Partial Grain Refinement in Al-3%Cu Alloy during ECAP at Elevated Temperatures

Microstructural changes during equal channel angular pressing (ECAP) in a temperature interval from 523 to 748 K (similar to 0.6-0.8 T-m) were studied in a coarse-grained binary aluminum alloy Al-3%Cu. Hot ECAP results in grain refinement taking place at all temperatures investigated, leading to a non-uniform development of deformation-induced fine grains and the remnant original grains containing subgrains with low-angle boundaries. Fine-grained structure is developed along microshear bands formed in grain interiors as well its along initial grain boundaries. The number and the average misorientation angle of the boundaries of microshear bands start to increase at above a critical strain of about 2, finally leading to development of new fine-grained structures. The volume fraction and the average misorientation of deformation-induced boundaries are reduced with rising temperature. The thermal stability of the evolved deformation microstructures and several factors controlling grain refinement during hot ECAP are discussed in details. [doi: 10.2320/matertrans.MD200807]