Phase relationships in the iron-rich Fe-Al alloys

A study of precipitation in DO3 ordered Fe–Al–Nb alloy

“…Lattice parameters determined were approximately 2.909 Å for the matrix and cZ7.936 Å and aZ4.855 Å for the Laves phase. These values are slightly larger than expected from Okamoto and Beck [18] for a matrix of Fe-25Al, and from the X-ray diffraction data files [19].…”

Ordering effects in the Fe-Al system

“…Physique 44 (1983) ; however there is now a qualitative agreement between different studies on the nature of the phases and on the order-disorder transitions in the Fe rich regions of the diagram [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. In fact this diagram is very complex and shows some very unusual features in metallurgical systems [15][16][17]. For instance Allen and Cahn [24] [24][25][26].…”

Nanoprecipitation of oxide particles and related high strength in oxide-dispersion-strengthened iron–aluminium–chromium intermetallics

“…It may be considered that the nucleation rate is enhanced by the low interface energy of the (0 1 0) m //(0 0 1) p habit plane which has a relatively small misfit related to the matrix lattice parameter (0.290 nm) and the metastable fcc phase (0.526 nm). Accordingly, both increasing the Al content of the matrix, which will lead to stronger order and a smaller lattice parameter of the FeAl matrix [29], as well as increasing Cr content, which also lowers the matrix lattice parameter [34,35], should decrease the matrix-particle misfit and thereby enhance particle nucleation. Examination of particle number densities in the present four materials (Tables 1-4) is completely consistent with the arguments above.…”

“…where m is the Taylor factor (taken as 2.5 for the body-centered matrix matrix), l the shear modulus, b the Burgers vector (5 Â 10 À10 m for the two-partial h111i superdislocations [29]), / is the particle size and k the particle separation deduced using the volume fraction of fine particles. For elastically anisotropic material such as iron aluminides [37], it is better to use the energy factor (K) [38] instead of the shear modulus to describe dislocation behaviour, and for ODS Fe-40Al alloys this has a value near 75 GPa [18,27].…”

“…The disk precipitate is confirmed to lie in the (0 1 0) matrix plane and examination of the HREM image as well as the fast Fourier transform (FFT) pattern shows that the precipitate has the face-centred cubic (fcc) structure. Taking the B2 matrix to have a reference lattice parameter of 0.290 nm [29], the lattice parameter of the fcc crystal is determined to be 0.526 nm. The orientation relationship of matrix and precipitate can be described as (0 0 1) m //(1 1 0) p , along the direction of observation, with [0 1 0] m //[0 0 1] p , the normal to the habit plane, and [1 0 0] m //[1 À1 0] p , the disk radial growth direction within the thin foil.…”