## 1 Introduction  
Titanium alloy material is a structural material with a high temperature resistance, low density, high strength, and has a very important application value and broad application prospects in the fields of aerospace, electronic communication and marine engineering [1, 2]. Due to their good mechanical properties, titanium alloys are mostly used in the manufacture of aerospace monolithic components such as integral wall panels and frame parts [3, 4, 5]. During the mechanical cutting process, due to the poor thermal conductivity of the titanium alloy materials and the strong adhesion between the tool and the workpiece material, tool wear easily occurs [6, 7], thereby requiring a frequent change of the tool. In addition, usually the monolithic components are directly processed from the whole blank to produce features such as cavities and webs. As a result, the material removal ratio may exceed 90% [8], which increases the processing cost of the titanium monolithic components prominently. For this reason, it is necessary to explore the efficient and low-cost processing methods of titanium alloy monolithic components. Electrochemical grinding (ECG) is an electrochemical mechanical composite machining method. During processing, the surface of the workpiece is oxidized into a dense anode passivation film under the effect of the current and the electrolyte [9; 10]. The passivation film can be quickly scraped off by the abrasive on the grinding wheel, so that the new metal is exposed on the surface of the workpiece, and the process of electrolysis can continue. Obviously, this advantage is suitable for the processing of the easily passivated metals such as titanium alloys. In addition, compared to mechanical grinding, ECG has a higher productivity and less tool wear [11; 12]. [PERSON] and [PERSON] [13] found that the maximum linear wear of the grinding wheel after the mechanical grinding of the hard alloy and titanium alloy for 3 min was 8 times and 6 times, respectively, compared to that of ECG. In addition, they also observed that within the parameter range of the cutting depth of 0.01 to 0.06 mm and a feed rate of 25 to 200 mm min\({}^{-1}\), the energy consumption of the ECG of titanium alloys was significantly lower than that of the mechanical grinding [14]. [PERSON] et al. [15] carried out ECG experiments on hard alloys with different compositions and found that compared to mechanical grinding; the grinding wheel loss was reduced by about 60% and the material removal rate increased by 73%. [PERSON] [16] and others found that in the machining of Al\({}_{2}\)O\({}_{3}\)/Al composites, the grinding force in ECG was reduced by about 75%-95% compared to that of mechanical grinding. In addition, under the test conditions of feed speed of 24 mm/min and cutting depth of 0.08 mm, the material removal rates obtained by the mechanical grinding and ECG were 0.053 g/min and 0.141 g/min, respectively. However, currently ECG is mostly used to improve the surface characteristics of the workpiece by making a very small thickness of the material removal in a single pass. In addition, due to the size and shape of the conductive grinding wheel, the ECG process is difficult to apply in the manufacturing of complex structures and profiles, and the processing flexibility is poor. Electrochemical mill-grinding (ECMG) is a flexible composite processing method of electrochemical processing and mechanical processing, which was developed on the basis of ECG processing technology in recent years. It uses a rod-shaped tool with abrasive grains to achieve the processing of complex structures through a method similar to milling, but has higher a flexibility and productivity than the ECG. [PERSON] et al. [17] integrated the advantages of the electrochemical milling and ECG and proposed the ECMG method for the first time with external liquid supply. Using a brazed diamond abrasive ball-end rod tool, they conducted an electrochemical mill-grinding test study on Inconel 718 using a cutting depth of 0.5 mm.