Microstructure evolution of as-cast AlN/AZ91 composites and room temperature compressive properties

The microstructures of as-cast AlN/AZ91 composites prepared by different in-situ nitridation reaction times are characterized. Increasing nitridation reaction times resulted in morphological changes of the primary α-Mg phase from coarse dendritic structures to fine cellular structures, the volume fraction decrease of eutectic β-Mg₁₇Al₁₂ phase, and the eutectic structure transformation from partial divorced eutectic to fully divorced eutectic. During the room temperature compression of as-cast AlN/AZ91 composites, the (0002) basal plane texture perpendicular to the compression direction was weakened effectively, and compression strength and plasticity were simultaneously improved compared with as-cast AZ91 alloy. When the nitridation reaction time is 2 h, i.e. the volume fraction of in-situ AlN particles is 1.5%, the compressive yield strength of 110 ± 2 MPa, the ultimate compressive strength of 371 ± 8 MPa and the compressive fraction elongation of 22.1 ± 0.4% are achieved in the in-situ AlN/AZ91 composites.