LAUSR

Abstract Extrusion welding of the 7xxx series aluminium alloys, especially these of high strengthened containing copper is still a barrier difficult to overcome. The main limitations are: poor weldability of the material which decreases a product quality, low permissible exit speed from the die decreasing the production efficiency, as well as severe thermal and mechanical working conditions for the die. The paper presents the results of weldability testing of the 7075 aluminium alloy, containing 5,59 % of Zn, 2,36 % of Mg and 1,49 % of Cu, with the use of an original authorial device. This device enables modelling the behavior of a material in the welding chamber of a porthole die. The tested material was submitted to non-conventional homogenization, what permitted to increase the solidus temperature of the alloy in comparison to the for cast material. The tests were conducted at 520°C and under the pressure of 200 MPa. The microstructure of the material was investigated both in the region of welds and in the basic material by using light microscope and scanning microscopy SEM. In addition, the chemical composition of the alloy was examined by using the ESD method. The microhardness test was performed perpendicularly to the surface of welding. The results indicate that the high-quality welds were not obtained. As it was stated, for the given temperature of welding, the welding factor limit value, i.e. relation of unit pressure to the yield strength (σn/k), was not reached.