Study on surface integrity of titanium alloy machined by electrical discharge-assisted milling

• Electrical discharge-assisted milling (EDAM) can improve the surface integrity of Ti-4Al-6 V. • EDAM can reduce the surface roughness compared with conventional milling (CM). • Compared with CM, the residual tensile stress generated by EDAM is smaller. • The microhardness of machined surface after EDAM is relatively smaller than CM. • Moderate capacitance has more positive influence for surface integrity. Electrical discharge-assisted milling (EDAM) is an efficient machining process for titanium alloys according to previous studies. However, a complete understanding of the surface integrity of titanium alloy machined with EDAM is not yet sufficient. Therefore, in this paper, surface defects such as chip layer adhesion, debris, feed marks, and burrs were investigated and identified. Among them, the adhesion of the chip layer is the most common surface defect and is the factor that has the greatest influence on the surface quality. In addition, surface roughness, micro-hardness, and residual stress were analyzed and discussed. The results show that the surface roughness of EDAM is significantly improved compared to conventional milling (CM). Also, the residual stress generated by EDAM is much smaller than that of CM, and the main type of residual stress is residual compressive stress. Similarly, the surface microhardness after EDAM is also slightly smaller than that of CM. This increased surface integrity is due to the material softening effect due to the heat generated by the discharge spark. Consequently, EDAM is a good candidate method for efficient machining of titanium alloys.