Correlation Between Heat Input and Mechanical Properties of Submerged Friction Stir Processed TIG-Welded AA8011/AA6082 Dissimilar Joint: Sampling Aspect

Abstract

This paper reports on the relationship between heat input and microstructure of the submerged friction stir processed TIG-welded AA8011/AA6082 dissimilar joint. The AA8011/AA6082 dissimilar joint was produced through the tungsten inert gas (TIG) technique before processing. The dissimilar welded joint was then subjected to a friction stir processing (FSP) technique that was fully submerged underwater. The temperature profile was measured using the K-type probes installed along the joint, and the properties of the joint were studied using various laboratory equipment. The variation in heat input was studied in correlation with the microstructural arrangement. The thermal instability was observed at the start of the joint, while thermal stability was observed from the middle to the end of the joint. The average grain size ranged between 5mm and 8 mm: the average grain size of 8 mm was measured on the sampled specimen from the start of the joint, while 5 mm was measured on the sampled specimen from the end of the joint. The tensile properties of the joint increased gradually along the joint. The ultimate tensile strength (UTS) recorded for the sampled specimen from the start of the joint was 76.9 MPa with a percentage elongation of 8.79%, while that of the sampled specimen from the middle of the joint was 80.3 MPa with a percentage elongation of 21.82%, and the UTS for the sampled specimen from the end of the joint was 87.2 MPa with a percentage elongation of 24.12%. The microhardness at the stir zone of the joint varied between 52 HV and 64 HV; these values were lower than AA6082 base metal but higher than AA8011 base metal. The lower microhardness value corresponds to the sampled specimen from the start of the joint, while the higher microhardness value corresponds to the sampled specimen from the end of the joint.