Uniaxial tension experiments were performed on single crystals of Cu-
13.95 wt% Al - 3.93 wt% Ni. Three specimens were prepared with
tension axes in directions that were chosen based on Schmid law
calculations using the 96 possible Austenite-Martensite (A-M)
interface orientations in this alloy. Specimen number one was chosen
to have a tensile axis of [2.43,1,0] which results in a very near
minimum value for its predicted tension transformation stress.
Specimen number two was oriented 15 degrees from the [111] direction
and has a [1,1,1.73] tensile axis direction. The third specimen has
the [111] direction as its tensile axis, which is the direction of
maximum tensile transformation stress. We find a strong relationship
between the mechanical behavior of the specimens in tension and their
observed microstructure. Specimen one exhibits an extremely flat
stress plateau during transformation and almost zero hysteresis. The
microstructure observed in this specimen consists of two nearly
perpendicular A-M interfaces that interact to form an X-structure that
results in a purely uniaxial deformation. This microstructure is
completely reversible and seems to present no restriction on the
motion of either interfaces. Specimen two was observed to have only a
single A-M interface after transformation. This interface appears to
preclude the formation of any other interfaces. Specimen three
required five times the normal stress that needed to transform
specimen one. This specimen also exhibited a large amount of
hysteresis. The microstructure observed consisted of two A-M
interface systems that meet to form wedges. Because the interfaces
must end at the wedge apex, the formation of the wedges resulted in a
kinematic coupling between the two A-M interface systems. This
coupling is a contributor to the observed hysteresis.