VISCOSITY OF METALLIC GLASSES PdCu_6Si_(16.5), PdNi_6Si_(16.5) AND CuZr_(43) AND THEIR ACTIVATION ENERGIES OF VISCOUS FLOW

用蠕变法测量了PdCu_6Si_(16.5),PdNi_6Si_(16.5)和CuZr_(43)三种金属玻璃在玻璃转变温度附近的粘度-温度依赖关系。在Newtonian粘度范围内,三种玻璃的粘度-温度依赖关系均可用Fulcher-Vogel方程进行描述。方程中的常数由实验曲线所确定,并由此计算出这些玻璃的粘滞性流变的表观激活能。同时用差热分析测定了金属玻璃PdNi_6Si_(16.5)和CuZr_(43)的热转变激活能。结果发现,PdNi_6Si_(16.5)合金的粘滞性流变激活能同热转变激活能的差别很小,而CuZr_(43)合金的差别则比较大。     

Dual phase metallic glassy composites with large-size and ultra-high strength fabricated by spark plasma sintering

Two-phase bulk metallic glasses (BMGs) have attracted increasing interest since phase separation might produce metallic glasses with new physical and mechanical properties. In this study, we fabricated the dual phase glassy BMG composites by a spark plasma sintering process using a mixed powder of the gas-atomized Ni-based and Fe-based metallic glassy alloy powders. The thermal stability, microstructure, mechanical and magnetic properties of the obtained dual-phase glassy composites were investigated. The dual-phase glassy composites exhibited ultra-high strength and good soft magnetic properties which satisfy large-size requirements.     

掺铒碲酸盐的热稳定性和Judd-Ofelt理论分析

利用熔融法制备掺铒TeO2-ZnO-Na2O-B2O3-GeO2碲酸盐玻璃。采用差热扫描分析法（DSC）和热分析（TMA）得到玻璃的玻璃转化温度（Tg）、玻璃析晶温度（Tx）、玻璃软化温度（Tf）和热膨胀系数（α）,应用Judd-Ofelt理论计算玻璃中Er3＋的振子强度Ωλ（λ=2,4,6）,跃迁几率Aed,荧光分支比β,辐射寿命τi。根据McCumber理论计算Er3＋离子4I13/2→4I15/2的受激发射截面σemis和荧光半高宽FWHM。得出此体系的玻璃具有高热稳定性和低热膨胀性,具有较高的Er3＋离子4I13/2→4I15/2能级跃迁效率和较好的增益带宽性能。     

超高强钴基块体非晶合金的组成设计

块体非晶合金是一类具有高强度、高硬度和大弹性极限的无序金属材料,其优异的力学性能是目前先进金属材料领域研究热点之一,如何提高材料的强度是材料研究领域永恒的主题。系统地总结了已知具有超高强度的一类块体非晶合金材料——钴基块体非晶合金的成分、热学稳定性及力学性能;同时研究了不同非晶合金的断裂强度与其弹性常数、硬度和特征温度的关联。研究结果表明：在非晶合金体系中杨氏模量、维氏硬度、玻璃转变温度与断裂强度之间都存在较好的线性变化关系。基于以上结果,本课题组提出了超高强钴基块体非晶合金的组成设计方法,即选取具有强共价键特性的非金属元素和高模量、高熔点过渡金属元素与钴元素进行组合。     

Optical and thermal properties of P2O5-Na2O-CaO-Al2O3:CoO glasses doped with transition metals

The aim of this paper is to report the optical and thermal properties of V₂O₅ and CuO doped P₂O₅-Na₂O-CaO-Al₂O₃:CoO glasses so as to investigate their possible use in solar collection applications. The optical absorption spectra of the glasses at room temperature were in the spectral range of 200-1100 nm. The optical band gaps of the glass samples were determined for direct and indirect transitions. When transition metal ions doped to the base glass, the optical band gap decreased. Changes in the refractive indices vs. wavelength for all the specimens were also examined by spectroscopic ellipsometry. By measuring the heat capacities and thermal diffusion coefficients of the specimens at varying temperatures, their thermal conductivities were calculated to be in the 320-620 K temperature range. The obtained glasses seem to be promising materials and can be used in solar collector applications.     

表面接枝含氟树脂改性HGB的制备及性能研究

目的对中空玻璃微珠(HGB)进行表面接枝含氟树脂改性,以其为填料制备含氟树脂涂料,并进行性能研究。方法将中空玻璃微珠分别经NaOH溶液、硅烷偶联剂KH550、HDI三聚体、含氟树脂处理,并通过FTIR、SEM、EDS等表征手段对接枝情况进行验证。以制备的表面接枝含氟树脂HGB(F-HGB)为填料,制备了含氟树脂隔热涂料,研究了HGB改性温度、时间对F-HGB接触角的影响,以及HGB粒径、添加量、改性、涂层厚度对涂料的疏水性能、隔热性能、拉伸强度的影响。结果成功制备出F-HGB,50℃下接枝含氟树脂反应8h,F-HGB与纯水的静态接触角为149.21°。与HGB/含氟树脂涂料相比,F-HGB/含氟树脂涂料的疏水性能、隔热性能、拉伸强度均有较大幅度的提高和改善。当F-IM16K添加量为20 phr时,F-HGB/含氟树脂涂层与水的接触角为100°,模拟曝晒实验涂层试板温差为7.4℃,拉伸强度为10.39 MPa。当F-K1添加量为20 phr时,F-HGB/含氟树脂涂层的导热系数为0.0701 W/(m·K),同时涂层隔热性能随HGB粒径、添加量的增大而增强,拉伸强度随之降低,但表面改性能有效减小涂料拉伸强度的降低幅度。结论 F-HGB具有疏水、隔热、与含氟树脂相容性好的特点,可作为功能填料制备疏水、隔热、力学性能优良的多功能涂料。     

熔体过热水平对Cu36Zr48Ag8Al8块体非晶合金热稳定性和力学性能的影响

熔体过热度对Cu36Zr48Ag8Al8块体非晶合金的热稳定性和力学行为有显著影响。高的过热水平制备非晶合金的比热容大,初始缺陷密度小,热稳定性高。过热度越小,压缩塑性越小;抗压强度和维氏硬度随着过热度的减小先增加后下降。自由体积和残余应力共同影响不同吸铸电压制得非晶合金的力学性能     

High Temperature Deformation Behavior of High Strength and Toughness Ti-Ni Base Bulk Metallic Glass CompositesEI北大核心CSCD

Room-temperature brittleness and strain-softening during deformation of bulk metallic glasses, and limited processability of shape memory alloys have been stumbling blocks for their advanced functional structural applications. To solve the key scientific problems, a new shape memory bulk metallic glass based composite, through the approach using transformation-induced plasticity (TRIP) effect of shape memory alloys to enhance both ductility and work-hardening capability of metallic glasses, and superplasticity of bulk metallic glass in supercooled liquid region to realize near net forming, was developed in this work. And the Ti-Ni base bulk metallic glass composites (BMGCs) rods were prepared by the levitation suspend melting-water cooled Cu mold process. Microstructure, thermal behavior, mechanical properties and high temperature deformation behavior of the alloy were investigated. The results show that the as-cast alloy microstructure consists of amorphous matrix, undercooled austenite and thermally-induced martensite. Besides, the size of the crystal phase precipitated on the amorphous matrix in-creases from the surface to the inside. The alloy exhibits excellent comprehensive mechanical properties at room temperature. The yield strength, fracture strength and the plastic strain of alloy are up to 1286 MPa, 2256 MPa and 12.2%, respectively. Under compressive loading in the supercooled liquid region, the composite exhibits approximate Newtonian behavior at lower strain rate in higher deformation temperature, and the optimum deformation temperature is T>480 degrees C and the intersection part with supercooled liquid region (SLR). When the temperature is 560 degrees C and the strain rate is 5x10(-4) s(-1), the stress sensitivity index m and the energy dissipation rate Psi are 0.81 and 0.895, respectively. Furthermore, the volume of activation is quantified to characterize the rheological behavior.     

Nondestructively determining local strength and residual stress of glass by Hertzian indentation

Hertzian indentation was used to evaluate the local strength of glasses and to estimate residual stresses in strengthened glasses. It was found that initiation of Hertzian crack in glasses depends on the mean stress within a surface thickness related to material properties, but independent of the peak stress. The maximum mean stress for crack initiation was a constant and was defined as the local strength of the specimen at the contact position. Indentation experiments, using alumina spheres with various sizes as indenters, were performed on unstrengthened and strengthened glasses, respectively. The results showed a good stability in the local strength and a good agreement between the residual stresses measured by the present method and by a polarizing device. In addition, the potential merits of this method are: a) Nondestructive and in-situ measurement of strength can be performed without using a standard specimen and a rupture test; b) Strength proof test and strength comparison can be easily preformed.     

过热处理时间对Zr-Cu基大块非晶合金力学性能的影响

在一定初始温度下经过不同时间的熔体过热处理,利用铜模吸铸法,制备纯非晶合金Zr_(48)Cu_(36)Ag_8Al_8棒状试样,通过X射线衍射仪(XRD)、差示扫描热分析仪(DSC)、万能力学试验机和场发射扫描电子显微镜(SEM)研究过热处理对其力学性能的影响。结果表明,在一定的处理时间范围内,随着处理时间的增长,Zr_(48)Cu_(36)Ag_8Al_8非晶合金原子排列的混乱度增加,非晶合金的平均自由体积增加,Zr_(48)Cu_(36)Ag_8Al_8非晶合金的变形局域化程度降低,变形能力随之增强,非晶合金的断裂强度和塑性得到了提高。     

Influence of the molten quenching temperature on the thermal physical behavior of quenched Zr-based metallic glasses

Thermo-physical behavior of some Zr-based metallic glasses prepared by different molten quenching temperatures was studied by Differential scanning calorimetry (DSC) measurements. The characteristic thermo-physical properties are normally used for evaluating the glass-forming ability (GFA) of metallic glasses. Our results show that the glass transition temperature, crystallization temperature and supercooled liquid region of these metallic glasses increased with increasing the molten quenching temperature. Their glass-forming abilities were discussed in terms of the GFA criterion γ and the reduced glass transition temperature, T_rg, using these thermo-physical properties.     

非晶合金冲击韧性研究现状及展望

非晶合金因其独特的内部结构,具有优异的力学性能。例如:高强度、高硬度、大弹性极限等,是一种先进的结构工程材料。材料的冲击韧性能够反映材料内部的细微缺陷和抗冲击性能,是材料强度和塑性的综合表征,是一种重要的力学指标。本文对非晶合金冲击韧性研究现状进行综述,介绍试样尺寸、服役温度、合金成分、热处理等因素对非晶合金冲击韧性的影响,总结了改善非晶合金冲击韧性的措施,并对今后非晶合金冲击韧性研究值得关注的问题进行展望。     

Glass formation,thermal and mechanical properties of ZrCuAlNi bulk metallic glasses

The glass forming ability, thermal and mechanical properties of some ZrCuAlNi bulk metallic glasses were analyzed. The compositions of the alloys were theoretically determined with the dense packing and kinetic fragility index models. Cylindrical and conical ingots were produced by copper mould suction-casting under Ar atmosphere. The conical ingots were characterized by means of X-ray diffraction in order to determine the glassy structure. It was found that both alloys have a critical glassy diameter, D_c, of 3 mm. Thermal behaviours were investigated by differential scanning calorimetry at heating rates of 0.5, 0.67 and 0.83 K/s. The gamma parameter γ, supercooled liquid region ΔT_x, and reduced glass transition temperature T_rg, of the experimentally obtained glasses indicated high glass forming ability. The glassy compositions showed a fragility index of ～40 GPa. The compression test of the investigated alloys was carried out at a strain rate of 0.016 s^?1, obtaining a elastic modulus of ～83 GPa, total deformation of ～5%, yield strength of 1.6 GPa and hardness of 4 GPa. It was concluded that the use of the dense packing and kinetic fragility index models helped to predict glass-forming compositions in the family alloy investigated.     

Misch metal based metallic glasses

In this paper, a glass-forming range of metallic glasses based on Ce-rich misch metal (Mm) was pinpointed in Mm-Al-Co composition map by melt spinning. The thermal analysis indicated that the wide supercooled liquid region (above 60 K) can be found out in a large composition range in Mm-Al-Co system. The investigation of the glass-forming ability (GFA) in this system indicated a glassy composition with a larger supercooled liquid region wouldn’t be the glassy former with higher GFA. The reduced glass transition temperature is a better indicator to explore metallic glasses with high GFA. Furthermore, the mechanical properties of Mm₆₅Al₁₀Co₂₅ bulk glassy samples were evaluated in a compressive measurement. The obvious advantages of the Mm-based BMGs with high GFA, good mechanical properties and low material cost make these BMGs hopeful to be applied in the future.     

耐热低膨胀高硅铝合金的成形与性能

利用超声振动半固态流变压铸成形的方法制备出含20%Si的AlSiCuMgNiRE合金,研究了这种合金的组织、高温性能及热膨胀性能。结果表明,P与稀土复合变质的高硅铝合金,300℃的高温抗拉强度达到167 MPa,室温强度达到310 MPa;25~300℃内的热膨胀系数为17.4×10-6(1/℃)。添加2%Fe的高硅铝合金,由于针状富Fe相割裂基体,力学性能大幅度降低。而通过超声处理可改变富Fe相的形态,其室温及高温力学性能提高。     

冷却速度对金属玻璃性能的影响

采用单辊真空薄带技术和真空吸铸法分别制备了相同成分的金属玻璃薄带和块体金属玻璃。通过示差扫描热分析(DSC)、X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)和纳米力学探针(Nano Indenter)等技术研究了冷却速度对金属玻璃的组织结构、热稳定性及力学性能的影响。结果表明:快速冷却得到的金属玻璃薄带和相同成分以较慢的冷却速度制备的块体金属玻璃相比,短程有序结构(SRO)的晶体结构相同,但数量较少,且自由体积含量相对较多;组织结构的差异导致金属玻璃薄带比块体金属玻璃有着更高的热稳定性、屈服强度,弹性模量和硬度。     

Gradual shear band cracking and apparent softening of metallic glass under low temperature compression

Metallic glasses (MGs) usually exhibit synchronously enhanced plasticity and strength with decreasing the testing temperature. Although great efforts have been made, why MGs show better plasticity at low temperature remains unclear. In this work, the shear band cracking and fracture mechanism of a relatively brittle TiZr-based MG was investigated through methods of low temperature compression and 3D X-ray tomography. Pronounced apparent softening and profuse internal shear-band cracks were observed along with the improved plasticity, enhanced yield strength, decreased average softening rate, and reduced area of vein pattern as decreasing the testing temperature. Moreover, the fracture features can be correlated well with the compressive properties; and the true rupture stress that is carried by the still-bonded part of major shear band was found to be very close to the yield strength, demonstrating that the apparent softening should mainly originate from the cracking rather than dilation of shear band. The decreased softening rate can be fitted by a diffusion model, implying reduced atomic mobility and increased cracking resistance. Consequently, the improved plasticity of TiZr-MG at low temperature was attributed to the suppression of instant fracture and the enhanced resistance to shear band cracking, rather than the change of shear band density.     

Electro-deposition of oxide-dispersed nickel composites and the behavior of their mechanical properties

Oxide-dispersed nickel composites were produced by electro-deposition of nickel with various types of oxide nano-powders in a sulfamate bath. The effect of the oxide concentration in the bath on the mechanical properties of the electro-deposited composites was studied. The current efficiency of the electro-deposition process was analyzed for different types of oxide nano-powders and for in terms of the amounts embedded in the nickel (Ni) matrix. To evaluate the mechanical strength and the thermal stability, micro-hardness, tensile strength and elongation were measured at room temperature for composites that were heat-treated in a temperature range of 298 K to 1123 K. The results of the experiments showed that a higher oxide powder concentration in the bath led to a greater amount of the oxide particle co-deposited in the nickel matrix. This resulted in higher micro-hardness and improved high-temperature thermal stability. However, an inhomogeneous distribution of the co-deposited oxide powders in the composites was observed to weaken the thermal stability of their tensile strength and elongation.     

低Ni型LNG钢的热变形行为及力学性能

通过单道次、双道次压缩试验,研究了低Ni型LNG钢的高温奥氏体动态再结晶及静态再结晶行为,并采用两阶段控制轧制及超快速冷却技术进行不同轧制工艺下的热轧试验,通过热模拟及热轧试验研究了低Ni型LNG钢的热变形行为及力学性能。结果表明,在高温(1000~1050 ℃)、低应变速率(0.1~0.5 s^-1)下奥氏体容易发生动态再结晶,确定了发生再结晶的临界条件,并建立了动态再结晶动力学模型。试验钢在较高温度(800~1050 ℃)、较长道次间隔时间(60 s)下静态软化现象明显,容易发生静态再结晶。依据热模拟试验结果制定热轧试验工艺,通过控制精轧开轧温度和终轧温度调控高温奥氏体再结晶行为,从而细化晶粒,改善低Ni钢的冲击性能。精轧开轧温度920 ℃、终轧温度770 ℃时,低Ni钢的低温冲击吸收能量为180.1 J,屈服强度为595.1 MPa,抗拉强度为717.8 MPa。     

Mechanical properties of MgO–Al2O3–SiO2 glass-infiltrated Al2O3–ZrO2 composite

This work attempts to improve the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.