Friction stir welding of rolled sheets made of heat-resistant copper alloy

An attempt is made to obtain a welded joint from rolled sheets of heat-resistant copper alloy using friction stir welding. This method differs from other types of welding in the absence of a cast weld structure. According to the test results, no defects are found. It is found that the weld metal in the mixing zone is noticeably softer than the base metal: the HV 0.1 microhardness values for the base metal are (143.4 ± 3.2) MPa, and for the weld the average value was 110 MPa with a fluctuation of values from 97.9 to 138 MPa. The application of annealing at 980 °C for 30 minutes ensures the alignment of hardness along the entire section of the joint: for the base metal — (62.9 ± 1.5) MPa, for the weld — (64.6 ± 4.5) MPa. At the points of transition of the base metal to the seam metal, the orientation of the initial structure changes in accordance with the direction of rotation of the welding tool. According to the results of micro-X-ray spectral analysis, it was revealed that with friction stir welding there is a uniform distribution of chromium, which is part of the heat-resistant copper alloy.