尽管金属玻璃具有高强度、高弹性以及高断裂韧性等诸多优异的力学性能，但是其在室温下的塑性变形能力极其有限，这严重阻碍了金属玻璃的实际应用。结构年轻化，即体系由低能态向高能态的转变过程，被普遍认为是增强金属玻璃塑性变形能力的有效策略。本文聚焦于结构年轻化及其对金属玻璃塑性变形能力的调控作用，为金属玻璃的性能优化提供机理指导。首先，通过研究金属玻璃多级弛豫动力学行为，揭示了结构年轻化的多尺度动力学图像。在此基础上，通过多脉冲纳秒激光冲击激活快弛豫动力学，成功调控了老化玻璃的年轻化状态，并改善其塑性变形能力。随后，在低温条件下，通过快弛豫的累积激活来启动β弛豫，使金属玻璃产生滞弹性变形，以调控其年轻化状态，进而系统评估了结构年轻化提升金属玻璃宏观拉伸塑性的可行性。最后，利用静弹性压缩和循环扭转分别激活α和β弛豫制备了两组年轻化金属玻璃，通过准静态压缩实验系统研究了不同年轻化路径对金属玻璃塑性变形的影响，并证明有效焓是度量年轻化金属玻璃塑性的关键物理量。本文的主要研究工作如下：

（1）深入分析十二种不同年轻化状态金属玻璃的弛豫动力学行为，发现玻色峰与α、β以及快弛豫的特征温度之间存在强正相关关系。这种跨尺度的动力学关联揭示结构年轻化并非仅由单一的α、β、或者快弛豫所主导，而是一个由多时空尺度的动力学事件相互耦合、共同驱动的复杂过程。

（2）热力学和弛豫动力学分析表明，多脉冲纳秒激光冲击通过诱导快弛豫发生劈裂，实现了老化玻璃的年轻化。原本在退火样品中，快弛豫表现为单一的弛豫峰，然而经过激光冲击处理后，它会发生劈裂，形成两个独立的子弛豫峰。再退火会使这种劈裂现象消失。结构分析发现，退火或再退火金属玻璃的中程序主要由稳定的面连接型和体交叉型结构组成，而激光冲击处理后，金属玻璃内的不稳定边连接型中程序结构含量显著增加。弛豫动力学与拓扑结构之间的对应关系证明，快弛豫源于中程序结构的激活，而其劈裂则与中程序的不稳定重构相关。纳米压痕实验表明，快弛豫的劈裂有利于变形过程中塑性事件的激活，改善了金属玻璃的室温塑性。

（3）通过低温拉伸循环预处理制备出不同年轻化状态的金属玻璃薄带，结合准静态拉伸和应力松弛实验探究了结构年轻化改善金属玻璃宏观拉伸塑性的内在机理。分析表明，单纯依赖提高自由体积含量来增强拉伸塑性的效果是有限的。相反，通过构建软硬区交织的结构，在增加自由体积含量的同时，提高结构异质性，可以更为有效地提升金属玻璃的拉伸塑性，甚至实现应变硬化效果。

（4）利用静弹性压缩和循环扭转预处理分别激活α和β弛豫实现金属玻璃的结构年轻化，并通过准静态压缩实验探究了不同年轻化路径对金属玻璃塑性的影响。结果显示，即使两组年轻化金属玻璃中存在放热焓或玻色峰相似的情况，但循环扭转样品的塑性变形能力仍优于静弹性压缩样品。这种塑性差异直观地体现在两组样品的剪切带拓展模式和断裂特征上。其中，静弹性压缩样品的剪切带以直线拓展，而循环扭转样品的剪切带则呈现出偏转拓展。为了捕捉不同年轻化路径对塑性的影响，对整个玻璃化转变过程的焓进行积分，得到有效焓，并发现有效焓与所有样品的塑性应变之间建立了线性相关。这从实验上证明金属玻璃的塑性屈服是应力驱动的玻璃化转变过程。结构分析表明，两组不同年轻化路径的金属玻璃塑性差异的根源来自与自由体积分布以及中程序结构有关的结构异质性的不同。循环扭转处理导致了金属玻璃更显著的结构异质性，从而赋予其更高的有效焓和塑性变形能力。

The practical applications of metallic glasses (MGs) are limited by the low plastic deformation capacity at room temperature, despite their excellent mechanical properties such as high strength, elasticity, and fracture toughness. Structural rejuvenation, i.e., the transition of the system from a low-energy state to a high-energy state, is widely recognized as an effective strategy to enhance the plastic deformation ability of MGs. In this paper, structural rejuvenation and its role in regulating the plasticity of MGs are systematically investigated, aiming to provide mechanistic guidance for the property optimization of MGs. Firstly, the kinetic picture of structural rejuvenation is revealed by investigating the multistage kinetic behaviors of rejuvenated MGs. On this basis, the fast relaxation is activated by multi-pulse nanosecond laser shocks, which successfully modulated the rejuvenation state of the aged MGs and improved its plastic deformation capacity. Subsequently, anelastic deformation is accumulated by repeatedly activating fast relaxation at low temperatures to modulate the rejuvenation state in MGs, and then the feasibility of structural rejuvenation in enhancing the macroscopic tensile plasticity of MGs is systematically evaluated. Finally, two sets of rejuvenated MGs are prepared by activating α and β relaxation, respectively. The effects of different rejuvenation paths on the plastic deformation of MGs are systematically investigated by quasi-static compression experiments, and it is demonstrated that the effective enthalpy is the key physical quantity to measure the plasticity of rejuvenated MGs. The key findings of these research are summarized as follows:

(1) By systematically analyzing the dynamic relaxation behaviors of a series of rejuvenated MGs, a strong positive correlation is found between the boson peaks and the characteristic temperatures of α, β, and fast relaxations. This cross-scale dynamic correlation reveals that structural rejuvenation is not driven by a single α- or β-relaxation alone. Instead, it is a complex process involving the coupling of kinetic events across multiple spatial and temporal scales.

(2) The rejuvenation states of MGs were modulated by nanosecond laser shocks and annealing. Kinetic analysis reveals that the rejuvenation introduced by nanosecond laser shocks is achieved by activating the fast relaxation. In the annealed samples, the fast relaxation manifests itself as a single relaxation peak, but after the laser shock treatment, it splits into two separate sub-relaxation peaks. Subsequently, this splitting phenomenon will vanish after re-annealing. Structural analysis reveals that the splitting of the fast relaxation is caused by the unstable reconstruction of the medium-range orders (MROs). The MROs of annealed or re-annealed glasses primarily consists of stable interpenetrating and face-sharing structures, whereas laser shock treatment enhances the unstable edge-sharing structures within the MGs. The correspondence between the dynamic relaxation behaviors and atomic structures demonstrates that the fast relaxation is attributed to the activation of MRO structures, while its splitting is associated with the unstable reconfiguration of the MRO. Nanoindentation results show that the splitting of fast relaxation facilitates the activation of plastic events during deformation and improves the room-temperature plasticity of MGs.

(3) By continuously activating fast relaxation through low-temperature tensile cycles, the ribbons of MGs in different rejuvenation states are prepared. The effect of structural rejuvenation on the macroscopic tensile plasticity of MGs is systematically investigated by analyzing the tensile behavior of ribbon samples. Quasi-static tensile and stress relaxation experiments show that the increase of free volume is not adequately to enhance tensile plasticity of MGs. Instead, by simultaneously increasing the free volume content and structural heterogeneity and constructing a structure in which soft and hard regions are intertwined, the tensile plasticity of MGs can be effectively improved, and even strain hardening can be achieved.

(4) The structural rejuvenation of metallic glass is achieved by activating α and β relaxations respectively through elastostatic compression and cycled twist pretreatment. The effect of different rejuvenation paths on the plasticity of MGs is investigated by quasi-static compression experiments. The results show that the cycle-twisted glasses have better plastic deformability than the elastostatic-compressed samples, although their exothermic enthalpies or boson peaks are similar. This plasticity difference is also reflected by their different shear band expansion patterns and fracture characteristics. The shear bands of the elastostatic-compressed MGs expand in a straight line, while those of the cycle-twisted ones show a deflection expansion. In order to capture the effect of different rejuvenation paths on plasticity, effective enthalpy is calculated by integrating the enthalpy change of the whole glass transition process. A linear correlation is established between the effective enthalpy and the plastic strain of all glasses. This demonstrates that plastic yielding of MGs is a stress-driven glass transition process. Further structural analysis shows that the plastic gap between two sets of MGs arises from differences in structural heterogeneity related to the free volume distribution, as well as the MRO structure. The cycled twist pretreatment leads to more pronounced structural heterogeneity of MGs, which confers a higher effective enthalpy and plastic deformation capacity.