Numerical modelling for the hardness evaluation of friction stir welded copper metals

This work aimed at exploring the hardness of a copper workpiece undergoing butt joint Friction Stir Welding (FSW). Hardness measurements and microstructural evaluations were performed on the welded specimens. Also a 3D Arbitrary Lagrangian Eulerian (ALE) numerical model was developed to obtain hardness values. Numerical results for hardness values showed good agreement with recorded experimental data. Experimental results suggested that with an increase in translational speed the size of grains reduces, and in a constant rotational speed with a decrease in grain size weld strength increases. Hardness in the nugget zone is higher than that in HAZ and TMAZ, and a range of maximum hardness is located around the centre of weld, whereas outside of this region hardness reduces slightly in TMAZ and HAZ, and then moving towards base metal rises sharply. Also using the insulator or increasing the plunge depth of tool shoulder lead to production of weld with no defect despite rising of weld temperature. These experimental results can offer useful knowledge for a FSW based process of copper butt joint.