Characterization of mechanical properties and adhesion of Ta-Zr-Cu-Al-Ag thin film metallic glasses

This study aims to develop a new Ta-Zr-Cu-Al-Ag thin film metallic glass (TFMG). The Zr-Cu-Al-Ag TFMGs were fabricated by co-sputtering of a Zr-Cu-Al-Ag bulk metallic glass target and a 99.9at.% Ta target, which was controlled under various DC power. A bipolar pulsed DC power unit was connected to the Zr-Cu-Al-Ag bulk metallic glass (BMG) target to avoid arcing. The chemical compositions of Ta-Zr-Cu-Al-Ag TFMGs were examined by an electron probe microanalyzer (EPMA). Nanoindentation and nanoscratch tests were adopted to evaluate the hardness, elastic modulus and adhesion properties of the TFMGs. The amorphous structures of all TFMGs were characterized by the X-ray diffractometry and transmission electron microscope. It was found that the Ta content ranging from 26 to 63at.% played an important role in the mechanical properties of the TFMGs. Abrupt enhancements of the hardness and elastic modulus were observed for this Ta-based TFMGs as compared with the Zr-Cu-Al-Ag TFMG. Relative atomic distance calculated from the XRD patterns reached a good agreement with the trend of variation of elastic modulus. The values of critical loads, L_C1 and L_C2, increased with Ta contents in the Ta-Zr-Cu-Al-Ag TFMGs. In addition, the lighter and shorter crack was found for the Ta-Zr-Cu-Al-Ag TFMGs with higher Ta content. The crack propagation resistance (CPR) value was applied to probe the toughness of TFMG semi-quantitatively, revealing that TFMG with 63at.% Ta possessed a CPR value six times higher than that of the TFMG with 26at.% Ta.