A high damping capacity is considered as one of the important functional properties of shape memory alloys. Those properties are related to a thermoelastic martensitic transformation. As a consequence of this transformation, the internal friction or damping can be investigated for three different states: 1. during thermal transformation cycling, 2. during martensite induced strain cycling at co...

The microstructure and martensitic transformation in the Ni-36.3Al-0.1Y (in at.%) alloy were investigated after ho~nogenisation and plastic deformation by hot upsetting at 1100°C. The alloy exhibited large, recrystallised grains of the Ni-A1 P phase wit11 spl~erical precipitates inside the grains and a thin layer of other phases located at the grain boundaries. The SEM and EDX analysis showed t...

The (001)-oriented surface of epitaxial off-stoichiometric Ni–Mn–Ga ferromagnetic shape memory alloys was studied in both austenitic and martensitic phases. Scanning tunneling microscopy (STM) imaging of the austenitic surface reveals a well-ordered and reconstruction-free surface exhibiting predominantly Mn–Ga termination. We found that only one of the two atomic species (Ga or Mn) is visible ...

The effect of different distributions of y-phase precipitates on the martensitic transformation of p Cu-Zn-A1 single crystals is reviewed. The changes of transformation temperatures brought about by the precipitates are related to the changes of the free energy terms included in the thermoelastic balance. In the same way, the evolution of the transformation in samples containing precipitates su...

Phase transformation tensor Q in the constitutive equation pmposed by Tanaka has been evaluated by employing experimental data of TiNi alloys in a constrained recovery process. It demonstrates that the absolute value of Q for the consmined recovery process is typically about 0.6 0.7 x103 MPa, which is much smaller than that for the stress induced martensitic transformation (typically 2.5 3.5 x1...

In the present work an experimental-numerical approach is used to study the thermo-mechanical behaviour of NiTi wire for defining what parameters are the most important in actuator designing. Tests were carried out heating, by an electrical current, a wire having a diameter of 150 m, under constant stresses of 200 MPa. Data concerning strain, applied current and voltage are acquired during the ...

Some of the most interesting and technologically important solid-solid transformations are the first-order diffusionless (martensitic) transformations that occur in certain ordered multi-atomic crystals. These include the reconstructive martensitic transformations, where no group-subgroup symmetry relationship exists between the phases, found in steel and ionic compounds such as CsCl. Additiona...

Submitted for the MAR07 Meeting of The American Physical Society Electronic Structure Theory of the Structural Transformation of Shape Memory NiTi1 NICHOLAS HATCHER, OLEG KONTSEVOI, ARTHUR FREEMAN, Northwestern University — The unique property of displacive phase transformations has created much interest in the study of martensitic materials. Among them, NiTi finds a wide range of applications ...