Tailoring the strengthening-toughening behavior of the MoSi2 film by doping trace solute Au

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Although the high hardness and wear resistance of transition metal silicides (TMSi) are widely used in protective films, overcoming the contradiction between hardness and toughness still faces huge challenges. Here the magnetron sputtering was used to introduce trace solute Au atoms into the MoSi2 to form a solid solution structure. X-ray diffraction and high-resolution transmission electron microscopy were used to characterize the microstructure of Mo-Si-Au film. In addition, hardness and toughness enhancement by solute Au was investigated the film through the combination of experimental and theoretical studies. The results show that the hardness and fracture toughness of Mo-Si-Au (Au/Mo atom ratio, R = 0.10) film is 15.4 GPa and 2.52 MPa m1/2, respectively. Compared with MoSi2, the hardness and toughness are increased by 41.3% and 68.0%, respectively. Density Function Theory calculations and electronic structure analyses further indicate that the increase in the hardness of the solid solution Mo-Si-Au film may be related to the increase in bulk modulus, C33, and C11. The increase in toughness is mainly due to the strengthening of the metal bonds in MoSi2 after doping a small amount of solute Au. The introduction of trace solute Au atoms in TMSi provides a new reliable scheme for overcoming the contradiction between hardness and toughness. As part of this research, a protective coating based on TMSi will be expected to be applied to aviation components.