New criterion in predicting glass forming ability of various glass-forming systems

It has been confirmed that glass-forming ability （GFA） of supercooled liquids is related to not only liquid phase stability but also the crystallization resistance. In this paper, it is found that the liquid region interval （T1 - Tg） characterized by the normalized parameter of Tg/T1 could reflect the stability of glass-forming liquids at the equilibrium state, whilst the normalization of supercooled liquid region △Tx=（Tx - Tg）, i.e. △Tx/Tx （wherein T1 is the liquidus temperature, Tg the glass transition temperature, and Tx the onset crystallization temperature） could indicate the crystallization resistance during glass formation. Thus, a new parameter, defined as ζ = Tg/T1＋△Tx/Tx is established to predict the GFA of supercooled liquids. In comparison with other commonly used criteria, this parameter demonstrates a better statistical correlation with the GFA for various glass-forming systems including metallic glasses, oxide glasses and cryoprotectants.     

非晶合金结构演变影响玻璃形成能力的分子动力学研究

通过分子动力学方法模拟了Ti75Al25、Ni50Zr50和Cu50Zr50非晶合金的玻璃转变过程, 得到并分析了平均原子体积和双体分布函数等结构参数, 并应用Voronoi多面体指数分析法统计了玻璃转变过程中二十面体及类二十面体团簇的数量, 通过分析团簇在玻璃转变过程中种类和数量的涨落趋势, 研究了非晶原子由短程序连接至中程序再至长程无序的动力学演化过程. 结果表明, 非晶合金的玻璃形成能力以及塑性变形能力与动力学演化过程中Voronoi团簇的种类和数量密切相关. 在玻璃转变过程中局部五次对称性高的团簇倾向于连接在一起形成链,从而密排整个空间, 降低系统的动力学行为从而提高玻璃形成能力. 塑性形变倾向于发生在局部五次对称性较低的区域. 在玻璃转变温度附近团簇种类和数量的突变反映出非晶合金的自组织临界行为, 蕴含着丰富的非线性动力学现象.     

Correlation between liquid structure and glass forming ability in glassy Ag-based binary alloys

The atomic structures of liquid Ag-based binary alloys have been investigated in the solidification process by means of X-ray diffraction. The results of liquid structure show that there is a break point in the mean nearest neighbor distance r1 and the coordination number Nmin for glass-forming liquid, while the correlation radius rc and the coordination number Nmin display a monotone variational trend above the break point. It means glass-forming liquids have a steady changing in structure above liquidus a...     

Alloying effects of the elements with a positive heat of mixing on the glass forming ability of Al-La-Ni amorphous alloys

The effects of Sn and Ga additions on the glass forming ability(GFA)of(Al86La5Ni9)100 xSnx(x=0,0.2,0.3,0.5,0.7,1 and 2at.%)and(Al86La5Ni9)100 xGax(x=0,0.2,0.5,1 and 1.5 at.%)alloys were systematically investigated.Unlike common microalloying methods,both Sn and Ga have a positive heat of mixing with the main component of Al.Our analysis confirmed that proper Sn addition can suppress the strong formation ofα-Al and enhance the GFA due to the positive heat of mixing between Sn and Al and the large difference in their atomic sizes.While the addition of Ga to the base alloy acted as the nucleation cites forα-Al and accelerated precipitation of theα-Al phase,thus deteriorating the GFA.     

The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

The dynamic viscosity of Al-Yb and Al-Ni-Yb superheated melts was measured using a torsional oscillation viscometer. The results show that the temperature dependence of viscosity fits the Arrhenius law well and the fitting factors are calculated. The amorphous ribbons of these alloys were produced by the melt spinning technique and the thermal properties were characterized by using a differential scanning calorimetry (DSC). E (the activation energy for viscous flow), which reflects the change rate of viscosity, has a good negative relation with the GFA in both Al-Yb and Al-Ni-Yb systems. However, there is no direct relation between liquidus viscosity (ηL) and GFA. The superheated fragility M can predict GFA in Al-Yb or Al-Ni-Yb alloy system.     

Y对Fe-Si-B 合金非晶形成能力及软磁性能的影响

本文通过铜模吸铸法和单辊甩带法分别制备出一系列楔形试样和非晶条带试样, 系统研究了稀土金属Y对Fe₇₈Si₉B₁₃合金非晶形成能力及其软磁性能的影响. 结果表明, 少量Y取代 Fe-Si-B 非晶合金中的Fe 可大大提高该合金的非晶形成能力并促进过冷液相区的产生. 当Y含量为3 at.%时, 合金具有最大的非晶形成能力, 其临界厚度为313 μm, 相应的非晶过冷液相区宽度达到65 K. 该系列非晶合金具有优良的软磁性能, 其矫顽力(H_c)均低于200 A/m, Y含量为1 at.%时, 饱和磁感应强度(B_s) 达到最大值1.67 T.     

块体非晶合金的黏度与玻璃形成能力的关系

基于经典结晶理论讨论了非晶合金的晶化动力学因素和晶化热力学因素对玻璃形成能力（GFA）的影响.分析表明,合金的等温转变（TTT）曲线“鼻尖”温度T_n对应的黏度与晶化阻力因子成正比;重新加热时晶化开始温度T_x对应的黏度与晶化驱动力因子成反比.由此得到了新的GFA参数ω₀=（T_g-T₀）/（T_x-T₀）-（T_g-T₀）/（T_n-T₀）,其中T_g为玻璃转变温度,T₀为理想玻璃转变温度.统计结果显示,ω₀与临界冷却速率具有较高的相关性,R²高达09626.进一步分析表明：新提出的ω₀参数可以合理地解释过冷熔体的黏度、脆性、液相稳定性、热稳定性以及T_rg、ΔT_x、γ、γ_m、ΔT_rg、α、β、δ和φ等参数与GFA的关系. 关键词： 块体非晶合金 黏度 脆性 玻璃形成能力     

Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.     

具有优良玻璃形成能力添加Al的CuZr基大块金属玻璃

在CuZr二元大块金属玻璃的基础上，利用铜模吸铸方法制备出了添加Al组元的CuZr 基大块 金属玻璃.CuZr基大块金属玻璃在很宽的成分范围内有很强的玻璃形成能力，在Al含量从4％ 到8％之间，CuZr基大块金属玻璃都可以做出直径至少5 mm的非晶样品.通过实验分析，解释 了CuZr基大块金属玻璃具有良好玻璃形成能力的物理机理.CuZr基金属玻璃组分简单、成本 低廉，有潜在的应用价值；同时，制备CuZr基金属玻璃的方法为开发新的大块金属玻璃体系 提供了一条切实有效的途经. 关键词： 大块金属玻璃 玻璃形成能力 CuZr基金属玻璃     

Zr基大块非晶中添加元素对非晶形成能力及耐蚀性的影响

运用实空间递归方法研究了添加元素Nb,Ta,Y,La对Zr基非晶合金的非晶形成能力和耐腐蚀性能的影响.用计算机编程构造了Zr基非晶中初始晶化相Zr₂Ni的原子结构模型,用Zr₂Ni中的二十面体原子团簇模拟非晶中的二十面体团簇.计算了替代二十面体中心或顶角位置原子前后Ni,Zr及合金元素的局域态密度、团簇中心Ni与近邻Zr原子及Ni与替代元素Nb,Ta,Y,La间的键级积分,还计算了合金元素替代前后团簇的费米能级.局域态密度计算结果表明：合金元素Cu占据二十面体团 关键词： 电子结构 Zr基大块非晶 非晶形成能力 耐蚀性     

金属玻璃形成液体的热力学特性

通过分析规则熔体的热力学模型，计算了典型金属玻璃的熔体混合焓ΔH^mix和混合熵ΔS^mix.结合临界冷却速率，归纳出典型金属玻璃形成液体的热力学特性,并提出基于原子尺寸、元素组成以及元素之间混合焓等参数的形成大块金属玻璃的成分判定方法.结果表明，当ΔH^mix<-15 kJ·mol^-1且ΔS^mix>0.6 J·K^-1mol^-1时，合金易于形成大块金属玻璃.金属玻璃的临界冷却速率R_c具有明显的尺寸效应，其值与熔体的ΔS^mix值呈指数关系，可以用R_c＝42.24×10⁴exp(-13.91ΔS^mix)+19.66粗略判断.运用该方法成功设计并制备出远离原有Zr基大块金属玻璃形成区域(55at%—65at%Zr)的Zr₄₀Al₁₀Ni₁₅Cu₃₅和四元Fe-B基Fe₅₃Co₅Nd₁₂B₃₀大块金属玻璃. 关键词： 混合焓 混合熵 大块金属玻璃 玻璃形成能力     

熵在非晶材料合成中的作用

熵作为系统的状态函数,对于真实物质体系而言是一个极为重要的物理量.在非晶态合金的制备过程中最具代表性的指导原则有"混乱原理"和井上三原则,二者皆与熵有着紧密的联系.在过去很长一段时间内,这些经验准则指导了大量新型非晶体系的发现,但近些年的实验结果对这些理论提出了质疑.除组元数目之外,还有其他尚待研究的因素也影响着合金体系的玻璃形成能力.本文总结了玻璃转变过程中熵在热力学条件、动力学条件和结构条件中所扮演的角色,阐述了其对玻璃形成能力产生的或正或反的影响.特别是对近几年发展起来的高熵非晶体系的研究有助于开发出临界尺寸更大的非晶合金,也有助于进一步探索多组元合金和非晶形成能力之间的关系.     

1at％ Ag替代Zr57Cu20Al10Ni8Ti5金属玻璃中各组元对玻璃形成能力及热稳定性的作用分析

以1at％ Ag元素分别等量替代Zr57Cu20Al10Ni8Ti5金属玻璃的各个组元,利用差示扫描量热升温分析获得不同试样的热力学参数,并结合不同尺寸(Φ8,Φ10,Φ12)吸铸试样的X-射线衍射分析结果,考察、验证元素替代后合金的实际玻璃形成能力及热稳定性的变化规律.经比较发现,Ag替代Ti元素,其玻璃形成能力显著提高(直径实际增大4 mm),同时热稳定性也明显改善,且临界冷却速率也明显降低,而Ag替代其他组元却无明显规律.针对玻璃形成能力的相关数据比较分析表明,本文结果未显示符合其Inoue的尺寸准则,混合焓判据也未显示出明显符合的现象.通过对堆垛密度的计算发现,1 at％ Ag替代Ti元素后使金属玻璃体系内部的堆垛密度增加.通过动力学分析,从晶化激活能、晶化反应速率常数两方面探讨了元素替代对玻璃形成能力和热稳定性的作用机理.     

Heredity of clusters in the rapidly cooling processes of Al-doped Zr_(50)Cu_(50) melts and its correlation with the glass-forming ability

The heredity of clusters in rapidly cooled(Zr_(50)Cu_(50))_(100-x)Al_x melts and its correlation with glass-forming ability(GFA) are studied via molecular dynamics simulations. Pair distribution function and the largest standard cluster(LSC)are adopted to characterize the local atomic structures in the(Zr_(50)Cu_(50))_(100-x)Al_x systems. The [12/555] icosahedra and their medium-range order(IMRO) play an important role in forming(Zr_(50)Cu_(50))_(100-x)Al_x metallic glasses(MGs). The fraction of [12/555], the number of IMRO, and the maximum size of IMRO in MGs increase significantly with increasing x. A tracking study further reveals that the configuration heredity of icosahedral clusters starts from supercooled liquids.No direct correlation exists between the GFA and the onset temperature of continuous or stated heredity. Instead, a larger hereditary supercooled degree of icosahedra matches with better GFA of Al-doped Zr_(50)Cu_(50) alloys.     

Pd-Si binary bulk metallic glass

Pd_80+x Si_20−x (x = 0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature T _g, the initial crystallization temperature T _x and the onset crystallization temperature T _p of Pd-Si binary glassy alloys increase. Moreover, the supercooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability, which can be greatly improved by fluxing treatment. Supported by the National Basic Research Program of China (Grant No. 2007CB613905) and the National Natural Science Foundation of China (Grant Nos. 50671050 and 50431030)     

Role of Bi incorporation on glass transition kinetics in glassy Se78Te20Sn2 alloy

In this communication, we report the results of calorimetric measurements on the samples of recently synthesized multi-component glassy alloys of Se_78?xTe₂₀Sn₂Bi_x (0 ≤ x ≤ 6) system. For calorimetric study of glass transition kinetics, differential scanning calorimetry (DSC) technique has been used in non-isothermal mode. Peak glass transition temperature (T_g) is determined using the DSC scans. Kinetic parameters A and B of glass transition are determined using heating rate dependence of T_g. Activation energy of glass transition (E_g) has been calculated using Moynihan and Kissinger methods. Glass-forming ability and thermal stability are also determined using Hurby and Saad–Poulin relations, respectively.     

Zr48Cu45Al7大块金属玻璃的原子结构研究

应用同步辐射X射线衍射(XRD)和广延X射线吸收精细结构边方法(EXAFS),结合反蒙特卡罗(RMC)拟合、Voronoi分形技术等对Zr₅₀Cu₅₀二元和Zr₄₈Cu₄₅Al₇三元金属玻璃材料的微观结构进行了系统的研究.结果表明:ZrCuAl三元金属玻璃中Al原子与Zr原子、Cu原子之间存在强相互作用,表现为键长的明显缩短,导致其微观结构中的Voronoi团簇体积普遍小于Zr_{50关键词： 大块金属玻璃 原子结构 玻璃形成能力 同步辐射技术}     

The fluidity and molding ability of glass-forming Zr-based alloy melt

The fluidity and filling ability of glass-forming Zr-based alloy melt in copper mould were investigated both theoretically and experimentally. The major factors which affected the flowing behavior of the metallic melt in the mold were determined, which provides the foundation for overcoming the contradiction between the filling and formation of amorphous alloy during the rapid cooling process of the metallic melts. The casting factors to prepare a metallic ring were discussed and selected. As a result, a Zr-based bulk metallic glass ring was prepared successfully. Supported by the National Natural Science Foundation of China (Grant No. 50731005), SKPBRC (Grant No. 2006CB605201/2007CB616915), PCSIRT (Grant No. IRT0650), the Natural Science Foundation of Hebei Province of China (Grant No. E2004000209), the Scientific Research Foundation of Education Department of Hebei Province of China (Grant No. 2004464), and the Experts and Scholars Fund of Personnel Department of Hebei Province, China (Grant No. 2003)     

二十面体团簇的遗传:一个与快凝Cu56Zr44合金玻璃形成能力有关的动力学参数

采用分子动力学方法模拟研究了液态Cu₅₆Zr₄₄合金在不同冷速γ与压力P下的快速凝固过程, 并通过基于Honeycutt-Andersen键型指数的扩展团簇类型指数法对其微结构演变特性进行了分析. 结果表明: 快凝玻璃合金的局域原子组态主要是(12 12/1551)规则二十面体、以及 (12 8/1551 2/1541 2/1431)与(12 2/1441 8/1551 2/1661) 缺陷二十面体. 通过原子轨迹的逆向跟踪分析发现: 从过冷液体中遗传下来的二十面体对快凝合金的玻璃形成能力(GFA)具有重要影响, 不仅其可遗传分数F_i =N_{300 K←Tg}ⁱ/N_Tg 与GFA密切相关, 而且其遗传起始温度(T_onset)与合金约化玻璃转变温度T_rg = T_g/T_m也存在很好的对应关系.     

基于成分连续变化计算黏度的合金系临界冷速模型

在大块非晶临界冷却速率的非等温转变计算模型基础上提出了基于成分连续变化计算黏度的合金系临界冷速模型. 依据此模型对Zr-Ni-Al-Cu四元合金的临界冷却速率进行了计算并预测了Zr_66.67(Ni_{xAlyCuz)33.33合金系中容易形成非晶的成分范围. 计算值与实验值符合得较好. 计算结果表明，此合金系具有很强的非晶形成能力，特别是在靠近共晶点的中心区域，临界冷却速率小于100 K/s，为容易形成非晶的成分范围. 冷却过程中，在高于1000K温度区间，没有发生明显的结晶现象，而在980 K至870 K温度范围内，结晶分数快速增大，低于870 K时不再发生明显改变. 此外，分析了合金系中Al，Cu，Ni原子摩尔分数的变化对临界冷速的影响. 关键词： 大块非晶 黏度 临界冷却速率 非晶形成能力}