Microstructural tailoring and improvement of mechanical properties in CuZr-based bulk metallic glass composites

A strategy for homogenizing the B2 CuZr phase in CuZr-based bulk metallic glass (BMG) composites based on inoculation is presented. The sizes and distribution of B2 CuZr particles can be effectively homogenized by Ta additions in rapidly solidified Cu47Zr48-xAl5Tax (0 <= x <= 1, at.%) alloys. Mechanisms of the homogenizing effect were investigated by analyzing the microstructures of the composites as well as the nucleation and growth processes of the B2 CuZr phase. Mechanical properties of the alloys were significantly improved by the uniform B2 CuZr particles under both compression and tension. The inhibition on the propagation of shear bands and cracks by the ductile crystals and deformation-induced martensitic transformation of the B2 phase was proved to account for the superior tensile properties. Fracture mechanisms were proposed to correlate the tensile fracture behaviors to microstructural features of the alloys. Furthermore, the tensile plastic strain was quantitatively modeled by using the empirical microstructural element body approach as well as percolation theory. This study has important implications for the development and structural applications of high-performance BMG composites. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.