Strategy for pinpointing the formation of B2 CuZr in metastable CuZr-based shape memory alloys

In the present work we systematically investigated the formation of high-temperature B2 CuZr intermetallics in 36 metastable CuZr-based alloys. The results demonstrate that a B2 CuZr solid-phase transformation exists at high temperature. Based on continuous heating transformation diagrams the CuZr-based alloys can be classified into three different types, related to the precipitation and stability of the B2 phase. A new prediction strategy for the formation of different sized CuZr-based shape memory bulk metallic glass composites (BMGC) is proposed by considering the competition between vitrification, the precipitation of metastable B2 CuZr and room-temperature equilibrium phases. These insights are condensed into a new parameter, K = T-f/T-L, where T-f and T-L, are the final temperature of the B2 CuZr phase transformation during heating and the liquidus temperature of the alloy, respectively, which is suggested to predict and select a compositional region of different sized BMGC. This new approach could be of great significance for the development of metastable CuZr-based shape memory alloys with enhanced deformability. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.