Influence of the presence of pre-existing thermal ε-martensite on the formation of stress-induced ε-martensite and on the shape memory effect of a FeMnCrSiNi shape memory alloy

Abstract

At present, many investigations are done on Fe-Mn-based shape memory alloys because of their particularly good one-way type shape memory effect and their low cost. With addition of Cr and Ni, it is possible to reach a good corrosion resistance, which confers to this type of alloys a commercial significance. The shape memory effect is associated with the formation of stress-induced [var epsilon]-martensite by deformation of an austenitic ([gamma]) sample. The reversion by heating of the [var epsilon]-martensite provides the shape memory effect. It is generally admitted that the presence of thermal [var epsilon]-martensite before deformation has a negative influence on the formation of the stress-induced martensite and on the shape memory effect. The authors' purpose is to evaluate the real influence of the pre-existing thermal [var epsilon]-martensite on the formation of the stress-induced [var epsilon]-martensite, its recovery and on the shape memory effect.