a b s t r a c t
The deformationandfractureprocessinAl–Cu–Mg alloywereinvestigatedbyusingtheinsitustraining
transmission electron microscopy (TEM) method.Some major aspects of the fracture process,including
dislocation emission and migration,thinning of dislocation free zone (DFZ),crack propagation (both in
continuous and discontinuous manners) and slipping/twinning deformation,can be observed.The rod-
like T dispersoids,which may increase the microcrack initiation sensitivity,also can effectively prevent
the fast and continuous propagation of the crack. DFZ ahead of crack tip can be thinned in a mixed mode
characterized by tearing and shear deformation,while nanovoids ,which are typical characteristics in DFZ
during discontinuous crack propagation,may originate from the enrichment of defects such as
dislocations and vacancies.Deformation twinning at crack tip can slow down crack propagation and
change crack propagation path,thus may be beneficial to the fracture toughness of the alloy.