MECHANISMS FOR MARTENSITE FORMATION AND THE SHAPE MEMORY EFFECT.

Abstract

The present study shows that the lattice invariant shear by twinning or faulting is a consequence of the transformation mechanism which leaves residual dislocations in the interface, and this The depend on the plate thickness. In general the habit plane will be independent of the plate thickness only if the interface has no residuals in it, or if the residuals in the interface are of random sign, with an average strain of zero. The former would apply if the transformation dislocations are generated by a pole mechanism, or if k//1 is the slip plane of the host lattice, and the latter would apply if all the neighboring network dislocations, regardless of their sign, move to the martensite plate. This may be possible for thermal martensite but not likely for stress induced martensite, where only those dislocations which are favored by the applied stress field will move to the interface.