High corrosion-resistance Fe-Mn-Si-based alloys exhibiting nearly perfect shape memory effects

摘要

Recently our group has succeeded, by producing very small particles of NbC carbides in austenite, in improvement of shape memory effect (SME) of the low-cost conventional Fe-Mn-Si based SMAs to such an extent that the so-called "training" treatment is no longer necessary. It was also found that the shape memory properties of the Fe-Mn-Si based SMAs were further unproved by pre-rolling at 870K. The present paper describes similar improvement of shape memory properties of an Fe-15Mn-5Si-9Cr-5Ni-0.5NbC (mass %) by more convenient way of pre-extension at room temperature. This alloy is high corrosion-resistant (equivalent to SUS430) as well as low cost material, which is also one of the important requisites for industry application in various fields. A nearly perfect shape recovery (90%) of an initial 4% strain was achieved when the alloy was pre-extended 12% at room temperature and then aged at 1070K for 10min. The origin of this improvement of SME has been studied by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is concluded that uniform distribution of fine martensite plates with the same variant on the primary system is the key factor to obtain a perfect shape memory recovery.