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中国物理学会期刊

金属玻璃蠕变与恢复的非对称黏弹性及其物理起源

Physical origin of asymmetric anelasticity in creep and recovery of a metallic glass

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  • 金属玻璃高温蠕变与恢复行为表现出显著的非对称演化路径,本文开展了La基金属玻璃蠕变与恢复实验,建立了双层级关联黏弹性本构模型。分析各分量在加载与卸载过程的激活能和激活体积,在蠕变与恢复方向上存在时间级联效应。正向快弛豫单元先激活并触发慢弛豫单元,反向时顺序逆转。慢弛豫单元近似完全可恢复,而快弛豫单元在高温/高应力下仅可部分恢复。计算了快弛豫单元锁并态激活能差约以及锁定态数目,通过差示扫描量热进行验证并揭示了变形态周围存在大量亚稳势阱。将可回复系数与势能图谱拓扑参数关联,为金属玻璃在热力耦合激励下的服役稳定性评估提供了定量预测工具,也为理解非晶态固体变形与恢复提供了具有明确物理基础的理论框架。

     

    The creep and recovery of metallic glasses exhibit pronounced asymmetric evolution, challenging the conventional anelastic assumption of time-reversal symmetry. We establish a two-level hierarchical anelastic constitutive model for a La25Ce25Ni10Co20Al20 metallic glass over 423–463 K and 20–100 MPa, decomposing anelastic strain into fast and slow relaxation units. The model captures the entire creep-recovery response with high fidelity. During creep, the fast unit activates first and triggers the slow one. Upon unloading, the slow unit recovers almost fully and rapidly, while the fast unit recovers only partially. The activation energy of the fast unit during creep decreases from 0.59 to 0.26 eV with increasing stress, with an activation volume of 0.7 nm3. Its recovery activation volume (0.91 nm3) exceeds the forward value, indicating more cooperative reverse motion. To unveil the microscopic origin, we correlate recovery coefficient with the potential energy landscape. The fast unit is trapped in a rough sub-basin with numerous metastable lock-in states. Statistical analysis yields the number of locked states M ≈ 8–35 and an energy barrier difference of 0.16 eV between reversible and locked pathways, consistent with sub-basin rugosity. Differential scanning calorimetry independently verifies the locked states via relaxation enthalpy measurements, with the irreversible enthalpy fraction decreasing monotonically with recovery coefficient. This work provides a thermodynamically consistent framework linking macroscopic anelasticity to potential energy landscape topology, offering a quantitative tool for evaluating structural stability of metallic glasses under service loading.

     

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