Martensites
Martensites are metastable configurations,
typically formed by
quenching a crystalline solid past a structural transition.
Structurally
they are quite distinctive, having a well defined substructure
consisting
of regular arrays of either twins or slipped regions occurring over
length
scales much larger than atomic dimensions. Also the nucleation and
growth
kinetics of Martensites differ in-general from that of the equilibrium
phase. Often their formation is athermal viz. the amount
of Martensite produced at any temperature is independent of time and in
many
system the Martensite front grows ballistically at speeds comparable to
the speed of sound. Martensites have been extensively studied by
metallurgists
because of their varied technological applications ranging from the
heat-treatment
of steels to the fabrication of smart structureswhich can be programmed
to respond to external stimuli by changing their shape. The overall
objective
of our research on Martensites is to understand and interpret these
empirical
observations as well as build up a consistent picture of Martensite
phenomenology
from the point of view of non-equilibrium statistical mechanics.
Publications:
- M. Rao and S. Sengupta, Nucleation of Solids in
Solids: Ferrites and Martensite
Phys. Rev. Lett.
91, 045502 (2003); Erratum: Phys.
Rev. Lett. 91, 209901 (2003).
- Surajit Sengupta and Madan Rao, Statistical mechanics
of nucleation
in solids: a kinetics driven morphological transition, Physica
A, 318, 251 (2003).
- Madan Rao and Surajit Sengupta, A model solid-state
structural
transformation: Tetragonal to Orthorhombic. arXiv/cond-mat/0106058
(2001).
- M. Rao and S. Sengupta, Arrested states in solids, Curr.
Sc. 77, 382 (1999).
- Madan Rao and Surajit Sengupta, First Passage Times and
Time Temperature Transformation curves for Martensites,
arXive/cond-mat/
9709022 (1997).
- Madan Rao and Surajit Sengupta, Droplet Fluctuations in
the Morphology and Kinetics of Martensites,
Phys. Rev. Lett. 78, 2168
(1997).
- Madan Rao and Surajit Sengupta, Rao and Sengupta reply,
Phys. Rev. Lett. 76,
3235 (1996).
- Madan Rao, Surajit Sengupta and H. K. Sahu, Kinematic Scaling and
Cross -over to Scale Invariance in Acicular Martensites,
Phys. Rev. Lett. 75, 2164,
(1995).
- Madan Rao and Surajit Sengupta,
Kinematic
Theory for Scale Invariant Patterns in Acicular Martensites,
Physica A 224, 403, (1996).
- Madan Rao, Surajit Sengupta and H. K. Sahu, Emergence of Scale
Invariance in Martensite Growth, Non Linear Phenomenona in
Materials Science III, Solid State Phenomena Vol. 42-43, G.
Ananthakrishna, L.P. Kubin and G. Martin, Eds. (SciTech Publications
Ltd. Switzerland, 1995). Proceedings of the Conference on Non Linear
Phenomenon in Materials Science, Bangalore, India, January, 1995.