High Entropy Alloys (HEA)

Lighter, stronger, more flexible, more wear and heat resistant are only some of the properties that are essential for materials these days. A systematic development of new materials is crucial to meet the constantly increasing requirements.

A completely new type of materials are High Entropy Alloys (HEAs). These multicomponent alloys consist mostly of a (near-) equimolar mixture of several different elements, e. g. CoCrFeMnNi [1, 2]. To further adjust the resulting properties, additional alloying elements with smaller content can be added, e. g. Aluminium in Al_0.1CoCrFeMnNi. Despite their unconventional composition, HEAs show a rather simple microstructure, which consists mostly of one or more solid solution phases, and show interesting properties, as for example [1-3]:

• High strength and ductility
• Good high temperature behaviour
• Low temperature ductility
• Good wear resistance

Material Development

• Alloy design according to request

Manufacturing Methods

• Powder: application of pre-alloyed powder or mechanical alloying and mixing of elemental powders
• Compaction: different methods, e.g. hot pressing, Spark Plasma Sintering, Selective Electron Beam Melting
• Post treatment: heat treatment etc.

Characterisation

• Accredited laboratory for mechanical analysis, thermal analysis and for powder analysis
• Friction and wear test
• Mechanical properties (e.g. density and microstructure)
• Characterisation of functional properties, as for example electrical resistivity

The automotive and aviation industry, mechanical engineering and construction industry have one thing in common: the urgent demand for innovative materials. As materials are also significantly involved in technical progress, they have in nearly all branches of industry a key role. Up to 70 % of all new products are predicated on material development [5].

High-entropy alloys are a highly suitable possibility to realise a completely new alloying concept and receive appropriate properties and property combinations.

Possible applications for HEAs are e.g. [1-3]:

• Refractory HEAs or precipitation hardened HEAs for high-temperature applications, e.g. furnace parts or grits
• Coating for biomedical applications
• Binder phase for composites
• HEAs as irradiation protection against ion radiation
• Wear resistant HEAs as protective coating
• HEAs for cryogenic applications in food industry or liquid gas tanks