Influence of rotation speeds on microstructure and mechanical properties of welded joints of friction stir welded AA2014-T6/AA6061-T6 alloys

Abstract

This study presents the joining process of plates with thickness of 4  mm in AA2014 and AA6061 through Friction Stir Welding (FSW) process under alternative tool rotating speeds. AA2014-T6 and AA 6061-T6 alloys were friction stir welded with cylindrical eased pin tool at different revolving speeds such as 700, 900 and 1100  rpm and constant welding speed of 50  mm/min. Mechanical behavior of the FSW of an aluminum alloy exposes a key role of the microstructure. The microstructure change in the interfacial region is characterized using Optical Microscopy (OM). The average grain size was determined based on ASTM E112 – 12 standards. The mechanical properties like tensile strength, micro hardness, and flexural strength of the dissimilar aluminum alloys were evaluated. The fracture examination of the tensile samples was evaluated using Scanning Electron Microscope (SEM). Distance Amplitude Curve (DAC) shows that no recordable internal discontinuities are observed for all three weldments. Further, the study articulated that the effect of rotational speed (900  rpm) exhibits better hardness, tensile and flexural strength. In addition, there was a significant improvement in the grain structure and the average % of grain structure with an average grain size was found to be 15.6 µm and it directly influences the mechanical properties.