Evaluating the Room Temperature ECAP Processing of a NiTi Alloy via Simulation and Experiments

The NiTi alloys are generally considered hard-to-deform materials when processing by equal-channel angular pressing (ECAP) at room temperature. Nevertheless, it is shown by experiment that a NiTi alloy may be successfully processed by ECAP for up to two passes using a core-sheath configuration. Three-dimensional finite element simulations were used to more fully evaluate the flow behavior after the first and second pass of ECAP. The values of the microhardness were recorded across transverse directions within the cores and the results show that the imposed strain both decreases by comparison with the processing of conventional sheath-free NiTi billet and increases by increasing the dimensions of the core. The lower areas of the cores undergo less deformation than the upper areas after successful ECAP processing but the imposed strain, and thus the microhardness values, become homogeneously distributed on the longitudinal planes after two passes of ECAP.