A feasibility study of continuous grain refinement of sheet metal

Abstract

Various severe plastic deformation (SPD) techniques have been used to develop ultrafine-grained (UFG) materials to enhance material properties. Equal channel angular extrusion/pressing (ECAE/ECAP) is an effective technique to severely deform material and refine grains, however, the drawback is that a continuous process on sheet metal is confined due to the process mechanism. Equal channel angular drawing (ECAD), a continuous strip drawing process, has limitations in achieving grain refinement because drawing is a stretching phenomenon contrary to an extrusion or pressing process. In the present work, experiments were conducted on interstitial-free (IF) steel to demonstrate that grain refinement of thin sheets can be achieved through pack extrusion; and while there was shear deformation, ECAD failed to produce UFG microstructure. The finite element analysis showed the sheet metals have distinctive stress-strain states after ECAE and ECAD. The feasibility of combining ECAE and ECAD to approach the stress-strain state of the sheet metal in pack extrusion for grain refinement was investigated. Simulation results showed that with proper loading conditions, continuous grain refinement of thin metal strips is sufficiently possible.