Quasi-static and dynamic deformation of aluminum matrix composites reinforced by core-shell Al35Ti15Cu10Mn20Cr20 high-entropy alloy particulates

Core-shell structured particles are potential reinforcement agents for metal matrix composites. In this work, aluminum matrix composites reinforced with core-shell structured Al35Ti15Cu10Mn20Cr20 high-entropy alloy (HEA) particles were fabricated by spark plasma sintering (SPS) and high-temperature diffusion post-treatment. Dynamic compression behavior and adiabatic shear failure mechanism in the composites were investigated by split Hopkinson pressure bar (SHPB), scanning electron microscopy and transmission electron microscopy. Results showed that the shell thickness of the core-shell particles ranged from 0.4 to 1.6 μm, which were formed by thermal diffusion between HEA core and aluminum alloy. The 30 vol% (Al35Ti15Cu10Mn20Cr20)p/2024Al composite showed a high compressive strength (594 MPa) and strain-to-failure (26.7 %) under quasi-static compression, as well as a high flow stress (602 MPa) and strain-to-failure (45.3 %) under dynamic compression, which are superior to common ceramic particles reinforced Al matrix composites. The (Al35Ti15Cu10Mn20Cr20)p/Al composites with ∼20–40 vol% core-shell HEA particles failed as bulging, 45° shearing or splitting when compressed at ∼1000-3000 s−1. Micro-damages in these composites were due to microcracks originated from the HEA core, while propagation of cracks was effectively restrained by the shell. Deformation bands and phase transformation (melting of aluminum) were both observed in the composites under dynamic loads. Chain-shaped deformation bands were formed by the fragmentation and rearrangement of the core-shell particles, instead of the recrystallized structure of metal matrix in particle-reinforced Al matrix composites reported previously. The formation of molten Al phase transformation bands was owing to shear localization and significant adiabatic temperature rise under dynamic compression.