The effect of Mo addition on the microstructural evolution and mechanical properties of Zr-Cu-based metallic glass thin films

Abstract

Ternary Zr-Cu-Mo metallic glass thin films (MGTFs) with various Mo contents were synthesized on Si (100) wafers and AISI 304 stainless steel substrates by a magnetron co-sputtering technique, using Zr64Cu36 and Mo targets in an Ar gas environment. The effects of Mo addition in a binary Zr64Cu36 MGTF were investigated, with regard to the microstructural evolution and mechanical properties of Zr-Cu-Mo thin films. Instrumental analyses, such as EPMA, XRD, and HR-TEM revealed that Zr-Cu-Mo films with an Mo content below 38 at.% maintained the monolithic amorphous phase structure. However, when Mo content is added above 46 at.%, the Zr-Cu-Mo films begin to have nanocomposite structures of well-distributed Mo2Zr and Mo crystallites embedded in an amorphous matrix. The hardness and elastic modulus of amorphous Zr-Cu-Mo films showed nearly constant values of 10 GPa and 166 GPa, respectively, regardless of their Mo content. As Zr-Cu-Mo films have nanocomposite structures at a Mo content of 52 at.%, their mechanical properties showed increased hardness and elastic moduli of 17 GPa and 240 GPa, respectively. The Mo addition generally reduced the average friction coefficient of the ternary Zr-Cu-Mo thin films regardless of phase structure, which can be attributed to the effect of the Mo addition.