EXPERIMENTAL-STUDY OF CREEP CRACK-GROWTH IN COARSE-GRAINED ALUMINUM

Tensile specimens of coarse-grained high purity aluminum were used in this study. With the employment of moire techniques, high temperature creep growth of a pre-existing edge crack perpendicular to the loading direction was quantitatively investigated. The results show that transgranular creep fracture by rupture after extensive localized necking ahead of the crack tip is the only failure mechanism, if no other cavities or microcracks pre-exist. During the process of creep growth of a pre-existing edge crack, the influence of grain boundary is less significant compared with that of room temperature plastic deformation, or high temperature creep deformation of non-damaged specimens. If the specimen has pre-existing cavities along the grain boundary, intergranular creep fracture by cavity growth and coalescence is the failure mode.