Design and development of heterogeneous aluminum matrix hybrid composites for enhanced ductility

Traditional aluminum-based composite materials are limited in application due to the contradiction between strength and ductility. To address this, a dual matrix composite system based on Al-TiO2-H3BO3 was developed using ball milling, cold pressing, and sintering. In this system, ball-milled aluminum forms the internal matrix with in-situ reinforcements, while unmilled aluminum, added in proportions from 0 to 75%, creates an outer matrix known as the reinforcement-lean zone (RLZ). By introducing un-ball-milled aluminum to form RLZ with scarce reinforcement, the strength and toughness were synergistically optimized. Dual matrix hybrid composites were sintered at temperatures between 600°C and 800°C, following differential thermal analysis that indicated the formation of reinforcing particles above 550°C. X-ray diffraction and Energy Dispersive Spectroscopy confirmed the presence of in situ reinforcements such as γAl2O3, AlB2, TiB2, and Al3Ti within the aluminum matrix. Microscopy demonstrated dual matrix morphology displaying rearrangement of the RLZ and reinforcement-rich zone (RRZ). Maximum microhardness and strength were observed at a sintering temperature of 800°C. The composite with 0% unmilled aluminum exhibited the highest hardness of 169.2 HV, whereas the highest toughness of 6.12 Jm-3 was achieved in the composite containing 75% unmilled aluminum. Atomic Force Microscopy revealed a progressive decrease in surface roughness from 19.70 nm to 7 nm as the proportion of unmilled aluminum increased from 0% to 75%. • Sintering temperature optimization controls structure-property relationships in aluminum metal matrix composites • Unmilled aluminum powder inhibits in-situ reactions, forming reinforcement-lean zones (RLZ), which indicate the outer matrix. • Ball-milled aluminum promotes in-situ reinforcement formation, forming reinforcement rich zone (RRZ) that indicates the inner matrix. • Increased unmilled aluminum content (75%) creates interconnected RLZ, enhancing composite toughness.