【作者】 杨卫明；

【导师】 赵玉成； 刘海顺；

【作者基本信息】 中国矿业大学 ， 一般力学与力学基础， 2014， 博士

【摘要】 铁基金属玻璃具有优异的力学、磁学及电化学等性能，在结构、功能、环保等领域具有广泛的应用前景。运用动力学研究金属玻璃是当前力学领域的热点，对于认识铁基金属玻璃高强度、大塑性等性能的起源具有重要意义。本文通过对铁基金属玻璃形成、演化的动力学进行分析，结合高分辨电子显微镜、拉曼光谱及光电子能谱等实验，系统研究了铁基金属玻璃动力学特性及断裂损伤机理，主要工作包括：(1)利用动力学理论和能谱分析实验研究了(Fe0.71Dy0.05B0.24)96Nb4金属玻璃的玻璃转变行为，揭露其过冷液相区出现峰值的原因，发现组元混合焓和原子半径存在较大差异时，组分在局部聚集或者分散，系统处于较高能量状态，这种不均匀结构弛豫时释放能量，形成过冷液相区的峰；组分不均匀导致系统的熵增加，结晶驱动力降低，利于非晶形成能力的提高；它还能够促进剪切带繁殖、形成多重剪切带、改善金属玻璃室温压缩塑性。(2)从晶化动力学出发，建立晶核生长理论模型，揭示了铁基金属玻璃晶粒尺寸随退火温度的变化规律；研究了淬态铁基金属玻璃微观组织结构不均匀对软磁性能的影响；揭示了铁基金属玻璃磁导率、磁致伸缩系数等随退火条件变化的机理；利用元素添加实现了对铁基金属玻璃软磁性能的调控。(3)引入两个爱因斯坦振动模，提出了金属玻璃波色峰的动力学机制；发现金属玻璃溶剂原子、短程有序团簇和中程有序团簇的尺寸比例约为1:3:7；探究了金属玻璃具有大弹性极限的原因，认为金属玻璃团簇类似于橡胶分子，在外力作用下通过相对旋转耗散能量；发现金属玻璃杨氏模量和断裂强度与溶剂原子直径的三次方成反比。(4)发现铁基金属玻璃断裂形貌具有自相似特征，引入分形几何提出金属玻璃的强度理论；揭示了金属玻璃强度随样品尺寸增加而降低的机理；研发了塑性应变超过20%的Fe50Ni30P13C7金属玻璃，是目前室温压缩塑性最大的铁基金属玻璃；利用光电子能谱等实验提出可描述金属玻璃形变和断裂微观过程的原子键合模型，揭示了Fe-Ni-P-C体系的韧脆转变机制。更多还原

【Abstract】 Owing to the combination of superior magnetic, mechanical, and electrochemicalproperties, Fe-based metallic glasses (MGs) are widely used in the structural,functional and environmental protection fields. Research on MGs by dynamics is apoorly understood fundamental problem in mechanics field. It is very important tounderstand the glass transition, soft magnetic properties and mechanism of brittle toductile transition of Fe-based MGs. In this dissertation, the dynamic characteristicsand fracture-damage mechanism of Fe-based MGs were systematically investigatedby integrating dynamic theory with high resolution transmission electron microscope,Raman scattering, photoelectron spectroscopy. The main works are given as follows:(1) The glass transition behavior of (Fe0.71Dy0.05B0.24)96Nb4MGs wasinvestigated by dynamics and energy-dispersive spectrometry. It is confirmed that thisabnormal behavior is attributed to the transition process of an amorphous state with ahigher energy to another amorphous state with a relative lower energy. Theamorphous state with higher energy comes from the uneven distribution ofcompositions in glasses, which is mainly caused by the component with significantdifference in atomic size and nonnegative values of enthalpy of mixing. This kind ofstructural heterogeneity can lead to entropy increase, which results in decreasing ofdriving force of crystallization and improving the glass-forming ability. The structuralheterogeneity can also lead to the initiation of shear bands, which results in anincreasing number of shear bands, thus enhancing the ductility of MGs.(2) The grain growth dynamic model was proposed by crystallization dynamics.The relationships between grain size and annealing temperature for Fe-based MGswere investigated. The effects of structural heterogeneity on soft magnetic propertiesof as quenched Fe-based MGs were studied. The mechanism of permeability andeffective magnetostriction change with annealing time and temperature was analyzed.The effects of partial substitution of Fe by Ni, Co, Cu in Fe-based MGs on theirmagnetic properties were also studied.(3) The mechanism of low-frequency dynamic characteristics was investigated. Itwas found that the Boson peak (BP) originates from two local harmonic vibrationmodes that are associated with the lengths of short-range order (SRO) andmedium-range order (MRO) in MGs. The atomic packing in MGs was also found tofollow a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are3and7, respectively, which exact match with length ratios of BPvibration frequencies to Debye frequency for the studied MGs. The clusters andsuperclusters in MGs may rotate slightly with respect to solute atoms like internalrotation in rubber, which is the origin of the MGs with large elastic strain limits. TheYoung’s moduli and fracture strength are inversely proportional to the cube ofdiameter of solvent atoms in MGs.(4) The self-similar characteristics of fracture surface in MGs were found. Thestrength theory of MGs was proposed by the fractal geometry. The fracture energy andstrength of brittle MGs are not only related to the plastic zone size, the length scalesof atomic order range and the surface energy, but also have significant relationshipwith the fractal dimension in fracture surface. Fe50Ni30P13C7MG which can be bendedwithout fracturing with unprecedented plasticity (~20%) at room temperature wasalso found. The atomic bonding model which can be described micro process ofdeformation and fracture was proposed by photoelectron spectroscopy, etc.experiments. The mechanism of brittle to ductile transition for Fe-based MGs wasrevealed.更多还原