Mechanical and thermal properties of friction-stir welded joints of high density polyethylene using a non-rotational shoulder tool

The effects of rotational and welding speed on the mechanical properties and thermal behavior in friction stir welded joints of high-density polyethylene using a non-rotational shoulder have been investigated experimentally. Tensile properties and hardness were measured to determine the mechanical properties, and the effect of the welding parameters. Heating and cooling cycles of differential scanning calorimetry were used to establish thermal properties. Microstructure observations complemented experimental observations. Results showed that tensile strength, hardness, and crystallinity decreased when rotational speed was increased, while the welding speed effect was weak. Deleterious phenomena on molecular structure of the stir region were explained by means combination of selected welding parameters and the material flow during the process.