Study of Elastic Behavior of Metallic Thin Films by 2D Synchrotron XRD and in situ Tensile Testing
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1027-D01-09
Study of Elastic Behavior of Metallic Thin Films by 2D Synchrotron XRD and in situ Tensile Testing Geandier Guillaume, Renault Pierre-Olivier, Goudeau Philippe, Eric Le Bourhis, and Girault Baptiste Laboratoire de Métallurgie Physique, University of Poitiers, UMR 6630 CNRS, SP2MI-Téléport 2-Bd Marie et Pierre Curie, BP 30179, Futuroscope-chasseneuil Cedex, F-86962, France ABSTRACT Understanding the mechanical behavior of nano-structured thin films in relation to their structure, in particular to the grain size, is of high importance for the development of technological applications. In this work, model nanometric multilayer W/Au systems exhibiting different structures are elaborated. These films are supported by a (thin) polyimide substrate. Films mechanical response is characterized experimentally by tensile tests carried out in-situ in a X-ray diffractometer set on a synchrotron source. Transmission X-ray diffraction has been used to study the deformations of both W and Au sublayers as a function of the applied load. This geometry has been developed in the aim of optimizing the experiment time. INTRODUCTION For a few years, there has been an increasing interest in the elastic properties of thin films [1-4]. Literature data seem to show that the elastic behavior of metallic thin films can differ significantly from their bulk counterparts because of their specific structure (texture, defects, high density of interfaces, interface mixing) and of size effects [5-8]. Studying and tailoring the size effect on elastic constants of polycrystalline thin films require controlling the structure (grain size, residual stresses, and texture). One way to control grain size along one direction at nanometric scales is to prepare multilayers. Elastic behavior of supported thin films can be determined by combining tensile test [9-11] or four point bending [12-14] and X-ray diffraction (XRD). X-ray diffraction is phase selective and hence is a unique technique that allows determination of both the mechanical and structural states of the diffracting phases. This technique can be used to study how the elastic constants are affected by the period thickness independently of the multilayer components. The main disadvantage of the XRD technique is that the X-ray measurements are time consuming for thin multilayers (as the diffracting volume is quite small) even for high flux synchrotron radiation sources. The aim of this paper is to show how the elastic behavior of multilayers can be studied from the in situ loading of the specimen during the X-ray diffraction experiment. We report a tensile test study of W/Au multilayers films deposited on kapton substrate. X-ray strain measurements with relevant precision being time consuming, measurements were performed using synchrotron Xray diffraction combined with a 2D detector in order to increase the amount of data which improves the analysis precision [15] as compared to usual point detector (0D) analysis [16].
SAMPLES The substrates used to support the multilayered films were 127.
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