Effect of Tool Pin Offset on Mechanical and Metallurgical Properties of Dissimilar FSW Joints of 6061t6 AL Alloy to Copper Material

In the present investigation effect of tool pin offset on mechanical and metallurgical properties of dissimilar FSW joints of 6061T6 Al alloy and Copper material was studied. Keeping other FSW variables constant, tool pin offset was varied from 1mm, 2mm and 3mm.The plunge load value decreases with increase in tool pin offset, because of the tool pin is immersed into soft material (Al), while at lower pin offset the plunge load increased.

Tensile Strength (TS) values decreases with increase the tool pin offset. Poor tensile properties were obtained at the very large pin offsets, due to the insufficient reaction between the Cu and Al material. Sufficient reaction was achieved in the FSW Al-Cu joints produced at pin offsets of 1mm and 2mm, resulting in the good tensile properties.

The distribution, amount and size of Cu particles strongly depend on tool pin offset. It is observed that content of dispersed particles decreases at larger tool pin offset. When the pin offset was larger, only few Cu pieces with relatively small size were scratched from the Cu bulk. It was easy for the small Cu pieces to mix into the Al base and react with the Al base in the nugget zone, and therefore no proper mixing of Cu with Al matrix. On the other hand, when the pin offset was smaller, more Al-Cu IMCs would be formed because the more Cu pieces were stirred into the nugget zone. Thus the joining between the Al and Cu became poor due to the brittle nature of the IMCs. Research investigation also highlights the fracture location at different tool pin offsets.