Influence of flux treatment on the glass forming ability of Pd-Si binary alloys

Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.     

Preparation and thermal stability of Pd_(40.5)Ni_(40.5)SixP_(19-x) bulk metallic glasses

With the addition of Si to replace some P,Pd_(40.5)Ni_(40.5)Si_xP_(19-x)(x=0,2.5,5,9.5,14,and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology.With the increase of Si content,the glass forming ability of Pd_(40.5)Ni_(40.5)Si-xP_(19-x) increases first for low Si content and then decreases for high Si content (Si≥9.5at%).The Pd_(40.50Ni_(40.5)Si_5P_(14) glassy alloy possesses the largest supe...     

Nd_(60)Al_(10)Ni_(10)Cu_(20)大块金属非晶的玻璃转变和晶化特性研究

用铜模吸铸法制得了一种直径为5 mm、成分为Nd60Al10Ni10Cu20的大块非晶合金.与富Fe类Nd基非晶不同的是,这种新型的Nd基大块非晶具有明显的玻璃转变过程和稳定的过冷液相区.磁性测试表明,在室温下表现为顺磁性.热分析实验发现,随着升温速率的增大,样品的过冷液相区变宽,并且玻璃转变温度和晶化温度有明显的向高温方向移动的趋势.研究了该大块非晶的玻璃转变动力学和晶化动力学,并给出了Kauzmann温度Tk,Vogel-Fulchers-Tamman温度T0g以及脆性系数m等重要参数.     

Tensile and compression properties of Zr-based bulk amorphous alloy at different temperatures

Since the discovery of the Au-Si metallic amorphous alloy ribbon in 1960 by Duwez and co-workers[1] by rapid quenching, rapid developments have been obtained on the preparation of the amorphous alloy with the rapid quenching technique. However, from 1960 to 1989, the amorphous alloy could be only produced into forms of ribbon, flake, wire and powder due to the limitation of the cooling rate (>105 K/s). In the late 1980s, the Inoue group at Tohoku University in Sendai, Japan, investigated th…     

Preparation of Plate Fe60 Co8 Zr10 Mo5 W2 B15 Bulk Amorphous Alloy and Its Fracture Toughness

With processes of arc melting, inductive melting and copper mold suction casting, a plate Febased bulk amorphous alloy Fe₆₀Co₈Zr₁₀Mo₅W₂B₁₅ with a thickness of 1 mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were aglean and with typical metallic luster. The glass transition temperature (T_g), supercooled liquid region (δT_x) and reduced glass transition temperature (T_g) of prepared Fe-based amorphous alloy are 884 K, 63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m^1/2. Funded by the Key Project of National Natural Science Foundation of China (No. 50431030) and the Natural Science Foundation of Jiangsu Province (No. BK2001053)     

Formation and thermal stability of Cu-Zr-Al-Er bulk metallic glasses with high glass-forming ability

The formation and thermal stabilities of Cu_46.25Zr_46.25-xAl_7.5Er_x, (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-forming ability of Cu_46.25Zr_46.25Al_7.5 alloy, and the glassy rod with a diameter of at least 12 mm can be formed. The glass transition temperature (T_g), temperature interval of supercooled liquid region ΔT_x (= T_x − T_g, and reduced glass transition temperature T_rg (=T_g/T₁) of Cu_46.25Zr_44.25Al_7.5Er₂ glassy alloy are 699 K, 62 K and 0.607, respectively.     

Effects of heating rate on the process parameters of superplastic forming for Zr<Subscript>55</Subscript>Cu<Subscript>30</Subscript>Al<Subscript>10</Subscript>Ni<Subscript>5</Subscript>

We investigated the effects of heating rate on the process parameters of superplastic forming for Zr₅₅Cu₃₀Al₁₀Ni₅₅ by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08–1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr₅₅Cu₃₀Al₁₀Ni₅.     

A cluster line approach to finding new Fe-B-Y-Nb-Zr bulk metallic glasses

The glass forming ability of the [(Fe_12/13Y_1/13)_100-xB_x]₉₆Nb₂Zr₂ (x=9–26) system was investigated using a series of cluster lines. Three types of clusters, an icosahedron (Fe₁₂Y), a capped Archimedes anti-prism (Fe₈B₃) and a capped trigonal prism (Fe₉B), as well as a binary eutectic (Fe₈₃B₁₇) were considered. Bulk glassy alloy rods of 3 mm in diameter were synthesized using a copper mold suction-casting method. The glass transition temperature was observed for all samples in the boron range of 15.9at%-25.7at%, with the alloy at 15.9at% of boron having the best thermal properties. The ferrous-based bulk metallic glasses (BMG) obtained have high reduced glass transition temperatures with the maximum reaching 0.63 and large supercooled liquid regions with the maximum reaching 111 K. Magnetic testing revealed a large value of coercive force and remanent magnetization, being 11 kA/m and 0.1 T, respectively.     

Effects of small amount Ta on the characteristics ofthe Zr-Al-Ni-Cu-Ta bulk metallic glass

The effects of Ta on the characteristics of the Zr-base BMG (bulk metallic glass) were investigated. Zr55Al10Ni5Cu30-xTax(x=1,2,4) bulk metallic glasses (BMGs) with 3.5 mm diameter and 70 mm length were successfully prepared by using combined jet and copper mold casting. A small amount of Ta addition does not change the glass transition temperature, crystallization temperature, and supercooled liquid region obviously, but Ta promotes composition separation and two-stage crystallization. The stable crystalline phases include ZrENi, CuZr2, AlEZr3 intermetallic compounds and Ta-rich solid solution after annealing the Zr-Al-Ni-Cu-Ta alloys at 753 K. Zr55Al10Ni5Cu30-xTax (x=1,2,4) bulk glassy alloys exhibit a better compressive strength. The stress-strain curve shows a zigzag feature, and the fracture surface shows intersecting of shear bands. It may correlate with the inhomogeneous feature of amorphous structure.     

Crystallization kinetics and magnetic properties of Fe73.5Si13.5B9Cu1Nb1V2 nanocrystalline powder cores

Amorphous ribbons of the alloy Fe_73.5Si_13.5B₉Cu₁Nb₁V₂ were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry (DSC) measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami (JMA) equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nucleation rate. The variation of soft magnetic properties of nanocrystalline Fe_73.5Si_13.5B₉Cu₁Nb₁V₂ alloy powder cores as a function of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.     

Al-Ni-Y三元合金玻璃形成能力及热稳定性

为了分析Al-Ni-Y三元合金的玻璃形成能力和热稳定性,采用熔体急冷法制备了Al₉₀Ni₂Y₈、Al₈₇Ni₅Y₈、Al₈₄Ni₈Y₈和Al₈₀Ni₁₂Y₈合金条带.利用x-射线衍射（XRD）表征了急冷态和部分晶化后条带的结构,运用示差扫描量热仪（DSC）分析了合金的玻璃转变和晶化行为.结果表明：除了Al₈₀Ni₁₂Y₈和Al₉₀Ni₂Y₈合金外,制备态的条带均为完全非晶态,部分晶化后有纳米铝晶体析出;Al₈₄Ni₈Y₈合金DSC曲线上可以明显地观察到玻璃转变温度Tg.〖JP2〗通过比较4种合金的热稳定性,发现随着Ni的原子分数升高,合金的初始晶化温度Tx也随着升高,合金的热稳定性增强.     

Glass formation of ternary Sin-based Sm-AI-Co bulk metallic glasses

Ternary Sm-based Sm-AI-Co alloys at specific compositions designed using an e/a- and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-casting method. Four compositions of bulk metallic glasses (BMGs) are Sm₅₀Al₂₅Co₂₅, Sm₅₂Al₂₄Co₂₄, Sm₅₄Al₂₃Co₂₃ and Sm₅₆Al₂₂Co₂₂, which all satisfy a constant conduction electron concentration of 1.5. Among them, the BMG exhibiting the largest reduced glass transition temperature (T_rg) is Sm₅₀Al₂₅Co₂₅, which reaches 0.648. The glass transition temperature T_g and the onset crystallization temperature T_x of this alloy are respectively 579 and 640 K at a heating rate of 20 K/min.     

Devitrification process in rapidly solidified Al-Ni-Cu-Nd metallic glass

In the present study, rapidly solidified ribbons of A187 Ni7 Cu3 Nd3 metallic glass was prepared by using melt spinning. Devitrification process of the totally amorphous ribbons was investigated by high temperature X-ray diffraction analysis, combining with differential scanning calorimetry, under continuous and isothermal heating regime. The X-ray diffraction intensity and full width at the half maximum (FWHM) were analyzed to investigate the increase of crystallized amount and growth of α-Al crystal particles. The results show that under continuous heating regime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture of α-Al plus residual amorphous phase, and secondary crystallization, corresponding to rapid precipitation of some inter-metallic phases in the form of dispersion or eutectic mixture. Under isothermal heating regime, only Al crystal precipitates from the Al-rich amorphous matrix at low temperature, and when heating at 280 ℃ only Al     

Fluxing Agents on Ceramification of Composites of MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al₂O₃-SiO₂/boron phenol formaldehyde resin (MAS/BPF) composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS / BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS / BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS / BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.     

Preparation of Poly （ethylene oxide） （PEO） Modified Tungsten Oxide Hybrid Films via Sol-Gel Processing

Poly ( ethylene axide ) ( PEO ) modified WO3 thin films were prepared on glass substrates with special temperature. The sol-gel transition proess was #westigated by using DTA - TG , SEM and XRD. The elec-trochemical characteristic of the films was studied by cyclic voltmmetry measurement. The results show that PEO has heavy effects on the crystallization of W03 during structure evolution because of the interaction between PEO and WO3. It increases the crystallization temperature of the gels and thus improves the electrochemical properties and cyclic life of WO3 film as electrochromic materials.     

Formation and corrosion properties of Fe-based bulk metallic glasses

Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at%-4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx, and supercooled liquid region (△Tx=Tx-Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young's modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3 wt% NaCl.     

Effects of Heating Rate on the Process Parameters of Superplastic Forming for Zr_(55)Cu_(30)Al_(10)Ni_5

We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08-1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr55Cu30Al10Ni5.     

A study of the crystallization kinetics of Ge-Te amorphous systems

The glass-forming ability of binary Ge_xTe_100-x (x=15, 20, 30) alloys was investigated. The crystallization mechanism of these amorphous bulks was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calo-rimetry (DSC). The temperature of glass transition, the temperature of crystallization, the activation energy for glass transition and crystallization, and the order of the crystallization mechanism were calculated from the different heating-rates.     

Investigation on phase evolution of the ZnO-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> glass ceramics

ZnO-B₂O₃-SiO₂-Al₂O₃-Na₂O glass doped with nucleating agent TiO₂ was prepared with melting-quenching method and the effect of nucleating agent on the crystallization behavior and phase evolution of this glass was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The experimental results show that the glass transition temperature and the first crystallization temperature decrease from 630 °C and 765 °C to 595 °C and 740 °C, respectively, with introduction of TiO₂ into glass. There is no diffraction peaks in the XRD pattern but it is no longer transparent for the base glass without nucleating agent after heat treatment, which suggests the serious phase separation occurred, and the observation by SEM indicates that the phase separation is developed by nucleation and growth mechanism. However, there are two different crystals ZnAl₂O₄ and NaAlSiO₄ present in the glass containing TiO₂ after heat treating at 575 °C for 2 h and 740 °C for 6 h, respectively. What is interesting is that NaAlSiO₄ disappears as the crystallization time at 740 °C increases from 6 h to 12 h, and more ZnAl₂O₄ crystal is formed, namely, the further formation of ZnAl₂O₄ is at cost of NaAlSiO₄ with increasing crystallization time. And observation of the morphology of glass ceramics shows great difference with increasing crystallization time. Moreover, the ability of ZnO-B₂O₃-SiO₂-Al₂O₃-Na₂O glass ceramics against attacking of 1M HCl solution is increased by the crystals precipitated in heat treatment process.     

Critical serrated flow features during nanoindentation in La-based bulk metallic glasses

La_57.6Al_17.5(Cu, Ni)_24.9 and La₆₄Al₁₄(Cu, Ni)₂₂ bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La_57.6Al_17.5(Cu, Ni)_24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La₆₄A1₁₄ (Cu, Ni)₂₂ BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.