Characteristics of friction welded joint between 6063 aluminum alloy and AISI 304 stainless steel through post-weld heat treatment

The characteristics of the friction welded joint between Al-Mg-Si alloy (AA6063) and austenitic stainless steel (AISI 304, 304SS) through post-weld heat treatment (PWHT) were investigated. The joints were made with a friction speed of 27.5 s(-1), friction pressure of 30 MPa, friction time of 1.5 s, and forge pressures of 30 or 240 MPa. As-welded joints had no intermetallic compound (IMC) interlayer at the weld interface. However, the joint with a forge pressure of 30 MPa was fractured between the weld interface and the AA6063 side, and that of 240 MPa was fractured from the AA6063 side. The tensile strength of joints through PWHT process decreased with increasing heating temperature and its holding time. The fractured portion of joints with a forge pressure of 30 MPa changed to the AA6063 side from between the weld interface and the AA6063 side, but that of joints with 240 MPa were fractured from the AA6063 side. Then, all joints with following PWHT conditions fractured at the weld interface; a heating temperature of 773 K and holding time of 3.6 ks, or those of 798 K and 21.6 ks. The fractured surface of joints through PWHT process had IMC interlayer. PWHT condition could express by the Larson-Miller parameter, and the weld interface fracture could divide with a threshold value of this parameter. In conclusion, the fractured point of the joint between AA6063 and 304SS was influenced by the IMC interlayer at the weld interface that was generated during the PWHT process.