Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

Abstract

International audienceComparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoid thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable beta-W phase

The influence of a brittle Cr interlayer on the deformation behavior of thin Cu films on flexible substrates: Experiment and model

“…Although the properties used in the presented simulations for the 50 nm and 200 nm films, see Table 1 , do not fully correspond with data from [40] , the principal trends regarding differences between bulk and thin film behavior are taken into account in the models. The assumed yield strength for the 200 nm Cu film is in good agreement with the experimental data presented in [42] . Due to the fact that the extremely thin 10 nm Cr film is highly constrained, its material behavior was assumed as fully elastic up to brittle failure by crack formation.…”

Initiation and Propagation of Plastic Yielding in Duplex Stainless Steel

“…To date, only a limited number of diffraction experiments have been conducted with in-situ biaxial loading. Geandier et al [9,10] and Djaziri et al [11,12] performed lattice strain measurements on thin film cruciform specimens. Foecke et al [13] use lab source x-rays to perform lattice strain measurements on washer-shaped sheet metal specimens undergoing a modified Marciniak biaxial stretching test.…”

An enhanced formulation to determine Young's and shear moduli of thin films by means of Impulse Excitation Technique

“…It can be clearly seen that the structure exhibits a presence of two phases: a stable cubic body centered W − α and a cubic metastable W − β. This has already been observed on pure tungsten films deposited by different out-equilibrium techniques [31,[34][35][36][37]. It was reported that the presence of the metastable phase in Table 4 Uncertainties on the coating elasticity constants obtained by IET and NI.…”