Experimental study of process parameters’ effect on surface residual stress magnitudes in equal channel angular rolled aluminium alloys

Abstract

The residual stress within a surface layer of aluminium alloy sheets introduced through equal channel angular rolling as a severe plastic deformation process is studied in this article. The channel oblique angle, the route of feeding and the number of passes are the main equal channel angular rolling parameters that are found to influence the residual stress magnitude and distribution. Two aluminium alloys (Al5083 and Al6061) are analysed with the residual stress magnitudes determined using the X-ray diffraction method. When a sheet metal is processed using the equal channel angular rolling method, the surface residual stress in the rolling direction becomes compressive at the top surface and tensile at the bottom surface. Therefore, a nonuniform stress distribution is introduced into the specimen. By reducing the channel oblique angle of the die set from 130° to 110°, the surface residual stress of Al5083 specimens decreased by a maximum value of up to 27%. Combined with this, the surface residual stress decreases as the number of passes increases from one to three passes. These values depend on the route of passing the specimen through the dies during the equal channel angular rolling process. In addition, for materials with different inherent mechanical properties, the introduced residual stress is found to vary. The results indicate that the magnitude of surface residual stress for the Al5083 specimens processed by equal channel angular rolling is about two and a half times greater than the Al6061 specimens. The equal channel angular rolling process and its parameters had a similar effect on both Al5083 and Al6061 specimens. Therefore, the obtained result can be applied for sheet and strip metals.