Martensite transformation entails a definite orientation relationship, a definite habit plane (the plane on which martensite plates form is also usually assumed to be an undistorted plane).
During this temperature interval between Ms and Mf, the interface, or habit plane does not move steadily and smoothly, but rather in a jerky fashion.
A Bain distortion, which forms the product lattice from the parent lattice, but which, in general, does not yield an undistorted plane that can be associated with the habit plane of the deformation.
One of the nice features of the Wechsler, Lieberman, and Read theory is that it shows quite clearly why the habit plane in marten-sitic transformations is usually irrational.
It is expected that AE source is of shear nature due to the generation of martensitic habit plane in this material.
The specimens showed the stress relaxation with appearance of habit plane on surface when tensile stress was applied to each specimen.
We can assume that the slip plane is replaced with the habit plane in the case of the shear deformation as shown in Fig.
We simulated the AE waves generated on the martensite habit plane using a shear-wave transducer (resonance frequency = 2.5 MHz).
As emphasized in the theoretical section, the connection between a single variant of martensite and the parent austenitic phase is provided by a twinned martensitic structure, which is able to satisfy the compatibility conditions both with the austenite (over the habit plane
) and with the single variant.
Type-(I) lamellae have the low energy habit plane as their lamellar interfaces, and have the same lamellar direction as the original primary lamellae.
In addition to [T.sub.1], additional strengthening arises from 3 other lath or plate-Like precipitates (S'-[Al.sub.2]CuMg, [eta]'-[Al.sub.2]Cu and an unknown phase), all lying on distinct habit planes in the matrix (Fig.
In order to identity martensites [[beta].sub.1]' or [[gamma.sub.1]' phase, we used the surface trace analysis with the [[beta].sub.1]' and [[gamma.sub.1]' habit plane
traces in the (100) stereographic projection [1, 4].