Bubbloy—Foamy Amorphous Metals

The foaming of metals is a challenge since foam is an unstable structure. However, metallic foams are known to have many interesting properties, offering high stiffness in conjunction with very low specific weight, high gas permeability, high thermal conductivity, and especially, high energy absorption capability. Jan Schroers, a recent post-doctoral scholar in Professor William Johnson’s lab, along with graduate student Chris Veazey, invented a method to foam bulk metallic glass. This micrograph from the article Amorphous Metallic Foam was featured on the cover of Applied Physics Letters in January 2003. Since the amount of energy that can be absorbed scales with the strength of a material, and since BMGs exhibit a yield strength of about 2 GPa (compared to 250 MPa for aluminum), a very large energy absorption ability is expected from BMG foams. Projected practical applications include possible use in the crumple zones of autos, for instance. This work in still in early developmental stages, but it has already moved into a Caltech spin-off company called Liquidmetal Technologies.