ABSTRACT
There has been a long-standing controversy on how dislocations interact with boundaries. This chapter reports in-situ observations that in a Cu-brass hetero-structured transmission electron microscopy (TEM) film Frank-Read sources are the primary dislocation sources. Recently, hetero-structured (HS) materials were found to be able to avoid the trade-off between strength and ductility. This makes it essential to understand how dislocations interact with HS boundaries so as to pave the scientific foundation for this new type of materials. The superior mechanical properties were attributed to hetero-deformation-induced synergistic strengthening and work hardening, which are produced by the piling-up of geometrically necessary dislocations at HS zone boundaries. In the current in-situ TEM observation, only two perfect dislocations and two thin twins were observed emitted from the boundary, as compared to about ten Frank-Read sources that were dynamically generated, each emitting a number of dislocations toward the boundary before being eventually deactivated. The dislocation pileups mostly disappeared after the deactivation of the dislocation sources.
