Effect of Adding AlN Ceramic Particles on the Micromorphology of the Mg₁₇Al₁₂ Phase in Magnesium Alloys

AlN particle–reinforced Mg–Al matrix composites are fabricated by introducing an Al–AlN master alloy in Mg melt during casting. The microstructure, tensile strength, and fracture behavior of the AlN/AZ91 composites are investigated. The introduction of AlN results in a modified dendrite morphology of the β‐Mg₁₇Al₁₂ phase and, thus, improves the mechanical properties of the AZ91 alloy. The results show that 2% (by weight) AlN reinforcement has the highest tensile strength and elongation, mainly due to the reduction of the size of the second phase and the uniform distribution. Consequently, compared to as‐cast AZ91 alloys, the strength and elongation of the AlN/AZ91 composites increase by 34% and 171%, respectively. For second‐phase β‐Mg₁₇Al₁₂, the enhancement mechanism and size model are constructed, and the model trends are analyzed, predicted, and verified experimentally.