Severe Deformation Based Process for Grain Subdivision and Resulting Microstructures

Abstract

Significant interest exists within the materials science community to create nanocrystalline microstructures in metallic alloys in an effort to obtain improved strength and processability of these alloys. Repeated deformation methods, such as 3-axis forging, ECAE (Equal Channel Angular Extrusion), pressurized torsion etc. have been used to create bulk materials with 50–500 nm size microstructures. Stability of these microstructures to further deformation and to thermal exposure is however a major problem which needs to be addressed in the future years. Another issue for process scale-up is die-wall sticking with the moving workpiece, which make scale-up of billet size a nontrivial problem. To minimize these structure-altering aspects of rolling deformation, a surface-shear based deformation technique has been developed and applied to plates and sheets of aluminum alloys to create desired fine-scale microstructures. Initial studies using this and other processes on several Al alloys with and without dispersoid particles have been analyzed by optical, and electron microscopy. Preliminary results on mechanical behavior and texture are reported.