Friction Stir Welding Of Small-dimension Al3003 And Pure Cu Pipes

“Replacing Cu by Al”is a developing trend in industry.Reliable and efficient joining between Cu and Al is therefore essential and has drawn considerable attention.In this study,small-dimension Al3003 pipe and pure copper pipe of thin wall and small diameter were successfully joined by FSW with a specially-designed system.A distinctive temperature history due to the heat accumulation was identified as an important feature for typical FSWed pipe joints with small-dimension,leading to distinctive variations of surface condition,macro-/micro-structure along the circumferential weld seam.Hardness distribution,tensile strength,ductility and fracture modes were found to change correspondingly along the weld seam.At the later region which experienced highest temperature,better surface condition,less intermetallic compound?IMC?and better mechanical properties?ductility:³%?were obtained.There were two fracture modes in different regions.One mode was that fracture occurred at the IMC-rich band structure.In another mode,fracture occurred at the heat affected zone or the stir zone with no Al-Cu intermixing at Al side.In the joints,IMC had 5 types of structure:Type I1,I2 at macro-Al/Cu interface,Type S1,S2 and S3 in stir zone.They consisted of Al₂Cu,Al₄Cu₉ and few AlCu.These five types of IMC had different formation mechanism,which were affected by the different shear effect,pressure effect and stirring effect during FSW.