低密度玻璃化液体中力学模量与脆性的关联研究

利用低密度玻璃化液体的径向分布函数,导出过冷液体脆性与玻璃化温度、体模量和剪切模量的比值及与柏松比之间简单明确的关系.此结论定性地与实验结果一致.并为各种玻璃化液体的研究,提供有效的途径.     

Magnetocaloric effect in Er-Al-Co bulk metallic glasses

A series of Er-Al-Co bulk metallic glasses (BMGs) have been prepared by the copper mold casting method. The glass forming ability and magnetocaloric effect (MCE) for these alloys have been investigated. The second-order magnetic transition from para-magnetic to ferromagnetic states takes place at about 9 K. These BMGs exhibit excellent MCE because of their large effective magneton number; Er56Al24Co20 BMG has a maximum entropy change and refrigeration capacity of 16.06 J kg-1 K-1 and 546 J kg-1,respectively,under the field of 50 kOe (10 kOe=795.775 kA/m) indicating that these BMGs are potential candidate magnetic materials for hydrogen liquefaction.     

块体非晶合金的室温力学行为研究新进展

块体非晶合金由于具有优异的力学性能、物理性能、化学性能,从而得到广泛研究.本文综述了块体非晶合金室温力学行为研究的最新进展,详细介绍了块体非晶合金的室温塑性、屈服行为以及变性机制.     

Magnetocaloric effect in Er-Al-Co bulk metallic glasses

A series of Er-Al-Co bulk metallic glasses (BMGs) have been prepared by the copper mold casting method. The glass forming ability and magnetocaloric effect (MCE) for these alloys have been investigated. The second-order magnetic transition from para-magnetic to ferromagnetic states takes place at about 9 K. These BMGs exhibit excellent MCE because of their large effective magneton number; Er56Al24Co20 BMG has a maximum entropy change and refrigeration capacity of 16.06 J kg-1 K-1 and 546 J kg-1,respectively...     

Effect of Ag addition on the thermal stability and glass-forming ability of Zr<Subscript>35</Subscript>Ti<Subscript>30</Subscript>Cu<Subscript>7.5</Subscript>Be<Subscript>27.5</Subscript> bulk metallic glass

The thermal stability and glass forming ability (GFA) of Zr35-xTi30Cu7.5Be27.5Agx (x = 0-10) alloys were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and ultrasonic techniques. We found that the addition of 1 at.% Ag can considerably enhance the GFA as indicated by an increase in the critical glass dimension from 15 mm in the Zr35Ti30Cu7.5Be27.5 alloy to 20 mm in the Zr34Ti30Cu7.5Be27.5Ag1 alloy. However, with the addition of more Ag the supercooled liquid region (△Tx) and y parameter (defined as Tx/(Tg+Tl)) drastically decreased from 155 K and 0.436 to 76 K and 0.363, respectively, resulting in a decrease in the GFA. Additionally, the elastic constant (the ratio of shear modulus to bulk modulus or Poisson’s ratio) was also used as a gauge to evaluate the GFA in Zr35-xTi30Cu7.5Be27.5Agx alloys.     

Cu_(60)Zr_(29)Ti_(11)大块非晶合金的黏度特征和强液体行为

采用铜模铸造法制备了Cu60Zr29Ti11大块非晶合金,用X射线衍射仪、三点压弯式黏度仪对该非晶合金的动力学性质进行了研究.测定了大块非晶合金Cu60Zr29Ti11在过冷液相区的黏度,得到了它的动力学脆性系数m=31,以及流变激活能E=63.4kJ/mol.表明大块非晶合金Cu60Zr29Ti11是一种强液体,有较强的非晶形成能力,形成非晶比较稳定.分析了合金在过冷态的流变激活能变化规律,发现流变激活能的变化并不符合Kivelson的Super-Arrhenius公式.     

Effect of Sn addition on the glass-forming ability and mechanical properties of Ni-Nb-Zr bulk metallic glasses

The effect of tin (Sn) addition on the glass forming ability (GFA) and mechanical properties of the Ni-Nb-Zr ternary alloy system has been studied. The addition of Sn improves the GFA; Ni61Nb35.5-xZr3.5Snx (in at.%) alloys with x=1 can be cast into amorphous samples at least 3 mm in diameter using a copper mold injection-casting method. The critical size for glass formation decreases to 2 mm when x=5 because Ni2SnZr phase precipitates readily. The addition of Sn is also effective in enhancing the stability ...     

球形波冲击压缩后Zr41Ti14Cu12.5Ni10Be22.5大块金属玻璃的损伤与断裂特性研究

研究了Zr41Ti14Cu12.5Ni10Be22．5大块金属玻璃在不同速度的球形弹丸高速撞击下的损伤与断裂特性。通过表面形貌、X射线衍射谱的变化情况，可以看出．随着弹丸速度的增加，弹坑变成球形，弹坑深度逐渐增大，剪切带／裂纹有轻微增大，弧形损伤带是球面波高速撞击后的独特损伤行为。球形弹丸高速撞击作用下大块金属玻璃的晶化和常温退火与静高压下非晶态合金的晶化有着不同的机制。     

Fe36 Co36 Nb4 Si4.8 B19.2合金带巨磁阻抗效应研究

在Fe36 Co36 Nb4 Si4.8 B19.2非晶合金中发现明显巨磁阻抗效应,最大磁阻比达到35．9％,并利用直流电流退火对样品进行热处理．实验表明：电流密度为35A／mm^2时退火600s灵敏度得到大幅提高,达到0．0067／（A·m^-1）;适当大小的张应力电流退火有效地提高了磁阻比幅度．     

Deformation induced structural evolution in bulk metallic glasses

The structural behavior of binary Cu50Zr50 and ternary Cu50Zr45Ti5 bulk metallic glasses (BMGs) under applied stress was investigated by means of in-situ high energy X-ray synchrotron diffraction. The components of the strain tensors were determined from the shifts of the maxima of the atomic pair correlation functions (PDF) in real space. The anisotropic atomic reorientation in the first-nearest-neighbor shell versus stress suggests structural rearrangements in short-range order. Within the plastic deformation range the overall strain of the metallic glass is equal to the yield strain. After unloading,the atomic structure returns to the stress-free state,and the short-range order is identical to that of the undeformed state. Plastic deformation,however,leads to localized shear bands whose contribution to the volume averaged diffraction pattern is too weak to be detected. A concordant region evidenced by the anisotropic component is activated to counterbalance the stress change due to the atomic bond reorientation in the first-nearest-neighbor shell. The size of the concordant region is an important factor dominating the yield strength and the plastic strain ability of the BMGs.     

基于概率的地震作用下桥梁结构易损性分析

应用能力谱方法和增量动力分析方法分别建立了用于评价地震作用下桥梁结构性能的桥梁结构易损性曲线。通过对用两种方法建立的易损性曲线的对比分析表明：对于保护层混凝土剥落破坏状态,两种方法分析的结果相差不大;对于纵筋屈曲和倒塌破坏状态,能力谱方法给出的桥梁结构在给定地面运动强度下的失效概率偏低。用能力谱方法建立结构的易损性曲线避免了对结构进行非线性动力时程分析,分析方便快速,但对于严重破坏状态分析精度较低;非线性动力分析方法需要对结构进行大量的动力时程分析,但结果更为精确可靠。     

普通高频感应加热设备的磁悬浮熔炼技术

采用普通高频感应加热装置实现了大块非晶合金的磁悬浮熔炼和铜模吹铸法制备．分析讨论了磁悬浮的原理,发现当装有物料的石英玻璃管位于加热直螺线管的中间偏上位置时,物料开始被高高弹起,随后在直螺线管的顶部振荡几次后基本稳定在一静止位置．感应涡流加热物料,待物料熔化后再从顶部通氩气把熔融物料从玻璃管小孔中吹入下方的铜模中快速冷却制取大块非晶台金．物料的密度太大或物料在感应线圈中位置太低时,物料不会被弹起和悬浮．     

Deformation induced structural evolution in bulk metallic glasses

The structural behavior of binary Cu50Zr50 and ternary Cu50Zr45Ti5 bulk metallic glasses (BMGs) under applied stress was investigated by means of in-situ high energy X-ray synchrotron diffraction. The components of the strain tensors were determined from the shifts of the maxima of the atomic pair correlation functions (PDF) in real space. The anisotropic atomic reorientation in the first-nearest-neighbor shell versus stress suggests structural rearrangements in short-range order. Within the plastic deforma...     

Effect of Mo on properties of the industrial Fe-B-alloy-derived Fe-based bulk metallic glasses

The experimental results concerning the effects of Mo on the glass-forming ability (GFA), thermal stability, and mechanical, anticorrosion, and magnetic properties of an (Fe71.2B24Y4.8)96Nb4 bulk metallic glass (BMG) were presented. An industrial Fe-B alloy was used as the raw material, and a series of Fe-based BMGs were synthesized. In BMGs with the Mo contents of approximately 1at%-2at%, the cast alloy reached a critical diameter of 6 mm. The hardness and fracture strength also reached their maximum values in this alloy system. However, the anticorrosion and magnetic properties of the BMGs were not substantially improved by the addition of Mo. The low cost, good GFA, high hardness, and high fracture strength of the Fe-based BMGs developed in this work suggest that they are potential candidates for commercial applications.     

Zr_（55）Al_（10）Cu_（30）Ni_5块体非晶合金轧制塑性变形三维有限元分析

利用ANSYS/LS-DYNA显式动力学分析有限元法对Zr55Al10Cu30Ni5块体非晶合金的室温轧制塑性变形过程进行模拟计算,分析了非晶合金变形区域内的最大剪切应力分布与压下率的关系。计算得出了稳定轧制阶段不同压下率下非晶合金的应力和应变分布。计算结果表明,轧制变形区的最大剪切应力随压下率的增大而增大,并且在最大剪切应力超过屈服应力的局部区域非晶合金发生了非均匀塑性变形。模拟分析的结果与实验研究结果相符合,从而为进一步研究室温轧制变形诱导非晶合金微观结构变化提供理论依据。     

太阳能热泵的有限时间热力学分析

基于内可逆三热源热泵的有限时间热力学理论和太阳能集热器的线性热损模型，研究太阳能热泵系统的优化性能，导出太阳能集热器的最佳工作温度、系统的最大总性能系数和最大泵热率，并指出现有文献中有关这类研究的错误，所得结果可为实际太阳能热泵系统的优化设计提供一些新的理论依据。     

影响d~x结构难溶硫化物溶解度的热力学因素

同种类型金属硫化物溶解度的大小主要取决于离子极化作用和阳离子水合焓,在某些硫化物中可能离子极化作用或阳离子水合焓单方面起决定作用,而另一些硫化物中这两种因素均不可忽视。     

Zr基大块非晶合金在过冷液相区内的本构关系的研究

在Zwick/Roell力学性能试验机上进行Zr₅₅Cu₃₀Al₁₀Ni₅大块非晶合金在过冷液相区的压缩试验, 根据应力-应变曲线的过冲现象, 提出了Maxwell-Pulse本构模型, 该模型由蠕变函数耦合脉冲函数得到. 通过对虚应力模型和脉冲指数模型的拟合, 得到了Maxwell-Pulse本构方程的各项参数. 对比试验及拟合所得的数据及曲线, 两者的真实应力-应变曲线吻合较好, 且能反映出应力过冲现象. 又通过数值模拟和杯形零件成形试验验证了该本构方程适于描述Zr55Cu30Al10Ni5大块非晶合金在过冷液相区的力学行为.     

乙醇汽油体系的热力学性质

用低温绝热量热计测量了国产93^#无铅汽油和乙醇混合体系（50wt％乙醇＋50wt％汽油及90Wt％乙醇＋10wt％汽油）在78—320K温区的热容．用最小二乘法拟合了热容与温度的函数关系．由热容随温度的变化曲线可知,E50和E90混合体系分别在95．61K和97．08K发生玻璃化转变;在118．03K和112．04K发生固一固相变;在156．26K和158．66K发生固一液相变．计算了以298．15K为基准的该混合体系的热力学函数．     

Low temperature thermodynamic study of the stable and metastable phases of vanadium

The low temperature thermodynamics of the stable phase of vanadium has been assessed by the polynomial and Debye models from the experimental data available in literature. By means of the con-strained nonlinear least squares curve fitting arithmetic,two sets of parameter values have been de-termined. Expressions of the thermodynamic functions Cp(T) and G(T)-H(298.15 K) at 0―298.15 K are presented. The low temperature thermodynamics of the metastable phase of vanadium can only be extrapolated by the Debye model. The expression of the thermodynamic function Cp(T) at 0―298.15 K is presented.