Sputter deposition of hard quaternary Al-Mg-B-Ti nanocomposite films

In the present work, and in the context of the development of hard lightweight materials, we systematically study the effect of Ti doping on the characteristics of Al-Mg-B films (Al-Mg-B-Ti) prepared by sputter deposition using unbalanced planar magnetrons equipped with Al-Mg alloy, TiB2 and B targets in a closed magnetic field configuration. The mechanical properties of Al-Mg-B-Ti films were investigated as a function of titanium concentration. We show that the maximum hardness of 40.7 GPa and Young's modulus of 298 GPa were achieved with a titanium concentration of 20.5 at.%. Detailed XPS, XRD and TEM analyses support a structural model that relates the experimentally reached superhardness (> 40 GPa) to the formation of AlMgB14 and TiB2 nanoparticles imbedded in an amorphous Al-Mg-B matrix. The presence of the densely packed matrix is also shown to be responsible for enhanced corrosion resistance documented by exposures to saturated vapors of hydrochloric acid (HCl).