Computer simulation of martensitic growth

Surface Science 144 (1984) 308 North-Holland. Amsterdam

308

COMPUTER D.M.

SIMULATION

HAEZEBROUCK,

Mossuchusetrs

Received

Instrtute

1 November

OF MARTENSITIC

G.B.

of Technology,

OLSON Cur&ridge,

GROWTH *

and M. COHEN Mussuchusetts

02139,

USA

1983

A model for the growth of a single martensitic particle is developed, incorporating the interrelations of thermodynamic driving force, intrinsic interfacial mobility, heat transfer, elastic strain energy, and rate- and size-dependent growth

plastic

accommodation.

Conditions

via interface/plastic-zone

martensitic time of nucleation

growth in Fe-31Ni

- 0.1 ps. Although

to cessation

are examined.

at its h4, temperature

the condition

at the plate periphery

leading

interactions

predicts

for accommodation

of radial

Simulation

of

a total growth slip dislocation

is met at a plate radius of - 2 pm, a plastic

zone does not immediately form due to the high strain-rate radial interfacial velocity of 1.4 X lo3 rns- ‘. A deceleration

associated with a due to heating at

the plate tip eventually brings the radial velocity down to a critical level where extensive plastic accommodation occurs at a plate radius of 80 pm, abruptly halting radial growth. This is followed by a slower stage of plate thickening associated with cooling of the broad interfaces. A similar growth simulation for a lath-forming

Fe-24Ni

alloy predicts

immediate

plastic accommodation

when

dislocation nucleation occurs. The major portion of the growth event occurs in a plastic state, and ceases at a radius of 12 pm. The results suggest three basic modes of martensitic growth termed fully elastic, elastic/plastic, and fully plastic; these growth modes are likely to underlie the well-known kinetic and morphological

* This research

transitions

is supported

in martensitic

by the National

transformations.

Science Foundation.

0039-6028/84/$03.00 0 Elsevier Science Publishers (North-Holland Physics Publishing Division)

B.V.