Damage behaviour of Al matrix composite reinforced with Ti–6Al–4V meshes under the hypervelocity impact

Abstract

15 vol.% Ti–6Al–4V meshes reinforced 5A06Al matrix composites (TC4m/5A06Al) were fabricated by pressure infiltration method. The resistance of TC4m/5A06Al composites to hypervelocity impact was tested by a two-stage light gas gun. Moreover, damage behaviour and residual microstructure of the composite were investigated. The depth of crater in TC4m/5A06Al composite was decreased 9.4–12.81% as compared to 5A06Al, indicating that the addition of TC4 fibre is beneficial to the hypervelocity impact resistance. Numerous dimples from plastic deformation were observed on the fracture surface of TC4 fibre near the pithead. Adiabatic shearing fracture was occurred in the middle part of crater. Porous structure and cracks were found at the bottom of crater. Interface separation of fibre and Al matrix along impact direction were observed in the region near the pithead. The original horizontal fibres deformed along the outline of the crater in the region around crater. Moreover, some fibres were sheared into two sections along 45° direction. Below the crater, fibre was adiabatically sheared and slid along 45° direction. Significant adiabatic shear band containing ultra-fined grains (grain size < 200 nm) was observed in the Al matrix at the bottom of the crater. The blocky (Fe, Mn)Al6 phase was sheared into two parts completely along the impact direction, followed with several cracks. Formation and fracture of twins in (Fe, Mn)Al6 were also observed. TiAl amorphous structure was formed at the interface far away from TC4 fibre. The inner layer close to TC4 fibre was composed of TiAl nanocrystalline and amorphous phase. Deformed band with elongated grains and transformed band with equiaxed recrystallized grains were observed at the interface between TC4 fibre and Al matrix at the bottom of crater.