Numerical and Experimental Study on ECAP-Processing Parameters for Efficient Grain Refinement of AA5083 Sheet Metal

Abstract

Equal-channel angular pressing (ECAP) is often used as effective tool for grain refinement for many different metallic materials. It is well known that grain size is an important microstructural feature influencing superplastic properties of fcc materials like aluminum alloys. The magnitude of introduced shear strain depends on geometrical parameters of the ECAP channel. In this contribution, the impact of different geometrical parameters of the ECAP channel on the resulting magnitude of introduced shear strain is analyzed. ECAP on AA5083 aluminum sheets with the dimensions of 200x200x1.8 mm3 is performed. Microhardness measurements reveal a considerable increase of hardness after ECAP and microstructural investigations by electron backscatter diffraction (EBSD) show the beginning formation of a deformation-induced substructure which is known to be a preliminary stage of the grain refinement process. It is assumed that this fine-grained microstructure results in an enhanced superplastic forming capability. Furthermore, a numerical model of the process based on the experimental results is established. The bending of the ECAP processed sheet metal as well as its microhardness are used for the validation of the model. The friction coefficient between the channel and the aluminum sheet significantly influences the results of the simulation. With the applied model different channel angles and inner corner radii are varied in order to determine a maximum magnitude of deformation resulting in sufficient grain refinement of the investigated material. With the help of the results gained in this study, suitable ECAP parameters for sheet metals can be derived that enable creating ultrafine-grained materials for superplastic forming operations.