Computer simulation of strain-induced phase transformations in thin Fe films

摘要

Using molecular-dynamics simulation and the Meyer-Entel potential, we study the response of thin Fe films (thickness 10 nm) to tensile in-plane strain. The simulations are performed at a temperature slightly below the equilibrium phase transition temperature. For the four surface orientations studied, we typically find the following sequence of transformations in the strained films: (i) a bcc → hcp transition; (ii) the partial back transformation to the bcc phase; (iii) grain refinement: (iv) finally, intergranular fracture occurs. The bcc → hcp transformation follow the Burgers path in all cases. The role of twinning and dislocation formation is minor compared to that of phase transformation. Film thickness does not play a major role in the sequence of occurring film transformations. However, thinner films allow for a faster nucleation of the new phase. Nucleation starts at the surface; the role of homogeneous nucleation in the film interior is minor.