退火工艺对Ce69Al10Cu20Co1非晶合金热稳定性与力学性能的影响

利用X射线衍射分析、差热扫描热分析仪和纳米压痕仪研究退火保温时间对Ce69Al10Cu20Co1非晶热稳定性和力学性能的影响。结果表明:在低于玻璃转变温度以下长时间等温退火,材料仍保持非晶结构,随退火时间的延长,合金的自由体积和缺陷浓度逐渐减少,合金玻璃转化温度逐渐升高,而晶化温度逐渐降低。纳米压痕结果表明,铸态和弛豫态非晶合金在压痕保载曲线均出现明显的蠕变平台,随退火时间延长,由于形成更加致密的堆垛结构,蠕变平台宽度不断减小,而合金的模量和硬度均有提高。     

结构弛豫对Cu36Zr48Ag8Al8块状非晶合金组织结构和力学性能的影响

利用铜模吸铸法在不同电压下制备出成分为Cu36Zr48Ag8Al8大块非晶合金。并将不同制备态的Cu36Zr48Ag8Al8大块非晶合金分别在低于玻璃转化温度以下进行低温(150℃)和高温(300℃)退火。利用X射线衍射(XRD)、扫描电子显微镜(SEM)和万能试验机等技术手段研究了低温和高温弛豫退火对不同制备态的Cu36Zr48Ag8Al8大块非晶合金的组织结构和力学性能的影响,并应用结构弛豫理论对其变化机制进行了分析。     

铸态及弛豫态Ce基块体非晶合金的玻璃转变动力学研究

采用铜模吸铸法制备出直径为2mm的Ce70Al10Cu20和Ce69AlCu20Ag1合金棒材,利用Kissinger方程和Vogel-Fulcher-Tammann(VFT)方程对其玻璃转变动力学在不同方面进行了研究.Kissinger方程拟合结果表明,两种Ce基非晶合金铸态及弛豫态都表现出明显的动力学特征,与铸态合金相比,弛豫态合金由于缺陷浓度减少,原子扩散迁移困难,增大了玻璃转变表观激活能.VFT方程拟合结果表明,两种Ce基非晶合金均属于强玻璃形成液体.     

Hf对Zr-Al-Ni-Cu金属玻璃弛豫行为的影响

通过测定快淬态和退火态比热与温度的关系,研究了Hf元素对Zr₇₀Al_7.5Ni₈Cu_14.5（70Zr）、Zr₅₅Al₁₀Ni₅Cu₃₀（55Zr）和(Zr_0.75Hf_0.25)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.75Hf_0.25）厘米级金属玻璃焓和硬度弛豫的影响。结果显示：70Zr和55Zr合金的结构弛豫表现为单峰现象,在退火温度（T_a）接近玻璃转变温度（T_g）时出现弛豫峰;而65Zr_0.75Hf_0.25合金的结构弛豫表现为双峰现象,分别在523和648 K（接近T_g）时出现焓弛豫峰。70Zr和55Zr合金在T_g温度附近出现明显的单峰弛豫行为,表明合金在T_g之前的整个温度范围内具有较高的抵抗退火诱导结构弛豫的能力;另一方面,65Zr_0.75Hf_0.25合金在523 K附近出现一个弛豫子峰,可能是由于Zr-Hf原子对的键合性较弱,混合焓接近于零,随后在T_g附近出现明显的主弛豫。65Zr_0.75Hf_0.25和(Zr_0.5Hf_0.5)₆₅Al_7.5Ni₁₀Cu_17.5（65Zr_0.5Hf_0.5）合金的硬度也表现出类似的双峰现象,导致第一峰的T_a与焓弛豫峰的T_a一致。结果表明,满足非晶形成三原则的Zr、Al、Ni和Cu组成的类二十面体中程有序结构在低T_a温度下保持稳定;只有背离非晶形成三原则的65Zr_0.75Hf_0.25和65Zr_0.5Hf_0.5金属玻璃焓弛豫和硬度弛豫出现了双峰,表明形成大块金属玻璃非必要组元的增加将导致合金结构在低温退火过程中的不稳定性。     

金属玻璃弛豫行为及其机理的模拟研究进展

金属玻璃的弛豫动力学研究非常复杂,极具挑战性。弛豫（α弛豫、慢β弛豫和快β弛豫）发生在不同的温度下。利用模拟可观测微观原子信息的优势,评述了模拟中3种典型弛豫的特征和机理,并讨论了它们对材料力学性能的影响。讨论了近年来通过模拟方法获得的与弛豫相关的动力学、结构和物理机理方面的研究进展。本综述有助于认识玻璃的本质,建立玻璃材料的动力学-结构-性能关联。     

金属玻璃蠕变及回复行为研究综述

由于非晶合金独特的无序结构,其结构动力学特征涉及较大时间与尺寸跨度的粒子重排。作为深入研究金属玻璃体系弛豫行为与老化动力学的基础,对非晶合金结构动力学的表征和理解至关重要。大量研究表明,以镧基和铈基为代表的稀土基非晶合金的弛豫谱呈现明显次级弛豫过程,该体系亦成为探究非晶合金结构动力学与力学性能关联的理想载体。本文主要就金属玻璃的滞弹性变形作了详细评述。作为蠕变实验中变形的主要成分,这类变形在卸载后可完全回复,对其合理描述是深入理解非晶合金结构动力学的关键。此外,总结了蠕变和蠕变回复过程中滞弹性变形的主要特征,并介绍了几种可用于定量或定性分析的理论模型。     

预退火时间对Pd40Cu30Ni10P20玻璃转变及晶化的影响

采用示差扫描量热(DSC)分析方法,测定了大块非晶合金Pd40Cu30Ni10P20经523 K((Tg-100 K)＜7＜Tg)不同时间(0～64 h)预退火后的玻璃转变温度7g、玻璃转变峰温度TM、起始晶化温度Tx、晶化峰的峰温Tp、晶化焓以及在玻璃转变过程中的比热容增量,并根据Kissinger公式计算了晶化的表观活化能.同时,测量了不同时间预退火后样品的显微硬度.结果表明:在玻璃转变温度以下的预退火处理使Pd40Cu30Ni10P20大块非晶合金的微观原子组态发生变化,从而影响了其随后的玻璃转变行为,但对晶化的影响不大.其显微硬度随预退火时间的延长而逐步增加后趋于稳定.并利用结构弛豫理论分析了预退火对玻璃转变、晶化和显微硬度的影响.     

Mg61Cu28Gd11和(Mg0.61Cu0.28Gd0.11)99.5Sb0.5非晶合金的晶化动力学和腐蚀行为（英文）

研究0.5%(摩尔分数)Sb的引入对Mg61Cu28Gd11块体非晶合金性能的影响。利用差热扫描量热仪测试样品的晶化动力学。结果表明:在等时加热的过程中,非晶合金的玻璃转变温度、起始晶化和峰值晶化温度都表现出对加热速率强的依赖性。基于Oawza方法可以确定非晶合金的起始晶化和峰值晶化激活能。Vogel-Fulcher-Tamman公式分析表明:含Sb元素的非晶合金具有更高的强度系数和更长的延迟时间。采用电化学极化和失重测试方法研究2种玻璃合金的腐蚀行为。与基体非晶合金相比,添加微量Sb降低了非晶合金的在含Cl-的碱性溶液中的钝化电流密度和腐蚀速率,表现出相比基体合金更为优越的耐蚀性。最后基于"点缺陷模型"进一步分析微量Sb元素对基体合金耐蚀性能的影响机理。     

Study on Structural Transformation Behavior of a Ti-Based Bulk Metallic Glass by Thermal Expansion Method

利用真空电弧熔炼和喷铸方法制备了直径为3 mm的Ti40Zr25Ni8Cu9Be18大块金属玻璃棒材。在推杆式热膨胀仪上利用连续升温热膨胀方法研究了该Ti基金属玻璃的结构转变行为。研究发现,该非晶合金的结构转变行为分为5个不同的阶段,分别为弛豫准备阶段,结构弛豫阶段,一级晶化阶段,二级晶化阶段和晶粒长大阶段。TEM观察发现,热膨胀后形成了20 nm左右的纳米晶。研究还发现,该Ti基金属玻璃热膨胀曲线上的特征温度与DSC曲线上的特征温度具有很好的一致性。     

热膨胀法研究一种Ti基块体金属玻璃的结构转变行为（英文）

利用真空电弧熔炼和喷铸方法制备了直径为3 mm的Ti40Zr25Ni8Cu9Be18大块金属玻璃棒材。在推杆式热膨胀仪上利用连续升温热膨胀方法研究了该Ti基金属玻璃的结构转变行为。研究发现,该非晶合金的结构转变行为分为5个不同的阶段,分别为弛豫准备阶段,结构弛豫阶段,一级晶化阶段,二级晶化阶段和晶粒长大阶段。TEM观察发现,热膨胀后形成了20 nm左右的纳米晶。研究还发现,该Ti基金属玻璃热膨胀曲线上的特征温度与DSC曲线上的特征温度具有很好的一致性。     

Ti48Zr20Nb12Cu5Be15 非晶复合材料的内耗行为

对Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅非晶复合材料的室温力学性能以及随温度变化的动态力学性能进行了研究。结果表明,该非晶复合材料的室温拉伸强度约为1350 MPa,断裂应变约为0.13。随着温度的升高,该非晶复合材料的整体状态由弹性转变为粘弹性。在准点缺陷模型框架下,引入了诸如损耗因子、相关系数等相关物理参数,全面分析了该非晶复合材料动态力学行为,并且模型的理论曲线与实验数据拟合程度较好。因此,准点缺陷模型可以很好地描述不同温度下的Ti₄₈Zr₂₀Nb₁₂Cu₅Be₁₅非晶复合材料的动态力学行为。     

Thermal behaviour of Pd40Cu30Ni10P20 bulk metallic glass

The thermal behaviour of differently milled Pd₄₀Cu₃₀Ni₁₀P₂₀ bulk metallic glass through the glass transition has been investigated by in situ high-energy synchrotron X-ray diffraction. Repeated heating and cooling were performed between the glassy and the supercooled liquid state. The changes in positions and intensities of the first and second diffraction maxima of the as-milled powder indicate irreversible changes during first heating up to the glass transition temperature T_g due to structural relaxation. After annealing, reversible structural changes with temperature are observed upon heating and cooling in the glassy phase, and in the supercooled liquid state respectively. The shift in the position of the first maximum scales approximately with the linear thermal expansion for the glassy state; however, this relation does not hold for the supercooled liquid. The structural transition from the glass to the supercooled liquid at the glass transition temperature is reflected by the intensity of the diffraction maxima and by a reversed temperature dependence of the position of the second diffuse maximum below and above T_g. The changes of the glass structure for the decrease of free volume by annealing are found to be different from those observed for the reversible volume expansion or shrinkage by varying the temperature. Therefore, the shift of the first diffuse maximum position of bulk metallic glasses cannot be used as a measure of the change in free volume.     

Pd20Pt20Cu20Ni20P20 高熵金属玻璃的热稳定性和热塑成形性

采用差示扫描量热法、X射线衍射和热力学分析研究了Pd₂₀Pt₂₀Cu₂₀Ni₂₀P₂₀高熵金属玻璃（HEMG）的热稳定性和热力学性能。结果表明,与其他经典贵金属基金属玻璃相比,Pd₂₀Pt₂₀Cu₂₀Ni₂₀P₂₀ HEMG具有相当的性能和鲜明的特点。     

Thermodynamic approach to free volume kinetics during isothermal relaxation in bulk Pd–Cu–Ni–P20 glasses

Isothermal relaxation behavior just under glass transition region was investigated for bulk Pd₄₀Ni₄₀P₂₀ and Pd_42.5Cu₃₀Ni_7.5P₂₀ metallic glasses. The densification of the bulk sample during relaxation was examined directly by density measurement using conventional Archimedean technique. The density of as-quenched Pd₄₀Ni₄₀P₂₀ increased monotonously with time. From the density data of Pd₄₀Ni₄₀P₂₀ glass, the free volume relaxation was examined and the kinetics was well described by a stretched exponential function with Kohlrausch exponent less than unity. These glasses also showed a clear two-step relaxation that may be a feature peculiar to bulk metallic glasses.     

FRICTION WELDING OF Zr55Al10Ni5Cu30 BULK METALLIC GLASS

采用摩擦焊对Zr₅₅Al₁₀Ni₅Cu₃₀块体金属玻璃进行了焊接, 当焊机主轴转速为4.0×10³---5.0×10³ r/min, 摩擦压力为80---100 MPa, 摩擦时间为0.2---0.4 s, 顶锻压力和保压时间分别为200 MPa和2 s时, 能够成功实施Zr₅₅Al₁₀Ni₅Cu₃₀金属玻璃的焊接. 用SEM, XRD和TEM观察分析未检测到晶化相, 焊缝处金属仍保持非晶状态. 金属玻璃的塑性在玻璃转变点T_g附近随温度变化很大, 在T_g以上具有良好的塑性变形能力, 这是实施摩擦焊焊接的重要基础.     

DEFORMATION BEHAVIOR AND CONSTITUTIVE EQUATION FOR Zr55Cu30Al10Ni5 BULK METALLIC GLASS IN SUPERCOOLED LIQUID REGION

Zr₅₅Cu₃₀Al₁₀Ni₅块体非晶合金(BMG)在过冷液态区内的单向压缩实验表明: 材料在过冷液态区内的形变行为强烈依赖于温度和变形速率. 随着应变速率的增加, 材料的流变特征由Newtonian流变转变为非Newtonian流变.利用扩展指数本构方程模型建立了非晶合金的流变应力、应变速率和温度的关系.     

Pd71.5Cu12Si16.5金属玻璃的氢相关性能

钯基金属玻璃在氢相关工业中具有潜在的应用价值。在本工作中,我们通过电弧熔炼、铜辊甩带的方法制备了Pd_71.5Cu₁₂Si_16.5 金属玻璃的宽带样品。通过常规X射线衍射仪和短波长X射线应力分析仪的X射线衍射谱确定了样品的完全非晶态结构。在室温、100kPa压力条件下,对样品进行了多次的吸、放氢循环实验。经过10次以上的循环后,样品没有发生破坏,表现出良好的抗氢脆性能。通过气体直接渗透的方法进一步测试了Pd_71.5Cu₁₂Si_16.5 金属玻璃及其同成分晶态合金的氢渗透性能。在金属玻璃的过冷液相区温度范围内,其氢渗透率明显高于晶态相,这一结果由金属玻璃在该区间内的等温保持引入了更多的自由体积进行解释。     

Superplasticity in a bulk amorphous Pd-40Ni-20P alloy:a compression study

Compressive deformation behavior of a cast Pd₄₀Ni₄₀P₂₀ bulk metallic glass in the supercooled liquid region (589–670 K) was investigated at strain rates ranging from 10⁻⁴ to 10⁻² s⁻¹. The material exhibited excellent mechanical formability in the supercooled liquid region. However, in contrast to a Newtonian behavior generally observed in oxide glasses, the present alloy also showed a non-Newtonian behavior, depending upon the temperature and applied strain rate. Specifically, the alloy is like a Newtonian fluid at high temperatures, but becomes non-Newtonian at low temperatures and high strain rates. Structures of the amorphous material, both before and after deformation, were examined using X-ray diffraction and high-resolution transmission electron microscopy. The non-Newtonian behavior is proposed to be associated with the glass instability during deformation.     

Approach of the spark plasma sintering mechanism in Zr57Cu20Al10Ni8Ti5 metallic glass

Spark plasma sintering (SPS) was used to sinter gas-atomized Zr₅₇Cu₂₀Al₁₀Ni₈Ti₅ amorphous powder. Systematic analyses were performed to study particle size and annealing time effects on the parts structure and properties. Partial devitrification and particles welding were observed and correlated to particle size and thermal conditions. Mechanical testing, through compression and micro-hardness, reveals that the sintered parts show strength similar to a quenched bulk metallic glass and damaging before failure. However, the pulsed current input does not seem the most relevant way to sinter amorphous powders: during the sintering initial stages (when necks are small), excessive over-heating is generated in the vicinity of particles necks, and is responsible for partial devitrification; further current input at large necks leads to complete densification. Effects of the stress, the thermo- and electro-transports on the sintering are evaluated to provide a better understanding of the SPS mechanisms of densification of metallic glasses.     

Temperature dependence of the yield strain of a Zr-based metallic glass at the glassy state

In the glassy temperature region from the ambient to glass transition temperature, an apparent Young's modulus (E_ap), the slope of the initial linear part on the stress–strain curve, in a Zr-based metallic glass clearly depends on both temperature and strain rate, indicating that viscous contribution is included in the elastic response. Because the yield stress depends on temperature and strain rate as the same manner with E_ap, the yield strain was found to keep the “universal” critical strain 0.020 for many metallic glasses at the ambient temperature. This suggests that the yield phenomenon is simply dominated by E_ap.