Nanoindentation characteristics of in-situ formed Cu-Hf-Ti-Ag-Ta bulk metallic glass composites

Multi-component Cu-Hf-Ti-Ag-Ta bulk metallic glass (BMG) composites containing in situ formed Ta-rich dendrites were prepared successfully. Composition analysis shows that about 7-11 at% component elements (Ti, Cu and Ag) were detected in Ta-rich dendrites, but no Hf element was found. With increasing the volume fractions of the dendrites (V_dendrite). the content of component elements dissolving into Ta-rich dendrites decreases from 11.35 at% for V_dendrite = 4.3% and 7.97 at% for V_dendrite = 26.5%. Indentation testing was also performed to evaluate the properties of the composites. With increasing V_dendrite, the hardness of the dendrites decreases from 6.0 GPa for x = 3 to 5.21 GPa for x = 12, and its elastic modulus increases from 151.2 GPa for x = 3 to 156.9 GPa for x = 12. The hardness and elastic modulus of the glassy matrix also decrease from 9.66 GPa and 148.7 GPa for x = 0 to 9.36 GPa and 137.4 GPa for x = 12 with increasing the precipitation of the dendrites. The variation of the properties is due to the compositional change originating from the opposite behavior of Hf and Ti elements to dissolve into the dendrites.