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 Youngʹs 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).