Unusual Glass-Forming Ability of Bulk Amorphous Alloys Based on Ordinary Metal Copper

We report the unusual glass-forming ability (GFA) of a family of Cu-based alloys, Cu46Zr47–xAl7Yx (0<x<=10, in at. %), and investigate the origin of this unique property. By an injection mold casting method, these alloys can be readily solidified into amorphous structures with the smallest dimension ranging from 4 mm up to 1 cm without detectable crystallinity. Such superior GFA is found primarily due to the alloying effect of Y, which lowers the alloy liquidus temperature and brings the composition closer to a quaternary eutectic. Other beneficial factors including appropriate atomic-size mismatch and large negative heat of mixing among constituent elements are also discussed

Isoconfigurational Elastic Constants and Liquid Fragility of a Bulk Metallic Glass Forming Alloy

Samples of Zr46.25Ti8.25Cu7.5Ni10Be27.5 were isothermally annealed and quenched near the glass transition temperature and studied by the pulse-echo overlap technique. The shear modulus G of the samples shows a strong reversible dependence on annealing temperatures and, thus, on the specific configurational potential energy of the equilibrium liquid. The low-T dependence of G of the configurationally frozen glasses shows linear temperature dependence as expected by Debye-Grüneisen theory. The T dependence of G in the liquid state is directly related to the viscosity and fragility of the liquid

Formation and properties of new Ni-based amorphous alloys with critical casting thickness up to 5 mm

New Ni-based bulk metallic glasses were synthesized in NixCua−xTiyZrb−yAl10 (a~b~45 at.%) system, based on a ternary alloy, Ni45Ti20Zr35. The additions of Al and Cu greatly increase the glass-forming ability (GFA). The best GFA is located around Ni40Cu5Ti16.5Zr28.5Al10, from which fully amorphous samples of up to 5 mm thickness were successfully fabricated by an injection mold casting method. These alloys exhibit high glass-transition temperatures Tg ~ 760 to 780 K, and relatively wide undercooled-liquid regions ΔT (defined by the difference between Tg and the first crystallization temperature Tx1 upon heating) ~ 40–50 K. Mechanical tests on these alloys show quite high Vicker's Hardness ~ 780 to 862 kg/mm^2, Young's modulus ~ 111 to 134 GPa, shear modulus ~ 40 to 50 GPa and high fracture strength ~ 2.3 to 2.4 GPa. The effect of small Si-addition and a discrepancy between GFA and ΔT are also reported. The exceptional GFA and the all-metallic compositions give these new alloys excellent promise for both scientific and engineering applications

Molecular dynamics study of the binary Cu_(46)Zr_(54) metallic glass motivated by experiments: Glass formation and atomic-level structure

We have identified a binary bulk metallic glass forming alloy Cu_(46_Zr_(54) by analyzing the structure and thermal behaviors of copper mold cast samples using x-ray diffraction, transmission electron microscopy, and differential scanning calorimeter. Motivated by these experimental results, we fitted the effective Rosato-Guillope-Legrand-type force field parameters for the binary Cu-Zr alloy system and the atomistic description of glass formation and structure analysis of the Cu_(46)Zr_(54) alloy based on molecular dynamics simulation will be also presented

Thermal and elastic properties of Cu–Zr–Be bulk metallic glass forming alloys

The compositional dependence of thermal and elastic properties of Cu–Zr–Be ternary bulk metallic glass forming alloys was systematically studied. There exists a linear relationship between the glass transition temperature Tg and the total Zr concentration. G decreases linearly with increasing Zr concentration as well. The results also show that Tg, shear modulus G, and Poisson's ratio nu are very sensitive to changes in compositions. Low Tg, low G, and relatively high nu can be achieved with high Zr and Ti concentration

Design and analysis of a novel CPT system with soft ferromagnetic material cores and electromagnetic resonant coupling for EVs

This paper describes a novel contactless power transfer (CPT) system with geometrically improved H-shape ferromagnetic cores and electromagnetically prospective modelling analysis methods for wireless power transmitting (WPT) applications of electric vehicles (EVs). A CPT prototype, using optimized H-shaped magnetic couplers and series-to-series (SS) compensation, is proposed to address and ensure the maximization of system efficiency, power transfer ratings, and air gaps of coupling coils. By focusing on the main factors such as various system operating frequencies, different geometric designs of coils, changeable inductive coupling distances, electromagnetic field performances and actual phase angle deviations when the inductive coupling system tends to be stable with its waveforms, this small-sized H-shape CPT system has been analytically considered and modelled in a finite-element method (FEM) environment, resulting in a maximum system efficiency of 59.5%, a coil transmitting efficiency of 83.8% and a maximum power output of 42.81 kW on the load end when the resonant coupling of CPT system tends to occur within a range of calculated resonant frequencies, with an air gap of 10 mm. Moreover, the system efficiency and coil transmitting efficiency can reach 47.75% and 77.22%, respectively, and the highest RMS real power to load can achieve 31.95 kW with an air gap of 20 mm. Besides, with an air gap of 30mm, this H-shape CPT system is measured to output 20.39-kW RMS power, along with the maximum system efficiency and coil efficiency of 41.78% and 63.23%, respectively. Furthermore, the improvements of flux linkage, magnetic flux density regarding the actual electromagnetic performance produced and the issues on the calculated natural resonant frequencies have been studied by result analysis and comparison of electromagnetic field parameters generated. In addition, the current limitations and further design considerations have been discussed in this paper

Understanding the Relationship Between Drug Overdose Death Rates and Socioeconomic Factors

Drug-overdose deaths increased rapidly recently. What are the causes? We believe socioeconomical factors play critical roles. Secondary data analyses are done on the US population, using mortality-data files from the National Vital Statistics System. Deaths are grouped by race, age, sex, education and marital status. We believe that the percentage-of-total-death (PoTD) value, which equals to the number-of-overdose-deaths divided by the total-number-of-deaths in the corresponding group, more accurately reflect the severity of overdose-deaths. Analysis of 2017 data reveals that among all age groups, PoTD is highest in the age 25-34 group, with dramatic differences between white (PoTD 24%) and black (PoTD 9%) populations, and between single (22%) and married (13%) populations. PoTD is generally higher for males than females; however, for the 15-24 age group, the PoTD for females (13%) is higher than males (10%), suggesting the need of special attention to young females in overdose prevention. PoTD is higher (~3%) for population with less-than-college education than college-or-higher education (~1%). However, the population with middle-school or less education has very low PoTD (0.6%). The PoTD vs. education relationship is similar between white and black populations. We also investigate dependencies of PoTD on factors such as day-of-week, and variations in PoTD over the past 15 years. In conclusion, large differences were revealed in the severity of overdose deaths among different socioeconomical groups by examining the PoTD values. We believe that PoTD values of individual groups should be given more considerations when developing health policies in response to the drug overdose crisis

Cooperative Shear Model for the Rheology of Glass-Forming Metallic Liquids

A rheological law based on the concept of cooperatively sheared flow zones is presented, in which the effective thermodynamic state variable controlling flow is identified to be the isoconfigurational shear modulus of the liquid. The law captures Newtonian as well as non-Newtonian viscosity data for glass-forming metallic liquids over a broad range of fragility. Acoustic measurements on specimens deformed at a constant strain rate correlate well with the measured steady-state viscosities, hence verifying that viscosity has a unique functional relationship with the isoconfigurational shear modulus

Patterns in Change of Opioid Overdose Death Rate with the Day of the Week and Their Implications

The objective of this study was to investigate the dependencies of opioid overdose death rates on the day of the week and understand the implications of the dependencies Understanding and presenting the dependencies is useful for first responders and for health care system resource planning It can provide additional insights in the opioid epidemic and should be considered in prevention effortshttps://jdc.jefferson.edu/phbposters/1002/thumbnail.jp