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

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Abstract
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.

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