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-m^1/2 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