Al-5Cu-0.3Sc-B₄C Nanocomposites: Microstructural Refinement, Strengthening Mechanisms, and Corrosion Behavior

In this study, Al-5Cu-0.3Sc nanocomposites reinforced with 0-20 wt.% B₄C were successfully fabricated using a combined melt-spinning, mechanical alloying, and sintering route. The rapid solidification achieved during melt spinning suppressed elemental segregation and refined the microstructure, producing a nanocrystalline Al-Cu-Sc matrix that served as a uniform host for B₄C particles. X-ray diffraction confirmed the coexistence of Al, Al₂Cu, Al₃Sc, and B₄C phases, indicating a dual-strengthening mechanism consisting of precipitation strengthening from Al₂Cu/Al₃Sc and particle strengthening from B₄C. Increasing B₄C content increased hardness from 44.9 HV to 188.2 HV (≈319%) via effective load transfer, interfacial dislocation accumulation, and particle-matrix interlocking. The wear rate decreased from 3.81 × 10^-3 mm³/m to 6.29 × 10^-3 mm³/m (≈98.35%), corresponding to a nearly 60-fold increase in wear resistance due to the formation of a stable ceramic tribofilm and the protective effect of embedded B₄C particles. Conversely, the corrosion rate increased from 0.117 mm/year to 6.136 mm/year (≈52-fold) due to intensified microgalvanic interactions among B₄C, Al₂Cu, and the Al matrix. Generally, the incorporation of B₄C reinforcement provides a great improvement in mechanical and tribological properties at the expense of corrosion resistance, highlighting a performance trade-off relevant for lightweight structural and surface critical applications.