Synthesis and characterization of metallic crystalline - amorphous Cu-Zr composites

Abstract

Commercial applications of bulk amorphous metallic glasses are restricted due to a sudden brittle failure mode. To overcome this limitation, a toughening strategy in metallic glasses based on the introduction of large quantities of crystalline – amorphous (C-A) interfaces has been widely proposed, e.g., to form various types of C-A composites. Accumulative roll boding (ARB) technique as a cost-effective synthesis method that can be potentially used for producing bulk sized C-A composites, has thus received significant attention in recent years. However, previous studies on expensive highly pure Cu-Zr multilayers did not show neither significant amorphization nor alloying during the ARB process. This research aims to modify the ARB technique for the synthesis of cost-effective bulk C-A composites based on commercially available Cu-Zr sheets. The proposed ARB guideline provides conditions which ensure mechanical alloying and amorphization of CuZr phases in a commercial Cu-Zr alloy system. The composition and structural analysis revealed that intermediate annealing facilitates the formation of several amorphous and crystalline CuZr phases during the ARB process. Additionally, mechanical tests based on nanoindentation indicated that the CuZr phases, whether they are crystalline or amorphous, show a higher hardness and elastic modulus than pure Cu and Zr phases. Numerical molecular dynamics technique was also employed to study the fundamental structure-property relation at the C-A interface. Based on the results, the interfacial energy demonstrated a weak dependence on the crystalline orientation. In contrast, the plasticity of C-A composites was mainly determined by crystalline orientation at the C-A interface.