物理时效和循环加载下高熵金属玻璃的弛豫行为

Relaxation behavior of high-entropy bulk metallic glass:Influences of physical aging and cyclic loading

金属玻璃微观结构非均匀性与其弛豫行为、形变机制的本征关联是本领域的重要科学问题之一.本研究以La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)高熵金属玻璃为研究载体,借助动态力学分析仪探究了物理时效和循环加载对金属玻璃弛豫行为和形变机制的影响,基于激活能图谱模型建立了变形载体和微观结构非均匀性之间的关联.研究结果表明, La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)高熵金属玻璃表现出明显的β弛豫行为.玻璃转变温度以下的物理时效和循环加载诱导金属玻璃跃迁至结构更稳定状态,抑制了原子协同重排运动.物理时效过程中类液区转变为弹性基底导致变形载体被冻结,需要更长时间才能激活.循环蠕变过程中变形载体数目在应力作用下减少.类液区体积减少诱导β弛豫强度降低表明β弛豫起源于类液区.

In this study, the correlation among the relaxation behavior, deformation mechanism, and structural heterogeneity of metallic glasses is examined using La30Ce30Ni10Al20Co10 high-entropy bulk metallic glass as the model glass. Dynamic mechanical analysis(DMA) was used to investigate the influences of physical aging and cyclic loading on the dynamic relaxation and deformation mechanism of the model glass. The correlation between the deformation units and the structural heterogeneity was analyzed on the basis of the activation energy spectrum(AES). The results demonstrated that La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) high-entropy bulk metallic glass displays an apparent β relaxation. A more stable state can be achieved during physical aging below the glass transition temperature and in cyclic loading because the atomic rearrangements are suppressed during these processes. This structural relaxation during the physical aging process enables the transition from liquid-like regions to an elastic matrix. Further, more time is required to activate the deformation units that are frozen during the transition. The applied stress results in a decrease in the number of liquid-like regions, which suppresses the activation of the deformation units during the cyclic loading process. As a result, the intensity of the β relaxation in the metallic glass decreases. Therefore, the origin of the β relaxation in La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) high-entropy bulk metallic glass is ascribed to the liquid-like regions.