Study of the “All-Round-Effect” generated by aging in traction in a Ni rich TiNi shape memory alloy

Following aging under stress, Ni-rich TiNi shape memory alloys are subject to a two-way shape memory effect known as the “All Round Memory Effect” (ARME). The latter causes a sample to return to its high temperature shape during heating after being spontaneously deformed on cooling during martensitic and R-phase transformations. This effect has been thoroughly studied for stresses in bending. In this work, we were able to generate ARME with tensile stresses, making it possible to make more quantitative measurements of the effect. Application of a static stress opposite spontaneous deformation during cooling also allowed quantifying the magnitude of internal stresses caused by Ti3Ni4 coherent precipitates during aging.