Microstructural Evolution and Hardness Behavior of Hot-Consolidated Al95(AlSi)5 Matrix Composite Reinforced with Mechanically Alloyed Al–Cu–Nb and Al–Co–Nb Phases

Hot Consolidation (HC) was employed to prepare high-performance aluminum matrix composites reinforced with mechanically alloyed powders. Two different reinforcements, Al65Cu20Nb15 and Al65Co20Nb15, synthesized by high-energy ball milling, were incorporated into an Al95(AlSi)5 matrix at 20 wt% after homogenization in a Turbula WAB mixer for 2 h. Microstructural characterization using laser granulometry, scanning electron microscopy, and X-ray diffraction confirmed significant particle refinement and the formation of stable intermetallic phases during milling. The Al65Cu20Nb15 system showed the formation of Al2Cu and Nb-containing intermetallic compounds, while the Al65Co20Nb15 reinforcement phases such as Al3Nb, AlNb2, and Al13Co4 were identified. The consolidated composite exhibited high densification levels, reaching relative densities of 99.6% and 96.77% for composite 1 and composite 2, respectively. In addition, the Vickers hardness increased significantly compared with the unreinforced aluminum matrix, attaining values of 96.34 HV and 68.28 HV for composite 1 and composite 2, corresponding to hardness improvement of approximately 182% and 100%, respectively. The superior densification and hardness of composite 1 were attributed to enhanced interfacial bonding, refined microstructure, and the effective strengthening effect of reinforcement phases. These results demonstrate that the combined use of high-energy mechanical alloying and Hot Consolidation proved to be an efficient approach for producing lightweight aluminum matrix composites with improved microstructural and mechanical properties suitable for advanced structural applications.