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1060 Al and Al0.1CoCrFeNi are friction stir lap welded in this study in order to improve the microstructure and mechanical property of the high-entropy alloy by adding Al element into the alloy through friction stir processing. The results indicate that a crescent-shaped aluminum-addition zone featured by limited upward material flow is formed in the high-entropy alloy. The aluminum-addition friction stir processing leads to the formation of fine and homogeneously distributed microstructures and the occurrence of body-centered cubic phases in the high-entropy alloy. Owing to the synthetical strengthening effects caused by friction stir modification and Al content increase, the hardness of the Al0.1CoCrFeNi alloy is increased significantly from 100 Hv to an average value over 400 Hv and a maximum value of 600 Hv. The present study is able to provide an effective approach for the preparation and strengthening of high-entropy alloys.

A non-thinning weld of 7N01 aluminum alloy was successfully friction stir welded by using a large shouldered welding tool. The layered band structures consisting of alternating white and dark bands are formed in the weld nugget zones. The layered bands whose numbers are consistent with the crests of tool pin threads are characterized by heterogeneous structure-property distributions. By analyzing the formation mechanisms of zigzag lines in the nugget zones, the layered band structures are found to be formed by the synthetical effects of the straight-through flow and the maelstrom flow from retreating side and advancing side respectively under the shearing effect of tool pin threads. In order to weaken the band structure and improve the homogeneities of the structure-property of nugget zone, lower heat-input welding parameters should be considered.