Shape Recovery in Stainless FeMnSiCrNi(-Co) SMA Processed by ECAE

Abstract

Stainless shape memory steel presents reasonable shape recovery but lower than the traditional NiTi shape memory alloys (SMA). However, recent results have shown that the shape recovery could be improved by decreasing the austenitic grain size. The present work describes the influence of the austenitic grain size on the shape recovery in stainless shape memory steel deformed by equal channel angular extrusion (ECAE) using a die intersection angle of 120o. Two alloys, FeMnSiCrNi and FeMnSiCrNiCo, were deformed by 1 ECAE pass and then they were compared in the deformed state; deformed and annealed in different temperatures for 1 h, resulting different grain sizes. Both alloys were evaluated by compression tests and the results shows an increase in total shape recovery related to grain size decrease. The best total shape recovery was 73% after a pre-strain of 4% for FeMnSiCrNi alloy.

ECAE processed NiTi shape memory alloy

“…Regarding thermo-mechanical processing, equalchannel angular extrusion 3 has been successfully applied to modify some properties of the shape memory materials [4][5][6][7] . Using ECAE process [8][9][10][11][12][13][14][15][16] , some studies have been done in NiTi SMA with respect to microstructural characteristics related to the change of the direct (B2→B19') martensitic transformation to intermediate B2→R martensitic transformation.…”

Is it Possible to Use Rolling Methods to Improve Textures on Fe–Mn–Si Shape Memory Alloys?

“…Looking for shear texture, many authors studied the effect of various rolling techniques as symmetric, asymmetric, continuous, snake, and reversed rolling in different materials . Equal Channel Angular Extrusion (ECAE), is also a fundamentally shearing deformation process, used for developing characteristic textures on many metals and alloys …”