Effect of friction stir welding heat input on the microstructure and tensile properties of Cu-Zn alloy containing disordered β phase

The microstructure and tensile behavior of stir zones in the friction stir welded brass plates containing disordered secondary beta phase at different heat inputs were investigated. At high heat inputs, beta was transformed completely to alpha, and hence the final microstructure was single-phase. At lower heat inputs, fine beta particles remained on a grain boundaries, causing a reduction in grain size from 3.78 to 1.08 mu m. Despite the smaller grain sizes of the stir zones, they revealed lower elongation compared to that of the base metal, which was due to their higher dislocation densities with tangle structures. The stir zones had higher tensile strength than the base metal due to both grain boundaries and dislocation density strengthening mechanisms. The low heat input stir zone showed a synergic increase in the tensile strength and elongation compared to the higher heat input stir zone due to its smaller grains and presence of beta particles on the grain boundaries. (C) 2020 The Authors. Published by Elsevier B.V.