In-Situ Produced Second Phase Particles and Grain Size in Weld Nugget Zone of Aluminum Plate after Friction Stir Processing

The friction stir processing (FSP) was performed on 1060-Al plates, and the Ti powders were added into the processing zone to in-situ produce the second phase particles of Al3Ti. The distributions of the second phase particles and the grains in the weld nugget zone were studied. The results show that at the advancing side of the weld nugget zone, the dispersity of Ti powders increased with the FSP passes increase and after 4-pass FSP reached a homogeneous state. Ti powders were reacted with Al and the nano-scale Al3Ti particles were obtained. The particles were peeled off from the interface but still aggregated around Ti powders. The second phase particles can inhibit the grain growth effectively. The more amounts of the second phase particles in the area, the finer grains were obtained and the grains almost did not grow during the heat treatment after processing.