The Reaction Products of the Al–Nb–B[sub.2]O[sub.3]–CuO System in an Al 6063 Alloy Melt and Their Influence on the Alloy’s Structure and Characteristics

To meet aero-engine aluminum skirt requirements, an experiment was carried out using Al-Nb-B[sub.2]O[sub.3]-CuO as the reaction system and a 6063 aluminum alloy melt as the reaction medium for a contact reaction, and 6063 aluminum matrix composites containing in situ particles were prepared with the near-liquid-phase line-casting method after the reaction was completed. The effects of the reactant molar ratio and the preheating temperature on the in situ reaction process and products were explored in order to determine the influence of in situ-reaction-product features on the organization and the qualities of the composites. Thermodynamic calculations, DSC analysis, and experiments revealed that the reaction could continue when the molar ratio of the reactants of Al-Nb-B[sub.2]O[sub.3]-CuO was 6:1:1:1.5. A kinetic study revealed that the Al thermal reaction in the system produced Al[sub.2]O[sub.3] and [B], and the [B] atoms interacted with Nb to generate NbB[sub.2]. With increasing temperature, the interaction between the Nb and the AlB[sub.2] produced hexagonal NbB[sub.2] particles with an average longitudinal size of 1 μm and subspherical Al[sub.2]O[sub.3] particles with an average longitudinal size of 0.2 μm. The microstructure of the composites was reasonably fine, with an estimated equiaxed crystal size of around 22 μm, a tensile strength of 170 MPa, a yield strength of 135 MPa, an elongation of 13.4%, and a fracture energy of 17.05 × 10[sup.5] KJ/m[sup.3], with a content of 2.3 wt% complex-phase particles. When compared to the matrix alloy without addition, the NbB[sub.2] and Al[sub.2]O[sub.3] particles produced by the in situ reaction had a significant refinement effect on the microstructure of the alloy, and the plasticity of the composite in the as-cast state was improved while maintaining higher strength and better overall mechanical properties, allowing for industrial mass production.