均匀塑性变形条件下块体非晶合金的回春行为研究

Metallic glasses as a kind of metastable metallic materials, there are various glassy states depending on the preparation conditions. Rejuvenation is a process that induces structure disordering into metallic glasses and consequently brings them into a higher energy state. Due to the unique structure and excellent performance of high energy state metallic glasses, rejuvenation becomes one of the most attractive topics and important scientific issues in this field. But how to achieve the high level of rejuvenation in bulk metallic glasses is still a challenge. In this project, rejuvenation behavior of bulk metallic glasses under homogeneous deformation will be systematically studied. First, homogeneous deformation in bulk metallic glasses will be achieved by introducing triaxial stress state under compression at room temperature and liquid nitrogen temperature. Then, the effect of the triaixality, initial state and deformation temperature on the rejuvenation behavior of bulk metallic glasses will be studied systematically, exploring the maximum level of rejuvenation in various metallic glasses. Based on the free volume model and the molecular dynamics simulation, the change of microstructure and free volume during rejuvenation will be analyzed. The intrinsic mechanism of rejuvenation under uniform deformation will also be discussed. Finally, by studying the deformation behavior of metallic glasses with different levels of rejuvenation, the intrinsic correlation between rejuvenation, elastic modulus and deformation behavior will be established, revealing the plastic deformation mechanism of metallic glasses at room temperature. This study not only provides the way for the preparation of amorphous alloys with excellent mechanical properties and understanding of the nature and characteristics of amorphous materials, but also enhances the understanding of the deformation mechanism of metallic glasses at room temperature.

非晶合金作为一种亚稳态金属材料，具有不同的能量状态，从低能态向高能态转变的过程称为回春。高能态非晶合金独特的结构和优异的性能，使回春行为成为非晶领域的研究热点和重要科学问题之一。但如何实现块体非晶合金最大程度回春仍是目前面临的瓶颈问题之一。本项目将通过均匀塑性变形方法研究块体非晶合金回春行为。首先在块体非晶合金中引入三维压应力状态使其产生均匀塑性变形，然后系统研究应力状态系数、合金初始状态和变形温度等对不同非晶合金回春行为的影响，探索最高回春状态。然后结合自由体积模型和分子动力学模拟，分析回春过程中微观结构和自由体积的变化规律，探讨非晶合金回春行为的内在机理。最后通过研究不同回春态非晶合金的变形行为，建立回春态、微观结构和变形行为间的内在关联，揭示非晶合金塑性变形机制。本项目的研究不仅能为高性能非晶合金的制备以及非晶态材料本质和特性的认识提供方法，也将有助于非晶合金室温变形理论的完善。

非晶合金作为一种亚稳态金属材料，在不同制备条件下会呈现出不同的能量状态，从低能态向高能态转变的过程称为回春。高能态非晶合金独特的结构和优异的性能，使回春行为成为非晶领域的研究热点和重要科学问题之一。但是，目前关于非晶合金回春行为仍缺乏系统研究和深入认识。在基金委资助下，本项目四年来围绕非晶合金的回春行为开展了以下研究：1）室温均匀塑性变形对非晶合金回春行为的影响规律；2）回春处理对非晶合金微观结构的影响规律；3）回春态非晶合金的变形行为和加工硬化机制；4）回春处理对非晶合金热力学性能的影响规律；5）回春态非晶合金的纳米压痕蠕变行为和机制；6）高能态钼氧非晶合金的剧烈结构弛豫现象。项目研究结果发现：通过在非晶合金中引入三维应力状态，可有效抑制剪切带的产生，从而使非晶合金发生室温均匀塑性变形，进而发生剧烈的软化和回春；探索了非晶合金室温变形下的回春极限，获得变形条件下最高回春态非晶合金(等效冷却速率为1010 K/s)；揭示了回春处理对非晶合金结构的影响，阐明了回春过程中结构变化主要发生在中程序范围；发现了回春态非晶合金在单轴压缩/拉伸时的加工硬化行为，改变了对非晶合金变形是由剪切软化主导的传统认识；发现了非晶合金的加工硬化是硬度升高、能量降低和结构的有序化的过程，不同于传统晶态金属材料加工硬化过程中能量升高的变形机理；发现了回春态非晶合金的反常室温蠕变行为，即具有较小硬度的非晶合金反而表现出更低的稳态蠕变速率；研究了高能态钼氧非晶合金剧烈的结构弛豫现象，发现了非晶合金中程序结构的剧烈变化是结构弛豫的内在原因。本项目在Nature，Science Advances，Acta Materialia, Journal of Materials Science & Technology，Intermetallics，Journal of Alloys and Compounds等国际期刊发表SCI论文10篇。项目的顺利完成对于探索非晶态材料复杂的构效关系开辟了新途径，也对非晶合金在结构应用方面具有重要的推动作用。