Influence of aging time of fracture toughness mechanisms of Al-Li alloys

The fracture toughness mechanisms in aluminum-lithium alloys aged for different time was studied. Based on semi-quantity statistical and analytical results, we specially discuss the effects of aging degree and the condition of stress on delamination. The results show that the percentage of delamination increase, the percentage of dimples decrease and little of quasicleavage can be found at the beginning zone with aging time prolonged. The maim fracture features is delamination at crack stable growth zone and is quasicleavage in near unstable crack growth zone. The percentage of delamination is increase at crack stable growth zone and decrease in near unstable crack growth zone with aging time prolonging. The aging degree and the rack growth stage can take apparently effect on delamination percent, the deeper aging degree the earlier delaminating, and those influence the effect of extrinsic toughness mechanism further. The high percent of dimples lead to the high toughness and the low strength, the high percent quasicleavage lead to the poor toughness. The high delamination percent lead to the high value both of toughness and strength.