Fatigue behavior and tribological properties of laser additive manufactured aluminum alloy/boron nitride nanosheet nanocomposites

Laser additive manufacturing is a promising approach to prepare near-neat shape parts from Al nanocomposites with high mechanical and tribological properties. Owing to its lubricious nature, boron nitride nanosheets (BNNSs) were added into AlSi10Mg alloy via high-speed ball milling and laser metal deposition (LMD) to manufacture self-lubricating Al alloy nanocomposites with outstanding wear resistance and fatigue performance. The study shows that number of cycles-to-failure due to tensile fatigue increased from 103 for pure AlSi10Mg to 106 upon adding only 0.1 wt% of BNNSs. At 0.2 wt% BNNSs, the friction coefficient and wear-out volume of AlSi10Mg alloy decrease by 58% and 57%, respectively. Scanning electron microscopy micrographs show that pure AlSi10Mg has a worn surface of grooves, wide ridges, debris and large protrusions of worn material along the groove edges. The wear mechanism is mainly plastic deformation, delamination and adhesion in pure AlSi10Mg. On the other hand, the LMD-built AlSi10Mg/BNNS composites exhibit less rough surface with clear wear trails due to the thin lubricant layer formed from the extruded BNNSs during the test. An extended finite element model for the crack propagation during fatigue testing is developed, where the obtained results are in accord with the experimental measurements. The present study shows that additive manufacturing technology is capable to fabricate Al matrix composites with tailored properties for various design applications.