High-strength aluminum alloy has the advantages of high specific strength and specific rigidity, and has become the preferred material for high-strength and lightweight components such as new-generation rocket cabins, aircraft tanks and attitude control wings, large passenger aircraft fuselages, and high-speed rail bodies. With the increasing demand for high-performance service and multi-functional integration of high-end equipment in the industrial field, the traditional "blank casting/forging-subtractive processing" and "welding" manufacturing modes can no longer meet the manufacturing needs of high-strength aluminum alloy components. It is urgent to break through the existing manufacturing mode and improve the manufacturing quality of high-strength aluminum alloy components.
Based on additive manufacturing technology, the material-structure integrated net forming of complex structure metal components can be realized, which provides a new technological approach for the design and manufacture of aluminum alloy high parts. So far, laser additive manufacturing and arc additive manufacturing technologies have become the current two mainstream technologies for aluminum alloy additive manufacturing, and have been applied in some industrial fields.
Despite these advances, due to the high reflectivity and thermal conductivity of aluminum alloys to lasers, laser additive manufacturing aluminum alloys are prone to defects such as cracks and pores; while the deposition efficiency of arc additive manufacturing technology is relatively high, but The performance of the formed part is low. The problem of uncontrollable structure-stress-performance has always limited the further application of aluminum alloy additive manufacturing technology, and is one of the problems in the field of aluminum alloy additive manufacturing.
Researchers from Dalian University of Technology proposed a laser-arc composite additive manufacturing method for aluminum alloys, and published a series of important works in authoritative journals Addtive Manufacturing, Virtual and Physical Prototyping, and Materials and Design. This work is based on the idea of "small area forming-layer by layer accumulation". As shown in Figure 1, a localized and controllable laser is used as one of the heat sources, and the welding wire is melted together with the arc with a large heat input to achieve high-quality manufacturing. The synergistic effect of laser and electric arc improves the stability of the additive manufacturing process, and is expected to achieve the goal of synergistic control of the structure-stress-performance of the additive manufacturing aluminum alloy and defect controllability.
Using the laser-arc composite additive manufacturing process, arc preheating can increase the absorption rate of the wire to the laser, which is conducive to the keyhole effect of the laser, and the plasma is generated by spraying the light. In turn, it is beneficial to start the arc and stabilize the arc, forming high energy Density heat flow, the synergy of the two can also reduce the temperature gradient of the molten pool; in addition, pulse lasers are used to impact and stir the molten pool to improve the flow characteristics of the molten pool, regulate the state of the solidification structure, and further improve the microstructure and reduce thermal stress , Suppress defects and realize the coordinated control of organization and performance.
Due to the compound effect of the pulsed laser, the microstructure of the formed component presents different characteristics in different regions. The average grain size of the laser action zone is significantly reduced, which is about 40% smaller than the average grain size of the arc action zone; in the laser action zone The alloying elements are evenly distributed and the segregation phenomenon is suppressed. Due to the unique microstructure characteristics of laser-arc composite additive manufacturing, the tensile limit of Al-Cu alloy formed parts before heat treatment exceeds 300 Mpa, and the elongation after fracture exceeds 12%; after heat treatment, the tensile limit can reach the standard of T6 forgings , The elongation after breaking reaches 15%. This technology can also be used for the additive manufacturing of metal components such as aluminum-zinc alloy, aluminum-lithium alloy, copper alloy, etc., to expand the application field of laser additive manufacturing technology.