HIGH-PRESSURE STUDY OF Ti50Ni25Fe25 POWDER PRODUCED BY MECHANICAL ALLOYING

Abstract

A nanostructured Ti 50 Ni 25 Fe 25 phase (B2) was formed by mechanical alloying and its structural stability was studied as a function of pressure. The changes were followed by X-ray diffraction. The B2 phase was observed up to 7 GPa, and for larger pressures, the B2 phase transformed into a trigonal/hexagonal phase (B19) that was observed up to the highest pressure used (18 GPa). Besides B2 and B19, a segregation of elemental Ni and the formation of FeNi 3 were observed. With decompression, the B2 phase was recovered. Values of bulk modulus for the B2, B19, elemental Ni and FeNi 3 phases were obtained by fitting the pressure dependence of the volume to a Birch-Murnaghan equation of state (BMEOS).