Microstructure evolution and mechanical properties of severely deformed Al alloy processed by differential speed rolling

A study was made to investigate the microstructure evolution and mechanical properties of Al alloy samples deformed by differential speed rolling (DSR) method as functions of the roll speed ratio as well as the number of operation. After a single DSR operation yielding an effective strain of ∼0.8, the microstructure comprised the most of the lamellar bands parallel to the deformation flow direction. After a second DSR deformation, the width of the lamellar bands became thinner and their distribution was also observed to be uniformed as the roll speed ratio increased. In addition, the present TEM observation exhibited that fine grains having an average grain size of ∼0.5 μm were detected inside the lamellae when the roll speed ratio was 1:4. Based on the microhardness maps of the deformed samples, the microhardness values of the sample deformed via DSR at the roll speed ratio of 1:4 was twice higher than that of initial counterpart.

► Effect of the roll speed ratio on microstructure evolution of 5052 Al alloy was significant. ► The formation of ultrafine grains was achieved after two-pass DSR at the roll speed ratio of 1:4. ► Microhardness values and their uniformity were improved with increasing roll speed ratio.