Effect of traverse speed on microstructure and mechanical properties of friction-stir-welded third-generation Al–Li alloy

Abstract

The aim of the study is to investigate the consequences of tool traverse speed on force and torque distribution of friction-stir-welded third-generation Al–Cu–Li alloy joints. The microstructure and corresponding mechanical properties of the joints are investigated on force and torque perspective. Thus, the contribution of the present work lies in establishing the relation between traverse speed and mechanical properties of the AA2050-T84 joint. Four welds have been considered at varying traverse speeds from 1 to 4 mm/s at constant tool rotational speed and tool tilt angle of 1400 rpm and 2°, respectively. A tool of H13 steel having a tapered screw-threaded pin profile was used. The investigation reveals that with the increase in traverse speed, longitudinal force (X-force), vertically downward force (Z-force) and spindle torque also increase. The grain size of the nugget zone reduces from 19.84 to 14.86 µm as traverse speed increases. It has been found that the mechanical strength of the joint increases as the traverse speed increases. The Vickers microhardness value increases from 115 HV0.1 to 131 HV0.1 in the nugget zone as traverse speed increases from 1 to 4 mm/s. The maximum tensile strength, % elongation and joint efficiency are 403.2 MPa, 7.2% and 75.5% for traverse speed of 4 mm/s. The tensile fracture samples are analyzed by scanning electron microscope and reveal ductile mode of fracture.