Multiple martensitic transformation induced by coherent precipitation in NiTiCo melt spun ribbons

Abstract

A study of a multiple martensitic transformation observed in melt spun ribbons cast with a relatively low melt temperature is presented. Transmission electron microscope (TEM) investigations allow the identification of fine plate-like precipitates as a metastable Ti2Ni phase. Analysis of high resolution microscope (HREM) images reveals the presence of a strain field in the matrix surrounding the precipitates which promote the martensitic transformation. Grow and loss of coherency of these precipitates coincides with disappearance of the higher temperature martensitic transformation. Attribution of the multiple transformation to this precipitation is discussed.