Effects of equal channel angular extrusion and aging treatment on R phase transformation behaviors and Ti3Ni4 precipitates of Ni-rich TiNi alloys

Ni-rich TiNi alloys were subjected to the effect of multiple equal channel angular extrusion (ECAE) treatments by BC path at 500 °C. The characteristics of R phase transformation in aging treatment were dissimilar in the appearance and the temperature range to those counterparts induced by ECAE treatments. The fine lens-like shape Ti3Ni4 particles precipitated mainly in the regions of near grain boundaries and on the tangled grain boundaries after ECAE treatments. The effects and mechanisms of aging treatments and ECAE treatments on R phase transformation behaviors and Ti3Ni4 precipitates were investigated and discussed.

► The characteristics of R phase transformation in aging treatment are very different with those counterparts induced by ECAE treatments.
► R transformation curves were sharp and no obvious change in aging treatment for the change of internal stress fields resulted from Ti3Ni4 precipitates.
► However, they changed distinctly and exhibited in a wider temperature range for the grain refinement and energy accumulation that produced in ECAE processes.