Joining Bulk Metallic Glass Using Nanostructured
Reactive Multilayer Foils
Jonathan C. Trenkle,
Department of Materials Science and Engineering, Johns Hopkins University
Metallic glasses are promising structural materials because of their high strength ( 2 GPa)
and toughness ( 20 MPa m1/2). Their widespread use, like other structural materials,
is dependent on their ability to be joined to form larger assemblies. Traditional metallic
welding techniques, however, compromise the metastable amorphous atomic structure,
resulting in a loss of desirable properties. Instead, localized heat sources that provide
rapid heating and cooling rates are necessary to retain the amorphous structure during
the joining process. One such source is nanostructured reactive multilayer foils. Comprised
of nanoscale layers of highly exothermic materials, reactive foils can sustain a
self-propagating reaction when a thermal pulse is applied. Depending on the foil architecture,
such as constituents and layer size, reaction temperatures and velocities can be
easily tailored with the potential to reach values in excess of 1000oC and 10 ms-1, respectively.
We have successfully joined Zr-based bulk metallic glass components using Al/Ni reactive
foils. Heating and cooling rates in these joints (108oC s-1
and 106oC s-1, respectively)
are sufficient to avoid devitrification in the gIass. In this presentation, I will discuss the
reactive joining process, the joint microstructure, and the mechanical properties of these
joints. I will focus specifically on the use of synchrotron radiation to measure residual
strains in the joints as well as to study phase transformations in situ in reactive foils in
an attempt to engineer better joints.
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