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

Abstract

Abstract. 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. The results are good with shape recovery of 95% for a pre-strain of 4% after some training cycles. In terms of workability the alloys produced are worse than the usual AISI304. However, adjusting the thermo-mechanical processing, it is perfectly possible to produce wire as thin as 1,20mm in dia. or down.

O efeito do tamanho de grão austenítico no número de orientações das variantes de martensita em ligas inoxidáveis com efeito de memória de forma

“…Em trabalhos anteriores, havia sido mostrado que materiais com granulometria mais fina comparados àqueleas com granulometria grosseira apresentavam: (1) a tensão de escoamento a 0,2% de deformação (tensão necessária para induzir a martensita ε mecanicamente) era tanto menor quanto menor o tamanho de grão; (2) a fração volumétrica da martensita ε induzida mecanicamente para uma mesma quantidade de deformação macroscópica era tanto maior quanto menor o tamanho de grão e que a reversão dessa martensita no aquecimento (para recuperação de forma) era tanto maior quanto menor o tamanho de grão e (3) sem contar o efeito do treinamento, tinha-se uma recuperação de forma, após 4% de deformação por tração e posterior aquecimento, de, praticamente, 80% e 65%, respectivamente para as amostras A e B [Otubo, 1995a, 1995b, 1996c, 2002e Nascimento, 2002. A esses dados vêm se somar os dados apresentados nesse trabalho, mostrando que a amostra A com granulometria menor (média de 60µm) apresenta fração de martensita térmica induzida termicamente, após imersão em nitrogênio líquido, 3 vezes superior que a amostra B de granulometria grosseira (média de 180µm).…”

“…Na década de 90, iniciaram-se as pesquisas no desenvolvimento de ligas inoxidáveis, no sentido de sanar os problemas anteriormente citados a um custo razoável [Inagaki, 1992, Moriya, 1991e Yang, 1992a, 1992be 1992c. No Brasil, o estudo de ligas inoxidáveis com EMF iniciou-se em meados de 90, tendo gerado inúmeros trabalhos [Otubo, 1994a, 1994b, 1995a, 1995b, 1996a, 1996b, 1996c, 1999e 2002, Nascimento, 1999, 2002e 2003e Bueno, 2006]. …”

Influence of Austenite Grain Size on Mechanical Properties of Stainless SMA

“…As it has been shown in the earlier work 8) the transformations temperatures M S , A S and A F for this alloy are 312, 368 and 468 K (the grain size was not measured in that work). Therefore the alloy is partially martensitic at room temperature.…”

“…Ogawa and Kajiwara 7) who were the first to obtain 80% shape recovery after 4% strain without cycling, attributed the good shape recovery to formation of a mixed of FCC and HCP structures of nanometric scale. Later, Otubo et al 8) studied two stainless shape memory alloys, Fe-Mn-Si-Cr-Ni-C and Fe-Mn-Si-Cr-Ni-Co-C, and showed that, after the same thermomechanical treatment, the alloy without Co addition, always showed a better shape recovery, almost 80% shape recovery after 4% tensile strain, while the Co-containing alloy displayed around 65% shape recovery for the same amount of pre-strain. Besides the difference in chemical composition that could influence the shape recovery, another striking difference was in their grain size.…”

Corrosion behavior of shape memory stainless steel in acid media

“…In order to develop these Fe-Mn-Si SMAs, much effort has focused on improving the SME and the corrosion resistance. In this context, additions of chromium (Cr), nickel (Ni), cobalt (Co) and other elements to the Fe-Mn-Si SMAs have been accomplished successfully, resulting in an improvement in the SME and corrosion resistance [7][8][9][10]. The newly developed Fe-Mn-Si-Cr-Ni-(Co) SMAs are called shape memory stainless steels (SMSS) and are suitable for constrained recovery applications in various industrial sectors such as the chemical, petrochemical and construction industries.…”