Y. Le Bouar, Atomistic study of the coherency loss during the b.c.c.-9R transformation of small copper precipitates in ferritic steels, ACT MATER, 49(14), 2001, pp. 2661-2669
Using 3D atomistic static simulations, we first investigate the atomic cohe
rency between a small twinned 9R embryo (less than 6 nm in diameter) and th
e b.c.c. Fe matrix. We show that the (11(4) over bar)(9R) planes of the pre
cipitate are aligned with the ( 1(1) over bar 0)(b.c.c.) planes of the matr
ix, and that the coherency loss of the precipitate/matrix interface is due
to the formation of dislocation loops inside the precipitate. Then, we use
3D atomistic simulations to study the structure changes of an initially b.c
.c. copper precipitate and show that the structure evolves towards a 9R str
ucture. Finally, we use the above results to propose a simple geometric mec
hanism which may be relevant for the b.c.c./9R transformation at low temper
ature and when the influence of vacancies can be neglected. (C) 2001 Acta M
aterialia Inc. Published by Elsevier Science Ltd. All rights reserved.