Reaction mechanism, microstructure, and mechanical properties of GNPs-PSZ promoted in-situ AlN reinforced Al matrix composites

This study presents a one-step fabrication of AlN-reinforced Al matrix composites via in-situ nitridation of Al powder during pressure infiltration sintering, promoted by a nitrogen-containing agent (polysilazane, PSZ) and nanocarbon (Graphene nanoplatelets, GNPs). Experimental results demonstrate that Al powder undergoes in-situ nitridation under ambient atmosphere at relatively low temperatures with the synergistic effect of GNPs and PSZ. The resulting nitride integrates with the infiltrating Al melt to form AlN/Al composites. By adjusting the ball milling method, the content and distribution of in-situ formed AlN were controlled, yielding two distinct composite structures: network reinforced AlN/Al composite and particle reinforced AlN/Al composite. XRD and TEM analyses revealed the amount, morphology, and microstructure of the formed AlN, and the formation mechanism was investigated. The nitrogen source for in-situ AlN was identified to originate not only from PSZ but also from atmospheric N₂. In the particle reinforced AlN/Al composite, extensive nitridation of Al powder was achieved, with an AlN mass fraction of approximately 21.0%. This composite exhibited a tensile strength of 393.8 MPa, an elongation of 4.5%, and an elastic modulus of 93.3 GPa. This work provides a simple and efficient one-step route for synthesizing AlN/Al composites in ambient air, advances the mechanistic understanding of in-situ AlN formation, and shows promising potential for low-cost industrial-scale production.