Tw. Shield, ORIENTATION DEPENDENCE OF THE PSEUDOELASTIC BEHAVIOR OF SINGLE-CRYSTALS OF CU-AL-NI IN TENSION, Journal of the mechanics and physics of solids, 43(6), 1995, pp. 869-895
Uniaxial tension experiments were performed on single crystals of Cu-1
3.95 wt% Al-3.93 wt% Ni. Three specimens were prepared with tension ax
es in directions that were chosen based on Schmid law calculations usi
ng the 96 possible Austenite-Martensite (A-M) interface orientations i
n 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 predict
ed tension transformation stress. Specimen number two was oriented 15
degrees from [111] direction and has a [1,1,1.73] tensile axis directi
on. The third specimen has the [111] direction as its tensile axis, wh
ich is the direction of maximum tensile transformation stress. A stron
g relationship is found between the mechanical behavior of the specime
ns in tension and their observed microstructure. Specimen one exhibits
an extremely flat stress plateau during transformation and almost no
hysteresis. The microstructure observed in this specimen consists of t
wo nearly perpendicular A-M interfaces that interact to form an X-stru
cture that results in a purely uniaxial deformation. This microstructu
re is completely reversible and seems to present no restriction on the
motion of either interface. Specimen two was observed to have only a
single A-M interface after transformation. This interface appears to p
reclude the formation of any other interfaces. Specimen three required
five times the normal stress of that needed to transform specimen one
. This specimen also exhibited a large amount of hysteresis. The micro
structure observed consisted of two A-M interface systems that meet to
form wedges. Because the interfaces must end at the wedge apex, the f
ormation of the wedges resulted in a kinematic coupling between the tw
o A-M interface systems. The amount of coupling between the interfaces
in the microstructure correlates to the amount of hysteresis observed
.