Impact fracture of rapid solidification processed Al-Li alloys

The deformation-fracture behavior in impact test of rapid solidification processed (RSP) Al-Li alloys has been studied systematically. The results show that there are both intrinsic and the extrinsic toughening effects in RSP Al-Li alloys. The intrinsic toughening effect is controlled by the micro-mechanism of fracture in the alloys, while the extrinsic toughening is produced by cracking of the prior powder boundaries (PPBs). The level of extrinsic toughening effect is determined by the relative strength of grains, grain boundaries, and PPBs. Large secondary cracks across the transverse section of impact specimens form easily along relatively weak PPBs in the as-quenched condition, leading to a marked extrinsic toughening effect. However, in the peak aged and overaged conditions, cracks propagate mainly along grain boundaries, and the extrinsic toughening effect is inhibited.