Rejuvenation of metallic glasses by disordering and relaxation controlling

非晶合金的弛豫被普遍认为是源于内在随机结构的重要现象之一。由于弛豫状态与金属玻璃的结构、相变、力学和磁学性质密切相关，因此在工业应用中必须严格控制弛豫状态。松弛状态取决于刚好高于玻璃化转变温度Tg的冷却速率。我们已经调查了恢复的低松弛状态的低温退火刚刚超过Tg和各种冷却条件下，在几个玻璃合金的实验和分子动力学（MD）模拟研究。通过在较高冷却速率下的这种低温退火，松弛焓增加，具有显著的机械软化。MD模拟清楚地表明，玻璃态合金可以在比初始冷却速率更高的冷却速率的情况下再生（即，玻璃初始制备中的冷却速率）。这种复原在高于Tg超过150 K的温度范围内是饱和的。这一结果与铜型铸造的实验结果一致。本文对弛豫态的恢复和控制的研究为金属玻璃的应用提供了有益的信息。

Relaxation of glassy alloys is generally regarded as one of the important phenomena originating from the intrinsic random structure. Due to a strong correlation with structure, transformation, mechanical and magnetic properties of metallic glasses, we have to control the relaxation state carefully for industrial use. Relaxation state depends on a cooling rate just above glass transition temperature, Tg. We have investigated the recovery of the less relaxation state by low temperature annealing just above Tg and various cooling conditions in several glassy alloys by experimental and molecular dynamics (MD) simulation studies. The enthalpy of relaxation increases by such low temperature annealing at higher cooling rates with a significant mechanical softening. The MD simulation clearly indicates that the glassy alloys can be rejuvenated in the case of higher cooling rates than the initial one (i.e., cooling rate in the initial preparation of glass) by annealing over Tg. Such rejuvenation is saturated in the temperature range over 150 K above Tg. The result is consistent with the experimental one using Cu mold casting. The present study on recovering and controlling relaxation state provides useful information on the application of metallic glasses.