Rw. Cahn, MULTIPHASE INTERMETALLICS, Philosophical transactions-Royal Society of London. Physical sciences and engineering, 351(1697), 1995, pp. 497-509
Ordered intermetallic compounds, notably the aluminides of nickel, tit
anium, iron and niobium, have been under intensive investigation for t
he past two decades as prospective load-bearing materials for high tem
peratures, with special emphasis on aerospace applications. The strong
er of these phases are all catastrophically brittle at and near ambien
t temperature and this difficulty has proved obdurate. A promising sol
ution appears to be to alloy such phases in such a way that the result
is a two-phase or multiphase material. The extra phases may be disord
ered and intrinsically ductile: the presence of such phases lowers the
high-temperature strength but is apt to enhance the plastic deformabi
lity of the material even at ambient temperature. There are also insta
nces of multiphase alloys in which all the phases are ordered intermet
allics, some stronger and more brittle, others weaker and more ductile
, and the end-result can be a promising combination of strength and du
ctility, as well as good creep resistance.