Machinablility of titanium matrix composites (TMC) reinforced with multi-walled carbon nanotubes

Abstract

Carbon nanotube (CNT) reinforced titanium matrix composite (TMC) is a type of new material with promising potentials in industry because of its superior properties such as low density and high elastic modulus. In this paper, the machinability of CNT-reinforced TMCs with different fabrication methods was studied experimentally. Multi-walled carbon nanotubes (MWCNTs) were dispersed in titanium (Ti) powder via different dispersive methods, and the Ti-MWCNTs powder mixtures were consolidated by spark plasma sintering (SPS) at different temperatures. The fabricated TMCs were machined by milling and electrical discharge machining (EDM), and their machinability was investigated by analysing the roughness, hardness, cutting forces and micro morphology of the machines surfaces. After milling, it was found that the machinability of the TMCs fabricated under different processing conditions was different, which was reflected by the difference in cutting force (values and frequecies), tool wear and facial morphology (roughness, hardness, flaws and element distribution). The main causes of these variances in machinability were attributed to the CNT agglomeration and presence of in situ formed titanium carbide (TiC) particles in Ti matrices. Also, the CNT agglomeration and TiC particles influenced the facial morphology of TMCs after EDM. The sizes and distribution of pores due to the erosion were different for the four TMCs. The results proved that the fabrication methods influence the properties of the TMCs which significantally impact their machinability.