Deformation behaviour of in-situ TiB_2 reinforced A357 aluminium alloy composite foams under compressive and impact loading

摘要

In-situ A357- xTiB_2 (x=5, 10 wt%) composite foams were prepared through liquid melt route using TiH_2 as blowing agent. The deformation and energy absorption characteristics of these foams with varying TiB_2 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 TiB_2 particles and for the given relative density, the energy absorption (area under the compressive stress-strain curve) of 5TiB_2 composite foams is superior to 10TiB_2 composite foam. X-ray computed tomography (XCT) study revealed the formation of TiB_2 clusters on the gas-metal interface of 10TiB_2 composite foams. The poor gas-metal interface and thick region of brittle interdendrites in 10TiB_2 composite foam is responsible for its inferior energy absorption behaviour as compared to 5TiB_2 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 l0m/s (impact).