Evaluation of the Machinability of Cast Ti-Si Alloys with Varying Si Content

This study evaluated the machinability of a series of binary Ti-Si alloys with a goal of developing a titanium alloy with better machinability than commercially pure titanium (c.p. Ti). The alloys were slotted using a milling machine and end mills under four cutting conditions. Machinability was evaluated through cutting force. The experimental results indicate that alloying with Si significantly improved the machinability of c.p. Ti in terms of cutting force under the present cutting conditions. As the Si content increases, the cutting force decreases then greatly increases. The cutting forces of c.p. Ti and the Ti-Si alloys increased as the feed rate increased from 30 to 60 m/min under the cutting speed of 55 or 110 m/min. The cutting force of Ti-5Si at cutting speed 55 m/min was approximately 49% lower than that of c.p. Ti; at cutting speed 110 m/min, it was approximately 62% lower than that of c.p. Ti. The cutting force of Ti-10Si was significantly higher than those of the other Ti-Si alloys and c.p. Ti, a result that can be explained by a higher degree of hardness (626 HV) and larger amounts of Ti5Si3 (47.10 vol.%). For Ti-5Si, there was no obvious adhesion of chips observed on the cut surfaces. Furthermore, the specimens had the lowest surface roughness (Ra) values, approximately 0.3-0.4 μm, under the four cutting conditions. When cutting force, chip length, and surface roughness results are considered, the Ti-5Si alloy developed in this study is a viable candidate for machining.