应变玻璃合金中随机场起源的原子模拟与实验验证

As a key member of the family of smart materials, strain glass alloys have attracted wide attention. It is found that strain glass alloys exhibit remarkable functional properties, such as shape memory effect and superelasticity. An open question related to this class of alloys is the formation mechanism of strain glassy state. It is theorized that quenched random field can change the stability of martensite, and further lead to the formation of strain glass, i.e., frozen disordered local strain states. However, it is still not clear how this randomness invoked. .. A comparable level of understanding has been studied on other glassy materials. In structural glasses, a mechanically stiff, percolating network of atoms with icosahedral local packing forms when approaching the glass transition. Recent studies on relaxor ferroelectrics also indicate that a hydrogen-bond-like network of dipoles is formed during the relaxor transition. Inspired from the above understanding, we propose that point defects induced strain network plays a dominate role in the generation of random field in strain glass materials... The project is organized as follows. Firstly, with the help of molecular dynamics methods, the applicant intends to investigate the formation mechanism of strain networks, and then to check the generality of strain networks within this class of materials. Secondly, the relationship between random field and strain networks will be clarified by using a combination of molecular dynamics and Monte Carlo simulations. Finally, the hypothesis and simulation results will be verified experimentally... The present project not only try to uncover the microscopic origin of random filed from atomic scale and enrich our understanding of glassy behavior in this class of materials, but also provides theoretic guidance in developing new strain glass alloys.

应变玻璃合金作为一类重要的智能材料具有很好的力学响应特性，其微观形成机制也引起了广泛的关注。文献和前期的理论研究认为，点缺陷诱发的随机场（Random field）是产生应变玻璃化转变的核心原因。但是迄今为止人们对点缺陷导致随机场产生的微观机制仍不清楚。本申请项目拟通过分析广义的玻璃态材料的物理图像的共性特点，从原子尺度提出应变玻璃合金中随机场的物理起源假说：应变玻璃中的随机场来源于以点缺陷为核心的应变网络，而不是单个点缺陷应力场的简单叠加。本项目拟运用基于半经验势函数的原子模拟方法，首先研究材料中应变网络的形成机制和存在的普遍性；进而研究应变网络对应变玻璃态转变行为的影响，并分析应变网络与体系中随机场之间的联系；最后本项目将通过实验手段来进一步验证上述理论假说与模拟结果。本项目将从原子尺度揭示应变玻璃中随机场的微观起源，可以为设计和开发新的应变玻璃合金材料提供理论指导。

应变玻璃合金作为一类重要的智能材料具有很好的力学响应特性，其微观形成机制也引起了广泛的关注。在高掺杂合金中，铁弹性玻璃被认为是一种新的物质状态，但对其随机场形成的微观机制仍然是不清楚的，并且随机场与铁性玻璃的动力学行为的关系也还没有进行相关的研究。文献和前期的理论研究认为，点缺陷诱发的随机场（Random field）是产生应变玻璃化转变的核心原因。但是迄今为止人们对点缺陷导致随机场产生的微观机制仍不清楚。在本项目中，我们首先使用数值和实验相结合的方法首次建立了铁弹性玻璃中随机场的形成机制，并基于此提出应变玻璃化转变伴随着应变团簇的渗滤转变，即掺杂点缺陷所诱发的局部应变形成全局网络从而达到渗滤状态。进一步，我们通过对不同的应变玻璃合金模型体系的模拟研究，结果表明应变网络的强度和玻璃化转变能力之间存在着标度律（scaling law） 和 普适性（universal behavior），该关系可以作为表征玻璃化转变能力的统一判据。在此基础上，我们验证了该物理模型在实验上的表现，我们发现该规律能够很好的描述现有的实验结果，并对应变玻璃合金的形成能力做出很好的预测。最后，我们的高分辨率的球差电镜的实验表征结果也观测到了与先前原子模拟类似的结构特征，进一步验证了本项目提出的假设，即随机场来源于点缺陷所诱发的应变网络。.此外，由于应变玻璃具有与广义的玻璃态材料相似的的微观物理图像，我们还研究了应变玻璃的动力学特征，发现与结构玻璃也存在共性，即在应变玻璃中也存在着动态上的不均匀性，这被认为是结构玻璃最本质的物理特征。目前的工作有效地丰富了我们对玻璃态无序材料的基本物理原理的理解。