Characterization of the graded distribution of primary particles and wear behavior in the A390 alloy ring with various Mg contents fabricated by centrifugal casting

•The centrifugal casting is one of the most effective methods for processing FGMs.•Functionally graded ring with high outer surface hardness can be produced by Al-Si alloys.•Functionally graded ring with high inner surface hardness can be produced by Al-Si-Mg alloys.•The addition of Mg element makes change the gradient distribution of the particles in Al-Si-Mg alloys.

Three kinds of functionally graded rings using A390 as a base alloy and containing 0, 6 and 12 wt%Mg were prepared by centrifugal casting, and their microstructure and mechanical properties were investigated and compared. It is shown that the A390 ring without Mg content takes a characteristic of the primary Si particles distribution in the inner and outer layers. The 6%Mg ring reinforced by Si/Mg2Si particles has a different performance with its particles distribution only in the inner layer. Regarding the 12%Mg ring, the Mg2Si reinforced particle is distributed near the entire cross-section. It is demonstrated that the existence of the light in situ Mg2Si particles with lower density rather Al liquid makes changes to the gradient distribution of particles across the cross-section. Characteristics and distribution of the primary particles were assessed by the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and image analyzer software. The hardness and wear rate along the thickness of samples were measured to investigate the variation in the mechanical properties corresponding to the variation in microstructure. Also, the worn surfaces of the material were examined by scanning electron microscopy (SEM) to study the dominant wear regime.