Bulk Metallic Glass -
Recent development of bulk metallic glasses (BMG's) has opened
the door for use of these fascinating materials in structural
applications.
These alloys require cooling rates of only 1-100 K/s, so fully
amorphous castings up to a centimeter thick can be manufactured
using conventional casting methods.
For a Zr-Ti-Ni-Cu-Be bulk amorphous alloy, tensile strengths of 2
GPa and fracture toughness values of ~20 MPa-m1/2 have been
reported. With a density of 6.1 g/cm3, this BMG has a higher
strength to weight ratio than steels and most of the super-alloys.
The alloy exhibits almost no plastic strain at failure, but typically
shows up to 2.5% elastic strains. This ability to elastically store
large amounts of energy per unit volume makes the alloy an
excellent spring. In fact, it's first commercial application is as a
golf club head. Figure below shows the microstructure of BMG –
you may note the absence of any periodicity in it.
Microstructure of a Bulk Metallic Glass
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