Unveiling the effect of consumable size during friction stir spot welding of AA6063-T6 and CRCA/IS-513 through experiments and finite element simulations
摘要
The current work investigates the effect of the size of the consumable sheet during friction stir spot welding of AA6063-T6 and CRCA/IS-513 thin sheets through experiments and finite element (FE) simulations. Size ratio, which is defined by shoulder diameter (SD) and consumable diameter (CD), was optimized through bend tests, material flow, and microstructure analysis. Temperature, axial force, torque, effective strain, and strain rate are measured through experiments and simulations. Bendability, joint grain size, intermetallic compounds, and microstructures are revealed following the joining process. FE simulations are performed in DEFORM 3D with calibrated Hollomon and Voce flow stress models. The peak temperature rose 52.7% when the SD was increased from 9 to 15 mm, but only 36% when the SD was increased from 18 to 21 mm. Stir zone with recrystallized grains of 4.3 μm size was observed in Case 3 (15 mm SD and 20 mm CD). Case 5 (21 mm SD and 28 mm CD) had higher hardness (298 HV) because of IMCs at the joint interface (1.8 µm thick AlFe and FeAl3). In case 3, the axial force during FSSW-C peaked at 2835 N, increasing 147% from case 1 before decreasing 38%. In case 1, the torque was 216 N-mm; in case 5, it was 864 N-mm. Root bend shear tests showed higher fracture loads than face bend tests. FE simulated temperatures agreed with experimental values within 6.5%. At the upper surface of the consumable sheet, Case 5 exhibited the highest effective strain of 121.08 mm/mm and strain rate of 115 s−1. On the other hand, case 1 recorded the lowest values of 47.12 mm/mm and 21.20 s−1, which is consistent with the literature on the impact of SD. Using the results, a size ratio of 0.75 is recommended for optimal joining of dissimilar sheets.