Microstructure, shape memory behavior and mechanical properties of hot rolled Fe-17Mn-5Si-5Cr-4Ni-0.3C-1Ti shape memory alloy

The relationship between microstructure, shape memory behavior and mechanical properties of a hot-rolled Fe-17Mn-5Si-5Cr-4Ni-1Ti-0.3C (wt.%) alloy was investigated. The microstructure of the alloy consisted of TiC precipitates regardless of the post aging heat treatment. It was found that the TiC precipitates appeared in two different sizes of a few micrometer and approximately 5 nm. The microstructural analyses showed that both the coarse and nano-sized TiC particles are stable during the aging heat treatment. The nano-sized TiC did not dissolved nor further grow during 600 degrees C aging heat treatment. The micromechanical in-situ tensile test results revealed that the nano-sized TiC rather than coarse TiC facilitate the stress induced gamma to epsilon phase transformations. The alloy in the as-rolled state without any aging heat treatment showed a relatively good recovery behavior and there was no remarkable enhancement in shape recovery behavior by aging heat treatment. This is explained by the nano-sized TiC that is already distributed in the as-rolled microstructure without aging heat treatment.