Todd C. Hufnagel

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Name: Hufnagel, Todd C.
Organization: Johns Hopkins University , USA
Department: Department of Materials Science and Engineering
Title: Professor(PhD)
Co-reporter:Todd C. Hufnagel, Christopher A. Schuh, Michael L. Falk
Acta Materialia 2016 Volume 109() pp:375-393
Publication Date(Web):1 May 2016
DOI:10.1016/j.actamat.2016.01.049

Abstract

We review recent research into elastic and plastic deformation of metallic glasses, with an emphasis on making connections between developments in theory and simulation (largely from the physics community) and experimental results (largely from the metallurgy community). Topics covered include strain measurement via scattering techniques, non-affine atomic displacements during elastic deformation, shear transformations, constitutive equations, shear bands, and strain hardening. Where possible we connect the observed behavior and properties to the structure of the glass on the atomic- and nano-scales.

Co-reporter:Jonathan C. Trenkle, Timothy P. Weihs, Todd C. Hufnagel
Scripta Materialia 2008 Volume 58(Issue 4) pp:315-318
Publication Date(Web):February 2008
DOI:10.1016/j.scriptamat.2007.09.060
We measured the fracture toughness of joints in amorphous Zr57Ti5Ni8Cu20Al10 made using Al/Ni reactive multilayer foils. The highest fracture toughness measured was ∼12 MPa m1/2. Based on the fracture toughness and the crack propagation paths, we conclude that virtually all of the toughness can be ascribed to the presence of metallic glass ligaments in the joint. Increasing the stress applied during joining increases the area fraction of these ligaments and so increases the fracture toughness as well.
Co-reporter:S.O. Hruszkewycz, T. Fujita, Mingwei W. Chen, Todd C. Hufnagel
Scripta Materialia 2008 Volume 58(Issue 4) pp:303-306
Publication Date(Web):February 2008
DOI:10.1016/j.scriptamat.2007.10.009
We present a selected area nanodiffraction fluctuation electron microscopy (FEM) technique implemented on a conventional transmission electron microscope. Nanodiffraction patterns from a Pd-based metallic glass, collected using a selected area aperture 15 × 15 nm in effective size, display inhomogeneous speckling due to the small volume sampled. We compare the azimuthal intensity variance from these patterns to the spatial intensity variance from tilted dark-field measurements on the same specimens and find reasonable qualitative agreement, including features characteristic of medium-range order.
Co-reporter:A.J. Swiston Jr., E. Besnoin, A. Duckham, O.M. Knio, T.P. Weihs, T.C. Hufnagel
Acta Materialia 2005 Volume 53(Issue 13) pp:3713-3719
Publication Date(Web):August 2005
DOI:10.1016/j.actamat.2005.04.030

Abstract

We have previously demonstrated that Zr-based metallic glass components can be welded using the heat produced by self-propagating exothermic reactions in multilayer metallic foils. Here, we examine the evolution of the temperature field during reactive joining of bulk amorphous Zr57Ti5Cu20Ni8Al10, as well as the microstructure of the resulting joints. Numerical simulations predict that the metallic glass near the glass/foil interface heats very rapidly (∼107 K s−1) to temperatures of ∼1350 K, well above the liquidus temperature of the amorphous alloy (∼1115 K), followed by rapid cooling (∼105 K s−1) once the reaction front has passed. The maximum temperature, heating rate, and cooling rate of the glass all decrease with increasing distance from the interface. Infrared measurements of the temperature of the metallic glass components during joining show that the cooling rate exceeds the critical cooling rate of the alloy. Optical and scanning electron microscopy reveal no evidence of crystallization of the glass components due to the joining process.

Aluminum, compd. with nickel (9:2)
Nickel, compound with zirconium (1:2)
Aluminum, compd. with nickel (3:2)
Copper, compd. with zirconium (1:2)
NICKEL ALUMINIDE
Aluminum, compd. with zirconium (4:5)
Aluminum, compd. with zirconium (3:2)