Effects of deformation strain and microstructure on shape recovery behavior in Ni-Al-Fe-Mn shape memory alloys

摘要

The shape recovery behavior in Ni-Al base shapememory alloy whose ductility is improved with Fe and Mnalloying has been investigated by using DSC, XRD and TEM. Onheating, the deformed alloys were experienced a double-stagerecovery process before they returned to the original shape : Thefirst-stage recovery occurred at lower temperature and the second-stage recovery take place at higher temperature. Increase of bend-ing or tensile strain affected total shape recovery such that it leadedto an increase of the second-stage shape recovery. The shaperecovery at a higher temperature, i.e., second-stage shape recoverywas attributed to the hinderance of β '?β transformation by thedislocations in β', martensite introduced during deformation.Possibly, the elastics stress field associated with dislocationswould hinder the motion of β'/β boundary. When the alloys werebended at the same strain, the second shape recovery increased withannealing at higher temperature because of the increase of volumefraction of the β' martensite in the alloys consisted of β' martensiteand γ phase.