Compression behaviour and micro-structure evaluation of Zr57Nb5Cu15.4Ni12.6Al10 bulk metallic glass under high pressure

Compression behaviour and micro-structure evaluation of Zr₅₇Nb₅Cu_15.4Ni_12.6Al₁₀ bulk metallic glass is investigated at room temperature up to 32.8 GPa using in-situ high pressure energy dispersive X-ray diffraction with a synchrotron radiation source. The equation of state of the bulk metallic glass is − ΔV / V = 0.012P − 2.49 × 10^− 4P² − 9.5 × 10^− 7P³ + 5.02 × 10^− 8P⁴. The result shows that the nearest atom pair of the as-quenched bulk metallic glass corresponds to Zr–Zr correlations. And with pressure increasing, the nearest atom pair changes to a new one at 32.8 GPa.     

新型Zr57Nb5Cu15.4Ni12.6Al10大块非晶态合金的制备及其室温单轴压缩断裂行为

应用铜模真空吸铸法制备直径达5mm的棒状新型Zr57Nb5Cu154Ni12.6Al10大块非晶样品.X射线衍射检测证明样品完全为非晶态.通过等温示差扫描量热法(DSC)测试了Zr57Nb5Cu15.4Ni12.6Al10大块非晶的晶化动力学效应,同时研究了大块非晶合金的室温单轴压缩变形和断裂行为.结果表明:Zr57Nb5Cu15.4Ni12.6Al10块体非晶晶化过程具有动力学效应;其室温压缩变形过程主要表现为弹性变形;断裂面与压缩方向约呈45°,断口呈现典型的脉状花样.     

Diffusion bonding of Zr55Cu30Ni5Al10 bulk metallic glass to Cu with Al as transition layer

In this work we demonstrate the diffusion bonding of Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glass (BMG) to aluminum and copper alloy. The process parameters including temperature, pressure and time are investigated experimentally, and we obtain appropriate ones for accomplishing diffusion bonding of the BMG to aluminum alloy successfully. Then we present a two-step diffusion bonding process to bond the BMG to copper alloy by using aluminum alloy as transition layers, and achieve a five-layer bonded joint of BMG/Al/Cu/Al/BMG. The mechanical properties of the multilayer joint are examined. The hardness of the BMG in the joint is enhanced while the bending strength decreases significantly compared with the as-received BMG. Besides, the crystalline metals alleviate and block the extension of cracks in the BMG, which results in the joint fracturing in an explosion-proof glass manner, dissimilar to rupturing in a catastrophic manner that is always happened in the BMGs. Therefore, diffusion bonding of BMG to crystalline metals is a promising way to extend its application.     

Effect of pressure on crystallization process of Zr55Al10Ni5Cu30 bulk metallic glass

The effects of high temperature and high pressure on the crystallization process of Zr₅₅Al₁₀Ni₅Cu₃₀ amorphous structure have been investigated by using high-resolution transmission electron microscope (HRTEM), differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The experimental results provide direct evidence that the pre-annealing at 763 K under 5 GPa significantly alter the amorphous structure, which can cause the obvious change in the glass transition temperature and crystallization path during subsequent heating process.     

Microstructural evolution during annealing and rolling Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass

The microstructural evolution of the Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ bulk metallic glass during annealing and rolling deformation was studied. After annealing at 680 K for 0.5 h, phase separation is observed, and nanocrystallization is further induced by the subsequent rolling deformation. Increasing annealing time to 1.5 h leads to the formation of both nanocrystals and large-size particles of the Zr–Cu fcc phase. After rolling, the volume fraction of nanocrystals increases slightly while the Zr–Cu particles disappear. The presence of phase separation and nanocrystals during annealing reduce the thermal stability of the glass and accelerate the subsequent crystallization driven by rolling. During rolling the two annealed specimens exhibit the good ductility.     

Micro and nano indentation studies on Zr60Cu10Al15Ni15 bulk metallic glass

Partially vitrified Zr₆₀Cu₁₀Al₁₅Ni₁₅ bulk metallic glass has been synthesized using water cooled copper mold drop casting technique. Kinetically favorable microstructures having different morphologies are observed throughout the volume of the bulk metallic glass sample. X-ray diffraction studies indicate formation of hard intermetallic compounds such as Zr₃Al₂ and Zr₂Ni in certain regions along with amorphous structures. Microindentation studies carried out in different regions of the sample reveal microstructure dependent deformation behavior. Highest hardness is observed in the fully crystallized regions compared to pure glassy regions in the same sample. Further nanoindentation in the same sample is used to understand dynamic mechanical properties of microstructures in different regions. The pile-up morphologies around the indent and differences in load–displacement curves provide vital information on deformation behavior of sample in different microstructure sensitive regions.     

Hydrogen‐enhanced plastic deformation during indentation for bulk metallic glass of Zr65Al7.5Ni10Cu17.5

The effect of hydrogen charging on shear bands and plastic zone during Vickers indentation for Zr₆₅Al_7.5Ni₁₀Cu_17.5 bulk metallic glass has been studied. The results showed that hardness increased gradually with charging time and reached saturation. The shear bands and the size of the plastic zone on the surface and subsurface of indentation increased evidently when charging time was less then 40 h at i = 10 mA/cm² or 10 h at i = 100 mA/cm², respectively. After that, the size of the plastic zone began to reduce with charging time because hydrogen blisterings began formation and growth.     

Dynamic mechanical relaxation behavior of Zr35Hf17.5Ti5.5Al12.5Co7.5Ni12Cu10 high entropy bulk metallic glass

Non-equiatomic high entropy bulk metallic glasses were reported recently and show unique mechanical and physical properties.Dynamic mechanical relaxation behavior of Zr35Hf17.5Ti5.5Al12.5C07.5Ni12Cu10 high entropy bulk metallic glass was investigated by dynamic mechanical analysis(DMA)and the mechanical spectra could be well described by the quasi-point defects(QPD)theory.Compared to typical metallic glasses,the intensity of the β relaxation of Zr35Hf17.5Ti5.5Al12.5Co7.5Ni12Cu10 high entropy bulk metallic glass is lower due to the sluggish diffusion.At the same time,the correlation factor χ is higher than that of conventional metallic glasses and this is ascribed to the high configuration entropy.In paral-lel,physical aging below the glass transition temperature leads to a decrease of atomic mobility,caused by a decrease of the concentration of defects.     

The effect of decomposition on crystallization in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass

The decomposition as well as its effects on the crystallization of the bulk metallic glass (MG) Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 has been investigated using transmission electron microscopy (TEM). It is found that the decomposition destabilizes the MG and makes the MG thermally less stable with respect to crystallization. The effects of the phase separation on the subsequent crystallization are discussed based on the microstructural characteristics of the MG.     

Cooling rate effects on the microstructure and phase formation in Zr51Cu20.7Ni12Al16.3 bulk metallic glass

A detailed transmission electron microscope (TEM) study has been conducted to investigate the microstructures of the Zr₅₁Cu_20.7Ni₁₂Al_16.3 metallic glass formed at different cooling rates. It has been found that the most competitive crystalline phase to the amorphous structure is an oxygen-stabilized FCC NiZr₂-type phase, which in turn acts as the leading phase to trigger the formation of other crystalline phases in the slow-cooled alloy.     

Atomic configuration evaluation of Zr60Ni21Al19 bulk metallic glass under high pressure

The atomic configuration evaluation in Zr₆₀Ni₂₁Al₁₉ bulk metallic glass at high pressures has been revealed by using in situ synchrotron X-ray diffraction. The radial distribution function is gained by Fourier transformation. The investigation shows that the amorphous structure is retained and the coordination number keeps 12.0 within the experimental pressures (0–24.5 GPa). The quantitative determination of the neighbor atomic distance suggests that high pressure alters topological but not chemical short range ordering through shortening the second nearest neighbor atomic distance. The atomic coordination is analyzed by the inherent chemical parameters of the ternary Zr₆₀Ni₂₁Al₁₉ amorphous alloy.     

Effect of ZrO2 and SiO2 on glass forming ability of Zr57Cu20Al10Ni8Ti5 alloy

Zr₅₇Cu₂₀Al₁₀Ni₈Ti₅ has very high glass forming ability (GFA) due to its low crystal growth rate which limits development of crystallites arising from container walls or nuclei. Effect of ZrO₂ and SiO₂ on GFA was studied by investigating the solidification microstructures of alloys containing different amount of the oxides. Amorphous ingots were formed by melting and freezing alloys without addition of the oxides using an arc furnace. Partially amorphous ingots were formed for addition of the oxides up to 0.2 wt %. Amorphous forming conditions of alloys containing greater concentration of the oxides were studied using a drop tube. GFA decreases with increasing concentration of the oxides. However, superheating of melts eliminates some effects of the oxides. Different types of oxides leads to different microstructures due to their different heterogeneous nucleation rates and nucleation temperature.     

大块非晶合金Zr55Cu30Al10Ni5的电子结构特征及电击穿行为

测定了大块非晶合金Zr55Cu30Al10Ni5晶化前后的费米能级和各元素的电子结合能,研究了非品合金的电子结构特征和电击穿行为．测试并讨论了非晶材料场发射能力和耐电压强度的关系．结果表明,对于Zr基合金,非品态比品态合金具有更大的功函数．比较了Zr55Cu30Al10Ni5合金非晶态与晶态的耐电压强度数值,发现非晶态合金的耐电压强度数值比较分散,品化合金的耐电压强度相对比较集中．耐电压强度平均值表明,Zr基合金非晶态具有更好的耐电压能力．     

In vitro biocompatibility assessment of Ti40Cu38Zr10Pd12 bulk metallic glass

The use of biocompatible materials has attained an increasing importance for tissue regeneration and transplantation. The excellent mechanical and corrosion properties of Ti₄₀Cu₃₈Zr₁₀Pd₁₂ bulk metallic glass (BMG) turn it into a potential candidate for its use in orthopaedic implants. Before being considered as a biomaterial, some biological parameters must be taken into account. In this study, mouse preosteoblasts were cultured in the presence or absence of the alloy at different times (24 h, 7 and 21 days) and no differences in cell viability were detected. Moreover, cells were able to adhere to the alloy surface by establishing focal contacts, and displayed a flattened polygonal morphology. After 14 days in culture, differentiation into osteoblasts was observed. Besides, the amount of Cu ions released and their potential toxic effects were analyzed, showing that the amount of Cu released did not increase cell death. Finally, the low levels of inflammatory cytokines secreted by THP-1 differentiated macrophages exposed to the alloy suggest the absence of an immunogenic response to the alloy. In conclusion, in vitro studies indicate that the Ti₄₀Cu₃₈Zr₁₀Pd₁₂ BMG could be considered as a biomaterial to be used in orthopaedic implants.     

Dilatometric measurements and calculation of effective pair potentials for Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass

Dilatation measurement was conducted on a Zr–Ti–Cu–Ni–Be bulk metallic glass to obtained information about the average pair potential in the five-component alloy. By assuming a Lannard–Jones type potential, the average nearest-neighbor separation and the effective depth of the pair potential are found to be 0.32 nm and 0.23 eV, respectively, which agrees very well with the published results measured with other distinctively different techniques.