Crystallization and mechanical properties of the NiNb(ZrTi)Al amorphous alloys with 10 and 25 at % of Nb and 3 to 7 at % Al content

Abstract

The results of the investigations of alloys of compositions Ni58Nbx(ZrTi)39-xAly and Ni58Nbx(ZrTi)32-yAly with x = 10, 25 and y = 3, 7 respectively, are presented. The structure of the all melt spun ribbons was amorphous, however the crystallization process proceeded in a very different way in the ribbons with x = 10, y = 7 and ribbons with x = 25 and y = 3. In the first compositions typical primary crystallization of the 50 nm grains of the NiTi(Zr) cubic phase was observed while the ribbons containing 25 at.% of Nb and 3 at.% of Al revealed very stable thermally amorphous phase, nano-crystallizing at the range of primary crystallization but preserving large fraction of the amorphous phase high above the primary crystallization temperature. The tensile curves were determined for ribbons of both compositions and were different, but revealed quite large range of the plastic elongation. The HREM experiments did not reveal any crystallization in the shear bands, after the fracture of the ribbons.