DETECTION OF THE R-PHASE IN Ni-Ti SHAPE MEMORY ALLOYS

In NiTi based shape memory alloys, a transient phase, called R-phase, occurs on cooling before the martensitic transformation. The detection of the R-phase seems to be dependent on various parameters and particularly on experimental technique. Indeed, in this study we examine the sensitivity of various methods as internal friction, transmission electron microscopy, X-ray diffraction, electrical resistance, differential scanning calorimetry. However thermal treatments and chemical content are also taken into account