Work softening characterization of alumina dispersion strengthened copper alloys

The effect of cold rolling on the hardness and microstructure of alumina dispersion strengthened copper (ADSC) alloys and oxygen free pure copper was investigated. With increased cold rolling deformation, a work softening phenomenon can be observed in ADSC alloys. The higher the alumina content is, the more difficult it is to observe the work softening phenomenon. This phenomenon is not observed in oxygen free pure copper, even after cold rolling 90%. The microstructural changes of the ADSC alloys were analyzed by TEM as a function of deformation. Initially, with an increase of the cold rolling deformation, a large number of dislocation cells are formed. Then, with further increased deformation, both a decrease of dislocation density and the formation of the smaller dislocation cells (subgrains) within the larger dislocation cells or the elongated bands are observed. Finally, as deformation attains a certain value, the smaller dislocation cells (subgrains) begin to coalesce, and the work softening phenomenon appears. All of these changes are the result of the interaction between the alumina particles and the dislocation line segments. In order to analyze the work softening mechanism for the ADSC alloys, a model is introduced in the paper.