Figure 1. Strength and strain limit of Cu–Zr metallic glasses.

The yellow shaded ellipse area represents the yield stress and yield strain range of Cu–Zr-based bulk samples. All other data are results from our in situ tensile tests of Cu₄₉Zr₅₁ samples with diameters in the range of 200–300 nm. The blue solid squares represent the yield strength (σ_y) and yield strain (ɛ_y) at the proportionality limit. The measured fracture strength (σ_f) and fracture strain (ɛ_f) are shown with green open diamonds. The theoretical elastic limit (σ_y^th, ɛ_y^th) given by equation (1) is marked by the red solid circle. The ɛ_f values exceed the theoretical elastic limit due to a small contribution from plastic deformation. When the latter (<1%) is deducted from ɛ_f, the resulting total elastic strain is consistent with the predicted ideal elastic strain limit.