BRANCHING OF TWINS NEAR AN AUSTENITE TWINNED-MARTENSITE INTERFACE

We study the role of surface energy in determining twin width near an austenite-twinned-martensite interface. We find that there are two distinct regimes, depending on the relative values of the elastic moduli, surface energy density and grain size. In the first regime the twin width w is constant, of order L1/2, where L is the grain size. In the other regime the twin width is not constant; rather, it varies as l2/3, where l is the distance to the austenite. Most prior analyses have captured only the first regime, and it seems to be the one most commonly observed. However, twin branching consistent with our second regime has been observed in some materials.