Stability of mechanical properties of fixed joints of 35-mm-thick AA5356 sheets produced by the friction stir welding

In the present work, the FSW-joint of 35 mm thick aluminum-magnesium alloy AA5056 sheets was investigated. It was observed that the microstructure is represented by a system of separate metal flows along the contour of the tool. This is caused by lower values of pressure in the area of joint formation relative to the material volume in comparison with welding products of smaller thicknesses. The results of microhardness measurements of the weld material and the near-weld area of fixed joints show that in the material of the main structural zones, there is no softening as compared to the base metal. Tensile tests conducted show high mechanical properties of the samples. The average ultimate tensile strength value is about 305 MPa. Deformation of specimens occurs with pronounced discontinuous fluidity or Portevin– Le Chatelier effect.