Improving fatigue performance of metallic glasses with crystalline metal coating revealed by atomistic simulations

In this work, a comparative study was undertaken to investigate the effects of Cu coating on the deformation behaviour of metallic glass (MG) and crystalline Cu-coated MG under monotonic tensile loading and cyclic compressive-tensile loading by means of atomistic simulations. The results showed that under monotonic tensile loading, yielding first occurs in the Cu coating due to its low elastic limit, while plasticity in the MG core is directly triggered by the transfer of crystal plasticity from the Cu coating across the well-bonded crystalline-amorphous interfaces. The Cu coating serves as an effective medium for nucleating multiple shear bands, thus resulting in an improvement of tensile ductility. However, under cyclic loading, yielding tends to initiate via shear band activation in the interior of the Cu-coated MG. The Cu coating serves as effective barrier to suppress shear band initiation on the free surfaces, thus giving rise to enhanced fatigue life of the Cu-coated MG. The interlay bounding condition is also verified as playing a crucial role on the fatigue performance in the Cu-coated MG. The findings provide valuable insights on the effect of crystalline metal coating on the tensile and cyclic deformation mechanisms of MGs from an atomistic perspective.