Special Issue "Amorphous Alloys"
A special issue of Metals (ISSN 2075-4701).
Deadline for manuscript submissions: closed (31 October 2012)
Prof. Dr. Hans-Jörg Fecht
Director Institute of Micro and Nanomaterials Ulm University Albert-Einstein-Allee 47, 89081 Ulm, Germany
Interests: nanocrystalline materials; bulk metallic glasses; nucleation theory; design and growth of thin films and layers
Bulk metallic glasses BMGs have been discovered about 30 years ago and constitute a new class of engineering materials with an increasing interest world-wide. They lack the long-range atomic order of crystalline materials exhibiting only short range atomic order in a thermodynamically metastable frozen state. They can be obtained when nucleation and growth of crystalline phases are suppressed during cooling of liquid alloys as bulk material with several mm3 volume.
Good glass forming alloys are usually multicomponent and eutectic or near eutectic liquid compositions with relatively high viscosities and strongly depressed melting temperatures that result in critical cooling rates of about 1 K/sec, i.e. typical for the metal casting industries. Typical examples are complex Zr-, Ti-, Fe-, Ni- or Mg-based alloys as well as precious metal systems.
Due to the absence of dislocations and grain boundaries BMGs have considerably improved mechanical properties and often better resistance to wear and corrosion than conventional metals. As such, they show perfect elastic behavior up to 2% strain and possess mechanical resilience far greater than crystalline metals and alloys with mechanical strength up to 5 GPa, i.e., several times the strength of conventional steels.
Furthermore, due to its glassy nature and drastical reduction of viscosity above the glass transition temperature, BMGs can be plastically deformed or moulded like plastic material in a certain time-temperature window. This combination of several advantageous properties opens a new way of designing materials, metal surfaces and components with intricate shapes and 3-D geometries never seen before. Engineering applications therefore range from structural components in electronic devices, shielding, springs and other MEMS parts to optical components, metallic foams and medical devices.
Prof. Dr. Hans Fecht
- bulk metallic glasses
- eutectic alloys
- critical cooling rate
- high strength materials
- plastic moulding
- engineering applications