2003 Volume 21 Issue 3 Pages 481-488
The present paper describes the relationship between joining phenomena, i.e. the friction stage and the yield strength of substrates of dissimilar friction welding. The materials used were oxygen free copper (OFC), commercially pure titanium (P-Ti), commercially pure aluminum (A1050) and type 7075 aluminum alloy (A7075). The combinations of P-Ti/OFC, A1050/OFC and A7075/OFC were joined by using a conventional friction welding machine. The same friction welding condition was used for all combinations.
Main conclusions are obtained as follows.
(1) The friction process, i.e. joining behavior, friction torque curve and welded interface behavior was observed different for each joint. The welded interface of P-Ti/OFC joint sparked, and intensively flew from P-Ti substrate. The upsetting (deformation) occurred at only P-Ti side during the friction stage after initial peak torque. The upsetting also occurred at only A1050 and A7075 substrates for A1050/OFC and A7075/OFC joints, respectively.
(2) The temperature of each joint during friction welding process was measured at centerline, half radius (1/2R) and periphery portions. The maximum temperature of P-Ti/OFC joint was much higher than those of both A1050/OFC and A7075/OFC joints. The maximum temperature of A1050/OFC joint was almost same as that of A7075/OFC joint after initial torque.
(3) In P-Ti/OFC joint, wear and adhesion of surfaces started at periphery portion (outer surface) of OFC substrate, and they extended toward center portion (center axis). Then, the P-Ti substrate adhered to OFC substrates after the weld faying surface of P-Ti substrate became the wear state. In A1050/OFC joint, the wear and the adhesion started at whole surface of A1050 substrate. In A7075/OFC joint, wear and adhesion started at periphery portion of both A7075 and OFC substrates, and they extended toward center portion.
(4) It is considered that the joining behavior, friction torque and welding temperature were affected by the relationship between the loaded friction pressure and the yield strength of substrates.