Effects of density difference of constituent elements on glass formation in TiCu-based bulk metallic glasses

Glass formation is generally favored by a large atomic size mismatch among constituent elements, which usually leads to large density differences among them as well. During melting, elemental segregation occurs due to Stokes’ law and then inevitably affects glass formation. In this paper, such effects on glass-forming ability in a TiCu-based alloy system have been demonstrated. In the bulk glass-forming composition Ti₄₃Cu₄₂Hf₁₄Si₁, macroscopic segregation of Si was observed in the as-melted ingots and silicon was completely depleted in the as-cast rods. In another Ti₃₃Cu₄₇Ni₈Zr₁₁Si₁ alloy, nevertheless, the effects of density differences among the constituent elements were less severe. It was also confirmed that using proper pre-alloys could be an effective way in alleviating the side effects of the elemental segregation.