Improvement of shape memory effect via strengthening austenite by virtue of thermally activated process in FCC-type metastable multicomponent alloys

FCC-type multicomponent alloys exhibit exceptional high strength during cryogenic deformation owing to thermally activated process. Inspired by this, we proposed that the γ-austenite of Fe-Mn-Cr-Si-Ni metastable multicomponent alloys would be strengthened by taking advantage of thermally activated process, and their shape memory effect would be improved by means of cryogenic deformation. As expected, the shape memory effect of Fe54.6Mn20.7Cr9.4Si10.5Ni4.8 metastable multicomponent alloy was enhanced by the cryogenic deformation of 77 K because γ-austenite was drastically strengthened by the remarkable increment of thermally activated stress. However, the shape memory effect of Fe61.6Mn14.2Cr8.8Si10.5Ni4.9 and Fe57.3Mn18.0Cr9.4Si10.5Ni4.8 metastable multicomponent alloys was not improved by cryogenic deformation. It is ascribed to that the occurrence of ε → α′ martensitic transformation would deteriorate the shape memory effect and thus weakened the positive effect of thermally activated process. It should be an effective way to improve the shape memory effect of other metastable multicomponent alloys by virtue of thermally activated process.