COMPUTER-SIMULATION OF MARTENSITIC-TRANSFORMATION IN FE-NI FACE-CENTERED-CUBIC ALLOYS

The F.C.C. --> B.C.C. martensitic transformation in Fe-Ni alloys conta ining between 20 and 40 at.% Ni was studied using molecular dynamics s imulations. The interatomic interactions were represented using the em bedded atom method pseudo-monoatomic potentials, which were shown to r epresent correctly the relative stability of the F.C.C. and B.C.C. str uctures as a function of the nickel content. The simulation results de arly demonstrate the important role that crystal defects, such as the free surface or grain boundary, play in the formation of martensite. T his is consistent with the experimental observations, which suggest th at the martensitic nucleation is of a heterogeneous nature. The simula tion results further indicate the need for lattice invariant deformati on, such as twinning and slip, for the continued growth of martensite.