LASER FORMING OF STRUCTURES OF HARDENED ALLOYS OF ALUMINUM

Abstract

This paper analyzes methods of obtaining thin-walled sheet structures from the pre-heat-treatable aluminum alloys. These drawbacks technology Drobotenko of shaping, which is currently widely used in aircraft industry. It is proved that the method of laser forming a more flexible and productive compared with the specified technology. On the basis of literary data analysis determined that for aged alloys barrier to introducing the technology of laser forming could be a weakening of the alloy in the heat affected zone as a result of dissolution or coagulation of strengthening phases. According to the traditional scheme of Dogville laser forming on samples of alloy D16 at CO2 - laser with radiation power P =1 kW, focal spot diameter d=4 mm, a speed of movement of the beam V=6.0 m/min. Determined the microhardness, yield stress, and strength parameters of the substructure and the residual stresses in the heat affected zone. It is shown that the processes of softening are not recorded up to angles of ≈30°. To obtain structures with large bend angles is proposed and implemented scheme of laser forming with cooling of the workpiece in pairs of liquid nitrogen. According to this technology held laser bending samples. Characterization of strength and substructure of heat affected zone. It is shown that the yield and strength of the alloy in the heat affected zone increases with the number of passes by increasing the dislocation density. The latter is a result of plastic deformation of the alloy when the relaxation time of thermal stresses on the heating stage of the thermal cycle. It is proved that laser forming with cooling of the workpiece is more productive in comparison with the traditional scheme due to the increase of bending moment in consequence of the increase of the temperature gradient normal to the sample surface. It is experimentally shown and theoretically proved that the laser forming leads to the appearance in the surface layers of the workpiece residual compressive stress. The latter should substantially increase the fatigue strength of the structure.