A novel high-dynamic actuator based in-situ micro-forging process for wire arc additive manufacturing of aluminum alloy

As a method of work hardening, the technology of in-situ forging was introduced to solve the problem of poor mechanical properties in the fabrication of large-structural aluminum alloys components using wire arc additive manufacturing (WAAM) technology. Unfortunately, at present, the in-situ forging devices reported could not provide the ability to flexibly adjust output forces over a wide range of frequencies and change the output mode of forces. In this work, a novel method of high-dynamic actuator based in-situ micro-forging process for WAAM was proposed. The system is of compact design and has the characteristics of high dynamic response. The terminal hammering head could automatically fits the surface of the deposited layer successfully, enabling the stable control of the real-time hammering force, meaning that it offers a solution for processing deposited layers with complex paths. In addition, the terminal hammering head could be sufficiently close to the molten pool to enable the cumulative rapid micro-deformation of the as-solidified metal. This new method significantly promotes the reduction of shrinking holes and the closure of spherical pores of the components. The microhardness and the compressive yield strength of the components increased by 12% and 13% respectively. A gradient microstructure was obtained due to the transfer of strain. The mechanism of hybrid dynamic recrystallisation induced by cumulative rapid micro-deformation is investigated. These promising results promote the possibility of applying in-situ micro-forging technology in the field of flexible and intelligent manufacturing in aerospace.