Mechanical behavior and microstructure of Cu54Zr22Ti18Ni6 bulk metallic glass at elevated temperatures

The deformation and fracture behaviors of Cu54Zr22Ti18Ni6 (numbers indicate at.%) bulk metallic glass were characterized at various temperatures. Cu54Zr22Ti18Ni6 amorphous alloy exhibited a marginal plastic strain with the fracture strength of ∼2150 MPa. In Cu54Zr22Ti18Ni6, significant strengthening was observed after the interruption below 740 K where the initial viscous flow was observed, suggesting the crystallization during the interruption. No appreciable increase of the strength was observed after the interruption above 760 K despite the presence of crystalline phases. The negligible increase of the strength indicates that the effect of annealing softening takes over the strengthening effect due to crystallization at high temperatures. The crystalline phases were found to be mostly Cu10Zr7 and Cu51Zr14. The rapid drop of the room temperature fracture strength after annealing is associated with the precipitation of crystalline phases. The room temperature fracture strength recovers partially after a rapid drop with increase of annealing time, supporting the softening process at high temperatures above 760 K.