STRUCTURAL STUDY OF Fe-Mn-Si AND Fe-Mn-Cr SHAPE MEMORY STEELS

Transformation Reversibility in Fe-Mn-Si Shape Memory Alloy

The change of the surface relief associated with stress-induced epsilon martensite before and after the reverse transformation in an Fe-33%Mn-6%Si alloy (Msz264K) has been investigated. The permanent strain of a 2.7% tensile-strained specimen was 1.1% after the reverse transformation. In this specimen, a large part of surface relief still remained after heating to 623K (above Af). When five tra...

Production and Characterization of Stainless Steel Based Fe-Cr-Ni-Mn-Si(-CO) Shape Memory Alloys

It is well known that the Fe based alloys can exhibit shape memory effect due to the y to E martensitic transformation. The effect may not be as striking as observed in the NiTi alloy but it might become attractive fkom the practical point of view. In this work, two compositions of Fe-Cr-Ni-Mn-Si(-Co) stainless steel based shape memory alloy, prepared by the VIM technique, will be presented. Th...

The Effect of Mn-Depleted Surface Layer on the Corrosion Resistance of Shape Memory Fe-Mn-Si-Cr Alloys

In this work, we have examined Fe-Mn-Si-Cr alloys possessing a good shape memory effect due to a high Mn content (28 wt pct). The addition of Cr (5 wt pct) was made in order to give fairly good corrosion resistance to the alloy. But we have verified that even in moderately corrosive environments, the presence of chromium does not bear any passivation. On the other hand, we have found that the a...

Improvement of the shape memory effect of a Fe-Mn-Cr-Si-Ni by original thermomechanical treatments

Formation Process of Lamella Structures by Deformation in an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

For Fe-Mn-Si-Cr-Ni shape memory alloys, it was previously found by HREM study that the formation of the nanometric lamella structures consisting of f.c.c. and h.c.p. phase is very important to exhibit good shape memory effect. In the present work, the formation process of such lamella structures has been studied in detail. The results are as follows. The transformation is initiated by random fo...