Investigation on Friction Stir Weldability Characteristics of AA7075-T651 and AA6061-T6 Based Nanocomposites

Table 6

Macrographs of the FSW composite welds.

Run	Macroimages	Inference
1		The nugget zone shows no tunnel defect and fusion is continuous along both the advancing and retreating sides of the process. Some agglomerates and tearing could be seen due to medium speed.
2		The nugget zone shows some agglomeration of the composite particles at the retreating side of the interface attributable to the stacking tendency due to thread geometry.
3		The nugget zone shows a tunnel defect measuring 2.5 mm diameter at the advancing side of the interface. However, fusion is continuous (attributable to incomplete formation due to low speed of 600 rpm).
4		The nugget zone shows tunnel defect at the advancing side and bottom of the FSW process. Moreover, fusion is continuous along both the advancing and retreating sides of the process.
5		The nugget zone shows some 2.0 mm long tunnel defect inside and close to the advancing side of the process. Better stirring of the material (joint formation) could be achieved by an equi-moment ratio like triangle/hexagonal than square. This results in the formation of the tunnel especially in advancing side.
6		The nugget zone shows tunnel defect at the retreating side top and advancing side bottom of the FSW process. The dark zone also could be due to the accumulation of h-BN composite particles added at the tunnel.