Probe-less friction stir spot processing (PFSSP) of AA5754/AA5083 joint by adding the B4C ceramics: Effect of shoulder features on mechanical properties and tribological behavior.

This study aims to improve the local shear behaviors of dissimilar spot welds of Al alloys through a particle-dispersion strengthening mechanism. Probe-less friction stir spot processing of the AA5083-H112 and AA5754-O alloys with B 4 C ceramic reinforcement was investigated by modifying the tool shoulder surfaces. The smooth and scrolled shoulder tools were utilized for this study. The mechanical properties of the B 4 C-reinforced spots were examined via the use of the miniaturized shear punch testing method and the tensile-shear test. At an unchanged process condition, the scrolled shoulder tool improved particle dispersion and dislocation density to an extent while it significantly reduced the average B 4 C particle size from 60 to 6.71 μm more than that of the smooth shoulder tool. The scroll-pattern-assisted straining, material flow. The wear rate was significantly reduced in the sample fabricated with the scroll tool. The scrolled shoulder tool is recommended for the fabrication of the B 4 C-reinforced spots. • The change in the tool shoulder surface has an insignificant impact on the shoulder indentation zone (SIZ). • The sample fabricated with a scrolled tool has a slightly more dislocation density due to the high straining and particle disintegration. • The scroll-pattern assisted straining, material flow and particle disintegration effects improved the shear force of the weld. • The sheared surfaces of the sample produced by scrolled tool had more elongated dimples as compared to the sample produced by the smooth tool. [ABSTRACT FROM AUTHOR]