The impact of Co micro-alloying on low temperature specific heat capacity and the relaxation processes in a model Pd40Ni40P20 bulk metallic glass in both as-cast and cold-rolled states was investigated. In addition to an excess (Boson) peak at low temperatures of about 12 to 14 K, a magnetic heat capacity anomaly in the Co alloyed glass below 10 K was observed. The measured Boson peak heights and the fictive temperatures both advocate a much faster β relaxation in the micro-alloyed glass. Yet, the micro-alloying does not measurably affect the enthalpy associated with α-relaxation. The impact of shear bands on the thermodynamic properties of the micro-alloyed glass is discussed.
The influence of Co micro-alloying (1 at. %) on the shear band diffusion and the relaxation processes in a model PdNiP bulk metallic glass is investigated. The shear bands are induced by one-pass cold-rolling. In addition to a fast shear band diffusion branch (Dsb≃10−16m2/s at 473 K), with the diffusivity being similar to that observed for the cold-rolled standard Pd40Ni40P20 composition, an ultrafast diffusion branch (Dsb≃10−14m2/s at the same temperature) is found to exist in the micro-alloyed glass. Combined with previously reported observations of faster relaxation of both the Boson peak height and the fictive temperature, the results indicate that Co micro-alloying affects the excess free volume distribution and thus changes the potential energy landscape of the glass, introducing a higher number of local atomic arrangements prone to the formation of shear transformation zones under plastic deformation.
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