Development of combined groove pressing and rolling to produce ultra-fine grained Al alloys and comparison with cryorolling

Abstract In the present work, aluminium alloys were subjected to two different severe plastic deformation (SPD) routes namely, cryorolling (CYR) and constrained groove pressing (CGP), to investigate their effect on microstructure and mechanical properties. Solutionized AA 5083 alloy and AA 6061 alloy sheets were cryorolled to a final thickness of 1 mm with a total logarithmic strain of 1.87. Samples of these alloys with 3 mm thickness were subjected to CGP with an equivalent plastic strain of 1.16. The CGP samples have been subsequently cold rolled (CR) to reduce the thickness to 1 mm (67% reduction). The microstructure of the deformed samples was characterized by electron backscatter diffraction (EBSD) coupled with kernel average misorientation (KAM) and X-ray diffraction (XRD). The techniques were employed to investigate the degree of grain refinement and local misorientation due to deformation. It has been found that the yield strength (YS) of 6061 alloy after CGP + CR is 19% higher than that of CYR sample while, in contrast, the YS of CGP + CR 5083 alloy is 18% less than that of CYR condition. A dislocation density-based model has been used to estimate the sub-structural changes during processing. The theoretical dislocation density estimated using the model agreed well with the experimental values of both the alloys with a difference of about 2.5% in the case of 5083 and 6.5% in the case of 6061. It is inferred from the analysis that the dislocation bow out is the predominant mechanism in both the materials.