Electrochemical machining of staggered square micro-columns on titanium alloy: Electric field regulation and shape evolution

• Two-step TMECM enables precision machining of columns with small center distances. • It clarifies the forming mechanism of micro-dimples on constrained surfaces. • The I-shaped through-holes in mask helps the generation of square columns. • It demonstrates how mask dimensions critically affect the column morphology. • The method realized large-area fabrication of staggered square microcolumn arrays. The ion thruster represents one of the most extensively utilized electric propulsion systems in aerospace applications. To effectively address the heat dissipation challenge within its discharge chamber, it is critical to design and fabricate square column arrays with flow-disturbing effects inside the double-walled cooling channels. The array structure, featuring a staggered arrangement, presents challenges to existing through-mask electrochemical machining methods due to its minimal center distance and significant lateral corrosion. This study proposed a novel two-step through-mask electrochemical machining(TMECM) process utilizing reusable masks including scanning TMECM and stamping TMECM. This method facilitated the creation of staggered columns by machining micro-dimples interspersed between micro-groove arrays. The formation of columns from micro-dimples on a constrained surface significantly differs from traditional machining on smooth surface. The formation process of micro-columns and micro-dimples were investigated via dynamic electric-field simulation, enabling the design of a reusable mask with I-shaped through-holes. When the micro-dimples are interconnected with the grooves, this mask can effectively intensify the electric field at the junction, thereby regulating the material removal rate at this position and enabling precise shape control of the square column. The design of the mask through-hole size was then conducted based on the simulation results. Thereafter, the effects of key machining parameters on the column formation were experimentally investigated. Using optimal parameters, we successfully fabricated over 400 staggered square columns on TC4 titanium alloy at one time. This approach permits the large-scale and efficient fabrication of micro-column arrays.