The application of aluminium tailor-welded blanks (TWB) is progressively increasing in automotive industries due to its high strength to weight ratio, superior corrosion resistance and crashworthiness. The weldments produced by Friction stir welding (FSW) retains high strength and formability as the process yields the sound joints at relatively lower temperatures in comparison to that of the conventional fusion welding processes. However, the FSW of aluminium alloy of different thicknesses in butt configuration is rarely studied. The primary objective of the present work is to investigate the feasibility of FSW process in joining of 1.5 to 2.5 mm thick AA5052 alloy tailored blank by tilting the workpiece with respect to machine bed. The effects of workpiece tilting angle with welding and rotational speeds on mechanical and metallurgical properties of the joints are studied. Minimum effective sheet thickness is found to be around 1.34 mm for tool rotational speed of 400 rpm and tilting angle of 0°. The highest joint strength around 212.6 MPa (95% of base metal strength) is achieved at a workpiece tilt angle of 1° for rotational and travel speed of 400 rpm and 1 mm/s, respectively. The maximum measured hardness is 60 Hv at tool roational speed of 400 rpm with tilting angle of 1°.
The effect of a welding process (electrogas welding (EGW) and flux cored arc welding (FCAW)) on the fracture toughness, CTOD (crack tip opening displacement), and mechanical properties (tensile, bending, impact strengths and hardness) of thick weld joints is examined. The CTOD value of the FCAW weld joints was higher than that of the EGW ones. The fractured welded specimen after the CTOD test reveals ductile and cleavage fractures of the weld joint faces after flux cored arc and electrogas weldings, respectively. The mechanical properties of the EGW welded specimens satisfied relevant classification rules. These results suggest that the EGW process is an effective substitute for the current welding process (FCAW) used for high-strength thick steel plates.
This study intends to investigate the weldability and mechanical characteristics of butt weld joints by LAFSW for dissimilar materials (Al6061-T6 and SS400). At optimum welding conditions, the tensile strength of dissimilar materials joints made by FSW is found to be lower than that of LAFSW. Due to the increase in plastic flow and formation of finer recrystallized grains at the TMAZ and SZ by laser preheating in LAFSW, the hardness in LAFSW appeared to be higher than that of FSW. Compared with FSW, finer grain size is observed and elongated grains in parent metal are deformed in the same direction around the nugget zone in TMAZ of Al6061-T6 by LAFSW. Whereas, at weld nugget zone, coarse grain size is appeared in LAFSW compared to FSW, which is owing to more plastic flow due to laser preheating effect. In dissimilar materials joints by LAFSW, ductile mode of fracture is found to occur at Al6061 side with fewer brittle particles. Mixed mode of cleavage area and ductile fracture is observed at SS400 side.
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