Nickel aluminide
Nickel aluminide (Ni3Al) is an intermetallic alloy of nickel and aluminum with properties similar to both a ceramic and a metal.
There are three materials called nickel aluminide:
An intermetallic compound can be defined as an ordered alloy phase formed between two metallic elements, where an alloy phase is ordered if two or more sublattices are required to describe its atomic structure. The ordered structure exhibits superior elevated-temperature properties because of the long-range ordered superlattice, which reduces dislocation mobility and diffusion processes at elevated temperatures.
Nickel aluminide is used as a strengthening constituent in high-temperature nickel-base superalloys, however, unalloyed nickel aluminide has a tendency to exhibit brittle fracture and low ductility at ambient temperatures. Nickel aluminide is unique in that it has very high thermal conductivity combined with high strength at high temperature. These properties, combined with its high strength and low density, make it ideal for special applications like coating blades in gas turbines and jet engines.
In 2005, the most abrasion-resistant material was reportedly created by embedding diamonds in a matrix of nickel aluminide.
An alloy of Ni3Al, known as IC-221M, is made up of nickel aluminide combined with several other metals including chromium, molybdenum, zirconium and boron. Adding boron increases the ductility of the alloy by positively altering the grain boundary chemistry and promoting grain refinement. The Hall-Petch parameters for this material were σy = 163 MPa and ky = 8.2 MPaˑcm1/2. Boron increases the hardness of bulk Ni3Al by a similar mechanism.
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