Phase formation and mechanical properties of Ti-Cu-Ni-Zr bulk metallic glass composites

Abstract

In this work, the glass-forming ability (GFA) and the correlation between the phase formation and the mechanical behaviour of Ti-Cu-Ni-based bulk metallic glass composites are discussed. The GFA increases with additions of CuZr to Ti-Cu-Ni alloys and composites with diameters ranging from 2 to 3 mm can be formed, which consist mainly of cubic shape memory B2 (Ti,Zr)(Cu,Ni) and an amorphous phase. The yield strength of the composites scales with the volume fraction of the B2 phase, following a rule of mixtures for values lower than 30 vol.% and the load-bearing model for higher values. The fracture strain reaches a maximum of 24% at around 30 vol.% of B2 (Ti,Zr)(Cu,Ni), in agreement with the "three-body element" model. A reduced ductility was obtained for the CuZr-richer composites, which is connected to precipitation of the brittle Cu2TiZr phase in the glassy matrix. This study provides important insights into the correlation between phase formation and plasticity in this new family of bulk metallic glass composites with large ductility. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.