Melt spreading behavior, microstructure evolution and wear resistance of selective laser melting additive manufactured AlN/AlSi10Mg nanocomposite

Abstract

The AlN/AlSi10Mg nanocomposites were successfully fabricated by selective laser melting using the mixture powder of AlSi10Mg and AlN particles with the weight ratio of 99:1. The surface morphology, densification behavior, microstructure features of the distribution state and size of nanoscale AlN particles combined with the grain sizes and the thickness of the eutectic phase within the matrix and the wear resistance were highly sensitive to the processing parameters. The appearance of the oxidation on the melt would promote the formation of defects due to the contrast variation of the surface tension gradient and the resultant radially inward flow, resulting in the formation of the continuous gaps between solidified tracks. However, the efficient melt spreading, the wetting behavior and the resultant high surface quality and the high densification rate were realized for the application of the high scan speed (>200 mm/s), due to the surface tension gradient and the resultant radially outward convection. The AlN nanoparticles tended to distribute in the grain border and the center region while the aggregation into clusters at high scan speed due to the high viscosity and the insufficient rearrangement. At the optimized laser volume energy density of 420 J/mm3, the nanocomposite showed the strain-hardened adherent tribolayer with the lowest wear rate of 3.4 × 10−4 mm3 N−1 m−1due to the high densification rate, nanoscale AlN particle and fine grain size of the matrix.