Formation, microstructure and mechanical properties of ductile Zr-rich Zr-Cu-Al bulk metallic glass composites

We examined the microstructure, phase stability, mechanical properties and deformation behaviors of cast (Zr0.58Cu0.42)(100-x)Al-x (x = 0, 3, 5, 7, 10) bulk metallic glass composites (BMGCs). With increasing Al content, the glass-forming ability of the new Zr-rich Zr-Cu-Al alloys gradually increases, enabling the fabrication of BMGCs for the alloys containing more than 3 at.% Al. The as-cast structure changes from Cu10Zr7 + CuZr2 for the Al-free base alloy to glass + crystal for the Al-added alloys. The new Zr-rich Zr-Cu-Al BMGCs exhibit a large fracture strain of similar to 3.4-7.8% and a high fracture strength of similar to 1731-1984 MPa under compression. The compressive fracture strain of Zr-rich Zr-Cu-Al alloys can be explained by the percolation theory. The (Zr0.58Cu0.42)(95)Al-5 composite containing similar to 70 vol.% crystalline phase possesses the largest plastic strain of similar to 6%, and fracture strength of over 1900 MPa under compressive condition. The superior plastic deformation capability under compression is related to the following factors: (1) The formation of three types of shear bands with distinct morphological characteristics, (2) the plastic deformation of B2-CuZr phase itself, together with stress-induced martensitic transformation from B2-Cu-Zr phase to B19' phase, and (3) the interaction between crystals and shear bands. The present results have implications for better understanding the deformation mechanisms of the Zr-rich Zr-Cu-Al BMGCs and for designing high-performance BMGCs with enhanced plasticity. (C) 2021 The Authors. Published by Elsevier B.V.