Effect of Alloying Additions on the SFE, Neel Temperature and Shape Memory Effect in Fe-Mn-Si-based Alloys

Abstract

A range of Fe-Mn-Si-based shape memory alloys has been investigated to examine the interplay of composition, stacking fault probability (SFP) and Neél temperature on the shape memory effect (SME). It has been found that the SFP (inversely proportional to stacking fault energy) showed little correlation to the SME for the range of alloy compositions examined. Further, the Neél temperature was not found to exhibit a significant effect on the SME. The addition of interstitial elements, however, was found to markedly decrease the SME.

Large recovery strain in Fe-Mn-Si-based shape memory steels obtained by engineering annealing twin boundaries

“…Therefore, increasing the SFE reduces the density of the TBs. This explains the result of Stanford et al 11 , that is, the RS increases with the rise of the SFE in Fe-29.9Mn-6Si-4.6Cr, Fe-28.4Mn-6Si-6.1Ni and Fe-33.7Mn-6Si steels. Unfortunately, the SFE must be lower than a certain threshold value to make the SIEM take place preferentially 34 .…”

“…For the bending test, the specimen was bent around a mould with different radii to 180°at 293 K or at M s þ 10 K for applying a specific amount of pre-strain to the specimen. The pre-strain e was taken as the maximum tensile strain at the outer edge of the sample thickness, and is determined by the equation: e ¼ t/(2R þ t), where R is the bend radius and t is the sample thickness 11 . The bent samples were photographed and then recovery annealed at 773 K for 15 min for shape recovery.…”

“…Unfortunately, Ti-Ni-based alloys are very expensive owing to their low productivity and the high-cost fabrication caused by the expensive alloy ingredients and their low cold workability 4 . Therefore, low-cost polycrystalline shape memory steels (SMSs), such as Fe-Mn-Si [5][6][7][8][9][10][11][12][13][14][15] , Fe-Ni-C 16 and Fe-Ni-Co-Ti [17][18][19] , have been developed. Recently, a major breakthrough in the superelasticity has been made in the polycrystalline SMSs.…”

Temperature dependence of critical stress and pseudoelasticity in a Fe–Mn–Si–Cr pre-rolled alloy

“…The accepted mechanism for the fcc/hcp transformation considers stacking faults in fcc as nucleation sites for the martensite [8]. At room temperature, the stacking fault energy (SFE) is low [14,20], so existing stacking faults are expected to be rather long and new ones are easy to nucleate. When external stress is applied on the samples, existing stacking faults grow by accumulating elastic tension around.…”

Characterization of phases in an Fe–Mn–Si–Cr–Ni shape memory alloy processed by different thermomechanical methods

“…Although up to 3 vol.% of the grain-boundary precipitates were generated by isothermal ageing in the range of 500-800°C, it was found not to markedly affect the mechanical properties or the shape memory behaviour. Afterwards, Stanford et al [15] examined the interplay of composition, stacking fault probability (SFP) and T N on the SME for a range of Fe-Mn-Sibased SMAs. The SFP (inversely proportional to stacking fault energy) showed little correlation to the SME for the range of examined alloy compositions.…”