A5059039041- Metallic Glasses and Amorphous Alloys
- Glass properties and applications
- Theoretical and Computational Physics
- Phase-change materials and chalcogenides
- Material Dynamics and Properties
- Microstructure and mechanical properties
- Magnetic properties of thin films
- Cultural Heritage Materials Analysis
- nanoparticles nucleation surface interactions
- Quasicrystal Structures and Properties
- Intermetallics and Advanced Alloy Properties
- High-pressure geophysics and materials
- Metal and Thin Film Mechanics
- High-Velocity Impact and Material Behavior
- Copper Interconnects and Reliability
- Advanced X-ray Imaging Techniques
- Electromagnetic wave absorption materials
- Magnesium Alloys: Properties and Applications
- Aluminum Alloys Composites Properties
- Aluminum Alloy Microstructure Properties
- Magnetic Properties and Applications
- Advanced Surface Polishing Techniques
- Advanced ceramic materials synthesis
- Ultrasonics and Acoustic Wave Propagation
- Numerical methods in engineering
Johns Hopkins University
2015-2024
Materials Science & Engineering
1991-2023
Cornell University
2020
Software (Spain)
2019
Johns Hopkins University Applied Physics Laboratory
2018
Stanford University
1991-1996
For the first time in metallic glasses, we extract both exponents and scaling functions that describe nature, statistics, dynamics of slip events during slow deformation, according to a simple mean field model. We model slips as avalanches rearrangements atoms coupled shear transformation zones (STZs). Using high temporal resolution measurements, find predicted, different statistics for small large thereby excluding self-organized criticality. The agreement between data across numerous...
We report a composite material consisting of precipitated micron-scale Ta-rich solid solution particles distributed in bulk metallic glass matrix. The reinforcing ductile are during melting the master alloy glass-forming (Zr70Ni10Cu20)82Ta8Al10, by using previously prepared metastable Zr–Ta binary ingots. Upon cooling from melt, matrix undergoes transition to produce an amorphous phase while Ta resulting not only shows high strength (∼2.1 GPa), but also has dramatically enhanced plastic...
Bulk metallic glasses subjected to quasistatic uniaxial compression at room temperature typically display large elastic strains but limited plastic flow of 0--2% before failure. We have developed an amorphous alloy, ${\mathrm{Zr}}_{59}{\mathrm{Ta}}_{5}{\mathrm{Cu}}_{18}{\mathrm{Ni}}_{8}{\mathrm{Al}}_{10},$ which experiences average macroscopic strain 4.5% The as-cast alloy shows no evidence for the presence crystalline phases, and displays a distinct glass transition wide supercooled liquid...
We have investigated the possibility of void nucleation from coalescence excess free volume generated in shear bands during deformation Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass. Excess a band results energy relative to relaxed glass with less volume. To calculate material volume, we model it as having same structure solidified at an elevated transition temperature, which call fictive temperature. This can be correlated chemical potential that provides driving force for nucleation....
The mechanical and structural properties of a surface play an important role in determining the morphology attached cells, ultimately their cellular functions. As such, integrity are design parameters for tissue scaffold. Electrospun fibrous meshes widely used engineering. When contact with electrospun scaffolds, cells see individual micro- or nanofibres as immediate microenvironment. In this study, tensile testing single composed poly(ε-caprolactone) (PCL), its copolymer,...
Abstract We have compared the structure of shear bands with that undeformed regions a metallic glass. Using quantitative high-resolution electron microscopy, we observed void-like defects, approximately 1 nm in diameter and at concentration one 100nm3, which are generated as result plastic deformation bands. These defects may from coalescence excess free volume upon cessation flow. By comparing energy band containing uniformly distributed relaxed voids present, show is thermo-dynamically possible.
Abstract Slowly-compressed single crystals, bulk metallic glasses (BMGs), rocks, granular materials and the earth all deform via intermittent slips or “quakes”. We find that although these systems span 12 decades in length scale, they show same scaling behavior for their slip size distributions other statistical properties. Remarkably, follow power law multiplied with exponential cutoff. The cutoff grows applied force spanning scales from nanometers to kilometers. tuneability of stress...
Although defects can have a significant effect on the properties of amorphous materials, in many cases these are poorly characterized and understood. This is at least partly due to difficulty imaging materials electron microscope. In this work, we demonstrate utility quantitative analysis high-resolution transmission microscopy for identification characterization nanometer-scale metallic glasses. For proper such defects, it important carefully consider effects conditions thickness variations...
We report the use of high-energy x-ray scattering to measure strain in a ${\mathrm{Zr}}_{57}{\mathrm{Ti}}_{5}{\mathrm{Cu}}_{20}{\mathrm{Ni}}_{8}{\mathrm{Al}}_{10}$ bulk metallic glass situ during uniaxial compression elastic regime up stresses approximately 60% yield stress. The strains extracted two ways---directly from normalized data and pair correlation functions---are good agreement with each other for length scales greater than $4\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. modulus...
We have examined the effect of Ti and cooling rate on crystallization Zr62−xTixCu20Ni8Al10(0⩽x⩽10) amorphous alloys. stabilizes an icosahedral phase in Without (x=0), produces cubic tetragonal intermetallic phases, temperature shows no dependence at which alloy was produced. The alloys containing (3⩽x⩽10) precipitate quasicrystalline upon annealing, show a significant reduction temperatures with decreasing rates casting. propose that undercooled melts short-range order. degree order or...
We have used self-propagating exothermic reactions in Al/Ni multilayers as a means to explore the effect of rapid heating on phase transformations. Using time-resolved synchrotron x-ray microdiffraction with an extremely fast detector, we were able examine reaction sequence detail at rates ∼106 K s−1. observed that intermediate phases formed during are different from those lower rates, even though final same. In situ characterization is essential, other studying (such quenching followed by...
We showed how intermetallic formation reactions can be studied under rapid heating (106–107 K s−1) using x-ray microdiffraction with temporal resolution on microsecond time scales. Rapid was achieved by initiating an exothermic reaction in multilayer foils comprising alternating nanoscale layers of elemental metals. The occurred a front ∼100 μm wide which propagated across the foil at ∼1–10 m s−1. By synchrotron x-rays focused to small spot (60 diameter) and fast pixel-array detector, we...