Deformation behaviour of in-situ TiB2 reinforced A357 aluminium alloy composite foams under compressive and impact loading

In-situ A357- xTiB2 (x=5, 10 wt%) composite foams were prepared through liquid melt route using TiH2 as blowing agent. The deformation and energy absorption characteristics of these foams with varying TiB2 content (5 and 10 wt%) were evaluated in terms of compression and high velocity impact tests. The compression test results showed that the plateau stress values of the composite foams are insensitive to weight fraction of TiB2 particles and for the given relative density, the energy absorption (area under the compressive stress-strain curve) of 5TiB2 composite foams is superior to 10TiB2 composite foam. X-ray computed tomography (XCT) study revealed the formation of TiB2 clusters on the gas-metal interface of 10TiB2 composite foams. The poor gas-metal interface and thick region of brittle interdendrites in 10TiB2 composite foam is responsible for its inferior energy absorption behaviour as compared to 5TiB2 foam. Fractographic analysis showed that the fracture takes place exactly at the inter-dendritic regions in both the foams. Energy absorption during compression and high velocity impact tests is almost same for either of the composite foams, which indicates the energy absorption is insensitive to a displacement rate of 1.6×10-5 m/s (compression) to a rate of 10 m/s (impact).