Martensitic Phase Transitions in Nanocrystalline Materials

摘要

The martensitic transformation in Fe-Ni alloys (Ni content between 31 wt% and 36 wt%) was studied by means of X-ray diffraction and transmission electron microscopy in nanocrystalline specimens (polycrystals with a crystal size of 4 nm) as well as in a loose powder of 4 nm sized, isolated Fe-Ni crystals with the same chemical compositions as the nanocrystalline materials. The isolated crystals were embedded in pure paraffin. The result obtained indicates that a martensitic transformation does not occur in the nanocrystalline material because the formation of a martensitic nuclei is inhibited due to the small size of the crystals. The inhibition of a martensitic phase transition may be of technological interest for the generation of improved superconducting, ferromagnetic and ferroelectric materials. Keywords: Iron alloys nickel; Martensitic phase transitions; Nucleation; Nanocrystalline materials; Superconducting ferromagnetic ferroelectric materials. (EDC)