Effects of pin geometry on the material flow behavior of friction stir spot welded 2A12 aluminum alloy

A three-dimensional finite volume model was established by the ANSYS FLUENT software to simulate the material flow behavior during the friction stir spot welding （FSSW） process. Effects of the full-threaded pin and the reverse-threaded pin on the material flow behavior were mainly discussed. Results showed that the biggest material flow velocity appeared at the outer edge of the tool shoulder. The velocity value became smaller with the increase of the distance away from the tool surface. In general, material flows downwards along the pin thread when the full-threaded pin is used. Meanwhile, both the materials of the upper and the lower plates flow towards the lap interface along the pin thread when the reverse-threaded pin is used. The numerical simulation results were investigated by experiment, in which 2A12 aluminum alloy was used as the research object. The effective sheet thickness （EST） and stir zone （SZ） width of the joint by the reverse-threaded pin were much bigger than those by the full-threaded pin. Accordingly, cross tension failure load of the joint by the reverse-threaded pin is 23% bigger than the joint by the full-threaded pin.

Microstructure and wear behavior of AA6061/SiC surface composite fabricated via friction stir processing with different pins and passes

In this investigation,the effects of pin geometry and number of passes on macrostructure,microstructure,wear rate and also microhardness profile of 6061-T6 aluminum alloy surface composites fabricated via friction stir processing(FSP)were discussed by reinforcement particles of silicon carbide(SiC).The results show that after each FSP pass,a modify distribution of SiC particles is acquired and the increase in the number of passes reduces the average grain size in stir zone(SZ).Furthermore,it is discovered that pin geometry and pass number play a dominant role in the grain size of SZ and distribution of SiC particles in SZ.It is found that after each FSP pass,wear rate is improved due to the uniform distribution of SiC particles in surface of Al/SiC composite.Additionally,the results show that the square pin and smooth(straight)cylindrical pin have the highest and lowest resistance to wear,respectively.