Chemical diffusion in bulk glass-forming Pd40Cu30Ni10P20 melts

Interdiffusion and self-diffusion of bulk metallic glass-forming Pd–Cu–Ni–P alloys have been investigated above the liquidus temperature at 993 K by the long-capillary method. Good agreement between the calculated partial mixing enthalpies and observed uphill-diffusion was found. The flow direction of uphill-diffusing elements is towards regions with the highest negative heat of mixing.     

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。     

一种具有优异玻璃形成能力的Zr50Ti5Cu27Ni10Al8大块非晶合金的开发

多组元的Zr基非晶合金成分的复杂性对开发具有优异玻璃形成能力的Zr基非晶合金提出巨大的挑战。另外,大部分Zr基非晶合金含有有毒元素Be或者贵金属。因此,采用一种简单有效的方法开发无毒无贵金属元素的多组元Zr基非晶合金十分必要。本文中采用二元共晶比例法和部分元素替代法快速的开发出了一种新的临界尺寸大于10mm的 Zr50Ti5Cu27Ni10Al8非晶合金。这个非晶合金的热稳定性和硬度也通过原位高温X射线衍射和纳米压痕方法测量得出。     

Enhanced glass forming ability and refrigerant capacity of a Gd55Ni22Mn3Al20 bulk metallic glass

In this work, a small amount of Mn was added to a Gd₅₅Ni₂₅Al₂₀ glass forming alloy, as a replacement for Ni, and a Gd₅₅Ni₂₂Mn₃Al₂₀ bulk metallic glass (BMG) was obtained by suction casting. Its glass forming ability (GFA) was characterized by X-ray diffraction and differential scanning calorimetry, and its magnetic properties were measured using a magnetic property measurement system. It is found that the minor Mn addition can significantly improve both the GFA and the magnetocaloric effect (MCE) of the alloy. The refrigerant capacity (RC) of the BMG can reach a high value of 825 J kg⁻¹ under a field of 3979 kA/m, which is about 29% larger than that of a Gd₅₅Ni₂₅Al₂₀ BMG. The effect of the minor Mn addition on the GFA and MCE of the BMG was investigated in the study.     

Zr_(55)Cu_(30)Ni_5Al_(10)大块金属玻璃的等时和等温晶化(英文)

采用差示扫描量热仪(DSC)和X射线衍射仪(XRD)研究Zr55Cu30Ni5Al10大块金属玻璃的非等温晶化转变动力学和在过冷液相区的等温晶化动力学行为。在非等温过程中,采用不同方法(Kissinger,Flynn-Wall-Ozawa和Augis-Bennett)得到的Zr55Cu30Ni5Al10大块金属玻璃平均激活能彼此之间吻合很好。此外,采用Johnson-Mehl-Avrami(JMA)模型描述Zr55Cu30Ni5Al10大块金属玻璃的等温转变动力学。研究结果表明:Zr55Cu30Ni5Al10大块金属玻璃的Avrami指数n介于2.2和2.9之间,表明其晶化机制主要是扩散控制过程。在等温晶化的过程中,晶核长大主要是三维的长程有序扩散控制的过程,平均激活能为469kJ/mol。     

添加微量Fe对Zr_(55)Al_(10)Ni_5Cu_(30)块体金属玻璃非晶形成能力和力学性能的影响(英文)

通过磁悬浮熔炼和铜模吸铸法制备直径3mm的(Zr0.55Al0.10Ni0.05Cu0.30)100-xFex(x=0,1,2,3,4)合金试样,研究Fe元素的微量添加对Zr55Al10Ni5Cu30块体金属玻璃非晶形成能力和力学性能的影响。研究表明,合理添加Fe元素(不超过3%,摩尔分数)导致约化玻璃转变温度Trg(=Tg/Tl)和参数γ(=Tx/(Tg+Tl))增大,因而其非晶形成能力增大,但添加过量的Fe元素(4%)会导致其非晶形成能力的降低。添加Fe元素也会显著地改善Zr55Al10Ni5Cu30块体金属玻璃的压缩塑性及提高其压缩断裂强度,当Fe元素的添加量为2%时,直径3mm、长度6mm的试样在压缩时出现一定的塑性及加工硬化现象。Fe元素添加量为4%形成的金属玻璃基复合材料,同样也显示良好的压缩塑性和高的压缩断裂强度。     

Effect of strain rate on compressive behavior of a Pd40Ni40P20 bulk metallic glass

Mechanical deformation of Pd₄₀Ni₄₀P₂₀ was characterized in compression over a wide strain rate range (3.3×10⁻⁵ to 2×10³ s⁻¹) at room temperature. The compression sample fractured with a shear plane inclined 42 degree with respect to the loading axis, in contrast to 56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about 1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×10² s⁻¹. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate.     

Zr41Ti14Cu12.5Ni10Be22.5非晶棒料摩擦焊接

设计了一种非晶合金摩擦焊装置,以Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5非晶棒料为研究对象,进行了摩擦焊试验.焊接样品经SEM,XRD,维氏硬度、TEM等检测,结果显示焊接界面无明显未熔合,样品仍然保持非晶态,接头硬度总体增大,接头处出现了纳米晶.采用ANSYS软件对非晶合金摩擦焊的温度场进行仿真.结果表明,在摩擦时间t=0.25s时摩擦界面中心温度超过非晶棒料玻璃转变温度,接触面全部进入过冷液相区,应进行顶锻.仿真结果与摩擦焊试验结果基本吻合,有利于指导焊接试验.     

Zr53.7Ni9.4Cu28.5AI8.4块体金属玻璃的激光焊接

采用激光焊接技术对Zr53.7Ni9.4Cu28.5Al8.4块体金属玻璃进行焊接试验,研究在激光焊接下不同工艺参量对焊接接头组织的影响,探讨了焊接热循环过程中焊缝和热影响区的晶化行为。结果表明,固定激光功率1 200 W,焊接速度从8 m/min提高到30 m/min,均成功获得了无气孔和裂纹等缺陷的焊接接头。焊缝熔化区保持了非晶结构,热影响区则出现不连续的呈弧形分布的点状晶粒。随着焊接速度的提高,热影响区的晶粒尺寸逐渐减小。     

Mechanical properties of monolithic Zr62Al8Ni13Cu17 bulk metallic glass

We present mechanical properties of monolithic bulk metallic glass (BMG) Zr₆₂Al₈Ni₁₃Cu₁₇ under uniaxial compression and tensile tests. It is found that the Zr₆₂Al₈Ni₁₃Cu₁₇ BMG exhibits pronounced plasticity of nearly 14% without catastrophic failure upon compression. However, it is destroyed under tension in a brittle manner. High energy X-ray diffraction has been used to detect the structural change in this BMG during both conditions. No deformation-induced nanocrystallization is detected in a 55% strained sample under compression while it only appears in the fracture-affected region upon tension. No excess free volume is obviously found in the fractured samples. We suggest that monolithic BMG alloys with small differences in atomic affinity and atomic sizes among components might have high plasticity under compression.     

Investigation of glass forming ability and crystallization kinetics of Zr63.5Al10.7Cu10.7Ni15.1 bulk metallic glass

The glass forming ability, thermal stability and non-isothermal crystallization kinetics of Zr_63.5Al_10.7Cu_10.7Ni_15.1 glass forming alloy were investigated. Its maximum glass forming dimension is up to 6 mm and its critical cooling rate is less than 40 K s⁻¹. It manifests two crystallization procedures and the second crystallization peak is more sensitive to heating rate than the first crystallization peak. The glass transition and crystallization both have remarkable kinetics effects. The ms fitted by Arrhenius and VF equations are consistent with each other. Small m value about 17 indicates better thermodynamic stability and GFA of Zr_63.5Al_10.7Cu_10.7Ni_15.1.     

Calorimetric study of non-isothermal crystallization kinetics of Zr60Cu20Al10Ni10 bulk metallic glass

The non-isothermal differential scanning calorimetric techniques were used to evaluate the thermal stability and crystallization kinetics of Zr₆₀Cu₂₀Al₁₀Ni₁₀ bulk metallic glass. Various models were used to analyze the non-isothermal DSC at the heating rates (?) ranging from 1 to 80 K/min. The Kissinger equation, Ozawa equation, Augis-Bennett equation, Lasocka equation, and Vogel-Fulcher-Tammann non-linear equation were employed to describe the relationship between the crystallization peak temperatures and the heating rates. The overall crystallization activation energies of the metallic glass were estimated using the Kissinger, Ozawa and Augis-Bennett methods, respectively. The local activation energies at various volume fraction of crystalline phases were obtained by general Ozawa's isoconversional method. The crystallization kinetics was specified by a function reflecting crystallization mechanism. It has been found that a critical heating rate exists at around 20 K/min, beyond which the shapes of the DSC curves and the various relationships are varied. The crystallization process of the metallic glass can be divided into two groups, i.e. a slow heating rates region with ? = 1-20 K/min, and a rapid heating rates region with ? = 30-80 K/min. The overall crystallization activation energy for the slow heating rates regions is much larger than that for the rapid heating rates region. The crystallization activation energy derived from the Kissinger's peak temperatures is 326.4 ± 11.3 kJ/mol for the slow heating rates region, and 202.2 ± 26.6 kJ/mol for rapid heating rates region, respectively. The crystallization mechanisms were discussed with Johnson-Mehl-Avrami (JMA) and normal grain growth (NGG) mode. The crystallization mechanisms are different for the two heating rates regions. A transition point was found at the NGG-controlled crystallization stage for the higher heating rates, while it was absent for the slower heating rates.     

表面粗糙度对Zr52.5Cu17.9Ni14.6Al10Ti5块体非晶合金塑性的影响（英文）

将Zr52.5Cu17.9Ni14.6Al10Ti5（Vit105）块体非晶合金棒用水砂纸和抛光膏打磨到不同粗糙度,研究表面粗糙度对试样压缩变形行为的影响。结果表明,随着试样表面粗糙度的降低,屈服强度并没有明显变化,但压缩塑性从2.3%提高到4.5%。在扫描电镜下观察断裂试样的侧面发现,塑性越大的试样,剪切带的密度越大。因此,对于非晶合金,要得到较大的塑性,降低表面粗糙度是必要的。     

Partial crystallization of as-quenched Zr55Cu30Al10Ni5 bulk metallic glass induced by oxygen

Dendritic crystals, randomly distributed into the as-quenched Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass were characterized by optical microscopy, electron probe microanalysis, X-ray diffraction and electron backscattering diffraction. Oxygen enrichment is observed into these crystallites (formula: Zr₇Cu₄Al₃O, space group: Fd m, cell parameter: 5.70 Å) demonstrating the negative effect of oxygen, inducing partial crystallization during casting.     

Thermal stability and crystallisation of a Zr55Cu30Al10Ni5 bulk metallic glass studied by in situ ultrasonic echography

An original in situ ultrasonic echography technique was used to study the thermal stability and crystallisation of a Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass between RT and 630 °C. Changes in Young's modulus with temperature were reported allowing to study the supercooled-liquid state and the crystallisation process. Investigations of viscoelastic properties gave information on the correlation factor (hierarchically correlated motion theory) and three distinct crystallisation stages were observed. Their kinetics were studied using Voigt's and Reuss' approximations for a two-phase material and comparisons with the Johnson–Mehl–Avrami–Kolmogorov theory allowed us to consider a mixed surface/internal nucleation for the first stage and a surface nucleation for the two last stages.     

Microstructure and electrochemical behavior of Ti-coatedZr55Al10Ni5Cu30 bulk metallic glass

In this study, pure Ti was coated on Zr₅₅Al₁₀Ni₅Cu₃₀ bulk metallic glass (BMG) using a physical vapour deposition (PVD) technique with magnetron sputtering. Microstructures of Ti coating, BMG substrate and interface were investigated by conventional and high-resolution transmission electron microscopy (TEM and HREM). The electrochemical behavior of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG was studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in Hanks' solution. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the coating after electrochemical testing. HRTEM observation reveals that the sputtering Ti coating consists of α-Ti nano-scale particles with the size about 10 nm. The polarization curves revealed that the open-circuit potential shifted to a more positive potential and the passive current density was lower after Ti coating was applied in comparison with that of the monolithic Zr₅₅Al₁₀Ni₅Cu₃₀ BMG. Electrochemical impedance spectroscopy (EIS) measurements showed that the Bode plots of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG presented one time constant for 1 h and 12 h immersion and two time constants after 24 h immersion. The good bonding condition between Ti coating and Zr₅₅Al₁₀Ni₅Cu₃₀ BMG substrate may be responsible for the high corrosion resistance of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG.     

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。     

过冷液态Zr48Cu36Ag8Al8块体非晶合金的相分离及组织演变

本文通过x射线衍射(XRD)、差示扫描量热法(DSC)和透射电子显微镜(TEM)研究了退火温度对Zr₄₈Cu₃₆Ag₈Al₈金属玻璃微观结构演化的影响。结果表明,快速凝固获得的样品为典型的非晶态结构。当样品在703K保温20分钟时,均一的非晶基体相分离成两种非晶合金,即,发生相分离。由于相分离结构与非晶基体在等温退火过程是竞争的关系,这个结构很容易向晶化态进行转变,形成AlZr₂ AlAg₃相。Zr₄₈Cu₃₆Ag₈Al₈金属玻璃的微观结构在过冷液相区等温退火过程中经历了的局部结构转变,相分离以及纳米晶转变,这个过程意味着Zr₄₈Cu₃₆Ag₈Al₈金属玻璃的微观结构对退火温度十分敏感。此外,相分离的形成可以加速纳米晶的形成。     

Effect of hydrostatic pressure on the decomposition behavior of Cu54Zr22Ti18Ni6 bulk metallic glass alloy in supercooled liquid region

The effect that hydrostatic pressure has on the decomposition behavior in Cu₅₄Ni₆Zr₂₂Ti₁₈ bulk metallic glass (BMG) alloy was assessed using samples, which were isothermally annealed in the supercooled liquid region (SLR) with and without application of hydrostatic pressure. During subsequent annealing for the thermal analysis, the samples annealed under hydrostatic pressure displayed a slower crystallization process in the SLR, which is attributed to a retarded compositional decomposition of the BMG alloy under pressure.