Project number: P31544-NBL
Project duration: 04/2019 - 04/2022
The aim of this project is a systematic study of deformation behavior and size effects in metallic glasses (MGs) by considering polymer-supported thin films with different compositions and thicknesses.
Sputter deposited Pd82Si18 MG films exhibit a clear size effect on deformation behavior as demonstrated in Fig. 1. Polymer-supported films with different thicknesses were subjected to tensile strain of 10% while the electrical resistance was recorded in-situ. The films with thickness 250 nm, 100 nm, and 60 nm (Fig. 1a) exhibit typical brittle-like fracture at strain of about 2% manifested by rapid resistance growth caused by long straight cracks (b, c). The 16 nm thick shows also brittle-like fracture but it occurs significantly later – at about 3% indicating extended elastic range. The crack morphology is also different from thicker films as can be seen in Fig. 1d. If the thickness of the film is further reduced then a qualitative change of deformation behavior is observed: there are only nanoscale cracks homogeneously distributed over the whole film (Fig. 1f). According to the resistance signal, no cracks are formed until the strain of 6%. For more details see [1]
Fig. 1. Tensile behaviour of sputter deposited Pd82Si18 metallic glass films on polyimide substrates. (a) Normalised electric resistance versus strain recorded in-situ during straining. The dashed line corresponds to the constant volume approximation. (b) through (f) are representative post-mortem SEM micrographs of 250, 60, 16, 9, and 7 nm thick PdSi films, respectively.