Effect of a minor element with a large mixing enthalpy difference on the plasticity of amorphous alloys

In this study, we investigated the role of a minor alloying element in improving the plasticity of amorphous alloys. The plasticity of the amorphous alloys, Cu_60−xZr₃₀Ti₁₀Be_x, was drastically improved with increasing amount of Be and reached a maximum of 23% at Cu₅₃Zr₃₀Ti₁₀Be₇. It was observed that an atomistic-scale phase separation existed within the alloy, which resulted from the large difference in mixing enthalpy between the binary pairs (Be–Cu, Be–Zr). This atomistic-scale phase separation resulted in an open structure in which atomic rearrangements in the form of the creation of free volume and crystallization were facilitated during deformation. Here we discuss the origin of the enhanced plasticity by clarifying the effect of an additional element, whose mixing enthalpies with the major elements are significantly different, on the structural change of the amorphous alloy.