Structure and mechanical properties of magnesium-titanium solid solution thin film alloys prepared by magnetron-sputter deposition

Mg alloys are being considered for wider application in automotive industry. Designing new alloys with improved mechanical properties is important to the development of new Mg alloy parts. Mg-Ti is an interesting alloying system that may have good corrosion resistance due to high passivity of Ti. However it is difficult to form through a conventional metallurgical method due to the mutual insolubility of Mg and Ti and the big difference in their melting point. Nevertheless, if the alloy can be formed, it may have other unexpected physical and chemical performance. Therefore, it is of significance to understand the properties of Mg-Ti alloy produced by non-conventional approach. In this report, Mg_(1-x)Ti_x thin film alloys containing 0, 21, 41, 51, 58, 81 and 100 at.% Ti were deposited by dc magnetron sputtering on Si substrates. The mechanical properties of the thin film alloys were obtained using nanoindentation. Electron probe microanalysis (EPMA) was used to determine the film compositions. X-ray diffraction (XRD) measurements showed that single phase magnesium-titanium solid solutions were obtained across the full range of magnesium and titanium mixtures. The topography and the rms roughness of the different alloys were studied using atomic force microscopy (AFM). The mechanical properties of the Mg_(1-x)Ti_x thin films were determined by analyzing the nanoindentation load-displacement curves based on the Oliver-Pharr method. The nanoindentation results show that both the elastic modulus and hardness of the Mg_(1-x)Ti_x alloy thin films are higher than those of conventional Mg alloys.