Zr-based metallic glass thin film coating for fatigue-properties improvement of 7075-T6 aluminum alloy

• Metallic glass thin film (MGTF) coatings sputtered on high strength aluminum alloy.
• 30-Time improvement of fatigue life of MGTF-coated samples at 250 MPa.
• Fatigue limit of MGTF-coated samples is 56% higher than the bare one.
• Lower surface roughness plays an important role to improve fatigue life.
• Compressive residue stress is the key to restrict fatigue cracks.

In order to improve the fatigue life of high strength aluminum alloy, a protection coating with 200 nm Zr-based metallic glass thin film (MGTF) coupled with 50 nm titanium thin film buffer layer was coated on the 7075-T6 aluminum alloy by DC sputtering. The results of four-point-bending fatigue test revealed that the fatigue life of 7075-T6 aluminum alloy with Zr-based MGTF could be improved by 30 times at a stress level of 250 MPa. The improvement of Zr-based MGTF coated samples in fatigue limit was 235 MPa (56.7% increase) in comparison with 150 MPa for the uncoated samples. The superior mechanical properties of Zr-based MGTF, such as high strength and good bending ductility, lower surface roughness, good adhesion between the film and the substrate, and high compressive residual stress are the key factors to improve the fatigue resistance of the coated aluminum alloy.