Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10620278 | Acta Materialia | 2013 | 14 Pages |
Abstract
The β â α transformation in plutonium is discussed in terms of the crystallography of the two phases and the resulting topological modeling of the β/α interface. There has been little microscopy work on the transformation, but it is probably martensitic. β-Pu is monoclinic I2/m, while α-Pu is monoclinic P21/m. α-Pu has been described as a hexagonal close-packed pseudostructure with AB stacking of the (0 2 0)α planes with pseudo-close-packing along [1 0 0]α and two other directions. β-Pu is less obvious, but X-ray diffraction suggests that the (1 0 3)β planes, which are selected as the terrace plane, have the highest structure factor and are therefore among the closest-packed planes. Other pseudo-close-packed planes, such as {222¯}β and {321¯}β, could also act as terrace planes for the transformation. The (1 0 3)β planes have a pseudo-hexagonal grid of Pu atoms with AB stacking and pseudo-close-packing along [301¯]β and two other directions. A selection of terrace planes as (0 2 0)α//(1 0 3)β with disconnections along [100]α//[301¯]β provides the basis for topological modeling. The model predicts a habit plane that is â¼6° from the terrace plane. The extra Pu atoms in the β structure (17 for every 16 in α) are accommodated by having 16 (1 0 3)β planes transform into 17 (0 2 0)α planes at steps in the interface. Short-range interstitial diffusion of Pu atoms from β to α is required for the transformation to proceed. Possible lattice invariant deformation systems are discussed.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
T.E. Mitchell, J.P. Hirth, D.S. Schwartz, J.N. Mitchell,