Investigating the self-healing behaviour of under-aged and 60Sn-40Pb alloy reinforced aluminium hybrid composites

An experimental investigation was carried out to assess the self-healing characteristics of aluminium hybrid composites reinforced primarily with mixed proportion of silica sand and bamboo leaf ash. Charpy impact test samples with 45° notch were machined from the aluminium hybrid composites and a ϕ1 mm hole was drilled at 1 mm away from the notch. Two different self-healing treatments were given to the test samples prepared from the composites. In the first treatment, a 3 mm diameter hole was drilled along the sample and a low melting point alloy (60Sn-40Pb) which served as secondary reinforcing material was pierced into the hole and then heat treated at a temperature of 250 °C. The second treatment that was adopted involved subjecting the test samples to two-steps under-ageing treatment. The first step involved ageing at 160 °C for 15 min and quenched in water. Thereafter, the second ageing treatment was carried out at 50 °C for 24 h. The samples were then subjected to Charpy impact testing. The results show that the composites had lower absorbed energy compared with Al-Mg-Si alloy. Self-healing treatment improved the energy absorbed in healed samples when compared to the damaged samples. Although, the under-aged samples had a slightly higher absorbed energy in comparison with the samples containing 60Sn-40Pb, the presence of silica sand and bamboo leaf ash did not have significant influence on the absorbed energy. The highest healing efficiency obtained using the low melting point alloy approach was 61%.