Pressure Effect on Crystallization of Zr55Cu30Al10Ni5 Bulk Metallic Glass

The effect of pressure on the variation of the crystallization phases of the Zr55u30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD)and differential scanning calorimeter(DSC).The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different pressure.At ambient pressure,the crystallization products consisted of NiZr2 and CuZr2,while at pressure of 1 Gpa and 3 Gpa,the alloys crystallized into NiZr2 and Cu10Zr7,respectively.The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 Gpa.DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.     

Quasistatic and Dynamic Tensile Behavior of Zr52.5Al10Ni10CU15Be12.5 Bulk Metallic Glass

Quasistatic and dynamic tensile behavior of Zr52.5Al10Ni10Cu15Be12.5 bulk amorphous alloy was investigated at the strain rates of 10^-4--10^3s^-1 by using a Shimadzu AG-100KNA autograph and a pneumatic tensile impact tester. It was shown that the tensile fracture strength and the fracture morphology were sensitive to the strain rate. With the increase of the strain rate,the tensile fracture strength decreased and the fracture morphology changed from cleavage into quasi-cleavage, and then into a mixture of microvoid-coalescence dimples and quasi-cleavage veins.     

Crystallization Behaviour and Mechanical Properties of Zr65Cu18Ni9A18 Bulk Metallic Glass

Designing and synthesis of cost effective bulk metallic glasses （BMGs） has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been reported extensively due to their attractive properties, An alloy having composition Zr65Cu18Ni9A18 was designed and synthesized using 2-3 N pure materials by Cu mould casting. The alloy was characterized by X- ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and high temperature differential scanning calorimetry （DSC）. Thermal parameters like supercooled liquid region △Tx, reduced glass transition temperature Trg, γ and δ parameters were evaluated. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The alloy showed wide supercooled liquid region of 129＋1 K with improved thermal stability. The alloy has considerable fracture strength along with fair amount of ductility.     

Glass-forming Ability and Corrosion Resistance of Zr—Cu—Al—Co Bulk Metallic Glass

Investigations were carried out to examine the effects of Co addition on the glass-forming ability(GFA)and corrosion resistance of Zr_(46)Cu_(46)(Al)_8 bulk metallic glass in chloride-containing solution. It is found that the GFA of(Zr_(46)Cu_(46)(Al)_8 )100-x Co x(x = 0, 1, 2, and 4 at.%) alloys reduces with the increase in Co content and correlates well with the parameters, such as the supercooled liquid region width ΔT x, the reduced glass transition temperature T rg and γ. The corrosion resistance is however found to be enhanced with the increase in Co concentration. The addition of Co causes the enrichment of Zr and Al, but depletes Cu in the surface films, which effectively enhances the corrosion potential and lowers the corrosion current densit     

新型Zr57Nb5Cu15.4Ni12.6Al10大块非晶态合金的制备及其室温单轴压缩断裂行为

应用铜模真空吸铸法制备直径达5mm的棒状新型Zr57Nb5Cu154Ni12.6Al10大块非晶样品.X射线衍射检测证明样品完全为非晶态.通过等温示差扫描量热法(DSC)测试了Zr57Nb5Cu15.4Ni12.6Al10大块非晶的晶化动力学效应,同时研究了大块非晶合金的室温单轴压缩变形和断裂行为.结果表明:Zr57Nb5Cu15.4Ni12.6Al10块体非晶晶化过程具有动力学效应;其室温压缩变形过程主要表现为弹性变形;断裂面与压缩方向约呈45°,断口呈现典型的脉状花样.     

Cu—Al—Ni—Ti合金的微观组织及其富Ti相的确定

用透射电镜、电子探针、X射线衍射仪对Cu-Al-Ni-Ti合金的微细结构进行了研究,结果发现,合金的微观组织为Zig-Zag形态,并且在条状结构上存在更精细的亚结构。确定了富Ti相的结构。     

用渗流铸造法制备Zr55Al10Ni5Cu30非晶复合材料

用渗流铸造法制备出以Zr55Al10Ni5Cu30合金为基体，以W丝束为增强相的大块非晶复合材料，采用X-射线衍射分析了基体的相组成，在扫描电镜（SEM）下观察了反应界面的形貌，利用电子探针研究了元素的迁移情况，通过改变渗流温度和时间。研究了W丝和基体间界面的作用过程，选择适当的渗流温度和时间，可以制备出长65mm直径4.3mm的大块W丝束增强Zr55Al10Ni5Cu30非晶复合材料，在一定范围内提高渗流温度降低渗流时间或降低渗流温度延长渗流时间能得到同样的结果，在渗流铸造前，液态金属的过热有利于提高基体的非晶形成能力，降低渗流铸造时产生的缺陷。     

Combustion Synthesis of Ti—2B—Cu／Ni and 3Ti—2BN—Cu／Ni Bilayered Cermets

The effects of Cu and Ni (x=0, 10, 20 and 40 wt pct) and compaction pressures (12, 24, 84 and 108 MPa)on combustion wave velocity and wave front shape for Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni bilayered cermets were investigated by a video camera. Since the boiling point of Cu is lower, the wave velocities of specimens are slower.Due to the higher specific heat of Ni than that of Cu, the wave velocities of specimens was slowed down a lot with increasing the Ni diluent. The wave velocity differences of the specimens containing Ni are more than that of the bilayered specimens containing Cu. Wave velocities of the specimens containing Ni increased more than that of the specimens containing Cu when higher pressure was employed for green mixture. The more the wave velocity difference of the bilayer, the more curved the specimen.     

Homogeneous Plastic Flow of Fully Amorphous and Partially Crystallized Zr41.2Ti13.8Cu12.5Nil0Be22.5 Bulk Metallic Glass

The homogeneous plastic flow of fully amorphous and partially crystallized Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory.Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystallized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.     

A Diagram for Glass Transition and Plastic Deformation in Model Metallic Glasses

In this paper, we report a strain rate related glass transition in model SrCaYbMg（Li）Zn（Cu） metallic glasses at room temperature. A critical strain rate, equivalent to glass transition temperature, is found for the strain rate induced glassy state to liquid-like viscoplastic state translation. The results show that the observation time, equivalent to temperature and stress, is a key parameter for the transition between the glass and supercooled liquid states. A three-dimension glass transition diagram involved in time, temperature and stress in metallic glasses is established.     

Crystallization and Glass Transition Kinetics of Na2s-P2s5-Based Super-Ionic Glasses

In the present study, sulfide glass xNa₂S-(100–x)P₂S₅, 35 ≤ x ≤ 55 has been synthesized by the melt quenched technique. All the glass samples are characterized by x-ray diffraction (XRD), differential thermal analysis (DTA), dilatometery, and impedance spectroscopy. The XRD pattern of a sample showing a broad halo indicates its amorphous nature. Dilatometric study demonstrates that for x = 45 and x = 55 mol% Na₂S samples exhibited higher thermal stability than x = 35, x = 40, and x = 50 samples. To understand the crystallization kinetics, DTA was carried out for x = 45 and 55 samples at different heating rates, viz. 10, 20, 30, and 40°C/min. Crystallization kinetics of synthesized glasses for x = 45 and 55 are calculated using Kissinger's model. The thermal expansion coefficient (TEC) of glasses for x = 45 and x = 55 is found to be almost comparable to β-alumina solid electrolyte, which is being used in rechargeable batteries.     

大块金属玻璃晶化过程的研究进展

大块金属玻璃具有许多独特的性能,有着广阔的应用前景.晶化过程对大块金属玻璃的应用有很大影响,是当前此领域研究的热点之一.介绍了大块金属玻璃在各种条件下晶化过程、影响因素等方面的研究进展.     

Crystallization Study of Cu_(56)Zr_7Ti_(37) Metallic Glass by Electrical Resistivity Measurement

In this paper,the crystallization behaviour of amorphous Cu56Zr7Ti37 alloy using thermal electrical resistivity(TER) and differential scanning calorimetry(DSC) studies has been described.Isochronal TER and DSC measurements indicate that crystallization occurs in two stages.Isothermal crystallization studies of the alloy by TER show that the kinetics conforms to Johnson-Mehl-Avrami model.Avrami exponents derived from kinetics,between 1.1 and 1.2,imply that the crystallization processes are diffusion controlled with near zero nucleation.Activation energy has been found to increase with the transformed volume fraction.A plausible explanation has been presented by separating the contributions due to nucleation and crystal growth towards total activation energy.     

Mg65Cu25Y10大块金属玻璃的玻璃转变行为与玻璃形成能力

简要回顾了Mg基大块金属玻璃(BMG)的历史,试图揭示其开发进程中所蕴藏的科学思想,以期能够给今后的研究工作带来某些启示;通过对一些实验结果的分析,探讨了Mg65Cu25Y10 BMG的玻璃转变行为与玻璃形成能力(GFA)之间的内在联系,并最终展示合金大的GFA.     

Crystallization Behaviour and Nanostructuring in Alkali Niobiosilicate Glasses

23K2O·27Nb2O5·50SiO 2(KNS),13K2O·10Na2O·27Nb2O5·50SiO 2(KNaNS) and 15K2O·12Li2O·27Nb2O5·46SiO2(KLiNS) transparent glasses were synthesized by melt-quenching technique,and studied by differential thermal analysis(DTA),X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) to reveal the effect of the devitrification behaviour on transparent nanostructure.Just above the glass transition temperature T g in the KNS glass,an unidentified phase was formed,while in KNaNS and KLiNS,mixed-alkali niobate phases with tungsten bronze structure were obtained by bulk crystallization.Heat treatments at T g performed on the KNS glass resulted in the transparent nanostructure with second order harmonic generation(SHG) activity.Heat treatment for 10 h on KNaNS and KLiNS decreased the first DTA exothermic peaks(at least 24C),indicating the bulk nucleation,which was confirmed by the DTA in comparison with the powdered as-quenched samples.KNaNS and KLiNS showed similar XRD profiles as the K3Li2Nb5O15 crystal with the five most intense peaks at 22.7,29.4,32.3,46.3 and 52.0 deg.HRTEM micrograph showed clear-cut nano-sized circular domains and spherical nanocrystals dispersed into the amorphous matrix.