Laser powder bed fusion of AlN and ZrN reinforced AlSi10Mg matrix composites: Effect of wettability and volume fraction on microstructure and mechanical properties

In this study, Laser Powder Bed Fusion (LPBF) technique was employed to obtain AlN- and ZrN-reinforced AlSi10Mg composites (De Brouckère diameter D[4,3] equals ∼2 μm). The wettability of AlN and ZrN by pure Al and AlSi10Mg melts was investigated, and the phase composition and microstructure of the bulk composites, as well as the hardness and tensile strength, were studied. The impact of wetting on the mechanical properties was also analyzed. The experimental results indicated that ZrN forms a strong interphase bond with Al as a result of reactive wetting. Due to the in-situ reaction, intermetallic inclusions of Zr(Al,Si) 3 were formed, which further strengthened the matrix. Accordingly, small amounts of ZrN (up to 1 vol%) increase the microhardness of AlSi10Mg from 108 to 126 HV 0.1 and the tensile strength from 410 to 448 MPa. In turn, insufficient inert wetting due to the short contact time of the melt during the LPBF process leads to the formation of gaps at the Al/AlN interphase boundary. This phenomenon, as well as the uneven coarsening of Si, results in a decrease in the strength of AlSi10Mg and an insignificant increase in microhardness regardless of the volume fraction of AlN. The obtained results contribute to the understanding of the role of wetting in LPBFed aluminum matrix composites, and also establish the foundation for further experimental and fundamental research in this area.