Abstract：To know the origin of shape memory effect in Co-Ni alloys showing ε martensitic transformation, different amounts of thermal-induced ε martensite were obtained before deformation through controlling the deforming temperatures. The evolutions of the pre-existing thermal-induced ε martensite and its effect on stress-induced ε martensitic transformation were studied during deformation by OM and XRD, and the shape memory effect was measured by bending method. The results showed that the shape memory effect of Co-Ni alloys resulted from the stress-induced ε martensitic transformation, rather than the coalescence of thermal martensite. The low yield strength accounted for its poor SME. The pre-existing thermal ε martensite can increase the yield strength and thus enhance shape memory effect in Co-Ni alloys.
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2014, Vol. 21 
