Development of quaternary Fe-based bulk metallic glasses

Fe-based bulk metallic glasses have been designed using several modeling criteria. Quaternary alloys were successfully developed in the Fe-rich compositional region where the only solutes used were Cr, Nb, and B. Furthermore, the exceedingly high level of Fe, exceeding 75 wt.% in some alloys, makes this series of alloys, compositionally very close to conventional steel alloys. Therefore, their production using conventional facilities and materials is more easily attainable than previously developed bulk metallic glasses. The modeling criteria used, simultaneously analyzes the thermodynamics and kinetics of the vitrification behavior in a potential glass-forming alloy. A liquidus model, which determines and ranks the presence of deep eutectics, is used to determine the optimal compositional region. This criterion is cross-checked with an elastic strain model. Alloys compositionally located near a deep eutectic, while simultaneously containing a topology that induces significant elastic strain in a developing crystalline lattice exhibits experimentally good glass forming ability.     

Internal friction and elastic modulus of bulk metallic glasses

The mechanical relaxation in binary, ternary, quaternary, and quitary bulk metallic glasses with widely different glass-forming ability, or the critical cooling rate, has been studied. A single-roller melt-spinning apparatus was used for preparing thin specimens. The internal friction Q⁻¹ and the oscillation frequency f of the specimens were measured using an inverted torsion pendulum with the free decay method. The measurements were performed from room temperature, through the glass transition temperature T_g, up to the crystallization temperature T_x. As the temperature is increased, the background Q⁻¹ increases, and peaks can usually be seen near T_g and T_x. The shear modulus, which is proportional to f², is changed near the Q⁻¹ peak. The experimental data are presented and overall features of the results are discussed.     

Effect of Er on properties of Zr-based bulk metallic glasses

(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xEr_x(x?=?0～6) bulk metallic glasses were fabricated by copper mould suction casting method, and the effect of Er on properties was studied. The compressive plastic strain (ε_p) and compressive strength (σ_max) at room temperature increases first and then decreases with the increase of Er content. The compressive plastic strain (ε_p) of the specimen is 35.1% when x?=?2.6, which is about eight times than that of the specimen with x?=?0. The compressive strength (σ_max) is 2513?MPa, which is much higher than that of the specimen with x?=?0. It indicates that Zr-based bulk metallic glasses could be strengthened and toughened by adding Er. The thermal stability decreases gradually and the glass-forming ability increases first and then decreases with the increase of Er content.     

Evolutionary intelligence in design and synthesis of bulk metallic glasses by mechanical alloying

The present work demonstrates a new approach of a combinatorial design of Bulk Metallic Glasses using evolutionary intelligence of genetic programming (GP) and genetic algorithm (GA). A glass-forming potential expression, carrying similar sense as the glass-forming ability (GFA) indicator expression, has been identified by principal component analysis and GP, enabling one to map the fitness of the composition from the multidimensional attribute space of the alloy in the course of GA search. The genetically inspired alloy compositions are evolved by GA search and subsequently validated through existing empirical knowledge. Two randomly chosen compositions are subjected to experimental trial where the glass-forming potential has been evaluated by amorphization potential through mechanical alloying. A literature-reported good glass -forming composition has been studied as a reference alloy and comparison was made for the proposed designed alloys.     

A Group of Cu（Zr）-based BMGs with Critical Diameter in the Range of 12 to 18 mm

A group of Cu（Zr）-based bulk metallic glasses （BMGs） with critical diameter （De） in the 12 to 18 mm range have been obtained using copper mould casting. In the Cu-Zr-Y-Al quaternary system, a new record of Dc=14 mm was established for Cu-based compositions, and 16 mm for compositions based on equi-atomic CuZr. Additional partial substitution of Hf for Zr further elevated the Dc to 18 mm at Cu42Zr43Hf1.5Y3.5Al10.     

Zr基块体非晶合金玻璃形成能力与压铸成型性能研究

本文分析了熔体温度、铸造压力和化学成分对非晶合金玻璃形成能力(GFA)与压铸成型性能的影响,并探究两种性能的工艺关联。研究发现:随熔体温度升高,Zr基非晶合金GFA先提高后减小,且合金成分不同,熔体化学成分,局域原子团簇特征和合金实际冷却速率就不同,非晶合金GFA与玻璃稳定性也就存在差异。非晶合金的压铸成型能力随熔体温度和铸造压力升高不断提高,但与GFA存在相互限制的作用:当合金GFA较强时,熔体内原子堆垛密实,粘滞系数较高严重阻碍过冷液流动成形,且玻璃稳定性越好压铸成型性能越差;而当熔体温度过高,非晶合金GFA减弱,过冷液粘度降低时,才能快速提高非晶合金的压铸成型性能。因此,选择最佳的合金成分、优化工艺参数有利于非晶精密结构件成型。     

Liquid dynamics and glass formation of Gd55Co20Al25 metallic glass with minor Si addition

Liquid dynamics plays an essential role in glass formation.Here we observed a distinct change of liquid dynamics in Gd55Co20Al25 metallic glass induced by microalloying Si element.In the equilibrium melt,minor Si(0.5 at.％)addition leads to a more fragile liquid behavior and a smaller strength of liquid-liquid transition with the transition strength(ΔF)decreasing from 0.76 to 0.35.However,in the supercooled liquid,Si-doped liquid exhibits a remarkable enhanced fragile-to-strong transition(FST),and the value of FST factor f increases sharply from 1.63 to 3.84,resulting in a stronger liquid behavior and more sluggish crystallization kinetics for Gd55Co20Al24.5Si0.5 metallic glass.Moreover,minor Si addition promotes the formation of a crystal-like structure with a size of 1-2 nm.The interactions between the crystal-like structures and other local favored clusters frustrate the further growth of crystal-like phases,thus sta-bilizes the amorphous structure.As a result,the glass-forming ability(GFA)was largely improved.The critical diameter of Gd55Co20Al25 metallic glass increased from 2 to 7 mm with 0.5 at.％Si addition with-out deterioration of the magnetocaloric effect.This study provides valuable insight for understanding the distinct effect of microalloying on GFA of metallic glasses from the aspect of the evolution of the liquid.     

Ultra-high strength Mg-Li based bulk metallic glasses: Preparation and performance research

In this paper, new Mg-Li based bulk metallic glasses (BMGs) are prepared by conventional copper mold injection casting method. The alloys exhibit excellent mechanical properties, such as ultra-high compressive fracture strength (maximal 729 MPa), high Vickers hardness (>2 GPa) and low elastic modulus (∼35 GPa). Compared with the corresponding crystal alloys, the density of the amorphous alloy samples is reduced by about 1.5% due to their free volume. Thus, it is believed that this new BMGs with these outstanding properties will broaden Mg-Li based alloys’ application fields.     

Mechanical behaviours of workhardening and worksoftening bulk metallic glasses

Abstract

The workhardening Cu_47·5Zr_47·5Al₅ and the worksoftening Zr_52·5Cu_17·9Ni_14·6Al_10·0Ti_5·0 bulk metallic glasses before and after precompression deformation were characterised for thermal and mechanical behaviours. The predeformation introduces excessive free volume in both glasses. Cu_47·5Zr_47·5Al₅ and Zr_52·5Cu_17·9Ni_14·6Al_10·0Ti_5·0 exhibit substantial workhardening and worksoftening behaviours respectively. For Cu_47·5Zr_47·5Al₅, the precompression has a negligible effect on serrations in the plastic flow during nanoindentation, which is related to the hardening of a shear band, while for Zr_52·5Cu_17·9Ni_14·6Al_10·0Ti_5·0, the precompression moderates serrations in the plastic flow during nanoindentation, which is associated with the softening of a shear band. Strengthening from mechanically induced nanocrystallites at shear bands is responsible for the workhardening of Cu_47·5Zr_47·5Al₅, which overwhelms softening due to the introduction of excessive free volume.     

Bulk metallic glasses: A new class of engineering materials

Bulk glass-forming alloys have emerged over the past fifteen years with attractive properties and technological promise. A number of alloy systems based on lanthanum, magnesium, zirconium, palladium, iron, cobalt and nickel have been discovered. Glass-forming ability depends on various factors like enthalpy of mixing, atomic size and multicomponent alloying. A number of processes is available to synthesise bulk metallic glasses. The crystallisation behaviour and mechanical properties of these alloys pose interesting scientific questions. Upon crystallisation many of these glasses transform to bulk nanocrystals and nanoquasicrystals. A detailed study of the structure and the crystallisation behaviour of glasses has enabled the elucidation of the possible atomic configuration in liquid alloys. Their crystallisation behaviour can be exploited to synthesise novel nanocomposite microstructures and their mechanical properties can be enhanced. A broad overview of the present status of the science and technology of bulk metallic glasses and their potential technological uses is presented.     

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.     

Synthesis of Zr-based bulk metallic glass-crystalline aluminum alloy composite by co-extrusion

The effects of co-extrusion conditions like extrusion temperature and deformation rate on the fabrication of a Zr-based bulk metallic glass-Al clad material were investigated under the extrusion ratio of 5.06. The ranges of extrusion temperature and deformation rate were varied from 658 to 703 K and from 10^− 3 to 10^− 1 mm/s, respectively. Both macroscopic and microstructural characterizations reveal that sound materials compatibility could be obtained under the low deformation rate-low temperature within supercooled liquid region combination, showing homogeneous distribution of the rate of cross-sectional area between core and sleeve without crack or intermetallic compound in the vicinity of the interface.     

Complete Composition Tunability of Cu(Ni)-Ti-Zr Alloys for Bulk Metallic Glass Formation

In the Cu-Zr-Ti ternary system, a new composition zone of bulk metallic glasses (BMGs) formation was discovered, locating at the 55-57 at. Pct Cu, 30-31 at. Pct Ti and 13-14 at. Pct Zr, and near Cu-Ti binary subsystem rather than the Cu-Zr binary. For these alloys, BMG rods of 2 mm in diameter can be fabricated by using copper mould casting. It is expected that these BMG-forming alloys correlate with (L→CuTi+Cu2TiZr+Cu61Zr14) eutectic reaction that the undercooled melt undergoes during solidification. Adopting 3D pinpointing ap-proach, compositional dependence of glass-forming ability (GFA) in Cu(Ni)-Ti-Zr pseudo ternary system was revisited. Optimized BMG-forming composition is located at Cu50.4Ni5.6Ti31Zr13, with a critical diameter of 6 mm for complete BMG formation. Its GFA is significantly superior to Vit 101 (Cu47Ni8Ti34Zr11) previously developed by Caltech group. The effect that the GFA of the ternary base alloy was improved by substitution of Ni for Cu is attributed to a role of retarding the crystallization of Cu51Zr14 intermetallics.     

Ni和Y影响Al-Ni-Y金属玻璃形成能力的本征机理

为了揭示Ni和Y元素对Al-Ni-Y三元金属玻璃的玻璃形成能力影响的本征机理,且基于费米面和伪布里渊区理论,提出了Ni和Y元素对Al-Ni-Y三元金属玻璃的玻璃形成能力的影响分为两种情况:Ni原子通过Al和Ni原子之间的电子轨道杂化效应,改变费米面直径(2KF),从而影响Al基金属玻璃的玻璃形成能力;Y原子通过整体原子的静态结构,改变伪布里渊区(KP),最终影响Al基金属玻璃的玻璃形成能力.费米面和伪布里渊区尺寸通过电子能量损失谱(EELS)、X射线衍射(XRD)和X射线光电子能谱(XPS)获得.研究表明,当两者相互作用机制满足2KF=KP,条件时,费米能级处电子态密度最低,金属玻璃整体结构的稳定性达到最佳.在此基础上,提出了δ=KP-2KF判据用于衡量Al-Ni-Y三元金属玻璃的玻璃形成能力,该判据在实验上得到验证.     

Corrosion performances in simulated body fluids and cytotoxicity evaluation of Fe-based bulk metallic glasses

The aim of this work is to investigate the corrosion resistance and biocompatibility of three kinds of Fe based bulk metallic glasses (BMGs), Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ (BMG1), (Fe₄₄Cr₅Co₅Mo₁₃Mn₁₁C₁₆B₆)₉₈Y₂ (BMG2), and Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Er₂ (BMG3) by electrochemical measurements and indirect contact cytotoxicity assays, respectively. In comparison with 316 L SS biomedical steel, Fe based BMGs show better corrosion resistance in both simulated body fluids (Hank's solution and artificial saliva). The OCP curves show that the passive film on the Fe based BMG surfaces is quite stable, like 316 L SS. The corrosion current densities obtained from the anodic polarization curves from the lowest to highest are as follows: BMG3 < BMG1 < BMG2 < 316 L SS. The EIS analysis indicates that the Fe Based BMGs have larger polarization resistance value than that of 316 L SS except for BMG2 in artificial saliva. The pitting corrosion potentials of Fe based BMGs are much higher than that of the 316 L SS, resulting in very few ions releasing into the electrolytes while a significant amount of Ni and Fe ions release was found for 316 L SS under the same condition. The indirect cytotoxicity results suggest that all three Fe based BMG extracts have no cytotoxicity to L929 and NIH3T3 cells. All these results demonstrate that Fe based BMGs will open up a new path for the biomedical applications, especially in dental implantology.     

全金属组元铁基块体非晶的制备与性能研究

为了获得良好的玻璃形成能力,通常在铁基非晶合金中添加类金属元素(P、C、B、Si等),但这些铁基非晶合金大多室温塑性很差,且其脆性与其类金属元素的种类、含量以及分布有密切关系,因而本文选取全金属组元铁基非晶合金(Fe_(0.52)Co_(0.3)Ni_(0.18))_(73)Cr_(17)Zr_(10),通过旋淬甩带与铜模喷铸的方法分别制备了条带与块体试样,并采用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、万能试验机等进行了相关性能研究.研究表明:(Fe_(0.52)Co_(0.3)Ni_(0.18))_(73)Cr_(17)Zr_(10)的临界尺寸在1～2 mm,玻璃转变温度为482℃,过冷液相区达到70℃;直径为1 mm的非晶棒材的屈服强度为2 190 MPa,断裂强度达到2 800 MPa,塑性应变量为3.6%.全金属成分中更多的金属-金属键合方式可能是其拥有较好塑性的原因.     

Effect of Au additions on the structure and properties of (Fe0.5Co0.5)71Nb4Si5B20 bulk metallic glass

The effect of addition of gold (Au) on the structure and mechanical properties of (Fe_0.5Co_0.5)₇₁Nb₄Si₅B₂₀ BMG alloy was studied. Addition of Au formed crystals in the BMG alloy. Gradual increase in the amount of Au added to the BMG alloy resulted in an increase in the amount of crystallinity and hardness of the alloy. Hardness values in excess of 1100 H_V were found in all the alloys with a maximum value of 1245 H_V. The thermal transition temperatures were also found to increase with an increasing amount of Au. Corner cracks were produced in the alloy with 1.5?at.-% Au content showing a low indentation fracture toughness value of 2.98?MPa-m^0.5.     

Effect of Nb addition on the subsurface deformation behavior in Cu47Ti34Zr11Ni8 bulk metallic glasses through Vickers indentation

In this paper, 3 mm diameter (Cu₄₇Ti₃₄Zr₁₁Ni₈)_100−xNb_x (x = 0,1,2) glass forming alloys were fabricated by water-cooled copper mould cast. Microstructural characterization reveals that the monolithic Cu₄₇Ti₃₄Zr₁₁Ni₈ bulk metallic glass exhibits homogenous amorphous structure. While the alloys with Nb addition exhibit a composite structure. For alloys with x = 1, micro-scaled crystalline particles were found to distribute in the glassy matrix. For alloys with x = 2, the microstructure is dominated by a high density of dendritic phase embedded in the glassy matrix. Bonded interface technique was adopted to study the deformation behavior of the alloys underneath the Vickers indentation. It reveals that the subsurface shear patterns are significantly affected by the precipitated phases. The different deformation mechanism of the alloys resulted from the minor Nb addition was put forward and discussed.     

Synthesis and properties of bulk metallic glasses in the ternary Ni–Nb–Zr alloy system

Bulk metallic glasses (BMGs) with high thermal stability, good mechanical properties and high corrosion resistance were synthesized in the Ni–Nb–Zr system. A large bulk glass-forming region with 60 < Ni < 64, 28 < Nb < 38 and 0 < Zr < 9 (in at.%) was found. The critical size for the glass formation is 3 mm. These investigated Ni-based BMGs process high glass transition temperature of about 880–900 K and high on-set crystallization temperature of 915–932 K as well as high compressive fracture strength of approximate 3.0–3.2 GPa along with some compressive plasticity of about 2%. Electrochemical measurements indicate they also exhibit high corrosion resistance, i.e., large passive region above 1.5 V (vs. saturated calomel reference electrode, SCE). The influence of the Zr content on the glass-forming ability (GFA) and corrosion behaviors was carefully studied, indicating that some Zr addition improves the GFA and corrosion resistance.     

Ferromagnetic resonance in metallic glasses: study of fracture,stress and thermal stability

Effects of fracture, stress and isothermal annealing of Fe-Ni based metallic glasses have been investigated using the ferromagnetic resonance technique.fmr linewidth is quite sensitive to changes in the magnetic and structural order in metallic glasses, andfmr lineshape seems to provide useful qualitative information on the mechanical state of these systems. Our observations are compared with recent work of Baianu and co-workers.