Complex metallic alloys

Complex metallic alloys (CMAs) are intermetallic compounds characterized by the following structural features:

1. large unit cells, comprising some tens up to thousands of atoms,
2. the presence of well-defined atom clusters, frequently of icosahedral point group symmetry,
3. the occurrence of inherent disorder in the ideal structure.

Research

Most physical properties of CMAs show distinct differences with respect to the behaviour of normal metallic alloys and therefore these materials possess a high potential for technological application.

Since 2005, the European Commission is funding the Network of Excellence CMA [1], which unites 19 core groups in 12 countries.

Examples

Example phases are:

• β-Al-Mg: 1168 atoms per unit cell, face centred cubic, atoms arranged in Friauf polyhedra.

• ξ'-Al-Pd-Mn: 318 atoms per unit cell, face centred orthorhombic, atoms arranged in Mackay-type clusters.

• T-Mg-Al-Zn (Bergman phase): 163 atoms per unit cell, body centred cubic, atoms arranged in Bergman clusters.

• T-Al₃Mn (Taylor phase): 204 atoms per unit cell, face centred orthorohombic, atoms arranged in Mackay-type clusters.

Further reading

• Urban, Knut; Feuerbacher, M. (2004-03-15). "Structurally complex alloy phases". Journal of Non-Crystalline Solids (Elsevier B.V.) 334–335: 143–150. doi:10.1016/j.jnoncrysol.2003.11.029. 

External links

1. EC Network of Excellence Complex Metallic Alloys