Investigation of structure and mechanical properties under quasi-static and planar impact loading of aluminum composite reinforced with Al2O3 nanoparticles of different shape

Abstract We report on an investigation of the structure and mechanical properties under quasi-static and planar impact loading of Al-based nanocomposites reinforced with alumina nanoparticles of ball, plate and sheet shape fabricated through accumulative roll bonding (ARB) for 4 and 10 cycles. The distribution of the nanoparticles and structural characteristics of the matrix were revealed using transmission electron microscopy. The microhardness, ultimate and yield strengths and ductility under tension at the strain rate of 1 × 10−3 s−1 were measured as mechanical characteristics under the quasi-static loading. The maximum pressure of the impact compression, Hugoniot elastic limit and spall strength were calculated using the free surface velocity data recorded during the impact by aluminum flyer-plates with the impact velocity of 630 ± 30 m/s. Our results show that nanoparticles tend to agglomeration inside the composite. The size of agglomerates depends on the nanoparticle shape and a number of ARB cycles. Only the part of the ball-shaped nanoparticles can be distributed uniformly as separate nanoparticles after 10 ARB cycles. The introduction of the nanoparticles into aluminum assists in the structural refinement in the nanocomposites relative to alumina-free aluminum. This effect is mostly exhibited in the composite reinforced with the ball-shaped nanoparticles, some of which are distributed separately. The nanoparticle of different shape affects the mechanical properties ambivalently under both quasi-static and shock-wave conditions due to their various distribution in the matrix and different properties of the agglomerates. The spall strength decreases with the nanoparticle introduction because the particles and their agglomerates are the stress concentrators and crack origins.