  Shape memory alloys inherit their macroscopic properties from their mesoscale
microstructure originated from the martensitic phase transformation. In a cubic
to orthorhombic transition, a single variant of marten- site can have a
compatible (exact) interface with the austenite for some special lattice
parameters in contrast to conventional austenite/twinned martensite interface
with a transition layer. Experimentally, the phase compat- ibility results in a
dramatic drop in thermal hysteresis and gives rise to very stable functional
properties over cycling. Here, we investigate the microstructures observed in
Ti50Ni50-xPdx alloys that undergo a cubic to orthorhombic martensitic
transformation using a three dimensional phase field approach. We will show
that the simulation results are in very good agreement with transmission
electron microscopy observations. However, the understanding of the drop in
thermal hysteresis requires the coupling of phase transformation with plastic
activity. We will discuss this point within the framework of thermoelasticity,
which is a generic feature of the martensitic transformation.
