TEM studies of structure in OFHC copper processed by equal channel angular rolling

In this study, UFG (ultrafine-grained) structure formed through ECAR (equal-channel angular rolling) process has been studied by methods of electron microscopy. The microstructure, mechanical properties and microhardness were investigated in OFHC (oxygen free high conductivity) copper after 1st–13th passes. The interpretation of microstructure changes was performed using a model which describes mechanism of UFG structures formation. It was found that ECAR is a tool used for the purpose of achieving significant structural refinement resulting in a final grain size d ∼ 400 nm. Moreover, this method provides such specific structural changes which have highly advantageous influence on mechanical properties (yield stress, ultimate tensile strength, reduction of area) as well as microhardness.

► The 13th passes of ECAR resulted in reduction of grain diameter from 40 to 0.4 μm.
► The substructural features were being strongly changed during ECAR processing.
► The strength significantly increased at the 1st pass, from initial 220 to 380 MPa.
► The maximum strength has been obtained after the 9th pass.
► After the 7th pass, the reduction of area started to increase.