Transition-metal alloy formation. The occurrence of topologically close packed phases-I
The occurrence or absence of topologically-close-packed (t.c.p.) phases is discussed in terms of atomic volumes (V) and d-band hole counts (N /SUB h/ ). It is necessary to consider the Laves structures as distinct from the other t.c.p. phases. A range in average N /SUB h/ values and a range in the relative sizes of the alloy constituents is associated with Laves phase formation and when (these factors both fall within their required ranges a Laves phase forms and when) either falls outside, it does not. The situation is different for non-Laves t.c.p. phases where compound formation tends to be weaker. Nonetheless there is a pattern in the occurrence of these phases involving different values of size and band filling factors. However, these two factors, taken together, do not determine whether these structures prevail over other competing phases). In the course of considering the non-Laves systems it becomes useful to introduce an effective N /SUB h/ scale incorporating effects other than just d-band occupancy. The ranges of stoichiometry over which such t.c.p. phases form is seen to be related to the relative sizes of the constituents. Some suggestions are given of alloy systems in which t.c.p. phases have not been reported and are expected and vice versa.
- Research Organization:
- Brookhaven National Laboratory, Upton, NY
- OSTI ID:
- 6069977
- Journal Information:
- Acta Metall.; (United States), Vol. 32:4
- Country of Publication:
- United States
- Language:
- English
Similar Records
Relative abundances of cyanogenated molecules
Formation criterion for binary metal diboride solid solutions established through combinatorial methods