Comparative study on micro-milling machinability of titanium alloys prepared by different processes: Forging process, additive manufacturing process and heat-treatment process

The application of additive manufactured titanium alloy is extensive in aerospace, biomedical, and various important industrial fields. To meet the precision requirements, post-treatment processes such as micro-milling become imperative for additive manufactured parts. In this work, the forged TC4 material and additive manufactured TC4 materials before and after heat-treatment were used as samples, the machinability of three TC4 materials in micro-milling with PCD micro end mill was assessed and compared. The results indicate that the additive manufactured TC4 material before heat-treatment exhibits the poorest surface quality due to its original microstructure defects, but it obtains the improved surface quality after heat-treatment, which even is better than the forged material. The most serious work hardening degree of 111.2% is exhibited on additive manufactured TC4 material after heat-treatment, under the combined action of large cutting force and pore closure. There is no obvious difference in top burr morphology of three materials, but the forged material displays the largest total average top burr size of 239.8 mu m owing to its lower hardness and superior plasticity characteristics.