Gum Metal thin films obtained by magnetron sputtering of a Ti-Nb-Zr-Ta target

Abstract : TNTZ quaternary superelastic coatings with a beta structure were successfully deposited by magnetron sputtering of a Ti-Nb-Zr-Ta target. In this work, we discuss the effects of argon pressure and negative substrate bias voltage on the microstructure, morphology, texture, mechanical properties and superelastic behavior of these coatings. The results show that the texture is random at high deposition pressure and it becomes {110} at the lowest deposition pressure (i.e. 0.2 Pa). Applying negative bias voltage causes the disappearance of {110} texture and promotes the appearance of {100} and {111} textures. The texture evolution is related to the ion bombardment of the growing film and to the surface mobility of adatoms. The highest hardness and Young’s modulus are obtained for the Gum Metal (GM) film deposited at the lowest deposition pressure (i.e. 0.2 Pa) and a bias of −200 V. The Evolution of the mechanical properties is discussed as a function of the film density, the compressive stress and grains' size changes. It was found that the film deposited at 0.2 Pa and floating potential presents the greatest depth recovery ratio. It is due to the fact that the film is dense and its texture is {110}. The negative bias voltage seems to have an unfavorable effect on the superelasticity.