中的本质区别及协同作用. 研究表明, 应力松弛行为在较低温度区间内由 \beta 弛豫主导. 此时体系势能景观分布各异, 动力学非均匀性增强, 弛豫行为呈现更广泛特征弛豫时间分布并表现出较强非指数性. 而在较高温度区间内, \alpha 弛豫逐渐占据主导地位. 原子团簇在热激活效应作用下运动速率加快, 体系激活能垒显著降低, 弛豫时间缩短并呈现更集中分布, 导致宏观弛豫行为更遵循指数型衰减特征. 基于不同退火状态样品的进一步研究表明, 物理老化通过结构致密化和势能谷重构强化了体系动力学非均匀性, 而温度升高则通过热激活机制促进了弛豫过程的均匀化与协同性, 两者共同塑造了非晶合金在不同能量状态下的动力学弛豫特性. 本研究深化了对非晶固体多尺度动力学弛豫行为的理解, 同时为高性能非晶材料的热稳定性优化提供了重要参考.

     

    Abstract: As a prototypical long-range disordered metastable material, the dynamic relaxation behavior of amorphous alloys is significantly influenced by factors such as temporal evolution, temperature history, and loading history. However, due to their inherent non-equilibrium spatiotemporal evolution and the presence of multi-scale relaxation dynamics under external stimuli, the underlying physical mechanisms governing the relationship between macroscopic deformation responses and microscopic structural evolution remain insufficiently understood, necessitating further investigation into the relevant dynamic regulation mechanisms. In this study, La60Ni15Al25 amorphous alloy, characterized by pronounced \beta relaxation, was selected as the model system to conduct stress relaxation experiments over a wide temperature range for samples with different initial energy states. By analyzing the evolution of key dynamic relaxation parameters, including the characteristic relaxation time, stretched exponent, nominal activation energy, and nominal activation volume, the intrinsic distinctions and synergistic effects of temperature and physical aging on the dynamical relaxation behavior of amorphous alloys were elucidated. The results reveal that stress relaxation is predominantly mediated by \beta relaxation at lower temperatures, where the system exhibits a highly heterogeneous potential energy landscape, leading to enhanced dynamic heterogeneity, a broad distribution of relaxation times, and pronounced non-exponential relaxation behavior. In contrast, α relaxation progressively dominates at higher temperatures, facilitated by increased atomic mobility under thermal activation. This transition is accompanied by a significant reduction in activation energy barriers, a narrowing of relaxation time distribution and the overall shift towards a more homogeneous and exponential relaxation response. Further investigations on samples subjected to different annealing states indicate that physical aging promotes dynamic heterogeneity by deepening potential energy valleys and enhancing structural densification, whereas elevated temperatures facilitate relaxation homogenization and cooperative atomic rearrangements via thermal activation. These effects collectively shape the kinetic relaxation characteristics of amorphous alloys across varying energy states. This study provides fundamental insights into the multi-scale relaxation dynamics of amorphous solids and offers a theoretical framework for understanding the interplay between thermal and aging effects, contributing to the design and optimization of amorphous alloys with enhanced thermal stability and mechanical performance.

     

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