History

First produced by vapour deposition techniques, thin films of metallically bonded

Metallic bond

Metallic bonding is the electrostatic attractive forces between the delocalized electrons, called conduction electrons, gathered in an "electron sea", and the positively charged metal ions...

 amorphous solids were initially characterised by X-ray diffraction. Despite the significant ramifications to longstanding solidification theory, it was not until 1960 that the first production of amorphous metal from the melt was demonstrated, with splat quenching of near-eutectic Au75Si25at.% producing fully vitreous samples of 10 µm thickness.

Mg-Zn-Ca based metallic glasses are a relatively new group of amorphous metals, possessing commercial and technical advantages over early compositions. Gu and co-workers produced the first Mg-Zn-Ca BMG in 2005, reporting high glass forming ability, high strength and most importantly exceptional plasticity

Plasticity

Plasticity may refer to:Science* Plasticity , in physics and engineering, plasticity is the propensity of a material to undergo permanent deformation under load...

. This lanthanide

Lanthanide

The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...

-free, Mg-based glass attracted immediate interest due to its low density and cost, and particularly because of its uncharacteristically high ductility

Ductility

In materials science, ductility is a solid material's ability to deform under tensile stress; this is often characterized by the material's ability to be stretched into a wire. Malleability, a similar property, is a material's ability to deform under compressive stress; this is often characterized...

. This property was unexpected for such compositions, as the constituent elements are found to be of relatively low Poisson ratio, and hence contribute little to the inherent plasticity of the glass. This unlikely asset was seized upon by Li in 2008 who, making use of the Poisson ratio principle, increased Mg content at the expense of Zn to further enhance plasticity. Further improvements were achieved by incremental addition of Ca to the Mg72Zn28 binary composition, producing numerous ternary alloys along the 350oC isotherm

Isotherm

Isotherm may refer to:* Isotherm a type of contour line that connects points of equal temperature at a given date or time on a geographic map* Isotherm in thermodynamics, a curve on a p-V diagram for an isothermal process...

of the Mg-Zn-Ca system.

Sources

• BUCKEL, W. & HILSCH, R. (1954) Influence of the condensation at low temperatures on the electrical resistance and the superconductor for different metals. Z. Phys., 138, 109-120.
• KLEMENT, W., WILLENS, R. H. & DUWEZ, P. O. L. (1960) Non-crystalline Structure in Solidified Gold-Silicon Alloys. Nature, 187, 869-870.
• GU, X., SHIFLET, G. J., GUO, F. Q. & POON, S. J. (2005) Mg-Ca-Zn bulk metallic glasses with high strength and significant ductility. Journal of Materials Research, 20, 1935-1938.
• LI, Q.-F., WENG, H.-R., SUO, Z.-Y., REN, Y.-L., YUAN, X.-G. & QIU, K.-Q. (2008) Microstructure and mechanical properties of bulk Mg-Zn-Ca amorphous alloys and amorphous matrix composites. Materials Science and Engineering: A, 487, 301-308.